In younger patients with ductal carcinoma in situ (DCIS), boost irradiation reduced local recurrences by at least half when added to standard radiotherapy, Gunther Gruber, MD
• PHILADELPHIAIn younger patients with ductal carcinoma in situ (DCIS), boost irradiation reduced local recurrences by at least half when added to standard radiotherapy, Gunther Gruber, MD, reported at the American Society for Therapeutic Radiation and Oncology annual meeting (abstract 56). Dr. Gruber, of the Institute of Radiation Oncology, Aarau, Switzerland, urged cautious interpretation of the results because of the retrospective nature of the analysis, which was based on data from the Rare Diseases Clinical Research Network. Nonetheless, he said, "until we have Level 1 evidence from a randomized trial, we would like to propose boost irradiation for younger patients with DCIS."
Eighteen institutions in Europe, Australia, and the United States contributed data on 373 patients who met the study's entry criteria. Patients were required to be no older than 45 and to have undergone breast-conserving surgery. They ranged in age from 23 to 45 (median, 41 years). Surprisingly, Dr. Gruber said, the tumor was detected by mammography in 70% of patients. Sixty-two percent of patients had surgical re-excision; 15% received no radiotherapy; 45% had whole-breast radiotherapy without a boost (median dose, 50 Gy); and 40% had radiotherapy plus a boost. Tamoxifen was used in only 7% of patients.
With a median of 6 years' follow-up, 15% of patients have experienced local failure, of which about half were invasive; 6% had a relapse in the contralateral breast, and 2% each had nodal or distant relapse. Seven patients (2%) died, five of an invasive breast cancer relapse. An estimated 90% of patients were free of local recurrence at 5 years, 75% at 10 years, and 70% at 15 years. Overall survival was estimated at 99% at 5 years, 97% at 10 years, and 95% at 15 years.
Local relapse-free survival results differed markedly depending on the use of radiation therapy, Dr. Gruber said. Of patients who received no radiation therapy, 45% had a local relapse at 10 years. Relapses occurred in 28% of patients who received external-beam radiation alone, and in only 14% who also had boost irradiation. Results in the boost irradiation group diverged from the other groups as early as 5 years after treatment.
Radiation therapy with no boost was associated with a "quite impressive reduction in local failure of more than 60%, which was further improved by the addition of boost therapy . . . resulting in a further 50% risk reduction," compared with standard radiation alone, he said.