Optimizing Breast Cancer Management by William J. Gradishar

Author:William J. Gradishar
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

7.5 Omission of Whole Breast Radiation After Breast-Conserving Surgery: Ductal Carcinoma in Situ (DCIS)

Though the standard of care for localized DCIS remains breast-conserving surgery to attain negative margins (defined as >2 mm) [54] followed by WBRT, the optimal management strategies for DCIS continue to be increasingly controversial, in light of the breast cancer-specific survival for DCIS which approaches nearly 100%, irrespective of local treatment choice, in addition to the absence of level 1 data demonstrating any direct effects of treatment on overall survival. Similar to invasive cancers, an area of active research has been to attempt to identify subsets of DCIS patients in whom WBRT may be omitted. To date, subgroups of DCIS patients for whom WBRT has not been beneficial in decreasing invasive in-breast recurrences have yet to be consistently defined. One of the largest controversies is defining the primary endpoint and goal(s) of treatment, since treating physicians do not agree whether it should be all in-breast recurrences, irrespective of invasive or in situ, (because any recurrence is generally very meaningful for the patient), or alternatively, whether it should be the measurement of only invasive events, which theoretically have the potential to metastasize and ultimately affect survival. Based on disease estimates from the long-term follow-up of the four randomized DCIS radiation trials, the 15-year in-breast recurrence with local excision alone across the whole spectrum of DCIS ranged between 20 and 30+%, which is decreased to 10–15% with WBRT, and is well under 10% with tamoxifen at 15 years [55–58]. Of these, less than 50% are invasive recurrences. Thus, radiation oncologists often use ‘<1% per year’ for a rule-of-thumb threshold for an acceptable upper limit of in-breast recurrences with breast radiation therapy [59], though these numbers may in fact be an over-representation of local relapse in the current era, given the improvements in pathologic handling, margin assessments, and more recent advancements in screening/earlier detection.

The only contemporary, prospective, phase III trial assessing omission of WBRT in low-risk DCIS is the RTOG 98-04, which randomized mammographically detected grade I/II DCIS measuring <2.5 cm treated with local excision and margins >3 mm to either WBRT versus observation. Tamoxifen receipt was documented as 62% of the entire cohort. Despite premature closing of the trial due to poor accrual with only one-third of its projected enrollment (n = 636 of 1800), the initial 7-year analysis demonstrated a significantly greater risk of in-breast recurrences for patients who did not receive WBRT (7% vs. <1%; p < 0.001), leading the authors to conclude that despite the perception of low-risk DCIS with widely negative margins and despite the limited number of events and underpowered sample size, WBRT nevertheless significantly reduced the number of in-breast events, and longer follow-up was needed because of the protracted clinical course of DCIS [60].

Two other prospective, single-arm studies assessed omission of WBRT for ‘low-risk’ DCIS. The first study, named ‘The Wide local Excision Alone’ (The WEA Study), defined as mammographically detected ‘low-risk’ DCIS lesions <2.5 cm in size with >10 mm margins and predominantly grade I/II.

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