Recurrence rates of ductal carcinoma in situ (DCIS ) have declined significantly over 3 decades, with the improvements likely because of better screening and pathologic assessment, investigators say.

A retrospective review of 2,996 women who underwent breast-conserving surgery (BCS) for DCIS at Memorial Sloan Kettering Cancer Center in New York from 1978 through 2010 showed that there were 363 recurrences within 5 years of treatment (12%). The 5-year recurrence rate for women treated from 1978 through 1998 was 13.6%, compared with 6.6% for women treated from 1999 through 2010.

The hazard ratio (HR) for more recent treatment was 0.62 (P less than .0001), report Dr. Kimberly J. Van Zee and colleagues at MSKCC in an oral abstract to be presented at the symposium sponsored by the American Society of Clinical Oncology.

The period of treatment remained a significant predictor of lower recurrence after multivariate analysis adjusting for age, family history, radiologic vs. clinical presentation, nuclear grade (nonhigh vs. high), necrosis, number of excisions (two or few vs. three or more), margin status (positive or close margins vs. negative), radiation, and use of endocrine therapy (HR 0.74, P = 0.02).

When the investigators stratified patients by whether they received radiation in addition to BCS, they found that recurrence rates dropped only for those patients who did not receive radiation (HR 0.62, P = 0.003). Among patients who received radiation, recurrence rates did not decline over time (HR 1.13, P = 0.6).

The authors conclude that the lower risk of recurrence over time is only partially explained by changes in clinical practice, such as screening, emphasis on negative surgical margins, and use of adjuvant therapies. The fact that the decline was seen only for women who did not receive radiation suggests that the improvements were not attributable to improvement in radiation therapy techniques. Rather, they may be due to improvements in mammography and in pathologic assessment, the investigators maintain.

“The lower recurrence risk observed for DCIS patients treated in more recent years is important for patient education, especially in view of the widely reported recent increase in use of mastectomy,” they write in the study abstract.