Randomized trials suggest adjuvant chemotherapy is effective for elderly patients with stage III colon cancer. However, the elderly are less likely to receive this therapy than younger patients, perhaps because of concern about adverse effects.
To evaluate adjuvant chemotherapy use and outcomes for older patients with stage III colon cancer from well-defined population-based settings and healthcare systems.
Observational study of adjuvant chemotherapy use and outcomes by age, using Poisson regression to estimate the number of adverse events adjusted for demographic and clinical factors, including comorbid illness and specific elements of chemotherapy regimens documented with clinically detailed medical record reviews and patient and surrogate surveys.
Five geographically defined regions (Alabama, Iowa, Los Angeles County, Northern California, and North Carolina), five integrated health-care delivery systems, and 15 Veterans hospitals.
All 675 patients diagnosed with stage III colon cancer during 2003-2005 who underwent surgical resection were followed up to 15 months post-diagnosis.
Main outcome measures
Chemotherapy regimen, dose, duration and annualized mean number of adverse events stratified by age.
Half of the 202 patients >=75 years received adjuvant chemotherapy compared with 87% of 473 younger patients (diff 37%, 95% CI 30%-45%). Among adjuvant chemotherapy users, 14 (14%) of patients >=75 years and 178 (44%) of younger patients received a regimen containing oxaliplatin (diff 30%, 95% CI 21%-38%). Older patients were less likely to continue. By 150 days, 99 (40%) patients >= 65 years and 68 (25%) younger patients had discontinued chemotherapy (diff 15%, 95% CI 7%-23%). Overall, 162 (24%) patients had at least one adverse clinical event, with more events among patients treated with vs. without adjuvant chemotherapy (mean 0.394 vs. 0.160, diff 0.234, 95% CI 0.11-0.36, p<0.001). Among adjuvant chemotherapy users, adjusted rates of late clinical adverse events show a reverse U-distribution with lower rates for patients >= 75 years (0.277) versus for younger patients (0.345 for 18-54, 0.519 for 55-64, and 0.446 for 65-75 years, p=0.008 for any age effect).
Older patients in the community receive less toxic and shorter chemotherapy regimens, and those treated had fewer adverse events than younger patients. The effect of these differences on clinical outcomes is not clear.