Cohort size required for prognostic genes analysis of stage II/III esophageal squamous cell carcinoma.

Background: Few overlaps between prognostic biomarkers are observed among different independently performed genomic studies of esophageal squamous cell carcinoma (ESCC). One of the reasons for this is the insufficient cohort size. How many cases are needed to prognostic genes analysis in ESCC? Methods: Here, based on 387 stage II/III ESCC cases analyzed by whole-genome sequencing from one single center, effects of cohort size on prognostic genes analysis were investigated. Prognostic genes analysis was performed in 100 replicates at each cohort size level using a random resampling method. Results: The number of prognostic genes followed a power-law increase with cohort size in ESCC patients with stage II and stage III, with exponents of 2.27 and 2.25, respectively. Power-law curves with increasing events number were also observed in stage II and III ESCC, respectively, and they almost overlapped. The probability of obtaining statistically significant prognostic genes shows a logistic cumulative distribution function with respect to cohort size. To achieve a 100% probability of obtaining statistically significant prognostic genes, the minimum cohort sizes required in stage II and III ESCC were approximately 95 and 60, respectively, corresponding to a number of outcome events of 33 and 36, respectively. Conclusion: In summary, the number of prognostic genes follows a power-law growth with the cohort size or events number in ESCC. The minimum events number required to achieve a 100% probability of obtaining a statistically significant prognostic gene is approximately 35.