Full Local Control With Accelerated Partial Breast Irradiation (Apbi) By Tomotherapy After Breast-Conservative Surgery For Patients Suitable, Or Not, According To Astro-2009 Consensus Statement: Interim Report After 2 Years Follow-Up

We present an interim report of an ongoing IRB-approved phase 2 study on APBI using a highly conformal external beam approach with a tomotherapy Linac. The study includes 111 of 570 women treated in our Breast Unit since December 2010 with breast-conservative surgery. The inclusion criteria were: age ≥ 50 years, unicentric and unifocal tumors smaller than 3 cm diameter, negative surgical margins without an extensive intraductal component (EIC) or lympho-vascular invasion (LVI), pN0 or pN1 nodal status. Patients received a total dose of 38.5 Gy in 3.85 Gy fractions daily for 2 weeks. The clinical target volume (CTV) was the tumor bed and the close area defined by surgical markers. The primary end points of the study are local control and acute and late toxicity. Secondary end points are survival, cosmetic outcome, and patient compliance. All the patients were evaluated at three, six, and twelve months for the first year and every six months thereafter. At each visit, a cosmetic questionnaire exploring breast outline, shape, size, consistency, color, and scar was independently filled in by patient and physician. Median tumor diameter was 10 mm (range: 3-30) and median age of patients 67 years (range: 51-88). Sixty-seven patients (60%) met the criteria of the “suitable” group of ASTRO-2009 consensus statement, while 44 patients (40%) did not because they lack one (31 pts) or two (13 pts) “suitable” factors as follows: age < 60 years (27 pts), invasive lobular histology (19 pts), pN1 (16 pts), pT2 (4 pts). With a median follow-up of 24 months (range: 4-38), in both groups no ipsilateral loco-regional recurrences have been reported, so far. One patient developed contralateral breast cancer 12 months after surgery. The treatment was well tolerated with acute or sub-acute toxicity according to RTOG scale grade 1 and grade 2, in 12 and in 2 patients respectively. Grade 1 late toxicity was recorded in 13 patients. The overall average mean dose to the whole heart was 0.6 Gy (range: 0.1-3.9 Gy). Treatment compliance was excellent (100%) with good cosmetic results both for patients and for physicians. The growing data obtained from phase 1-2 studies supports the use of APBI in early-stage breast cancer and new evidence guides the ongoing patient selection. In our preliminary experience, selected patients with one or two specific non-suitable tumor-related features according to ASTRO-2009 consensus statement may benefit from APBI with tomotherapy, and this technique can significantly decrease the mean dose to the whole heart, while providing the same local control.