Adjuvant chemotherapy after stage III colon cancer resection is effective in older patients, but isn't always administered due to concerns about adverse events. Older patients who do receive the therapy, however, get lower doses and durations than recommended. In addition, late clinical adverse events are less common than in younger patients, a new study reports.
Researchers analyzed adjuvant chemotherapy and adverse events by age in 675 patients diagnosed with stage III colon cancer from 2003 through 2005 who underwent colon resection. Results were published in the March 17 Journal of the American Medical Association.
Of 202 patients aged 75 years and older, 101 (50%) received adjuvant chemotherapy compared with 87% of 473 younger patients (difference, 37%; 95% CI, 30% to 45%). Among patients who received adjuvant chemotherapy, 14 patients (14%) aged 75 years and older and 178 younger patients (44%) received a regimen containing oxaliplatin (difference, 30%; 95% CI, 21% to 38%), which has been shown to be more effective but also more toxic.
Older patients were less likely to continue treatment at all follow-up times. By 150 days, 99 patients (40%) aged 65 years and older and 68 younger patients (25%) had discontinued chemotherapy (difference, 15%; 95% CI, 7% to 23%).
Overall, 162 patients (24%) had at least one adverse clinical event, with more events among patients treated with than without adjuvant chemotherapy (mean, 0.39 vs. 0.16; difference, 0.23; 95% CI, 0.11 to 0.36; P<0.001). Among patients receiving adjuvant chemotherapy, adjusted rates of late clinical adverse events were lower for patients 75 years and older (mean, 0.28) than for younger patients (0.35 for ages 18 to 54 years, 0.52 for ages 55 to 64 years, and 0.45 for ages 65 to 74 years; P=0.008 for any age effect).
Chemotherapy is meant to prolong survival for patients with at least five years of life expectancy. Women and men age 70 have a median life expectancy of 16.2 and 13.7 years, respectively, and those age 80 and older have a median life expectancy of 9.8 and 8.2 years, respectively, “suggesting that adjuvant chemotherapy should be considered for many older patients,” the authors wrote.