DENVERRadiation therapy (RT) reduces the risk of breast cancer recurrence even in women with favorable early disease, researchers reported at the 47th Annual Meeting of the American Society for Therapeutic Radiology and Oncology (abstract 3). Although recurrence was uncommon with combined breast-conserving surgery and hormonal therapy, it was one-half less common when whole-breast radiation therapy was further added to treatment.
"The background of this study is the current standard of care for early breast cancer (and also for favorable early breast cancer), which consists of breast-conserving surgery, whole-breast radiotherapy, and hormone therapy in hormone-responsive tumors, and the question that has been discussed in the last decade with a growing intensityIs whole-breast radiotherapy beneficial in favorable early breast cancer?" said lead author Richard Ptter, MD, professor and chairman of radiotherapy and radiobiology, University of Vienna, Austria.
The 826 patients included in intention-to-treat analyses were participants in a prospective, multicenter trial of hormonal therapy (Austrian Breast and Colorectal Cancer Study Group trial 8). All were postmenopausal women with hormone-receptor-positive breast cancer, smaller tumors (T1 or T2, less than 3 cm), lower pathologic grades (1 or 2), and no lymph node involvement.
They underwent breast-conserving surgery (wide excision or lumpectomy with a negative resection, plus either axillary lymph node dissection or sentinel lymph node biopsy) followed by hormonal therapy (2 years of tamoxifen followed by 3 years of tamoxifen or anastrozole [Arimidex]). By random assignment, half of the patients also received adjuvant whole-breast radiation therapy (a mean dose of 51 Gy alone, or with an added boost to 60 Gy in two-thirds of patients in this arm).
After a median follow-up of 42 months, the 5-year actuarial rate of survival free of a local relapse (the trial's primary endpoint) was significantly higher in patients who received radiation therapy than in those who did not (99.4% vs 95.5%; hazard ratio [HR] 13.5).
The rate of distant metastases did not differ between groups, but patients in the radiation therapy group had a significantly higher rate of survival free of local relapse, distant metastases, or both (97.3% vs 94.8%; HR 2.8), corresponding to a one-half reduction in any recurrence. The rate of freedom from any event (local relapse, distant metastases, contralateral breast cancer, or any combination of these) was also higher with added radiation therapy (97.2% vs 93.7%; HR 3.3). Overall survival did not differ between groups.
Summing up the results, Dr. Ptter said that although breast-conserving surgery plus hormone therapy alone leads to "excellent results" in this patient population, adding radiation therapy further improves clinical outcomes. "I think we can conclude from these data that, even in the favorable early breast cancer patients treated with breast-conserving surgery and hormone therapy for 5 years, whole-breast radiotherapy remains the standard of care," he said.