Proton Reirradiation for High-Risk Recurrent or New Primary Breast Cancer

Abstract

Radiotherapy is an integral component of multidisciplinary breast cancer care. Given how commonly radiotherapy is used in the treatment of breast cancer, many patients with recurrences have received previous radiotherapy. Patients with new primary breast cancer may also have received previous radiotherapy to the thoracic region. Curative doses and comprehensive field photon reirradiation (reRT) have often been avoided in these patients due to concerns for severe toxicities to organs-at-risk (OARs), such as the heart, lungs, brachial plexus, and soft tissue. However, many patients may benefit from definitive-intent reRT, such as patients with high-risk disease features such as lymph node involvement and dermal/epidermal invasion. Proton therapy is a potentially advantageous treatment option for delivery of reRT due to its lack of exit dose and greater conformality that allow for enhanced non-target tissue sparing of previously irradiated tissues. In this review, we discuss the clinical applications of proton therapy for patients with breast cancer requiring reRT, the currently available literature and how it compares to historical photon reRT outcomes, treatment planning considerations, and questions in this area warranting further study. Given the dosimetric advantages of protons and the data reported to date, proton therapy is a promising option for patients who would benefit from the added locoregional disease control provided by reRT for recurrent or new primary breast cancer.

FLASH proton reirradiation, with or without hypofractionation, mitigates chronic toxicity in the normal murine intestine, skin, and bone

“…Reirradiation with FLASH PRT after an initial scheme of Standard PRT is shown to mitigate RTinduced dermatitis, fibrosis, lymphedema, and bone damage. These acute and late toxicities are observed in the clinical setting after proton reirradiation, including in the treatment of sarcomas 27 , abdominal tumors 19,[28][29][30] , head and neck tumors 15,31 , esophageal cancer 17 , breast cancer 4,32 , and lung cancer 14,33,34 .…”

“…Reirradiation presents a major challenge to the radiation oncologist, as it is well documented that high cumulative doses are associated with early and late severe morbidities 1,[3][4][5] . Reirradiation could be considered in the case of a local recurrence or for a new primary cancer that arises in a previously irradiated field.…”