P3-13-12: Electrons for Intraoperative Breast Radiotherapy in Selected Patients: Long-Term Results of the Montpellier Phase II Trial.

Abstract

Abstract Background and purpose: Postoperative whole breast external radiotherapy remains the current standard of care for patients with early operable breast cancer. In the elderly, the low crude numbers of recurrence and the frequency of comorbidities urged teams to investigate the feasibility and the results of intraoperative radiotherapy (IORT) delivered in one fraction during the surgical procedure. Material and methods: 94 patients (> 65 years old) accepted to be included in this phase II trial according to clinical and histopathology criteria and signed the informed consent. Among them, 42 presented all the inclusion criteria, namely pT0-1 pN0, non lobular invasive unifocal carcinoma, margin ≥ 2 mm (assessed during the surgical procedure) and estrogen receptors positivity. All patients were operated upon in a dedicated IORT facility (linear accelerator) located centrally among six operated rooms. After tumor removal, the surgical bed was approximated by sutures to bring the tissue within the radiation target volume. The tumor beds were completely encompassed by 4 to 6 cm circular fields using flattened applicators at a 110 cm distance. One fraction of 21 Gy was prescribed and specified at the 90% isodose using electron with energies ranging from 6 to 10 MeV. In vivo dosimetry was performed for all patients using real-time in vivo semiconductor detectors (PTW) fixed by the surgeon within the surgical bed. A 5 year adjuvant hormonotherapy was prescribed according to the recommendations. Primary end-point was the quality index [QI] - ratio between the prescribed dose and the in vivo measured dose-. Secondary endpoints corresponded to quality of life, local recurrences, cosmetic results, specific and overall survival. Results: Median follow-up is now 54 months [range 12–62]. Median age was 72 years [66-80] and median tumor diameter was 10 mm [3-19 mm]. 36 tumors were grade 1 or 2 and 100 % of the tumors expresses estrogen receptors. All patients received the total prescribed dose. No external postoperative radiotherapy was delivered. Intraoperative dosimetry demonstrated a good accordance between the delivered and the prescribed doses for 97% of the 37 evaluable patients. No acute grade 2 or greater toxicities were observed. Scores for quality of life were collected for all patients and showed no modification between pre and posttreatment evaluations. Late cosmetic result was good to excellent. All patients are still alive and the 4 year-disease-free-survival is currently 97%. Two patients recurred: (i) one infracentimetric superficial recurrence in the border of the surgical bed and close to the skin (at 18 months) (ii) a second primary tumor in another quadrant (at 6 months). These two patients underwent salvage mastectomy and are free of disease at the time of analysis. Conclusion: For a very selected population, these results confirm that partial breast IORT with electrons may be considered as an interesting alternative to the standard 6-weeks radiotherapy, offering therefore a safe one-step procedure treatment. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-13-12.