Background: The size and importance of socioeconomic status (SES)-based disparities in use of surgery for non-advanced stage gastrointestinal (GI) cancers have not been quantified.
Methods: The exposure in this study of patients age 18-80 with one of nine non-advanced stage GI cancers in the 2007-2015 SEER database was a census tract-level SES composite. Multivariable models assessed associations of SES with use of surgery. Causal mediation analysis was used to estimate the proportion of survival disparities in SES quintiles 1 versus 5 that were mediated by disparities in use of surgery.
Results: Lowest SES quintile patients underwent surgery at significantly lower rates than highest quintile patients in each cancer. SES-based disparities in use of surgery were large and graded in esophagus adenocarcinoma, intrahepatic and extrahepatic cholangiocarcinoma, and pancreatic adenocarcinoma. Smaller but clinically relevant disparities were present in stomach, ampulla, and small bowel adenocarcinoma, whereas disparities were small in colorectal adenocarcinoma. Five-year all-stage overall survival (OS) was correlated with the size of disparities in use of surgery in SES quintiles 1 versus 5 (r = - 0.87; p = 0.003). Mean OS was significantly longer (range 3.5-8.9 months) in SES quintile 5 versus 1. Approximately one third of SES-based survival disparities in poor prognosis GI cancers were mediated by disparities in use of surgery. The size of disparities in use of surgery in SES quintiles 1 versus 5 was correlated with the proportion mediated (r = 0.98; p < 0.001).
Conclusions: Low SES patients with poor prognosis GI cancers are at substantial risk of undertreatment. Disparities in use of surgery contribute to diminished survival.