Adjuvant Chemotherapy Less Likely in Elderly Stage III Colon Cancer Patients

Adjuvant chemotherapy was underutilized in elderly patients with stage III colon cancer, according to the results of a recent study. Although younger patients received greater benefit from adjuvant chemotherapy, elderly patients in the study still had improved long-term survival after treatment. The results of the study were published in Cancer.

“These patients merit referral to medical oncology for a full discussion regarding systemic treatment,” said Shaila J. Merchant, MSc, MHSc, MD, of the departments of oncology and surgery at Queen’s University in Kingston, Ontario, Canada. “Further work is required to understand patient preference and decision making as well as more subtle factors not captured in standard databases to ensure the optimal treatment of elderly patients with colon cancer.”

The majority of patients with stage III colon cancer undergo surgical resection and adjuvant chemotherapy; however, the efficacy of this strategy among elderly patients is unclear. In this study, Merchant and colleagues evaluated management and outcomes of stage III colon cancer among elderly patients.

They looked at all cases of surgically resected colon cancer from 2002 to 2008 in the Ontario Cancer Registry. They randomly sampled 25% of these cases and those with stage III disease constituted the study population (n = 2,920).

Of the included patients, 52% were elderly (70 years or older). Data showed that 30-day and 90-day mortality rates increased with advanced age. In patients younger than age 70, the 30-day mortality rate was 2% and the 90-day mortality rate was 5%; in patients 70 to 74 years old, 3% and 7%; in patients 75 to 79 years, 5% and 8%; and in patients 80 years or older, 9% and 16% (P < .001).

Although 81% of younger patients received adjuvant chemotherapy, a little less than one-half (48%) of older patients received adjuvant therapy (P < .001). Elderly patients who were younger (P < .001), male (P = .041), and had no comorbidities (P = .001) were all more likely to receive adjuvant chemotherapy. In addition, a longer postoperative hospital stay was also associated with lower use of adjuvant chemotherapy (P < .001).

“Our results suggest that the magnitude of benefit from adjuvant chemotherapy is less among elderly patients than younger patients; more specifically, on the basis of tests for interaction, the effect of adjuvant chemotherapy on cancer-specific survival is significantly greater in patients less than 70 years old vs those greater than or equal to 70 years old,” the researchers wrote.

Those elderly patients who did receive adjuvant chemotherapy had improved cancer-specific survival (hazard ratio [HR], 0.73) and overall survival (HR, 0.71). Younger patients who received adjuvant chemotherapy had even greater improvements in cancer-specific survival (HR, 0.53) and overall survival (HR, 0.56).

“Reasons for differential treatment effect among elderly and nonelderly patients are unclear, but potential explanations include a delayed initiation of chemotherapy due to a longer postoperative recovery and differences in regimens delivered across age groups,” the researchers noted. “It is also important to emphasize that, as expected, with increasing age, there is a greater reduction in 5-year overall survival vs cancer-specific survival, and this reflects the fact that very elderly patients (80 years or older) are dying of diseases other than their cancer.”