ESTRO 2024 - Abstract Book

S570

Clinical - Breast

ESTRO 2024

Pozuelo de Alarcon, Spain. 7 San Francisco de Asís Hospital, Radiation Oncology Department, Madrid, Spain. 8 La Milagrosa Hospital, Radiation Oncology Department, Madrid, Spain

Purpose/Objective:

The carcinogenic effect of tobacco is widely recognized, and data exists regarding its detrimental effects on tumor control, survival, quality of life, and the toxicity of cancer treatments (1,2). Radiotherapy plays a major role in the treatment of breast cancer (BC), and it has been observed that smoking may be associated with an increased risk of side effects such as reconstruction complications and skin reactions (3). Modern irradiation techniques such as IMRT or the use of hypofractionation have been shown to reduce radiation toxicity, but it is not entirely clear whether and to what degree smoking has a negative impact on these patients (4,5). The aim of this study is to identify the real-life effect of smoking on acute and chronic toxicity in a homogeneous cohort of patients treated with hypofractionated contemporary radiotherapy after breast-conserving surgery (BCS) for early breast cancer.

Material/Methods:

The research protocol of this descriptive, retrospective, longitudinal, observational study was approved by the local Research and Ethics Committee. Patients diagnosed with ductal carcinoma in situ (DCIS) and early invasive carcinomas were included. All patients underwent BCS, none had indication for elective nodal irradiation, and adjuvant whole-breast (WB) radiotherapy was performed with a Forward-Planned-IMRT (FP-IMRT) technique to a total dose of 40.05Gy in 15 sessions. WB-IMRT was completed with a single-dose high-dose-rate brachytherapy (HDR-BT) boost. The association between tobacco consumption and the prevalence of acute (radiodermatitis, bleeding, infection) and chronic (edema, pain, fibrosis) toxicity was assessed.

Results:

Between June 2009 and December 2017, 638 patients with a median age of 52 [29-81] years were treated. Of these, 328 (51.41%) were right breasts, 491 (77.1%) infiltrating ductal carcinomas and 96 (15.1%) DCIS. Related to the HDR BT boost, 578 (90.6%) patients received 8Gy. Table 1 shows the acute and chronic toxicity in our 638 patient-cohort with their respective 95% confidence intervals (95% CI). Smoking status was available for 566 (88.7%) patients, of whom 177 (31.3%) reported being smokers. Table 2 shows the comparison of smoking status with the existence or not of acute and chronic toxicity. The risk of fibrosis was 39% higher (Relative risk, RR: 1.393, 95% CI: 1.077 - 1.803), and the risk of pain was more than double (RR: 2.271, 95% CI: 1.094 - 4.715) in smokers compared to non-smokers. However, there were no differences in the risk of radiodermatitis, bleeding, infection, or edema. Median oncologic follow-up of patients was 6 years during which 13 local relapses (2.2%) and 14 second primaries in the same breast (2.4%) were identified. With a maximum follow-up of 11 years, survival free of any local or distant event was 85.5%, local relapse-free survival was 96.8% and overall survival was 95.7%.