Clinical outcomes after post-operative radiotherapy for breast cancer patients presenting with ipsilateral supraclavicular metastasis: considerations on the cranial border of irradiation field.

Abstract

Disease recurrence at lower neck adjacent to ipsilateral supraclavicular (SCV) region represents a concern in locally advanced breast cancer patients presenting with SCV metastasis at diagnosis. This study aims to report the outcomes following post-operative radical radiation therapy and discuss the reasonable cranial border of the irradiation field for N3c patients. Between July 2016 and January 2022, a total of 268 patients were eligible for analysis. The endpoints included in-field and out-field cervical failures, local-regional recurrence-free survival (LRRFS), SCV recurrence-free survival (SRFS), distant metastasis-free survival (DMFS), relapse-free survival (RFS), and overall survival (OS). During a median follow-up of 37months (range 3-89months), 17 patients (6.3%) developed local-regional recurrence as the first recurrence event, with 13 having concomitant distant-metastasis (DM); 56 patients (20.9%) had DM alone. The 3-year rates of LRRFS, SRF, DMFS, RFS, and OS were 92.3%, 94.5%, 74.5%, 73.0%, and 90.0%, respectively. 89.2% of patients received RT with the cranial border at the top of hyoid bone, and 95.1% of patients received a boost not exceeding the level of cricoid cartilage. A total of 11 patients (4.1%) developed ipsilateral SCV failure, and 3 patients (1.1%) experienced cervical failure, including 2 in-field failures and 1 out-field failure. Neoadjuvant systemic therapy (NST) was administered to 234 patients (87.3%). In the multivariate analysis, non-ypN0, triple-negative subtype and cT4 at diagnosis were predictors of worse SRFS and RFS in NST subgroup. Our findings suggest that radical RT with cranial border of irradiation field at the hyoid bone level lead to excellent local-regional control, and out-field cervical failure was rare. The irradiation field might not extend to mastoid process.