. Author manuscript; available in PMC: 2020 Nov 4.

Published in final edited form as: J Natl Cancer Inst Monogr. 2020 Jul 1;2020(56):97–113. doi: 10.1093/jncimonographs/lgaa009

Table A1.

PECO statement^a

PECO element¹	Evidence stream	Articles or features included	Articles or features excluded
Population	Human	• Any population • All life stages • Study designs • Cohort • Case-cohort • Case-control • Nested case-control	• Residential radon exposed, uranium miners and millers, Mayak workers, radiation therapy patients • RCT, controlled exposure, case series, cross-sectional, ecologic, mechanistic studies
Exposure	Human	• Ionizing radiation exposure • Gamma • X-ray • Low-LET • Quantitative in units of equivalent or effective dose (eg, mSv, Sv) or absorbed dose (eg, mGy, Gy)	• Primary route of exposure by inhalation, oral, or dermal type (eg, intraperitoneal, injection) • Semiquantitative or qualitative estimates of exposure
Comparator	Human	• A comparison population [not exposed, exposed to lower levels, exposed below detection] • Effect measurements reported as RR, ERR, excess absolute risk, or attributable risk	• No comparison group
Outcome	Human	• Endpoints: Cancers (death or incidence)	• Cancer endpoints not described
General considerations
		• Reports primary source • Full text available • Limit 2006 to current	• Reports a secondary source (eg, review articles) • Editorials • Proceedings • Correspondence

ERR = excess relative risk; LET = linear energy transfer; PECO = Population, Exposure, Comparator, and Outcome; RCT = randomized control trial; RR = relative risk.