Left-digit bias occurs when people give more weight to the leftmost digit in a number. In this study, researchers investigated how much left-digit age bias influences doctors’ recommendations for treating localized prostate cancer. They analyzed data from Surveillance, Epidemiology, and End Results (2004-2018) and the National Cancer Database (2004-2016) for men with clinically localized prostate cancer. Primary results included suggestions for radical prostatectomy and radiation therapy. They utilized regression discontinuity to see if the year-and-a-half jump in age from 69 to 70 was related to a significant shift in recommended therapies. Discontinuities in the proportion of patients recommended for radiation were found in Surveillance, Epidemiology, and End Results for the entire cohort (effect size 2.2%, P<.01), Gleason 6 (1.6%, P<.01), Gleason 7 (2.5%, P<.01), and Gleason ≥8 (2.1%, P<.01), although both the overall cohort and those with Gleason 7 cancer  had decreases in the proportion of men advised to have prostatectomy (-1.4%, P<.01). The proportion of men recommended for prostatectomy decreased at this cutoff in the entire cohort (effect size: -2.7%, P<.01) and in patients with Gleason 6 (-2.2%, P<.01) and Gleason 7 (-3.7%, P<.01) cancer, according to data from the National Cancer Database. Radiation therapy was recommended more often and prostatectomy less often for males with localized prostate cancer when their age jumped from 69 to 70 on the left side of their birthdays.

Source: auajournals.org/doi/10.1097/JU.0000000000002857