Purpose: To report the 3-year median follow-up of a prospective Phase II partial breast irradiation (PBI) trial utilizing the MammoSite® interstitial balloon as the sole radiation therapy treatment after lumpectomy for ductal carcinoma in situ (DCIS).Materials and Methods: One hundred and thirty-three patients were enrolled from May 2003 through January 2006 to reach the 100-patient partial breast irradiation (PBI) target goal of 34 Gy in 10 fractions, 1 cm peripheral to the MammoSite® balloon surface, b.i.d. with Iridium192 HDR brachytherapy. The eligibility criteria were age 45, unicentric pure DCIS, mammographic size ≤3cm, negative margin of ≥1 mm, gross pathology size ≤5 cm, clinically node negative, post-lumpectomy mammogram absent of residual microcalcificaion. A USC/VNPI score was then calculated based on age, tumor size, margin width, and nuclear grade [ref: Silverstein MJ, Am J Surg 2003;186(4):337-343]. Placement of the balloon was performed at the time of lumpectomy or post-lumpectomy with a required minimum distance of the balloon surface to skin (skin bridge) of 5 mm. Data was collected at enrollment, at implant, 3 and 6-months, then yearly for local control, cosmesis (Harvard Scale), toxicity, adverse events, disease-free survival, cause-specific survival, and contralateral breast failure. Local recurrence is defined as either invasive or non-invasive within the target volume. Ipsilateral elsewhere recurrence (IER) is defined as invasive or non-invasive outside of the target volume.Results: Of the 133 patients enrolled, thirty-three were not treated for the following reasons: less than 5 mm skin bridge (n=13), poor cavity conformance (n=10), positive margin (n=3), microinvasion (n=3), MD decision (n=2), patient request (1), and other (1). The nuclear grade distribution of the tumors were: NG1(17%), NG2(44%), and NG3(39%). The mean age was 60.8 years. The mean tumor size was 10.6 mm; mean closest surgical margin was 6.8 mm (R=0.1-40mm); post-lumpectomy placement in 72%; mean skin bridge distance was 13 mm with 89% ≥7mm. No patients have been lost to follow-up, and at a median 3-year follow-up, the cosmetic results have been rated as excellent/good in 94 and fair in 6 patients. There have been only four recurrences, all non-invasive with the following histological patterns listed in the table below. One was an IER.No serious adverse events were reported with an infection rate of 9% (7 breast infections; 2 cellulitis).Conclusion: This is the longest reported prospective Phase II study using a PBI technique for pure DCIS patients, and continues to demonstrate the efficacy of the MammoSite® balloon for treating pure DCIS breast tumors, with no new recurrences since our last report at SABCS 2007. All the recurrences were noninvasive, and had at least one or more risk factors of a high USC/VNPI score, high nuclear tumor grade, or had a comedo necrosis pattern. There have been no recurrences in nuclear grade 1 or 2 patients in the absence of a comedo necrosis pattern. The cosmesis also continues to be excellent or good long-term in 96% patients.
Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 952.