ESTRO 38 Abstract book

S704 ESTRO 38

elderly breast cancer (BC) patients (pts) treated with hypofractionated radiotherapy (Hypo-RT). Material and Methods From June 2009 to December 2017, 734 ER-positive BC pts (stage pT1-T2, pNx-1, M0 and age over 65 years) receiving Hypo-RT and followed until September 2018, were analyzed. Hypo-RT consisted of 42.4 Gy in 16 daily fractions (2.65 Gy per fraction), while a sequential boost was administered in cases of grade 3 tumor and close or positive margins. Baseline comorbidities included in the hypertension-augmented Charlson Comorbidity Index (hCCI) were retrospectively retrieved. Baseline pts and tumour characteristics were analyzed in relation to HT status (never/discontinued, ongoing) at last contact by chi-2 test. Five-year disease-free survival (DFS) and overall survival (OS) were estimated by Kaplan-Meier method. The log-rank test was used to compare groups. Adjusted hazard ratios (HRs) were estimated by Cox proportional hazards models. In survival analysis, HT use was treated as time-dependent variable. A subgroup analysis was performed on pts aged ≥70 with a pT1 luminal A BC. Results The comorbidity was present in about 70% of pts (median age: 74 years).HT has been prescribed in 653 (88.9%) out 734 analyzed pts. Most of them assumed the prescribed HT and 51 pts (7.8%) discontinued the treatment. Current HT use was less frequent for pts aged ≥80 (p<0.001) and pts with high comorbidity burden (hCCI≥2) (p=0.001). At the time of the analysis, 673 (91.7%) pts were still alive and 33 pts (4.5%) experienced a disease progression (local or nodal recurrences and metastases). At a median follow-up 46.8 months (range 4-115 months), the overall 5-year DFS was 86.8% (95% CI 83.2-89.6%) varying between 89.5% for current HT use and 76.6% for no/discontinued HT use (log- rank p<0.001). The prognostic effect of HT was confirmed for pts aged≥70 with a pT1 luminal A BC: 5-year DFS were 91.3% and 79% for ongoing HT user and no/discontinued HT user, respectively (log-rank p<0.018). The hazard of disease progression was significantly increased for pts with hCCI≥2 and with tumour size ≥1 cm and strongly decreased for currently ongoing HT users. HT did not impact on OS neither in the whole group nor in pts pT1 luminal A ≥70 years. Conclusion This study shows that disease progression was strongly increased for pts with hCCI≥2 and tumor size>1 cm and decreased for HT users. In elderly pts, HT assumption did not showed a benefit in terms of survival. Further studies with tailored treatment approaches (RT alone versus RT+HT versus HT alone) are needed on elderly women with BC. EP-1285 Hypofractionated irradiation in elderly breast cancer patients: an observational study E. La Rocca 1,2 , M. Dispinzieri 1,2 , E. Meneghini 3 , A. Fiorentino 4 , F. Bonfantini 5 , S. Di Cosimo 6 , M. Gennaro 7 , V. Cosentino 5 , M. Sant 3 , E. Pignoli 5 , R. Valdagni 1,8 , L. Lozza 2 , M.C. De Santis 2 1 University of Milan, Department of Oncology and Hemato-Oncology, Milan, Italy ; 2 Fondazione IRCCS Istituto Nazionale dei Tumori, Radiotherapy Unit 1, Milan, Italy ; 3 Fondazione IRCCS Istituto Nazionale dei Tumori, Analytical Epidemiology and Health Impact Unit, Milan, Italy ; 4 Regional General Hospital “F Miulli”, Radiation Oncology Department, Acquaviva delle Fonti Ba, Italy ; 5 Fondazione IRCCS Istituto Nazionale dei Tumori, Medical Physics Unit, Milan, Italy ; 6 Fondazione IRCCS Istituto Nazionale dei Tumori, Department of Applied Research and Technological Development DRAST, Milan, Italy ; 7 Fondazione IRCCS Istituto Nazionale dei Tumori, Breast Surgery Unit, Milan, Italy ; 8 Fondazione IRCCS Istituto Nazionale dei Tumori, Director- Radiation Oncology 1 and Prostate Cancer Program, Milan, Italy

Purpose or Objective To assess efficacy, acute and late toxicity of hypofractionated radiotherapy (Hypo-RT) and impact of age and comorbidities in elderly breast cancer (BC) patients (pts). Material and Methods From June 2009 to December 2017 we analyzed 808 pts receiving 42.4 Gy in 16 daily fractions (2.65 Gy per fraction). A boost was only administered in cases of grade 3 primary tumor and close or positive margins. Acute and late toxicity was prospectively assessed during and after hypo-RT, based on the RTOG scale. Baseline comorbidities included in the hypertension-augmented Charlson Comorbidity Index (hCCI) were retrospectively retrieved. Five-year disease-free survival (DFS) and overall survival (OS) were assessed by Kaplan-Meier method and log-rank test was used to compare groups of age and comorbidity. Hazard ratios (HRs) were estimated by Cox proportional hazards models adjusting for tumor size, lymph node status, molecular subtype, grading, chemotherapy. Odds ratios (ORs) and 95% confidence intervals (CIs) of acute and late toxicity by of age, comorbidity and boost administration were estimated by ordinal or multinomial logistic models. Results The median age was 74 years (range 65-91 years), and 76.1% of the pts were over 70 years old. The median follow-up was 46.8 months (range 4-115 months). At baseline, 70.4% of pts were affected by at least one comorbidity. Invasive ductal carcinoma was the most common histological type (81.2%), and the most common subtype was luminal A (46.5%). 21.5% of pts underwent chemotherapy with anthracycline and taxane. Hormonotherapy has been prescribed in 657 (81.4%) pts. At the latest follow-up date, 730 (90.4%) pts were still alive, 47 (5.8%) experienced disease progression (local or nodal recurrences, contralateral BC, metastases), 18 died of BC and 60 died of other causes. Older age and baseline comorbidity burden were associated with worst prognosis. Five-year DFS was 92.6, 87.2, 83.5 and 71.3% for 65-69, 70-74, 75-79 and ≥80 years, respectively (log-rank p<0.001). Five-year OS for increasing age-class was 94.7, 93.0, 86.7 and 80.9% (log- rank p=0.002). Five-year DFS and OS were 91.9% and 94.3% for pts without comorbidity and 74.3% and 84.5% for pts with high comorbidity burden (hCCI≥2) (DFS log-rank p<0.001, OS log-rank p=0.017). Elderly pts had significantly higher odds of increasing score in acute asthenia. Pts with hCCI≥2 had significantly increased odds of late edema and late fibrosis. Boost administration was significantly related to increasing score of acute skin toxicity and late fibrosis and edema. Conclusion Hypo-RT in elderly BC pts aged ≥65 years is effective and well-tolerated. This study also shows that age and comorbidities negatively impact DFS and OS. Further studies focusing on a better selection of elderly BC pts based on genomic and biological features and with tailored treatment approaches are warranted. EP-1286 StrataXRT is non inferior to Mepitel Film in preventing radiation induced moist desquamation M.W.T. Chao 1 , S. Spencer 1 , C. Kai 1 , C. Baker 2 , S. Jassal 3 , M. Law 4 , M. Cheng 4 , N. Zantuck 4 , V. Yu 4 , D. Stoney 4 , S.W. Loh 3 , E. Bevington 3 , G. Chew 3 , A. Hyett 3 , M. Guerrieri 1 , H. Ho 1 , M. Ng 1 , J. Wasiak 5 , F. Foroudi 5 1 Ringwood Radiation Oncology Centre, Department of Radiotherapy, Ringwood, Australia ; 2 St Vincents Hospital, Surgical Oncology, Melbourne, Australia ; 3 Austin Hospital, Surgical Oncology, Melbourne, Australia ; 4 Maroondah Hospital, Surgical Oncology, Melbourne, Australia ; 5 Austin Hospital, Department of Radiation Oncology, Melbourne, Australia