ASTRO 2024: French Trial of Radiotherapy Plus T-DXd in HER2-Positive Breast Cancer

By: Vanessa A. Carter, BS
Posted: Wednesday, October 9, 2024

Kamel Debbi, MD, of Henri Mondor University Hospital and Faculté de Médecine de Créteil, Paris, and colleagues conducted the TENDANCE trial to evaluate the toxicity and efficacy of radiotherapy combined with the antibody-drug conjugate fam-trastuzumab deruxtecan-nxki (T-DXd) in patients with HER2-positive, metastatic breast cancer. Presented during the 2024 American Society for Radiation Oncology (ASTRO) Annual Meeting (Abstract 279), the results are reportedly the first to support this treatment combination in this patient population.

“These results suggest very limited and manageable grade 1 to 2 toxicity, with an optimal clinical benefit from a nondiscontinued T-DXd–radiotherapy combination,” the investigators concluded. “Our results are encouraging for practice but require confirmation with longer follow-up and by further prospective studies.”

This retrospective, multicenter study enrolled 54 patients from five French centers with HER2-positive or HER2-low metastatic breast cancer who were treated with both radiotherapy and T-DXd. Patient clinical data were obtained from medical records and patient questionnaires, and the local ethical committee validated the protocol. 

Approximately 72.2% of patients received radiation for palliative therapy, and 27.8% received it for curative intent. Just over half of patients received 3D conformal radiotherapy (57.4%), followed by stereotactic radiation therapy (37%) and intensity-modulated radiation therapy/volumetric-modulated arc therapy (5.6%). The median time between the last radiotherapy session and the next T-DXd treatment was 11 days; the median time between the first radiotherapy session and T-DXd initiation was 10 days; the median time between T-DXd initiation and radiotherapy initiation was 48 days.

Most patients achieved a partial response or stable disease (77.8%), whereas 22.2% experienced a complete response. After a median follow-up of 6 months, grade 1 to 2 toxicities attributable to radiotherapy were reported in 13% of patients. Of note, no toxicities greater than grade 3 were observed, and no therapy discontinuations were attributed to radiotherapy.

Disclosure: Dr. Debbi reported no conflicts of interest.

2024 ASTRO Annual Meeting

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