Boost Radiotherapy for the Treatment of Ductal Carcinoma In Situ Remains Controversial

Abstract

Over the past 40 years, technological advances and improved screening practices have resulted in a substantial increase in the diagnosis of ductal carcinoma in situ (DCIS). Accounting for approximately 20% to 30% of breast cancer cases, DCIS is associated with low mortality rates, but local relapse is a matter of concern, and death may occur in cases of insufficient local treatment. As demonstrated in previous studies, one predictive factor for local relapse is age, with younger patients having a higher risk of an ipsilateral breast tumor recurrence as DCIS or invasive cancer. Other risk factors include close or positive surgical margins and tumor necrosis. Whole-breast irradiation following breastconserving surgery for DCIS statistically significantly reduces the risk of local relapse compared with breastconserving surgery alone. Accepted as the current standard of care, adjuvant whole-breast radiotherapy has been demonstrated to reduce local invasive and noninvasive recurrence in patients with DCIS undergoing breast-conservation therapy in 4 large prospective randomized controlled trials (National Surgical Adjuvant Breast and Bowel Project B-17, European Organisation for Research and Treatment of Cancer 10853, United Kingdom/Australia and New Zealand, and SweDCIS) and in an Oxford overview. Although a complementary radiotherapy boost to the tumor bed has been shown to considerably improve local disease control in patients with invasive breast cancer, this strategy remains controversial for DCIS, with the majority of studies resulting in no therapeutic or survival advantage. In a study of boost radiotherapy involving one of the largest populations to date, Rakovitch and colleagues focused on a population of individuals with confirmed DCIS who were treated with breast-conservation therapy and boost radiotherapy. The participants were followed for 10 years, which allowed for a high study power and provided data on the 10-year rates of local recurrence and local recurrence-free survival (LRFS). The population of this study included 235 patients who were younger than 45 years of age, although the median age was 56 years. In addition, it included patients who had positive surgical margins before radiotherapy, 39% of whom underwent a hypofractionated scheme of 40-44 Gy in 16 fractions rather than the conventional scheme of 50 Gy in 25 fractions. This study, unique in several patient and treatment characteristics, did not identify a subset of women for whom the administration of boost radiotherapy was associated with a lower rate of