Diverging Trends in Registry-Coded No Primary-Site Surgery for Colon and Rectal Cancer: A SEER Study, 2000-2023

BackgroundWe evaluated temporal trends in registry-coded no primary-site surgery separately for colon and rectal adenocarcinoma using SEER data from 2000 through 2023.MethodsColon and rectal adenocarcinomas were identified. The endpoint was registry-coded no primary-site surgery, which cannot distinguish planned organ preservation, refusal, inoperability, or incomplete treatment capture. Site-specific trends were evaluated using linear and piecewise logistic models. Principal analyses, including post-2018 trends, were not stage-adjusted because AJCC stage in the extract covered only 2004-2015. Survival comparisons were descriptive.ResultsThe cohort included 397 116 colon and 120 487 rectal cancers. Between 2000-2005 and 2018-2023, no primary-site surgery increased from 10.2% to 30.1% in rectal cancer and from 2.9% to 6.5% in colon cancer. Rectal cancer odds increased by 5.4% per year before 2018 and 17.5% per year after 2018. The colon trend was approximately linear, with a 4.2% annual increase in odds. A stage-adjusted analysis in the 2004-2015 stage I-III subset supported an earlier increase but could not evaluate the post-2018 acceleration.DiscussionRegistry-coded no primary-site surgery increased in both cancers, with a greater and accelerating rise in rectal cancer. These descriptive findings extend contemporary observations and support site-specific interpretation. The unadjusted post-2018 pattern cannot establish changes independent of stage or identify planned watch-and-wait, treatment refusal, or absence of cancer-directed therapy.