Adjuvant radiotherapy continues to protect against recurrences – albeit “modestly” – for a full 20 years after women undergo breast-conserving surgery for DCIS, according to a report published online Oct. 13 in the Journal of Clinical Oncology.
In an extended follow-up study involving 1,046 of the 1,067 original participants in the Swedish Ductal Carcinoma in Situ (SweDCIS) clinical trial in 1987-1999, there were 258 recurrences: 129 cases of DCIS and 129 cases of invasive cancer in the ipsilateral breast. Another 115 women developed contralateral DCIS or invasive cancer. A total of 232 women died, including 41 who died from breast cancer, said Dr. Fredrik Warnberg of the department of surgical sciences, Uppsala (Sweden) Academic Hospital, and his associates.
There were 93 recurrences among women who had been randomized to adjuvant radiotherapy, compared with 165 recurrences in the control group treated with breast-conserving surgery only. This corresponds to an absolute risk reduction of 12% and a relative risk reduction of 37.5% for adjuvant radiotherapy. The absolute risk reduction was more pronounced for recurrent DCIS (10%) than for invasive cancer (2%), and it occurred mainly among women in the older age groups – those aged 52 years and older at diagnosis, the investigators said (J. Clin. Oncol. 2014 October 13 [doi:10.1200/JCO.2014.56.2595]).
Contralateral breast cancer developed more often in the radiotherapy group (67 cases) than in the control group (48 cases), but this difference was not statistically significant, said Dr. Warnberg and his associates.
“The balance between protection against local recurrences and the downsides of radiotherapy currently speaks in favor of adjuvant breast irradiation. However, the more modest protective effect specifically for invasive recurrences and the possible increase in risk of contralateral cancer still call for the need to find groups of patients for whom radiotherapy could be avoided,” they noted.