The onset of the COVID-19 pandemic disrupted many aspects of human life, not least healthcare. As resources were redistributed towards the crisis, social isolation rules also limited access to medical professionals. In particular, these measures may have affected many aspects of cancer care, such as early detection or treatment.

Many studies have aimed to capture the impact of these changes, but most have been observational, with researchers recording events without trying to impose a controlled design. These investigations also often faced limitations such as small sample sizes, or only focusing on one aspect of cancer care. Systemic reviews, which synthetize and assess existing research on a topic, have helped to bypass these constraints. However, they are themselves not devoid of biases. Overall, a clear, unified picture of the impact of COVID-19 on cancer care is yet to emerge.

In response, Muka et al. carried an umbrella analysis of 51 systematic reviews on this topic. They used a well-known critical appraisal tool to assess the methodological rigor of each of these studies, while also summarising their findings. This work aimed to capture many aspects of the patients’ experience, from diagnosis to treatment and the financial, psychological, physical and social impact of the disease.

The results confirmed that the pandemic had a substantial impact on cancer care, including delays in screening, diagnosis and treatment. Throughout this period cancer patients experienced increased rates of depression, post-traumatic stress and fear of their cancer progressing. The long-term consequences of these disruptions remain to be uncovered.

However, Muka et al. also showed that, overall, these conclusions rely on low-quality studies which may have introduced unaccountable biases. In addition, their review highlights that most of the data currently available has been collected in high- and middle-income countries, with evidence lacking from regions of the world with more limited resources.

In the short-term, these results indicate that interventions may be needed to mitigate the negative impact of the pandemic on cancer care; in the long-term, they also demonstrate the importance of rigorous systematic reviews in guiding decision making. By shining a light on the ripple effects of certain decisions about healthcare resources, this work could also help to shape the response to future pandemics.

The coronavirus disease 2019 (COVID-19) pandemic and the mitigation measures that were undertaken posed major challenges to cancer care. The rapid spread of COVID-19 and early data showing patients with cancer were at increased risk of morbidity and mortality after Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) infection, prompted changes in healthcare delivery (Venkatesulu et al., 2020). These changes included reduction of medical activities, reallocation of healthcare workers, shifting in-person appointments to remote consultations, and limiting access of patients to care facilities (Dhada et al., 2021).

Concerns have been raised that disruption of healthcare services might have had multidimensional impact in cancer care. Indeed, several studies have described delays and cancellation in treatment, screening, and diagnosis (Teglia et al., 2022a; Teglia et al., 2022b; Nikolopoulos et al., 2022). For example, two meta-analyses showed that during the pandemic there was a ~50% reduction in breast and cervical cancer screening, and that there was 18.7% reduction for all cancer treatments, with surgical treatment showing the highest reduction (Teglia et al., 2022a; Teglia et al., 2022b). In addition, several studies have highlighted deterioration of psychological well-being of patients with cancer, and psychological, ethical, spiritual, and financial needs of patients with cancer were also affected (Zhang et al., 2022; Kirby et al., 2022). While several systematic reviews have examined the impact of COVID-19 on cancer care, they evaluated different outcomes and periods of the pandemic, and thus the available review findings are rather fragmented (Teglia et al., 2022a; Teglia et al., 2022b; Donkor et al., 2021; Gascon et al., 2022; Hojaij et al., 2020; Legge et al., 2022; Murphy et al., 2022; Gadsden et al., 2022; Majeed et al., 2022). A comprehensive review of impact of COVID-19 on several aspects of cancer would be essential to understand gaps and scale-up evidence-based interventions, including learning lessons for future pandemics. In addition, although systematic reviews are important for public health and policy decision-making during the pandemic, the level of methodological rigor they implemented is unclear.

In the current study, we performed an umbrella review of systematic reviews to summarize the impact of COVID-19 on several aspects of cancer care, including treatment, diagnosis, financial, psychological, and social dimensions. We assessed the amount and geographical breadth of the available evidence and methodological rigor of the primary studies included in each review (as assessed by the reviewers) and of the systematic reviews themselves; and summarized the conclusions from different reviews on COVID-19 impact.

Our search strategy identified 1172 citations. Based on title and abstract screening, we retrieved full texts of 96 articles for further screening. Of those, 45 articles did not meet our eligibility criteria, thus leaving 51 articles to be included in our final analysis. Figure 1 summarizes our screening procedure. No additional study was found from screening of references of the included studies.

Figure 1

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Results and conclusions of systematic reviews and of meta-analyses

The main results and conclusions of the eligible systematic reviews are presented in Supplementary file 1c-j for various aspects of cancer care. Table 4 lists the effect sizes and confidence intervals (CIs) for the systematic reviews that used formal meta-analysis as well as heterogeneity metrics. Figure 2 provides a summary of main findings of this umbrella review. Here, we present some key findings for each type of outcome:

Modification of treatment

Figure 2

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Table 4

Author	No. of studies	Outcome	Estimate	LCI	UCI	I2	p-heterogeniety	Metric
Ayubi et al., 2021	15	Depression	0.37	0.27	0.47	99	<0.001	Prev†
	17	Anxiety	0.38	0.31	0.46	99	<0.001	Prev†
	4	Anxiety	0.25	0.08	0.42	68	0.02	SMD†
Zhang et al., 2022	28	Depression	0.325	0.263	0.392	99	<0.001	Prev†
	34	Anxiety	0.313	0.254	0.375	99	<0.001	Prev†
	8	PTSD	0.288	0.207	0.368	99	<0.001	Prev†
	5	Distress	0.539	0.469	0.609	67	0.016	Prev†
	5	Insomia	0.232	0.171	0.293	91	<0.001	Prev†
	3	Fear of cancer progression	0.674	0.437	0.91	93	<0.001	Prev†
Di Cosimo et al., 2022	28	Cancellation/delay of treatment	0.58	0.48	0.67	98	<0.01	Prop*†
	14	Modification of treatment	0.65	0.53	0.75	98	<0.01	Prop*†
	10	Delay of clinic visits	0.75	0.49	0.95	99	<0.01	Prop*†
	14	Reduction in activity	0.58	0.47	0.68	93	<0.01	Prop*†
	25	Use of remote consultation	0.72	0.59	0.84	99	<0.01	Prop*†
	7	Routine use of PPE (patients)	0.81	0.75	0.95	96	<0.01	Prop*†
	16	Routine use of PPE (workers)	0.8	0.61	0.94	99	<0.01	Prop*†
	18	Routine screening SARA-CoV-2 swab	0.41	0.3	0.53	96	<0.01	Prop*†
de Bock et al., 2022	5	≥T2 stage during the COVID-19 pandemic compared to the pre-pandemic control group	1.00	0.72	1.38	58	0.05	OR‡
	4	≥T3 stage during the COVID-19 pandemic compared to the pre-pandemic control group	0.95	0.69	1.32	39	0.18	OR‡
	5	≥N1 stage during the COVID-19 pandemic compared to the pre-pandemic control group	1.55	0.87	2.74	3	0.39	OR‡
Mayo et al., 2021	6	Screening breast cancer	0.63	0.53	0.77	100	<0.001	IRR‡
	5	Screening conlonc cancer	0.11	0.05	0.24	100	<0.001	IRR‡
	3	Screening cervical cancer	0.1	0.04	0.24	100	<0.001	IRR‡
Ng and Hamilton, 2022	3	Screening breast cancer registry-based study	0.59	0.46	0.7	100	<0.001	RR‡
	10	Screening breast cancer non-registry-based study	0.47	0.38	0.58	100	<0.001	RR‡
	4	Diagnosis breast cancer registry-based study	0.82	0.63	1.06	99	<0.001	RR‡
	18	Diagnosis breast cancer non-registry-based study	0.71	0.63	0.8	92	<0.001	RR‡
Pararas et al., 2022	5	Tis-T1 stage	1.14	0.87	1.48	41	0.15	OR‡
	5	T2 stage	0.91	0.78	1.06	0	0.6	OR‡
	5	T3 stage	1.18	0.82	1.7	88	<0.001	OR‡
	6	T4 stage	1.19	0.79	1.8	80	<0.001	OR‡
	6	N+ stage	1	0.89	1.11	0	0.54	OR‡
	6	M+ stage	1.65	1.02	2.67	91	<0.001	OR‡
	7	Right-sided tumors	0.88	0.51	1.52	99	<0.001	OR‡
	7	Left-sided tumors	0.91	0.56	1.5	96	<0.001	OR‡
	8	Rectal tumors	0.93	0.63	1.37	95	<0.001	OR‡
	3	Emergency presantations	1.74	1.07	2.84	95	<0.001	OR‡
	3	Complicated tumor	1.72	0.78	3.78	82	0.004	OR‡
	3	Neoadjuvant therapy	1.22	1.09	1.37	0	0.4	OR‡
	4	Palliative internt surgery	1.95	1.13	3.36	54	0.09	OR‡
	6	Minimally invasive surgery	0.68	0.37	1.24	98	<0.001	OR‡
	5	Stoma formation	0.91	0.51	1.62	94	<0.001	OR‡
	2	Morbidity	0.92	0.55	1.55	25	0.25	OR‡
	3	Leng of hospital stay	0.51	−0.93	1.94	79	0.008	WMD‡
	3	Lymph node harvest	1.57	−1.99	5.13	64	0.06	WMD‡
Sarich et al., 2022	12	Smoking prevalence	0.87	0.79	0.97	99	<0.001	PR‡
	17	Among smokers, smoking less prevalence	0.21	0.14	0.3	99	<0.001	Prev†
	22	Among smokers, smoking more	0.27	0.22	0.32	98	<0.001	Prev†
	17	Among smokers, smoking unchanged	0.5	0.41	0.58	99	<0.001	Prev†
	6	Among smokers, quit smoking	0.04	0.01	0.09	95	<0.001	Prev†
	4	Among non-smokers, started smoking	0.02	0.01	0.03	92	<0.001	Prev†
Sasidharanpillai and Ravishankar, 2022	7	Women screened before the COVID-19 pandemic	0.0979	0.06	0.1359	100	<0.001	Prop
	7	Women screened during the COVID-19 pandemic	0.0424	0.0277	0.0571	100	<0.001	Prop
Tang et al., 2022	10	Postoperative morbidity	0.9	0.8	1.01	26	0.22	OR‡
	8	Postoperative mortality	1.27	0.92	1.75	0	0.57	OR‡
	4	Converion rate	1.07	0.75	1.52	31	0.23	OR‡
	5	Incidence of anastomotic leakage	0.71	0.07	19.22	0	0.74	OR‡
	2	Intensive care unit demand rate	0.73	0.29	1.85	0	0.5	OR‡
	4	R1 resections rate	0.46	0.11	1.9	0	0.48	OR‡
	5	Mean lymph node yield	0.16	−2.26	2.59	54	0.07	MD‡
	7	Length of hospital stay	−0.05	−2.28	2.19	98	<0.001	MD‡
Teglia et al., 2022a	21	Breast cancer screening January–October 2020	0.467	0.378	0.378	NP	NP	PRED‡
	21	Breast cancer screening April 2020	0.74	0.567	0.918	NP	NP	PRED‡
	21	Breast cancer screening June–October 2020	0.13	−0.07	0.33	NP	NP	PRED‡
	22	Colorectal cancer screening January–October 2020	0.449	0.361	0.538	NP	NP	PRED‡
	21	Colonoscopy screening January–October 2020	0.525	0.388	0.663	NP	NP	PRED‡
	21	Fecal occult blood test or fecal immunochemical test January–October 2020	0.378	0.258	0.499	NP	NP	PRED‡
	21	Colorectal cancer screening April 2020	0.693	0.369	1	NP	NP	PRED‡
	21	Colorectal cancer screening June–October 2020	0.234	0.024	0.444	NP	NP	PRED‡
	11	Cervical cancer screening January–October 2020	0.518	0.389	0.647	NP	NP	PRED‡
	21	Cervical cancer screening March 2020	0.788	0.583	0.993	NP	NP	PRED‡
								PRED‡
Teglia et al., 2022b	NP	Overall treatment January–October 2020	0.187	0.133	0.241	NP	NP	PRED‡
	NP	Overall treatment January–February 2020	0.027	0.045	0.1	NP	NP	PRED‡
	NP	Overall treatment March 2020	0.156	0.076	0.237	NP	NP	PRED‡
	NP	Overall treatment April 2020	0.283	0.194	0.372	NP	NP	PRED‡
	NP	Overall treatment May 2020	0.262	0.176	0.041	NP	NP	PRED‡
	NP	Overall treatment June–October 2020	0.16	0.041	0.279	NP	NP	PRED‡
	NP	Overall surgical treatment January–October 2020	0.339	0.279	0.399	NP	NP	PRED‡
	NP	Overall surgical treatment January–February 2020	0.072	−0.093	0.238	NP	NP	PRED‡
	NP	Overall surgical treatment March 2020	0.307	0.219	0.396	NP	NP	PRED‡
	NP	Overall surgical treatment April 2020	0.342	0.239	0.445	NP	NP	PRED‡
	NP	Overall surgical treatment May 2020	0.416	0.318	0.514	NP	NP	PRED‡
	NP	Overall surgical treatment June–October 2020	0.351	0.186	0.516	NP	NP	PRED‡
	NP	Overall medical treatment January–October 2020	0.126	0.048	0.204	NP	NP	PRED‡
	NP	Overall medical treatment January–February 2020	0.015	−0.055	0.084	NP	NP	PRED‡
	NP	Overall medical treatment March 2020	0.116	−0.012	0.233	NP	NP	PRED‡
	NP	Overall medical treatment April 2020	0.248	0.09	0.407	NP	NP	PRED‡
	NP	Overall medical treatment May 2020	0.196	0.085	0.306	NP	NP	PRED‡
	NP	Overall medical treatment June–October 2020	0.079	−0.078	0.236	NP	NP	PRED‡
								PRED‡
Vigliar et al., 2020	41	Cytological samples over 4 weeks of the COVID-19 pandemic	0.453	0.001	0.98	NP	NP	PRED‡
	41	Ratio of exfoliative to fine needle aspiration samples	0.89	0.74	1.08	95	<0.01	OR‡
	27	Malignant diagnosis	0.0556	0.0377	0.0735	81	<0.01	RD‡

1. *

   Surveyed centers/operators.

2. †

   Estimates are during pandemic.

3. ‡

   Estimates are pandemic vs. pre-pandemic.

4. LCI, lower confidence interval; IRR, incidence rate ratio; MD, mean difference; OR, odds ratio; PRED, percent reduction; PR, prevalence ratio; Prev, prevalence: Prop, proportion; RD, risk difference; RR, rate ratio; PPE, personal protective equipment; NP, not provided; UCI, upper confidence interval; SMD, standardized mean difference; WMD, weighted mean difference.

There were 15 reviews assessing modification of treatment (Nikolopoulos et al., 2022; Gascon et al., 2022; Hojaij et al., 2020; Adham et al., 2022; Alom et al., 2021; Garg et al., 2020; Moujaess et al., 2020; Sun et al., 2021; Di Cosimo et al., 2022; Hesary and Salehiniya, 2022; Mazidimoradi et al., 2021; Crosby and Sharma, 2020; Azab and Azzam, 2021; Pascual et al., 2022; Piras et al., 2022). Main findings for each individual review are outlined in Supplementary file 1c and Table 4. All reviews were consistent reporting changes in treatment, with downscaling treatments plans in patients with cancer being a significant intervention. Di Cosimo et al., 2022 reported changes in treatment plans in 65% (95% CI, 53–75%; I², 98%) of centers (Di Cosimo et al., 2022). Guidelines recommended use of non-surgical treatment over surgical treatments, as it was seen in head and neck cancer management. However, reviews suggested patients being assessed in a case-by-case basis and that individual factors should be considered for individualized treatment (Supplementary file 1c). Garg et al., 2020 found that available guidelines were based on low level of evidence and had significant discordance for the role and timing of surgery, especially in early tumors (Garg et al., 2020).

Delayed and/or canceled treatment

Supplementary file 1d and Table 4 summarize the main findings from the 15 reviewes (Dhada et al., 2021; Teglia et al., 2022b; Nikolopoulos et al., 2022; Gadsden et al., 2022; Majeed et al., 2022; Jammu et al., 2021; Pacheco et al., 2021; Zapała et al., 2022; Di Cosimo et al., 2022; Ferrara et al., 2022; Lignou et al., 2022; Mazidimoradi et al., 2021; Riera et al., 2021; de Bock et al., 2022; Piras et al., 2022) that assessed and reported on treatment delays and cancellations of cancer treatment. Most reviews mentioned that cancellations of treatment were observed, although to what extend this happened was not consistently provided (Jammu et al., 2021; Pacheco et al., 2021; Zapała et al., 2022; Di Cosimo et al., 2022; Ferrara et al., 2022; Mazidimoradi et al., 2021; Riera et al., 2021). However, reviews reported that these reductions were more pronounced during a lockdown. In the meta-analysis by Teglia et al., 2022a, it was found an overall reduction of −18.7% (95% CI, −13.3 to −24.1) in the total number of cancer treatments administered during January–October 2020 compared to the previous periods, with surgical treatment having a larger decrease compared to medical treatment (−33.9% versus −12.6%); among cancers, the largest decrease was observed for skin cancer (−34.7% [95% CI, −22.5 to −46.8 ]) (Teglia et al., 2022b). This difference would depend on the period, with the review reporting a U-shape for the period January–October 2020. Lignou et al., 2022 reported that between 18th and 31st of January 2021, pediatric and noncancer surgical activities were occurring at less than a third of the rate of the previous year, while Di Cosimo et al., 2022 reported cancellation/delays of treatment in 58% (95%CI, 48–67%; I², 98%) of centers. Majeed et al., 2022 showed that shortage of treatment and delays and interruptions to cancer therapies in general were more common in low- and middle-income countries.

Delayed and/or canceled screening

The results of 11 reviews (Teglia et al., 2022a; Alkatout et al., 2021; Fancellu et al., 2022; Ferrara et al., 2022; Hesary and Salehiniya, 2022; Mayo et al., 2021; Mazidimoradi et al., 2022; Ng and Hamilton, 2022; Sasidharanpillai and Ravishankar, 2022; Vigliar et al., 2020; Bougioukas et al., 2018) reporting on cancer screening are summarized in Supplementary file 1e and Table 4. Of these, five included a meta-analysis. Overall, reviews showed a decline in screening rates across all cancer types, and that differences by demographic area and time periods were observed; for instance, countries that implemented lockdowns showed a higher decline in screening rates. Within colorectal and gastric cancers, most reviews reported a reduction of at least 50% in number of endoscopies and gastroscopies compared to previous years. In the meta-analysis by Teglia et al., 2022a, while colorectal screening on average was reduced by 44.9% (95% CI, −53.8% to −36.1%) during January–October 2020, a U-shape association was observed. Within women-specific cancers, the meta-analyses showed a decrease in breast and cervical cancers screening rates of at least 40–50% (Teglia et al., 2022a). A meta-analysis focused on cytopathology practice showed that on average there was a sample volume reduction of 45.3% (range, 0.1–98.0%), although the results would depend on the tissue sampled (Vigliar et al., 2020). Similar findings were reported by Alkatout et al., 2021.

Reduced cancer diagnosis

Main findings of the 11 reviews (Nikolopoulos et al., 2022; Majeed et al., 2022; Alkatout et al., 2021; Fancellu et al., 2022; Ferrara et al., 2022; Hesary and Salehiniya, 2022; Lignou et al., 2022; Mazidimoradi et al., 2021; Ng and Hamilton, 2022; Vigliar et al., 2020; Pascual et al., 2022) providing data on reduction in cancer diagnosis are provided in Supplementary file 1f and Table 4. Reviews were consistent in reporting decreased diagnosis of new cancer cases during the pandemic, although the reduction depended on the geographical area, the period being investigated and type of cancer. For example, there was a 73.4% decrease in cervical cancer diagnoses in Portugal during 2020, and in Italy, while there was up to 62% reduced diagnosis of colorectal cancer in 2020 compared to pre-pandemic years, the reduction was more pronounced in Northern Italy where strict lockdowns were implemented. Indeed, reviews showed that countries that implemented lockdowns measures showed the highest reduction in number of new cancer cases being diagnosed. Breast cancer diagnosis rates dropped by an estimate between 18% and 29% between 2019 and 2021 (Ng and Hamilton, 2022).

Reduced uptake of HPV vaccination

There was only one review to summarize data on HPV vaccination, showing up to 96% reduction in number of vaccine doses administered in March–May 2020 among adolescents and young girls aged 9–26 years; the 1-year period reduction reported was much smaller (13%) (Ferrara et al., 2022).

Psychological needs/distress

Thirteen reviews covered topics related to psychological needs and distress that patients with cancer experienced during the pandemic (Dhada et al., 2021; Nikolopoulos et al., 2022; Zhang et al., 2022; Kirby et al., 2022; Legge et al., 2022; Ayubi et al., 2021; Jammu et al., 2021; Momenimovahed et al., 2021; Muls et al., 2022; Rohilla et al., 2021; Zapała et al., 2022; Hesary and Salehiniya, 2022; Piras et al., 2022); the findings are summarized in Supplementary file 1f and Table 4. Reviews reported that the pandemic negatively impacted the psychosocial and physical well-being of cancer survivors and patients with cancer experienced different levels of anxiety, depression, and insomnia. In a meta-analysis, Ayubi et al., 2021 reported an overall prevalence of depression and anxiety of 37% (95% CI, 27–47, I², 99.05) and 38% (95% CI, 31–46%, I², 99.08) in patients with cancer, respectively (Ayubi et al., 2021). Similar findings were reported by Zhang et al., 2022. Compared to controls, patients with cancer had higher anxiety level [standard mean difference (SMD 0.25 (95% CI, 0.08, 0.42)) Ayubi et al., 2021].

Telemedicine

Telehealth was investigated and reported in 12 of the included reviews (Dhada et al., 2021; Hojaij et al., 2020; Murphy et al., 2022; Alom et al., 2021; Lu et al., 2021; Mostafaei et al., 2022; Salehi et al., 2022; Zapała et al., 2022; Di Cosimo et al., 2022; Lignou et al., 2022; Pascual et al., 2022; Bezerra et al., 2022); a summary of main findings is provided in Supplementary file 1h. Salehi et al., 2022 reported that telemedicine use in breast cancer patients was the most common investigated in studies exploring cancer-specific use of telemedicine. Telemedicine was used for various reasons, with provision of virtual visit services and consultation being the most common (Salehi et al., 2022). One study explored various symptom tracking apps for patients with cancer, available in the mobile health market, and found that only a limited number of apps exist for cancer-specific symptom tracking (27%) (Lu et al., 2021). In addition, of the 41 apps found, only one was tested in a clinical trial for usability among patients with cancer (Lu et al., 2021). While little research exists on how patients perceived telemedicine during the COVID-19 pandemic, early data showed that majority of patients found telemedicine service helpful and that obtaining a telemedicine service helped solve their health problem. Nevertheless, there were concerns that use of telehealth for people with cancer suggests a greater proportion of missed diagnoses (Lignou et al., 2022), and that telemedicine cannot be a substitute for face-to-face appointments (Mostafaei et al., 2022).

Financial distress and social isolation

Five reviews reported the economic impact of COVID-19 and social isolation of patients with cancer during the pandemic (Supplementary file 1i; Dhada et al., 2021; Kirby et al., 2022; Legge et al., 2022; Jammu et al., 2021; Piras et al., 2022). While there is little research on this topic, overall, the reviews suggested financial distress with direct and indirect costs burden and social isolation being a common issue for patients with cancer. Reviews also were consistent in reporting social isolation and loneliness among patients with cancer. Several factors contributed to social isolation, including fear of infection, social distancing measures, not having visitors and lack of social interaction during treatment.

Tobacco use and cessation

There was only one systematic review and meta-analysis to explore tobacco use and cessation during the pandemic (Sarich et al., 2022). Based on data from 31 studies, Sarich et al., 2022 found that, compared to pre-pandemic period, the proportion of people smoking during the pandemic was lower (pooled prevalence ratio of 0·87 (95%CI, 0·79–0·97)). In addition, there was similar proportions among smokers before pandemic who smoked more or smoked less during the pandemic, and on average 4% (95% CI, 1–9%) reported stopping smoking. 2% reported starting smoking during the pandemic. High heterogeneity was observed across the meta-analyses results.

Other aspects of cancer care

Eighteen reviews (Donkor et al., 2021; Gascon et al., 2022; Hojaij et al., 2020; Gadsden et al., 2022; Majeed et al., 2022; Adham et al., 2022; Alom et al., 2021; Moujaess et al., 2020; Pacheco et al., 2021; Rohilla et al., 2021; Di Cosimo et al., 2022; Lignou et al., 2022; Pararas et al., 2022; Tang et al., 2022; Thomson et al., 2020; de Bock et al., 2022; Pascual et al., 2022) reported on mitigations strategies and cancer service restructuring, impact of measures on cancer prognosis, and on quality of recommendations provided during COVID-19 for cancer care; findings are summarized in Supplementary file 1j. In the meta-analysis by Di Cosimo et al., 2022 routine use of PPE by patient and healthcare personnel was reported by 81% and 80% of centers, respectively; systematic SARS-CoV-2 screening by nasopharyngeal swabs was reported by only 41% of centers (Di Cosimo et al., 2022). Five reviews also reported on potential impact of mitigation strategies on cancer outcomes/prognosis (Alkatout et al., 2021; Lignou et al., 2022; Pararas et al., 2022; Tang et al., 2022; de Bock et al., 2022). It was estimated that 59,204–63,229 years of life lost might be attributable to delays in cancer diagnosis alone because of the first COVID-19 lockdown in the UK, albeit the findings were based on single study. Delayed cancer screening was estimated to cause globally the following additional numbers of cancer deaths secondary to breast, esophageal, lung, and colorectal cancer, respectively: 54,112–65,756, 31,556–32,644, 86,214–95,195, and 143,081–155,238 (Alkatout et al., 2021). Tang et al., 2022, de Bock et al., 2022 found no deterioration in the surgical outcomes of all types of cancer or colorectal cancer surgery: also no reduction in the quality of cancer removal was observed. Similar findings were also reported by Pararas et al., 2022, despite the number of patients presenting with metastases during the pandemic was significantly increased. Thomson et al., 2020, by exploring recommendations for hypofractionated radiation therapy, found that in general the recommendations during the pandemic were based on lower quality of evidence than the highest quality routinely used dose fractionation schedules.

The current umbrella review summarized and appraised systematically the evidence on the extent to which several aspects of cancer care were disrupted during the COVID-19 pandemic. The summary message provided by 51 systematic reviews is that there have been modifications, delays and cancellation of treatment, delays and cancellation in cancer screening and diagnosis, and patients with cancer may have experienced additional psychological, social, and financial distress. Nevertheless, appraisal of the impact of COVID-19 on cancer care is mainly based on limited and low-quality evidence, and that data mainly derive from high-income countries, with little understanding of consequences of COVID-19 on cancer care in low- and middle-income countries. In addition, limited evidence exists on whether disruptions in cancer care during the pandemic had adverse impact in prognosis of patients with cancer and mortality.

Several guidelines were provided for cancer care during the pandemic, including recommendations on mitigation strategies to prevent SARS-CoV-2 infection and cancer treatment modalities. Nevertheless, most recommendations were based on expert opinions, and little quantitative evidence was provided to support them. This aspect was highlighted also in the systematic review by Thomson et al., 2020. The authors explored recommendations for hypofranctionated radiation therapy before and during pandemic and found that during the pandemic there was a significant shift from established higher-quality evidence to lower-quality evidence and expert opinions for the recommended hypofractionated radiation schedules. Similar findings were reported also by Garg et al., 2020, suggesting not only guidelines were based on low level of evidence, but also there was significant discordance for the role and timing of surgery, especially in early tumors.

Specific recommendations established from the guidelines such as prioritization of high-grade malignancy, as well as other aspects such as lockdowns, social restrictions, restructure of cancer care with prioritization of high-risk malignancies and use of telemedicine, fear of infection, financial distress and shortage in medications could explain the delays and cancellation in cancer treatment, screening, and diagnosis reported in several studies. For example, Lignou et al., 2022 raised concerns that use of telehealth for people with cancer suggests a greater proportion of missed diagnoses. Most of examined systematic reviews reported a substantial reduction in treatment, screening, and diagnosis of several cancers during the pandemic, which was more pronounced for countries that implemented a lockdown. In addition, differences were observed by geographical area, suggesting that the impact on cancer treatment, screening and diagnosis could depend on mitigation strategies countries implemented as well as on country-specific healthcare organization and resources. For example, shortage of treatment and delays and interruptions to cancer therapies in general were more pronounced in low- and middle-income countries (Majeed et al., 2022). The findings on disruption of cancer treatment, screening, and diagnosis are in line with findings reported for other chronic diseases, such as cardiovascular disease (Williams et al., 2021), suggesting the adverse impact might not be cancer specific. Future research should explore and compare how different chronic diseases were impacted.

Evidence is limited on evaluating how disruption of cancer care during COVID-19 affected prognosis of patients with cancer. Limited evidence showed that the number of patients presenting with metastases during the pandemic was significantly increased, and emergency presentations and palliative surgeries were more frequent during the pandemic (Pararas et al., 2022). No deterioration in the surgical outcomes of colorectal cancer surgery including mortality or reduction in the quality of cancer removal was observed (Pararas et al., 2022; Tang et al., 2022). A study (Maringe et al., 2020) in UK estimated that 59,204–63,229 years of life lost might be attributable to delays in cancer diagnosis alone because of the first COVID-19 lockdown, but estimates were based on modeling. Several studies Cui et al., 2022; Smith et al., 2021 have shown a decline in elective cancer such as colorectal cancer, despite findings showing that gastrointestinal cancer surgery during pandemic is safe with appropriate isolation measures and no delays should be implemented for both early and advanced cancer (Sozutek et al., 2021). A recent meta-analysis (Whittaker et al., 2021) showed that delaying colorectal cancer longer than 4 weeks could be associated with poorer outcomes.

Several studies and systematic reviews thereof have investigated the impact of the pandemic on psychological well-being, financial distress, and social isolation of patients with cancer, as well as the role of telemedicine in cancer care. While studies suggested depression, anxiety, post-traumatic disorder, insomnia, and fear of cancer progression being highly reported by cancer patients with estimates reaching beyond 50%, high heterogeneity was observed, and in general systemic analysis comparing the findings with pre-pandemic period rates was lacking. The pandemic was reported to have financial burden on cancer patients with direct and indirect costs. Social isolation was commonly reported and mainly driven by fear of infection, social distancing measures, and lack of social interaction during treatment. Nevertheless, there was limited effort to quantify social isolation and economic impact on cancer care. Telemedicine and remote consultations were sharply increased in use for different aspects of cancer care, including treatment, screening, and rehabilitation. However, evidence is limited in evaluating and quantifying the positive and negative impact, as well as cost-effectiveness of telemedicine. While limited evidence suggested telemedicine reduced costs of cancer care for both patients and healthcare provider, there were concerns especially from patients that telemedicine could not have similar benefits to on-site consultations.

Our study has certain limitations. Although our search was based on recent recommendations on optimal databases needed to be searched for umbrella reviews (Goossen et al., 2020), we cannot rule out missing some other relevant systematic reviews. Most systematic reviews included in this umbrella review were based on intermediate and high risk of bias studies, and the findings were mainly based on case-series, cross-sectional and retrospective observational study designs which are prone to residual confounding and poor in determining temporal associations. Prevalence and incidence estimates are also subject to selection biases. In some instances, data were derived from one study or from studies with small sample sizes and limited number of events, leading to large uncertainty. Many studies did not include any pre-pandemic controls. Furthermore, some of the evidence overlapped among the systematic reviews that were included in this umbrella review, but this allows comparing notes on results and conclusions for the overlapping efforts. Some systematic reviews were published early (in 2020), and thus they had even more limited evidence and the impact of the disruptions may have differed across different pandemic waves. Most findings were derived from high-income and/or western countries, limiting the generalizability of the findings to low- and middle-income countries. Lastly, concreate conclusions on intermediate, and long-term impact remain unclear. Finally, the suboptimal methodological rigor of many included reviews is notable.

In summary, evidence shows a diverse and substantial impact of the COVID-19 pandemic on cancer care, including delays in treatment, screening, and diagnosis. Also, patients with cancer had been affected psychologically, socially, and financially during the COVID-19 crisis. However, large uncertainty and gaps exist in the literature on this topic. Most of the evidence on the topic is derived mainly from high- and middle-income countries, and low-quality studies, and thus, future high-quality studies with larger geographical capture and properly performed, rigorous systematic reviews with careful meta-analyses will continue to have value in this field.

We performed an umbrella review following the recent published guideline (Belbasis et al., 2022), and for reporting we adhered to the Preferred Reporting Items for Overviews of Reviews – PRIOR checklist (Gates et al., 2022; Supplementary file 1k). The protocol has been registered with the Open Science Framework (https://osf.io/qjgxv).

All data are in the manuscript and supplements.

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Author details

1. Taulant Muka

   1. Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
   2. Meta-Research Innovation Center at Stanford (METRICS), Stanford University, Stanford, United States
   3. Epistudia, Bern, Switzerland

   Contribution

   Conceptualization, Data curation, Formal analysis, Validation, Investigation, Methodology, Writing – original draft, Writing – review and editing

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0003-3235-3073

2. Joshua JX Li

   Department of Anatomical and Cellular Pathology, Prince of Wales Hospital, The Chinese University of Hong Kong, Sha Tin, Hong Kong

   Contribution

   Conceptualization, Data curation, Formal analysis, Writing – review and editing

   Competing interests

   No competing interests declared

3. Sahar J Farahani

   Department of Pathology and Laboratory Medicine, Stony Brook University, Long Island, New York, United States

   Contribution

   Conceptualization, Data curation, Formal analysis, Writing – review and editing

   Competing interests

   No competing interests declared

4. John PA Ioannidis

   1. Meta-Research Innovation Center at Stanford (METRICS), Stanford University, Stanford, United States
   2. Stanford Prevention Research Center, Department of Medicine, Stanford University School of Medicine, Stanford, United States
   3. Department of Epidemiology and Population Health, Stanford University School of Medicine, Stanford, United States

   Contribution

   Conceptualization, Data curation, Formal analysis, Supervision, Validation, Investigation, Methodology, Writing – original draft, Writing – review and editing

   For correspondence

   jioannid@stanford.edu

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0003-3118-6859

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