Abstract. Liver metastasis from breast cancer (LMBC) is an incurable, fatal disease with a very poor prognosis. Although various local treatments have been applied, their clinical utility has not been established. The purpose of this study was to investigate the safety and effectiveness of proton beam therapy (PBT) for the treatment of patients with LMGC. A total of 8 female patients (aged 38-63 years) with LMBC who received PBT between 2002 and 2012 were retrospectively reviewed. Patients who had tumors confined to the liver were investigated, whereas patients with extrahepatic tumors were excluded. A total of 5 patients had solitary tumors and 3 had multiple tumors. The total irradiation dose was 66-72.6 Gray equivalent [Gy relative biological effectiveness (RBE)] and 2 patients received concurrent chemotherapy or hormone therapy. The overall and progression-free survival (OS and PFS) rates, local control (LC) rate and adverse effects were investigated. All the patients completed treatment without interruption and late adverse effects of grade >3 were not observed. The OS rate was 88/73/58%, the PFS rate was 50/25/0% and the LC rate was 86/86/86% at 1/3/5 years, respectively. Thus, PBT is a safe treatment and the OS and PFS rates are comparable to those with other local treatments. PBT may be considered as an effective local treatment option for the treatment of LMBC patients.
IntroductionApproximately 50% of breast cancer patients will develop distant metastasis (1,2), which is a major cause of cancer-related mortality among women (3). In most series, isolated liver metastases are found in 5-25% of the cases (1,2,4-6). As the majority of LMBC patients may have systemic disease, only a limited number of patients are candidates for local treatment.Although systemic chemotherapy regimens with new molecular-targeted agents have been developed, LMBC is an incurable, fatal disease, with a median survival of 3-15 months (5,7,8) and the management of liver metastases remains challenging. Thus, the treatment of patients with LMBC is considered as palliative. To improve the treatment outcome, various local treatments, such as surgery and transcatheter arterial chemoembolization (TACE) have been applied, in combination with chemotherapy or performed alternatively. However, the clinical utility of local treatment has not been established in LMBC; by contrast, surgery is widely considered to be a useful treatment option in liver metastasis from colorectal cancer (9).Proton beam therapy (PBT) is characterized by precisely delivering a high dose of radiation to the target, while significantly limiting the exposure of regions beyond the target. It is well known that PBT for primary liver cancer achieves excellent local control rates with few adverse effects (10-14). The preliminary outcome of 5 LMBC cases who received PBT during a maximum follow-up period of 8 years in 2012 was previously reported (15). The cases were further followed up and new patients with LMBC who were treated using PBT were included in order to investig...