Abstract P1-15-05: Long-term outcome of electron intraoperative boost and hypofractionated external beam radiotherapy after breast-conserving surgery in premenopausal women
Authors: Leonardi Maria Cristina , Morra Anna , Fodor Cristiana , Santoro Luigi , Dicuonzo Samantha , Lazzari Roberta , Dell'acqua Veronica , Rondi Elena , Cattani Federica , Pansini Floriana , Luini Alberto , Orecchia Roberto 
Published: May 2015

Purpose: To report long-term clinical results on breast cancer patients treated with a electron intraoperative boost followed by hypofractionated external beam radiotherapy (HEBRT) to the whole breast inside a clinical protocol.

Materials and Methods: Between June 2004 and December 2008, 357 premenopausal women with a diagnosis of early-stage breast cancer were given breast conservative surgery (quadrantectomy and sentinel node biopsy +\- axillary dissection). During surgery, an electron intraoperative boost of 12 Gy was administered to the tumour bed. Within 4 weeks after having received the IORT boost, the whole breast was irradiated with hypofractionated scheme. HEBRT consisted of 13 daily fractions of 2.85 Gy up to a total dose of 37.05 Gy, with 3-D conformal technique. Median age was 42 years (24-48). Pathologic stages were distributed as follow: stage 0 4 (1.1%), I 192(53.8%), stage IIA 108 (30.3%), stage IIB 28 (7.8%), stage IIIA 18 (5%), stage IIIC 6 (1.7%), CR 1(0.3 %).

The biomolecular classification included 33 triple negative patients.

All patients but one received adjuvant systemic treatment, according to tumor features. Chemotherapy +/- endocrinotherapy was offered to 149 patients, while endocrinotherapy alone was given to 197 patients. In all cases, adjuvant chemotherapy commenced after the completion of HEBRT. Follow-up was carried out on a regular basis by breast surgeons and radiation oncologists.

Results: Median follow-up was 83.1 months (range 9.1-118.9). 340 patients were alive and 317 were free of any disease (89%). Three patients (0.8%) had nodal regional recurrence, 12 patients (3.4%) had local recurrence, 26 patients (7.3%) had distant metastasis.13 patients (3.6%) developed contralateral breast cancer.12 patients (3.4%) had a new primary tumor in other site.

15 patients (4.2%) died due to progression of disease, while two died of other causes not related to the breast cancer.

Conclusions: This shortened scheme including intraoperative anticipated boost and hypofractionated whole breast radiotherapy showed a good local control at 5 years follow-up. The patients’ compliance is very high and in patients who are in need of chemotherapy, the time gap between surgery and radiotherapy treatment is avoided.

As follow-up length increases, a greater number of patients will achieve the minimum 5 -year period to receive the first long-term evaluation and the strength of the results on efficacy is bound to increase.

Citation Format: Maria Cristina Leonardi, Anna Morra, Cristiana Fodor, Luigi Santoro, Samantha Dicuonzo, Roberta Lazzari, Veronica Dell'acqua, Elena Rondi, Federica Cattani, Floriana Pansini, Alberto Luini, Roberto Orecchia. Long-term outcome of electron intraoperative boost and hypofractionated external beam radiotherapy after breast-conserving surgery in premenopausal women [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-15-05.