One of the reasons large population-based studies are important is based on the “difference between efficacy—does a treatment work in a highly controlled setting of a phase III randomized clinical trial—and effectiveness—does a treatment work in general practice,” according to Benjamin D. Smith, MD. Dr. Smith is corresponding author of a retrospective population-based study of more than 92,000 older women with invasive breast cancer treated with lumpectomy followed by either whole-breast irradiation or brachytherapy. “It is important to understand the effectiveness of a treatment approach in addition to its efficacy,” he said.

Dr. Smith noted that the study also adds to a considerable volume of previous work looking at large population-based data sets with women similar to those in the study cohort, treated with either lumpectomy alone or lumpectomy plus conventional whole-breast radiation therapy. “We found previously that women who receive conventional whole-breast irradiation have about a threefold reduction in their risk of subsequent mastectomy, suggesting that whole-breast irradiation is an effective treatment. Indeed, it is effective when used widely in the community setting,” he said. ■