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Session Item

Monday
May 24
08:00 - 18:00
Mining the radiotherapy dose: exploring dose-response patterns in radiation therapy (no online session)
Choice of workshop
Safety of concurrent TDM-1 and radiotherapy for patients with residual HER2-positive breast cancer
Carlotta Becherini, Italy
PO-1096

Abstract

Safety of concurrent TDM-1 and radiotherapy for patients with residual HER2-positive breast cancer
Authors:

Carlotta Becherini1, Giulia Stocchi1, Luca Visani1, Maria Carmen De Santis2, Riccardo Ray Colciago2, Sara Pedretti3, Stefano Maria Magrini3, Marianna Nuzzo4, Domenico Genovesi4, Lucia Anna Ursini4, Alessio Bonanni5, Edy Ippolito6, Sara Ramella6, Filippo De Renzi7, Antonella Fontana8, Pasquale Vitucci9, Lucia Angelini1, Carolina Orsatti1, Isacco Desideri1, Vieri Scotti1, Lorenzo Orzalesi10, Marco Bernini10, Luis Sanchez10, Jacopo Nori11, Simonetta Bianchi12, Icro Meattini1, Lorenzo Livi1

1University of Florence, Department of Experimental and Clinical Biomedical Sciences, Florence, Italy; 2Istituto Nazionale dei Tumori, Radiation Oncology Unit, Milan, Italy; 3Spedali Civili di Brescia, Radiotherapy Unit, Brescia, Italy; 4SS. Annunziata Hospital, Radiotherapy Unit, Chieti, Italy; 5Fatebenefratelli Hospital, Radiotherapy Unit, Rome, Italy; 6Campus-Biomedico University, Radiation Oncology Unit, Rome, Italy; 7San Martino Hospital, Radiotherapy Unit, Belluno, Italy; 8Santa Maria Goretti Hospital, Radiotherapy Unit, Latina, Italy; 9Pugliese Ciaccio Hospital, Radiotherapy Unit, Catanzaro, Italy; 10Azienda Ospedaliero-Universitaria Careggi, Breast Surgery Unit, Florence, Italy; 11Azienda Ospedaliero-Universitaria Careggi, Diagnostic Senology Unit, Florence, Italy; 12Azienda Ospedaliero-Universitaria Careggi, Pathology Unit, Florence, Italy

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Purpose or Objective

Patients with HER2-positive early breast cancer with residual invasive disease after primary systemic therapy (PST) have a higher risk of recurrence and death than those achieving pathologic complete response (pCR). In the phase III KATHERINE study, adjuvant Trastuzumab Emtansine (TDM-1) reduced the risk of recurrence or death by 50% compared with trastuzumab prosecution in this population. A recently presented subgroup analysis by Loibl et al showed an increase in grade ≥3 adverse events in the TDM-1 arm in patients treated with adjuvant radiotherapy as compared to patients not receiving radiotherapy (27.4% vs 16.4%) or patients treated with trastuzumab with or without radiotherapy (15.6% vs 14.6%). Our aim was to evaluate the acute side effects of TDM-1 administered concurrently with adjuvant radiotherapy in a real life multicentric register.

Material and Methods

We retrospectively evaluated data of patients treated between January 2019 and December 2020 with concurrent TDM-1 and radiotherapy in adjuvant setting. Left ventricular ejection fraction (LVEF) was assessed at baseline, before and after radiotherapy. All toxicities were evaluated and scored using Common Terminology Criteria of Adverse Events (CTCAE) version 5.0.

Results

A total of 25 women treated in 7 Italian institutions were included in the analysis. Baseline patients’ characteristics are summarized in Table 1. In the acute setting, G1-2 dermatitis was recorded in 20 patients (80%), with no G3 events described. Breast pain was reported in 3 cases (12%). Blood tests showed 3 cases of G1 leucopenia (12%) and 1 case of G1 anemia (4%); 6 patients had thrombocytopenia (24%), with 3 cases (12%) of ≥G2 toxicity. Nine cases (36%) of elevation of liver transaminases were reported, with 1 G2 (4%) and 1 G3 (4%) toxicities. Treatment with TDM-1 was interrupted in 4 patients (16%) due to the onset of thrombocytopenia or elevation of liver transaminases. Left ventricular ejection fraction (LVEF) remains stable between TDM-1 start and the end of RT with an average reduction of 0.79 point% (SD + 3.9), only 1 patient registered an asymptomatic LVEF reduction >10%.



Conclusion

The acute toxicity rate, especially focusing on skin and cardiac adverse events, were assumed acceptable in our cohort. To safely administer this concomitant treatment. Further evidence coming from larger series and prospective experiences are needed.