ESTRO 37 Abstract book

S732

ESTRO 37

(pN+ in 65% vs 34.4%, p=0.046). Accordingly, there was a higher ratio of patients receiving an axillary lymph node dissection in the RT group (52.4% vs 28.6%). Mastectomy was performed in 31/37 (86.1%) in the surgery only group as compared to 14/21 (66.7%) of patients receiving postoperative RT. Additionally, patients undergoing RT also received additional endocrine therapy significantly more often (78.9% vs 39.3%, p=0.016). Outcome was not significantly different between the groups (5-year local recurrence free survival: 89.8% vs 80.0%, p=0.471 and 5- year overall survival 82.8 % vs 77.8%, p=0.819). Conclusion To date, few data are available on MBC. The present observational study evaluated the pattern of care of BMC patients treated in clinical practice. Due to its rarity, randomized clinical trials are unlikely and MBC remains a neglected entity. Nevertheless, RT still remains a crucial component of the multidisciplinary treatment strategy in MBC. EP-1337 Exclusive IORT in breast cancer: outcome analysis of a pilot trial at two different single doses L. Belgioia 1 , M. Guenzi 2 , E. Bonzano 2 , G. Blandino 2 , F. Cavagnetto 3 , S. Garelli 3 , D. Friedman 4 , R. Corvò 5 1 University of Genoa, Department of Health Science DISSAL, Genoa, Italy 2 Ospedale Policlinico San Martino Genova, Radiation Oncology, Genoa, Italy 3 Ospedale Policlinico San Martino Genova, Medical Physics, Genoa, Italy 4 University of Genoa-Ospedale Policlinico San Martino Genova, Surgery, Genoa, Italy 5 University of Genoa-Ospedale Policlinico San Martino Genova, Radiation Oncology, Genoa, Italy Purpose or Objective To evaluate outcomes to exclusive intra-operative radiotherapy (IORT) with different single doses for conservative breast cancer treatment. Material and Methods From October 2009 to December 2011, 178 patients candidates for IORT were included in a monoinstitutional pilot study approved by ethic committee (NCT01276938). Eligibility criteria included: patients aged 45 to 85 years with unifocal and non lobular invasive carcinoma (LIC), a maximum tumor diameter of 2.5 cm, negative margin, intraductal component <25% and no previous history of cancer. Prescription dose depends on tumor size evaluated with frozen section examination; if < 1 cm total dose was 18 Gy, if > 1cm (up to 2.5 cm) the pts received 21 Gy. Using α/β ratio for breast tumor of 4 Gy, 21 Gy in 1 fraction would be biologically equivalent to 70 Gy while 18 Gy was equivalent to 60 Gy. Full-dose intraoperative radiotherapy with electrons was delivered using a LIAC (Sordina, Padova, Italy), a mobile linear accelerator delivering an electron beam with energies ranging from 4 to 10 Mev. Primary endpoint was local relapse free survival (LRFS), secondary endpoints were disease free survival (DFS) and overall survival (OS). Results 169 (95%) patients were analyzed, 9 were excluded as lost at follow up. The median follow-up is 72 months (9- 96 months). Median age was 67 years (range 45-85). 71 (42%) and 98 (58%) patients received 18 Gy and 21 Gy, respectively. 7 patients presented local relapse (2 and 5 pts in 18 Gy and 21 Gy arm, respectively) and 1 patients metastatic disease in 21 Gy arm. The cumulative 5 yy LRFS, DFS and OS were 96.7%, 96% and 96.4%, respectively. No significative difference in LRFS, DFS and OS was detected in 18 Gy arm vs 21 Gy arm (5 yy LRFS 96.8% vs 97.8% - P=0.6, 5 yy DFS 96.8% vs 96.6% - P=0.266, 5 yy OS 95.8% vs 96.9%- P=0.83). At definitive histological examination 154 pts presented DCI and 15 pts other histology (none LIC or DCSI), 19 pts positive nodes, 4 pts positive or close margins and 33 pts underwent to

adjuvant chemotherapy. As regards hystology (DCI vs other) and molecular subtypes (Luminal A, Luminal B, HER2+, basal like) no significant differences (P=0.139 and 0.238, respectively) were detected in the two groups (18 Gy vs 21 Gy). Grouping the patients according to ASTRO guidelines for accelerated partial breast irradiation, 114 (67%), 38 (22%) and 17 (10%) pts resulted suitable, cautionary and unsuitable, respectively. As regards toxicity, in 9 patients (3 and 9 in 18 Gy and 21 Gy arm, respectively) breast ultrasound showed liponecrosis. Conclusion Although 21 Gy remains the standard dose for exclusive IORT in breast cancer, from our data emerged no differences for 18 Gy group. A longer follow up and further randomized trials are necessary to confirm these results. EP-1338 No Axillary Dissection Among Women With Invasive Breast Cancer and Sentinel Node wit Macrometastasis I. García Ríos 1 , A. Fernández Forné 1 , I. Domenech Navarro 1 , M.J. Garcia Anaya 1 , M. Pamos Ureña 1 , R. Correa Generoso 1 , R. Ordoñez Marmolejo 1 , A. Otero Romero 1 , A. Román Jobacho 1 , J. Gomez Millán 1 , J.E. Montes García 1 , J.A. Medina Carmona 1 1 HOSPITAL UNIVERSITARIO VIRGEN DE LA VICTORIA, Radiation Oncology, Málaga, Spain Purpose or Objective Clinical practice has changed since publication of the ACOSOG Z0011 trial. Recently have been reported, 10- year overall survival for patients treated with sentinel lymph node dissection alone was noninferior to overall survival for those treated with axillary lymph node dissection. These findings do not support routine use of axillary lymph node dissection in this patient population based on 10-year outcomes. The Breast Cancer Committee of our hospital approved the implementation of the protocol ACOSOG Z0011. The primary end point was to determine disease free survival, defined as the time from diagnosis to the first documented recurrence of breast cancer. Breast cancer recurrence was categorized as locoregional disease (tumor in the breast or ipsilateral supraclavicular, subclavicular, internal mammary or axillary nodes) or distant metastases. These morbidities have been reported. Material and Methods

I Inclusion criteria: adult women with histologically confirmed breast carcinoma T1-T2, no palpable adenopathy, negative axilla evaluated by ultrasound, and SLNs positive for metastatic breast cancer documented by or hematoxylin-eosin staining on permanent section. Women were ineligible if they had 3 or more positive SLNs (they received axillary lymph node dissection in the second time) and patients candidates to mastectomy. All women received whole-breast opposing tangential-field radiation therapy and axillary radiotherapy included levels I and II, but no levels III and IV. All patients. The use of adjuvant systemic treatment