An assessment of left-digit bias in the treatment of older patients with potentially curable rectal cancer

Patient age is associated with poorer rectal cancer treatment compliance. However, it is unknown whether left-digit bias (disproportionate influence of leftmost age digit) influences this association. The patients diagnosed with stage I–III rectal cancer between 2006 to 2017 in the National Cancer Database were identified. The association between age and receipt of guideline-adherent care was assessed using mixed-effects multivariable analyses. Among 97,960 patients, 46.2% received guideline-adherent overall treatment and 73.3% underwent guideline-adherent surgical resection. Of those who underwent guideline-adherent surgery, 86.4% received guideline-adherent radiotherapy and 56.6% received guideline-adherent chemotherapy. After risk-adjustment, each decade increase in age was associated with 36% decreased odds of guideline-adherent therapy (odds ratio = 0.64, 95% confidence interval = 0.63–0.65). Patients aged 58 to 59 (odds ratio = 1.15, 95% confidence interval = 1.02–1.27) and 78 to 79 (odds ratio = 1.28, 95% confidence interval = 1.08–1.51) had higher odds of guideline-adherent overall treatment compared with patients aged 60 and 80, respectively. However, there were no significant differences in the receipt of guideline-adherent treatment between patients aged 60 vs 61–62 and 80 vs 81–82. Older patients with rectal cancer are less likely to receive guideline-adherent care, and a left-digit bias is present. Geriatric assessment-guided treatment decisions could help mitigate this bias.