Additional Option for Salvage After Breast Cancer Recurrence

Presenting author:
Isabelle Choi, MD

By J. Ben Wilkinson, MD, GenesisCare, Santa Maria, California

Whether treated initially with breast-conserving therapy or mastectomy, a local or regional relapse for women with non-metastatic breast cancer presents a unique challenge in the clinical management of the recurrent disease, as many patients have received full-dose adjuvant radiation therapy as part of their initial treatment course. Because of this, patients may only be offered local resection or salvage mastectomy alone with the assumption that additional radiation may not be safe or possible.

In the intact-breast setting, there are phase II data demonstrating that salvage reirradiation in the form of accelerated partial breast irradiation (APBI) can be considered based on the initial results of RTOG 1014. Many other institutional experiences have also been published lending support to reirradiation of the chest wall; however, recurrences within previously irradiated nodal regions lead many practitioners to be concerned about the effects of reirradiation to the brachial plexus. A potential solution for deeper reirradiation targets or for patients who are reluctant to undergo a second course of conventional radiation might be to consider proton beam therapy (PBT) due to its unique beam profile at depth in tissue.

Here in Chicago at ASTRO 2021, Isabelle Choi, MD, and her co-authors present the largest single-institution series of patients with breast cancer treated to date with salvage adjuvant reirradiation of both local and nodal targets using proton therapy. In their analysis, the investigators from Memorial Sloan Kettering Cancer Center, New York Proton Center (MSKCC/NYPC) and ProCure Proton Therapy Center in New Jersey carefully reviewed close to 50 consecutive patients treated with proton beam therapy and found that reirradiation using either uniform scanning or pencil beam scanning proton therapy resulted in excellent local control with minimal toxicity for most patients. Grade 3 dermatitis was observed in 30% of patients, while late grade 3 capsule contracture was seen in three patients (6.5%). Rib fracture was also seen in two patients, which has been reported in other series with high biologic doses and/or cumulative doses delivered near the chest wall.

Unique attributes of this series from MSKCC/NYPC and ProCure New Jersey include a high locoregional control rate (100%, median follow up 21 months) and no persistent skin ulceration, which has been reported in other reirradiation series. It is also notable that five patients (11% of series) had treatment to only the axillary lymph nodes, including four patients with overlapped treatment volume with previous irradiation of the brachial plexus, yet no patients have developed neuropathy at the time of this initial analysis.

According to Dr. Choi, “Reirradiation for recurrent or new primary breast cancer is an area of oncology that requires additional study to identify a safe and effective salvage treatment approach for a growing population of our patients who are experiencing increased longevity thanks to improvements in multimodality therapy. Our study demonstrates that reirradiation using proton therapy to curative doses is generally very well tolerated and can provide excellent locoregional disease control.”

This study highlights that radiation after local resection of recurrent breast cancer can offer important improvement in local control. Because of concerns of toxicities, many prior reports of reirradiation have employed relatively small retreatment volumes. This series importantly includes nodal targets within reirradiation fields without observed neurotoxicity. Longer follow-up and reports of potentially similar experience at other proton centers will be needed to help confirm the efficacy and safety of additional proton beam therapy to the list of modalities suitable for reirradiation of recurrent breast carcinoma.

Abstract 1029 - Proton Reirradiation for Recurrent or New Primary Breast Cancer in the Setting of Prior Breast Irradiation was presented on October 25, 2021, during the QP 05 - Breast session.

Published October 27, 2021

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