CLO20-031: Radiotherapy-Induced Malignancies in Breast Cancer Patients With Pathogenic Germline Variants TP53 in an R337H-Mutation Enriched Cohort

Purpose: The risk of radiotherapy-induced malignancies is an important concern when treating Li-Fraumeni patients. We aimed to evaluate the outcomes of Li-Fraumeni patients treated for localized breast cancer in a Brazilian cohort. Methods: We evaluated retrospectively a cohort of patients with pathogenic variants (PV) TP53 treated for localized breast cancer between Dec-1999 and Oct-2017. Our primary objective was to evaluate the occurrence of radiotherapy-induced malignancies among patients who received adjuvant radiotherapy for breast cancer treatment. Results: Sixteen patients with PV TP53 and localized breast cancer were evaluated. Thirteen patients had invasive ductal carcinoma. Three patients had ductal carcinoma in-situ. Only 3 patients had TP53 status known by the time of breast cancer treatment. Most patients (N=12, 75%) received adjuvant radiotherapy; two had radiotherapy-induced malignancies (2/12, 16.6%). Conclusion: In this cohort of Li-Fraumeni patients, the incidence of radiotherapy-induced malignancies after localized breast cancer treatment was lower than previous literature. Careful evaluation of risks and benefits is essential for the treatment decision-making process, especially for Li-Fraumeni patients. Importantly, physicians should be attentive to Li-Fraumeni diagnostic criteria and early molecular diagnosis is of utmost importance due to its impact in treatment decision.

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Corresponding Author: Vanessa Petry Helena Bragaia, MD