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

Abstract

Background: 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.

Methods: 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.

Results: 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.

Conclusion: 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.