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were recently published with a median follow-up of 13.9 years. These long-term results further confirm a local control benefit for the use of radiation therapy (RT) and a reduction in the incidence of invasive recurrences.

Previous reports of this study with a median follow-up of 7 years showed an ipsilateral breast tumor recurrence rate of 0.8% in the RT arm and 7.2% in the observation arm. With longer follow-up, the benefit of RT has persisted with a 15-year cumulative incidence of ipsilateral breast tumor recurrence of 7.1 versus 15.1% (P=0.0007) and invasive recurrence rates of 5.4 versus 9.5% (P=0.027).

This study was a randomized trial of whole breast irradiation without a boost versus observation in women who had received a lumpectomy for good-risk DCIS. Radiation therapy was delivered as 50 or 50.4 Gy in 2.0 or 1.8 Gy fractions or 42.5 Gy in 16 fractions after 2001.

The study enrolled 636 women with screen-only detected DCIS that was < 2.5 cm with > 3 mm margins and grade 1 or 2. Tamoxifen use was slightly less in the RT group: 58% versus 66% (P=0.05), although the intention to use tamoxifen was balanced between the arms.

The median time to any ipsilateral recurrence was 11.5 years in the RT arm and 7 years in the observation arm. On multivariate analysis, receipt of RT and tamoxifen remained statistically significant whereas age, tumor size, and grade did not. These data continue to confirm that long-term patience is warranted as the risk of recurrence continues to increase over time.

One of the unique criteria for this clinical trial was that the DCIS was asymptomatic with low-risk features. This particular population of patients is one where many have felt patients are "over-treated" and have looked to avoid RT. These long-term data continue to affirm a benefit to RT even in those with favorable features and continue to affirm that RT potentially has more of an impact in risk reduction than tamoxifen, which can be critical information when counseling patients who only opt for one therapy.

Alternatively, women meeting study eligibility are also suitable candidates for accelerated partial breast irradiation (APBI). At the time of this trial, APBI was not widely utilized for breast cancer treatment and it would be interesting to compare the benefit of adjuvant whole-breast RT with partial breast RT in this setting. NSABP B-39/RTOG 0413 included women with DCIS; however, this accounted for only 24% of patients enrolled. The 10-year cumulative incidence of breast ipsilateral breast tumor recurrence for patients treated with DCIS was 6.5% in the whole-breast arm versus 6% in the APBI arm, indicating that this may be an equivalent and shorter treatment for women.

These data affirm the benefits of RT in women with good-risk DCIS. When making adjuvant therapy recommendations, clinicians should continue to weigh factors of comorbidities and life expectancy along with further fractionated courses of RT such as APBI and ultra-hypofractionated regimens.

Elizabeth Nichols, MD, is Associate Professor and Vice Chair, Clinical Affairs, Department of Radiation Oncology, at the University of Maryland School of Medicine in Baltimore.

Read the study here and an interview about it here.