PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): Patients with early stage breast cancer are offered adjuvant breast irradiation after lumpectomy to reduce the likelihood of recurrence . This is usually in the form of whole breast irradiation. However, large multi-institutional randomized data show that partial breast irradiation using single fraction intraoperative electron radiotherapy ( IOERT) may be safe and appropriate in a subset of patients with early stage disease. Our goal was to prospectively determine the local in-breast tumor recurrence ( IBTR) rate at a single community center using IOERT.
Materials/Methods: Patients with early stage breast cancer treated with breast conservation +/- SLNB and single fraction IOERT were enrolled prospectively in an in-house trial . Patient demographics , clinical/ pathologic staging , tumor histology , grade and receptor status were recorded. Patient eligibility included women age >/=40 yrs , primary tumor = 2.5 cm and node negative on preoperative clinical and imaging examination. Breast MRI was encouraged. Patient were treated with 6-12 Mev electrons using the IntraOp Mobetron device to a dose of 2100 cGy. A chest wall shield was used. Oncoplastic closure was used as indicated. Patients were scheduled for follow up at post op week 2, months 6,12,18 and then yearly until year five. Patients had mammograms yearly or as clinically indicated.
Results: 220 single fraction IOERT treatments were delivered between 2012-2017. Sixteen patients were subsequently excluded from this analysis because they received subsequent whole breast radiation based on adverse pathology. Of the remaining 203 treatment, 6 patients had bilateral IOERT ( total pts=197).The median follow up was 2.4 years. The median age was 65 yrs ( range 40-91). Pathology was as follows: 23% pure DCIS, 71% IDC +/- DCIS, 5% ILC , 1% mixed. 24% were stage 0, 72% were stage 1 and 5% stage 2 . 89% were low-intermediate grade while 11% were high grade. 90% were ER/PR positive. 11/197 patients recurred (5.6%). Of those, 7 developed ipsilateral in-breast tumor recurrence (6 local recurrences and 1 new primary). IBTR= 3.6%. Two developed systemic recurrence and two developed a new contralateral primary. Median time to recurrence was 2.7 years.
Conclusion: Our results show in -breast tumor recurrence rates for breast conservation with single fraction IOERT at 3.6%. These results are consistent with that of recently published randomized multicenter trials. Median follow up for this review is 2.4 years and further follow-up is required.
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