Background and methods: Women with ductal carcinoma in situ have been treated both by lumpectomy and by lumpectomy followed by radiation therapy, but the benefit of combined therapy is uncertain. A group of 818 women with ductal carcinoma in situ were randomly assigned to undergo lumpectomy or lumpectomy followed by breast irradiation (50 Gy). Sufficient tissue was removed that the margins of the resected specimens were histologically tumor-free. The mean duration of follow-up was 43 months (range, 11 to 86). The principal end point of the study was event-free survival, as defined by the presence of no new ipsilateral or contralateral breast cancers, regional or distant metastases, or other cancers and by no deaths from causes other than cancer.
Results: Five-year event-free survival was better in the women who received breast irradiation (84.4 percent, vs. 73.8 percent for the women treated by lumpectomy alone; P = 0.001). The improvement was due to a reduction in the occurrence of second ipsilateral breast cancers; the incidence of each of the other events was similar in the two groups. Of 391 women treated by lumpectomy alone, ipsilateral breast cancer developed in 64 (16.4 percent); it was noninvasive in 32 and invasive in the remaining 32. Of 399 women treated with lumpectomy and breast irradiation, ipsilateral breast cancer developed in 28 (7.0 percent) (noninvasive in 20 and invasive in 8). The five-year cumulative incidence of second cancers in the ipsilateral breast was reduced by irradiation from 10.4 percent to 7.5 percent for noninvasive cancers and from 10.5 percent to 2.9 percent for invasive cancers (P = 0.055 and P < 0.001, respectively).
Conclusions: Breast irradiation after lumpectomy is more appropriate than lumpectomy alone for women with localized ductal carcinoma in situ.