Table 1. Eligibility criteria and rationale.

No.	Inclusion criteria:	Rationale:
1.	• English-language publications (only)	• Limited access to translation services
2.	• Published between December 2019 and 24 November 2022	• Timeline corresponds with first identification of SARS-CoV-2 in December 2019, in Wuhan, China
3.	• Country-of-origin: Any	• For comprehensive appraisal of evidence on global outcomes
4.	• Pre-prints (not excluded)	• For comprehensive appraisal of evidence • Evidence is emerging contemporaneously on this current global health challenge
5.	Scope: • Elective breast- or colorectal cancer surgery backlogs, attribu mortality and/or implemented health system responses during the COVID-19 pandemic	• To synthesise known findings and, identify existing gaps in the evidence base • To address the research aims
6.	Data synthesis on surgical case performance backlogs: • Articles based on global and/or institution-level reductions in surgical activity (i.e., number of elective procedures performed) during the COVID-19 pandemic, as compared to surgical activity pre-COVID-19	• Included due to a prevalent scarcity of evidence on absolute backlogs outcomes • Global and institution-level reductions in surgical activity would, by reasonable inference, contribute to overall case performance backlogs
No.	Exclusion criteria	Rationale
	• Non-English language publications (Unable to locate translated version)	• Limited access to translation services
	• Unable to locate full-text article	• Avoid potential bias from incomplete appraisal of study findings
	• Significant methodological quality deficit	• Findings insufficiently reliable
	• Opinion pieces, correspondence articles (apart from research letters) • Guidelines on operative aspects • Protocols, posters • Conference abstracts • Symposium minutes	• Opinion pieces–Findings subjective • Operative guidelines–Limited relevance to research question, specialist operative techniques fall beyond the scope of this review • Other–Definitive, complete evidence prioritised for review
	Out of scope: • Reported on outcomes for other diagnoses (apart from breast- or colorectal cancer, in isolation)	• Small-scale review, hence approximately 1,288 articles on impact for other cancer types excluded • Other conditions not relevant to research question
	Out of scope: • Focused on emergent surgery, without reporting on outcomes for elective surgery in isolation	• To avoid misclassification bias between outcomes for emergent surgery and those for elective surgery