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Primary tumor resection does not reduce mortality in stage IV colon cancer
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Primary tumor resection did not improve survival compared with systemic chemotherapy among patients with metastatic colon cancer, according to data from an observational cohort study.
“There has been renewed interest in the potential associations between primary tumor resection and improved survival, even among patients who have asymptomatic, intact primary tumors,” Zeinab Alawadi, MD, MS, surgeon at University of Texas Health Science Center, and colleagues wrote. “Because of important, unaddressed potential biases in those retrospective analyses, the question of whether primary tumor resection improves oncologic outcomes remains unanswered.”
The researchers used the National Cancer Data Base to identify 15,154 patients diagnosed with stage IV colon adenocarcinoma between 2003 and 2005.
Fifty-seven percent (n = 8,641) of those patients underwent primary tumor resection. The majority of surgeries (n = 4,115; 82.3%) were performed within 30 days of diagnosis. Approximately 25% of patients did not receive systemic chemotherapy.
Patients who had received nonelective tumor resection or surgeries for metastatic tumors were excluded from the study.
Alawadi and colleagues performed multivariate Cox regression analyses both with and without propensity score weighting, and they used a landmark method to account for survivor treatment bias in cases in which patients may have died shortly after diagnosis.
Cox regression analysis showed that primary tumor resection was associated with a significant reduction in mortality (HR = 0.45; 95% CI, 0.44-0.47). However, instrumental variable analysis showed no survival benefit (relative mortality rate, 0.97; 95% CI, 0.87-0.96).
Cox regression analysis for the landmark group revealed a smaller survival benefit from primary tumor resection (HR = 0.6; 95% CI, 0.55-0.64). However, instrumental variable analysis showed no survival benefit (relative mortality rate, 0.97; 95% CI, 0.87-1.06).
“By using standard statistical risk-adjustment methods, which inadequately account for confounder effects, primary tumor resection appeared to be associated with a significant reduction in mortality. However, instrument variable analysis to control for treatment selection and survivor time bias at the 1-year landmark demonstrated that primary tumor resection was not associated with a survival benefit over systemic chemotherapy,” Alawadi and colleagues wrote. “Thus, we demonstrate that the routine use of primary tumor resection in patients with stage IV colon cancer and unresectable metastatic disease does not improve survival.” – by Andy Polhamus
Disclosure: Alawadi reports no relevant financial disclosures. Please see the full study for a list of all other researchers’ relevant financial disclosures.
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