LISBON, PortugalA 16-Gy boost to the tumor bed can slash the local recurrence rate by as much as 50% in younger women with breast cancer who undergo breast-conserving therapy, said Harry Bartelink, MD, PhD, of the Netherlands Cancer Institute, Amsterdam.
Speaking at the 11th European Cancer Conference (ECCO), he reported the results of a phase III trial conducted by the European Organization for Research and Treatment of Cancer (EORTC).
The National Surgical Adjuvant Breast and Bowel Project (NSABP) and Scottish trials have convincingly shown that whole-breast irradiation after breast conservation treatment can reduce the odds of local recurrence by a factor of 4. However, the EORTC trial went a step further by asking whether 50 Gy was enough or whether an extra radiation dose might be even better.
To resolve this issue, the EORTC investigators randomly assigned 5,569 women with breast tumors up to 5 cm in size to receive whole-breast irradiation alone or supplemented by a 16-Gy boost to the tumor bed. Microscopically complete resection had been achieved in 95% of study participants.
"Only 30% of our postmenopausal patients received tamoxifen(Drug information on tamoxifen) (Nolvadex) and only 12% received chemotherapy, so these were really prognostically favorable tumors," Dr. Bartelink commented.
After a median follow-up of 5.1 years, Dr. Bartelink and his fellow investigators found that the 16-Gy boost strikingly reduced the local failure rate by nearly a factor of 2. No-boost patients experienced 182 local recurrences, compared with 109 local recurrences among boost patients (for a complete report, see N Engl J Med 345:1378-1387, 2001).
"About half of these recurrences are located outside the primary tumor bed, so even if you do a quadrantectomy, you need whole-breast irradiation," Dr. Bartelink said.