More than 80% of breast cancer cases in British Columbia are funneled through the British Columbia (BC) Cancer Agency for treatment. This unique centralized system gives researchers the opportunity to test whether the outcomes seen in well-controlled clinical trials reflect what happens when clinicians at the community level deal with all comersnot just carefully selected patients who meet specific eligibility criteria and are willing to participate. In a presentation at the 27th annual San Antonio Breast Cancer Symposium, a group of researchers reported that the results achieved in British Columbia do in fact mirror the overall outcomes seen in clinical trials.
"We know that randomized clinical trials have shown that adjuvant chemotherapy and tamoxifen reduce recurrences and improve survival in patients with stage I and II breast cancer," said Ivo Olivotto, M.D., who presented the study. But, he added, "we also know that a very small proportion of patients actually participate in these clinical trials. Potentially, the general population may be quite different than those who participate in randomized trials."
Olivotto, of the BC Cancer Agency in Victoria, and his colleagues decided to compare the theoretical results one should expect to see in patients with stage I or II breast cancer treated with tamoxifen and/or adjuvant therapy and what actually occurred among patients seen by the clinics in British Columbia. They reviewed and followed outcomes in more than 4,700 women treated by the BC Cancer Agency from 1989 to 1993 and compared treatment and outcomes to results from the Early Breast Cancer Trialists' Collaborative Group, a collection of data from randomized clinical trials of operable breast cancer.
In general, the reductions in mortality and in risk of recurrence after treatment observed in clinical trials were also seen among the women treated outside of clinical trials in British Columbia. In the clinical trials, women receiving 5 years of tamoxifen treatment had a 50% relative improvement in breast cancerspecific survival. In British Columbia, women under 50 years of age receiving 3 years of tamoxifen had about a 30% relative improvement in breast cancerspecific survival, and women older than age 50 had a 15% relative improvement.
Olivotto suggested that the results may be less pronounced in older women because the data on patients outside of clinical trials included women who ranged in age up to 90 years. He is still analyzing data to see if the greater age differences between the clinical trials cohort and the British Columbia cohort account for the discrepancy.
"These findings are what we would expect to see in the real world," said Larry Norton, M.D., deputy physician-in-chief and director of breast cancer programs at Memorial Sloan-Kettering Cancer Center in New York. "We have built a really good clinical trial system. We believe the patients in these clinical trials are a fair sample of the type of patient clinicians are likely to see in practice. The British Columbia experience bears out that these trials are relevant. We are very encouraged by that."
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