ESTRO 2021 Abstract Book

S919

ESTRO 2021

Conclusion Single weekly hypofractionated WBI protocol for early breast cancer, regardless of LN status, shows favourable acute skin toxicity, cosmetic outcome and QoL. Longer follow-up is warranted for better evaluation of late toxicity, cosmetic, and clinical outcomes. PO-1105 hypofractionated adjuvant radiotherapy in locally advanced breast cancer A. Aly 1 , S. Lasheen 1 , H. Attia 2 , E. Khalaf 3 1 Cairo University, Oncology Department, Cairo, Egypt; 2 Cairo University, Oncology, Cairo, Egypt; 3 Naser Institute, Oncology Departmemt, Cairo, Egypt Purpose or Objective Conventionally fractionated radiation therapy over 5 weeks for postoperative radiotherapy (RT) in patients with locally advanced breast cancer is the standard of care. This prospective study assesses the feasibility of using an accelerated RT course in an attempt to improve patients’ compliance as well as well as reduce waiting lists and machine load in institutions with high patients flow. Materials and Methods Patients with locally advanced (≥T3, N+, M0) breast cancer who underwent breast conservative surgery (BCS) or modified radical mastectomy (MRM) were recruited to receive adjuvant hypofractionated radiotherapy (HypoRT) at a dose of 40Gy in 15 fractions over 3 weeks. Target volumes included the breast or chest wall (CW), para-clavicular lymph nodes (PCLN), with or without the inclusion of the internal mammary chain (IMC) or axillary lymph node (LN) groups I and II. Delineation was done in accordance with ESTRO guidelines and dosimetric constraints were set using the ICRU-62 and 83 parameters. Follow-up at the end of RT and 6 months thereafter was done for the assessment of acute toxicity, using the RTOG graded scale, and the cosmetic outcome, according to the Harvard cosmetic score. Results Between January 2018 and September 2019, a total of 73 consecutive women were enrolled, with a median age of 51 years (range 40-62 years). Forty-eight percent of patients were postmenopausal, 45% underwent MRM and 54% had left-sided tumors. The most common biological subtype was luminal (62%), the most common T-stage was T2 (44%), and the most common N-stage was N2 (52%). Of note, 96% of patients had node-positive disease at presentation. All patients received HypoRT to breast or CW and PCLN, of whom 51% received RT to axillary LN, and 26% had IMC irradiation. The dosimetric parameters for target volume coverage and risk structures constraints were in compliance with our departmental guidelines. With regards to acute skin toxicity, 71% experienced G1 and 19% had G2 toxicity at the end of RT. At 6 months, 66% had G1 and 10% had G2 skin toxicity, with no higher grades observed. At the end of RT, 41%, 41%, and 18% of patients had good, fair, and poor cosmetic scores, respectively. By 6 months post-RT, 4%, 48%, 33%, and 15% had excellent, good, fair, and poor cosmetic scores, respectively. The 6-month disease-free survival was 88%; two patients developed bone metastasis, one had lung spread, another developed malignant pleural effusion, and one suffered from local chest wall recurrence.