ESTRO 2024 - Abstract Book

S678

Clinical - Breast

ESTRO 2024

1 Fondazione Policlinico Universitario Campus Bio-Medico, Radiation Oncology, Rome, Italy. 2 Università Campus Bio Medico di Roma, Radiation Oncology, Rome, Italy. 3 Università Campus Bio-Medico di Roma, Medical Oncology, Rome, Italy. 4 Fondazione Policlinico Universitario Campus Bio-Medico, Medical Oncology, Rome, Italy

Purpose/Objective:

Antibody drug conjugates (ADCs) are novel drugs that combine monoclonal antibodies with cytotoxic agent, enabling the selective delivery to cancer cells expressing specific antigens. ADCs were introduced in order to overcome resistance to chemotherapy and enhance drug delivery. Trastuzumab Deruxtecan (T-DXd) and Sacituzumab Govitecan (SG) are among the last ADCs approved in clinical practice for HER2+ and triple negative (TN) metastatic breast cancer patients, respectively. There is little evidence regarding the safety and efficacy of the combination of radiotherapy (RT) with these two drugs. The aim of study is to evaluate the early toxicity of concurrent use of RT with T-Dxd and Sacituzumab Govitecan in metastatic breast cancer (BC) patients.

Material/Methods:

Patients with stage IV breast cancer undergoing a systemic treatment with T-DXd and SG, who were candidates for a radiation treatment (both palliative or curative), after being informed about the study and giving written informed consent, were enrolled in this observational study. Toxicity was assessed according to the NCI-CTCAE V5.0.

Results:

From May 2023 to October 2023 a total of 23 patients treated with ADCs were enrolled in this observational study. A total of 53 radiotherapy treatments were delivered concurrently with ADCs (32 with T-DXd and 21 with SG). ADCs were delivered within 1 week or concurrently with RT. Median age was 58 years (range 33-81). Treatment description according to concomitant ADC is summarized in table 1.

No patient suspended RT. Any type all grades toxicity occurred in 11 patients (47.8%). Grade >2 toxicity was observed in 2 patients (8.7%). No grade 3 toxicity was recorded. Overall haematological toxicity was 13.3%. In T-DXd cohort one patient treated to a large femur metastasis developed grade 2 neutropenia. Also in SG cohort a patient developed a grade 2 brain radionecrosis. This patient received multiple brain SRT treatments. Toxicity details according to the type of ADCs are described in Table 2.