Use of postoperative chemotherapy for stage III colon cancer is becoming more common in US medical practice, and the strategy has resulted in a significant increase in five-year survival, according to an article in the December 7 issue of the Journal of the American Medical Association.

Based on results of two trials, the National Institutes of Health Consensus Conference recommended in 1990 that adjuvant chemotherapy be given to all patients with stage III colon cancer who were not enrolled in a clinical trial. According to background information in the article, however, as with most recommendations, it is not clear to what extent they are followed or contributed to outcome in the general population.

J. Milburn Jessup, MD, of the National Cancer Institute, Rockville, Md. and Georgetown University, Washington, D.C., and colleagues assessed to what extent the 1990 Consensus Conference recommendation has been followed in the community and whether adjuvant chemotherapy has improved the five-year survival of patients with stage III colon cancer.

The current analysis included data from 85,934 patients with stage III colon cancer from 560 hospital cancer registries who were entered into the National Cancer Data Base (NCDB) between 1990 and 2002. The data included standard clinical, pathological, and first course of treatment variables.

The researchers found an increase in the use of adjuvant chemotherapy for all patients with stage III colon cancers from 39 percent of patients in 1990 to 64 percent in 2002, but use was lower in black, female, and elderly patients.

The associated difference in five-year survival increased from an 8 percent improvement in the 1991 subgroup to 16 percent in the 1997 subgroup that received adjuvant chemotherapy compared with surgery alone. The researchers also found that adjuvant chemotherapy increases survival in elderly patients as much as it does in younger patients. However, the benefit of adjuvant chemotherapy in blacks and those with high-grade cancers was not as great.

“Future studies are needed to identify whether newer agents such as irinotecan and oxaliplatin may be more effective in patients with high-grade cancers or in blacks than the 5-fluorouracil and leucovorin regimens that were dominant during the time that the cohorts reported herein were followed up for survival,” the authors concluded.

In an accompanying editorial, Eric Van Cutsem, MD, PhD, of University Hospital Gasthuisberg, Leuven, Belgium, and Frederico Costa, MD, of Hospital Sirio Libanes, Sao Paulo, Brazil, commented on the study by Jessup et al:

“The central issue regarding adjuvant chemotherapy is the difficulty in assessing its real benefit for an individual patient. The recommendation is generally based on the proof of efficacy in a selected population at risk for disease recurrence. The decision-making process is always complex. On the one hand, the physician’s understanding of the potential benefit is influenced by his or her own prejudice; on the other hand, the patient’s confidence is influenced by beliefs and fear. Factors such as comorbidities, socioeconomic status, and low adherence to therapy are among the well-described causes for not using adjuvant chemotherapy. Ongoing studies of molecular markers for colorectal cancer should help determine which patients benefit most from adjuvant therapy.”

“Even though causes for recommending or not recommending adjuvant chemotherapy are multifactorial, Jessup et al observed an increase in the use of adjuvant chemotherapy over time. It is not clear why it took so many years for a majority of patients to receive adjuvant treatment despite the clear demonstration of a survival benefit. Hopefully, further progress in the knowledge of adjuvant therapy will have a more rapid influence on clinical practice in the near future,” the authors concluded.