The results of an observational study evaluating adjuvant chemotherapy use and outcomes for older patients with stage III colon cancer have been published in JAMA.

The authors note that adjuvant chemotherapy has been shown to reduce cancer death and recurrence in patients with stage III colon cancer.  In practice, older patients are much less likely to receive this treatment; the most common reasons for this given by physicians include the lack of randomised controlled trials evaluating its effectiveness in patients older than 80 years, concern regarding co-morbid conditions, and drug toxicities.

This study used data from patients who participated in the Cancer Care Outcomes Research and Surveillance (CanCORS) study.  This US study examined care delivered to population- and health system–based cohorts of patients, including 4713 newly diagnosed with colorectal cancer between 2003 and 2005 and followed up for as long as 15 months.  The current analysis included 675 of these patients, who underwent surgical resection and had survey and medical record data available.  The main outcome measures of interest included chemotherapy regimen, dose, duration, and annualised mean number of adverse events stratified by age.

The main findings were as follows (taken from the abstract):

• 50% (101/202) of those aged ≥75 years received adjuvant chemotherapy compared with 87% of 473 younger patients (difference of 37%; 95% CI 30%-45%).

• Among patients who received adjuvant chemotherapy, 14% of those aged ≥75 years and 44% of the younger patients received a regimen containing oxaliplatin (difference of 30%; 95% CI 21%-38%).

• Older patients were less likely to continue treatment: by 150 days, 40% of those aged ≥65 years and 25% of younger patients had discontinued chemotherapy (difference of 15%; 95% CI 7%-23%).

• Adjusted rates of late clinical adverse events in those receiving adjuvant chemotherapy were lower for patients aged ≥75 years (mean: 0.28) than for younger patients (0.35 for ages 18-54 years, 0.52 for ages 55-64 years, and 0.45 for ages 65-74 years; P=0.008 for any age effect).

The authors say that, according to their analysis, approximately 50% of older patients with stage III colon cancer who underwent surgical therapy received adjuvant chemotherapy, usually with the less-toxic non–oxaliplatin-based regimens. Although they appear to tolerate adjuvant chemotherapy, it is more often associated with earlier treatment discontinuation and doses and durations were lower than recommended based on clinical trial data.  The authors discuss the limitations of their study and note that further research is needed to determine the effects of this treatment on survival and recurrence rates.