Erschienen in:
01.06.2014 | Colorectal Cancer
Adjuvant Chemotherapy for Stage II Right-Sided and Left-Sided Colon Cancer: Analysis of SEER-Medicare Data
verfasst von:
Jennifer M. Weiss, MD, MS, Jessica Schumacher, PhD, Glenn O. Allen, MPH, Heather Neuman, MD, MS, Erin O’Connor Lange, MD, MSPH, Noelle K. LoConte, MD, Caprice C. Greenberg, MD, MPH, Maureen A. Smith, MD, MPH, PhD
Erschienen in:
Annals of Surgical Oncology
|
Ausgabe 6/2014
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Abstract
Background
Survival benefit from adjuvant chemotherapy is established for stage III colon cancer; however, uncertainty exists for stage II patients. Tumor heterogeneity, specifically microsatellite instability (MSI), which is more common in right-sided cancers, may be the reason for this observation. We examined the relationship between adjuvant chemotherapy and overall 5-year mortality for stage II colon cancer by location (right- vs left-side) as a surrogate for MSI.
Methods
Using Surveillance, Epidemiology, and End Results (SEER)-Medicare data, we identified Medicare beneficiaries from 1992 to 2005 with AJCC stage II (n = 23,578) and III (n = 17,148) primary adenocarcinoma of the colon who underwent surgery for curative intent. Overall 5-year mortality was examined with Kaplan–Meier survival analysis and Cox proportional hazards regression with propensity score weighting.
Results
It was found that 18 % of stage II patients (n = 2941) with right-sided cancer and 22 % (n = 1693) with left-sided cancer received adjuvant chemotherapy. After adjustment, overall 5-year survival benefit from chemotherapy was observed only for stage III patients (right-sided: hazard ratio [HR], 0.64; 95 % CI, 0.59–0.68; p < .001 and left-sided: HR, 0.61; 95 % CI, 0.56–0.68; p < .001). No survival benefit was observed for stage II patients with either right-sided (HR, 0.97; 95 % CI, 0.87–1.09; p = .64) or left-sided cancer (HR, 0.97; 95 % CI, 0.84–1.12; p = .68).
Conclusions
Among Medicare patients with stage II colon cancer, a substantial number receive adjuvant chemotherapy. Adjuvant chemotherapy did not improve overall 5-year survival for either right- or left-sided colon cancers. Our results reinforce existing guidelines and should be considered in treatment algorithms for older adults with stage II colon cancer.