ESTRO 2021 Abstract Book

S918

ESTRO 2021

The median follow-up was 6.4 years (interquartile range, 3.0–10.3 years). BC cases who received only radiotherapy (cSMR = 0.93; 95%CI: 0.77–1.13), only chemotherapy (cSMR = 0.91; 0.62–1.33), and radio-and chemotherapy (cSMR = 1.04; 0.77–1.39) had no evidence of increased lung cancer mortality relative to the general population. The adjusted model identified that lung cancer mortality was higher for women who were older at diagnosis compared to those <50 years (ranging from HR50-59 = 3.41 [95%CI: 2.72–4.28] to HR70- 79 = 10.53 [95%CI: 8.44–13.13]) and for cases with negative estrogen and progesterone receptors (HR =1.38; 95% CI: 1.21–1.57). Compared to married cases, widowed, divorced, single or others had a 76%, 45%, and 25% higher hazard of lung cancer mortality, respectively. Lung cancer mortality was lower for American Indian/Alaska Native and Asian/Pacific Islander ethnicities (HR = 0.51; 95% CI: 0.40–0.64) compared to BC cases with white ethnic background. Conclusion There is no evidence for a higher lung cancer mortality in BC patients when compared to the general population. PO-1104 Once-weekly Hypofractionated Adjuvant Radiotherapy for Early Stage Breast Cancer M. Salem 1 , S. Lasheen 1 , A. S. Aly 1 , H. Attia 1 1 NEMROCK Center- Kaser Al-AINI- Faculty of Medicine- Cairo University, Department of clinical oncology, Cairo, Egypt Purpose or Objective The safety and efficacy of single weekly hypofractionated adjuvant radiotherapy for early node-negative breast cancer was proven by the UK-FAST trial, favouring the 28.5 Gy arm in terms of toxicity and cosmesis. This protocol can potentially improve patients` convenience and compliance, in addition to reducing the workload in high-volume centres. The aim of this study is to assess the feasibility of this single weekly hypofractionated protocol in breast cancer patients who underwent breast conservative surgery (BCS) regardless of their lymph node (LN) status. Materials and Methods In this prospective phase II study, breast cancer patients indicated for post-operative radiotherapy following BCS, regardless of their LN status, were recruited to receive a single weekly hypofractionated whole breast irradiation (WBI) schedule of 28.5 Gy in 5 fractions over 5 weeks (5.7 Gy per fraction). Target volume delineation was done in accordance with ESTRO guidelines while dosimetric constraints were set using the ICRU-62 and 83 parameters. Follow-up of acute toxicity was done using the RTOG graded scale, late toxicity using the RTOG/EORTC Late Radiation Morbidity Scoring Scheme and cosmetic outcome using the Harvard cosmetic score. Patients` quality of life (QoL) was assessed using the FACT-B QoL questionnaire and their treatment satisfaction was scored using the FACIT-PS-TS QoL questionnaire. Results Thirty-one consecutive patients were recruited from March 2018 to February 2020. The median duration of follow-up was 18 months (range 12-32 months). The patients’ median age was 55 years (range 35-70 years), the mean tumour size was 2.1 cm (range 1-4.5 cm) and most of our patients (93.5%) had node negative disease. Following radiotherapy, no G4 acute skin toxicity was reported, while 42%, 52%, and 6% of patients developed G≤1, G2, and G3 toxicity, respectively. With regard to late skin toxicity, 82% of patients had G1, 18% had G0, and no patients experienced G2,3, or-4 toxicity (table 1). Notably, none of our patients developed lung or heart toxicity. In terms of cosmesis, 22% of patients had excellent cosmetic score, 56% had- good score, while 22% had fair score and none had poor cosmetic outcome. The QoL assessment revealed no deterioration in breast cancer well-being (FACIT-B QoL) and patients’ level of satisfaction with treatment (PS- TS QoL) remained consistent during follow-up (figure 1). There were no instances of local and/or distant relapse reported.