ESTRO 38 Abstract book

S165 ESTRO 38

while patient information remains crucial for the discussion of treatment choice. OC-0318 10-year clinical and cosmetic outcomes of high-dose-rate brachytherapy for early breast cancer F. Arcidiacono 1 , F. Trippa 1 , P. Anselmo 1 , M. Italiani 1 , M. Casale 1 , L. Draghini 1 , S. Fabiani 1 , A. Di Marzo 1 , S. Terenzi 1 , E. Maranzano 1 1 Radiotherapy Oncology Centre, “S.Maria” Hospital, Terni, Italy Purpose or Objective In GEC-ESTRO randomised trial accelerated partial breast irradiation (PBI) with high-dose-rate brachytherapy (HDR- BRT) was not inferior to adjuvant whole breast irradiation at 5-year follow-up. The long-term results are lacking in literature. We report 10-year clinical and cosmetic outcomes of PBI with 192 Ir HDR-BRT in early breast cancer patients (pts). Material and Methods From May 2005 to July 2013,129 early breast cancer pts were recruited in a phase II trial of exclusive 192 Ir HDR- BRT. Inclusion criteria were: age >40, PS 0-2, unifocal invasive ductal cancer, intraductal cancer component <25%, negative axillary nodes and tumor size ≤2.5 cm. Treatment schedule was 4 Gy twice a day for 4-5 days, up to a total dose of 32 Gy in 8 fractions with a minimum interval between daily fractions of at least 6 hours. Late toxicity was graded according to RTOG/EORTC scoring criteria and cosmetic outcomes according to Harvard criteria (i.e., excellent, good, fair and poor). Results Median age was 67 years (range,42-85). There were 11 (8.5%) pT1a, 44 (34%) pT1b, 68 (53%) pT1c and 6 (4.5%) pT2. Estrogenic and/or progestinic receptors were positive in 118 (91.5%) pts.116 (90%) and 20 (15.5%) patients received adjuvant hormonal therapy and chemotherapy, respectively. Median follow-up was 108 months (range, 8-162). 3(2%) isolated in-field breast relapse occurred 92,123 and 129 months after HDR-BRT; 1(0.7%) isolated out-field breast relapse occurred 107 months after HDR-BRT.4(3%) patients developed contralateral breast cancer, another one (0,7%) isolated regional relapse in axillary node and 4(3%) distant progression of disease. 16(12.5%) patients reported a second primary cancer. 5- and 10-year overall survival and cancer specific survival were 95% and 86%, 100% and 100%, respectively.At last follow-up, 105(81%) patients were alive without disease and 4(3%) with systemic disease. 20 (16%) patients died: 10 (8%) for other cancers and 10 (8%) for other causes. Cosmetic outcomes were excellent in 106 (82.5%), good in 12 (9.5%), fair in 8 (6%) and unknown in 3 (2%) pts. Late skin toxicity was registered in 29 (23,4%) pts, grade 1-2 in 28 (22,5%), grade 3 in 1 (0,8%). Late toxicity was significantly related to the skin administered doses (≤ 55% vs. > 55%, P< 0.05). Conclusion PBI delivered with 192Ir HDR-BRT in selected breast cancer patients was associated to high local control and survival with excellent cosmetic outcomes overall when skin dose was ≤ 55%. OC-0319 Twelve-year clinical outcomes with APBI with interstitial multicathether brachytherapy after BCS S. Kellas-Sleczka 1 , B. Bialas 1 , P. Wojcieszek 1 , A. Cholewka 2 , M. Szlag 2 , M. Fijalkowski 1 , T. Krzysztofiak 1 , K. Trzaska 2 , A. Pruefer 2 , L. Piotr 1 , M. Wesołowski 3 , B. Lange 4 1 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Brachytherapy Department, Gliwice, Poland ; 2 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, Radiotherapy Planning Department, Gliwice, Poland ; 3 Maria Sklodowska-Curie Memorial Cancer Center and Institute

of Oncology, Tumor Pathology Department, Gliwice, Poland; 4 Maria Sklodowska-Curie Memorial Cancer Center and Institute of Oncology, III Department of Radiotherapy and Chemotherapy, Gliwice, Poland Purpose or Objective To report the long-term results, toxicity, and pattern of failure of 481 patients treated with APBI using interstitial multicatheter high-dose-rate brachytherapy (HDR-BT) after breast-conserving surgery in a single institution. Material and Methods Between July 2006 and September 2018, a total of 481 women with low-risk invasive and in-situ carcinoma after breast-conserving surgery (BCS) were treated with APBI using interstitial multicatheter HDR-BT at our department. The inclusion criteria were: ZUBROD 0 or 1, age ³50 years, T1-2aN0M0, T≤3 cm, unifocally, invasive carcinoma without neuroinvasion, angioinvasion, a minimal surgical margin of 2 mm or DCIS with a minimal margin of 5 mm, without extensive intraductal component (EIC), positive estrogen receptors. The total dose was 32 Gy in 8 fractions delivered twice daily with a minimum 6-hour break. The primary endpoint was local recurrence. Results The median age was 61 years (range 47-86 years). The median follow-up was 55 months (range 1-146 months). In the analyzed group, 262 patients were followed up for 5 years or longer. The mean volume of the PTV was 71.5 cm 3 , with the mean value of its coverage with the prescribed dose (PTV ref) amounting to 94.6%. The PTV mean value was 67.6%, and D90 was 105%. The mean values of key indices were acceptable, with a mean conformity index (COIN) of 0.69 and a mean dose homogeneity index (DHI) of 0.68. The mean value of the maximum skin dose was 41% of the prescribed dose. The mean value of the ipsilateral lung dose to 2 cm 3 volume was 40.3% of the prescribed dose, and the mean valu to 10 cm 3 volume was 30.1%; the maximum dose for ipsilateral lung was 50% on average. The mean maximum dose for the closest rib was 77.8% of prescribed dose. There was no acute severe toxicity. The treatment was well tolerated. In 19.7% a hematoma following catheter insertion was noted. In 2.1% local inflammation requiring oral antibiotic therapy was noted, but in 22.2% of cases prophylactic antibiotic therapy was given. There was no late severe toxicity, and cosmetic outcome was good. In the whole group of patients, 11 failures (2.3%) were noted: seven local recurrences (1.5%) treated with amputations and four cases (0.8%) of distant metastases. All patients with local recurrence are alive without any symptoms of disease; two patients with distant metastases have died; two are still undergoing therapy. The 5- and 10-year OS was 94.4% and 83.5 % respectively. The 5- and 10-year DFS was 92.3% and 78.6% respectively. Conclusion APBI with Interstitial Multicatheter High-Dose-Rate Brachytherapy is an effective treatment modality, associated with very low toxicity and a low relapse rate. In our opinion, patient selection criteria should be revised and could likely be extended. Further studies are needed to validate this approach. OC-0320 Comparing toxicities between Multicatheter Brachytherapy and Whole Breast External Beam Radiotherapy T. Chan 1 , P.W. Tan 1 , J.I.H. Tang 1 1 The National University Cancer Institute- Singapore NCIS, Radiation Oncology, Singapore, Singapore