2971 - Survival Determinants and Toxicity of Second-Course Radiotherapy for Isolated Nodal Recurrencein Breast Cancer

03:00pm - 04:00pm PT

Hall F

Screen: 10

Presenter(s)

Pierre Loap, MD - Institut Curie, Paris, Ile de France

C. Cheptea¹, Y. M. Kirova², J. Baude³, F. Laki², A. Fourquet², and P. Loap¹; ¹Department of Radiation Oncology-Institut Curie, Paris, France, ²Institut Curie, Paris, France, ³Centre Georges-François Leclerc, Dijon, France

Purpose/Objective(s):

Isolated nodal recurrence (INR) after localized breast cancer are rare, with an incidence of less than 1%. Curative management typically includes surgical resection, often with axillary lymph node dissection (ALND), followed by regional nodal radiotherapy. However, evidence-based guidelines remain limited due to the rarity of this clinical scenario. The aim of this study was to evaluate the survival determinants and the acute and long-term toxicities associated with second-course regional nodal irradiation as part of curative strategies for INR after localized breast cancer.

Materials/Methods:

This retrospective study included 11 patients with localized breast cancer who developed ipsilateral, non-metastatic INR between 2003 and 2019. All patients were treated with curative intent, including regional nodal irradiation. Overall survival (OS), cancer-specific survival (CSS), metastasis-free survival (MFS), local control, and treatment toxicities were analyzed. Survival probabilities were calculated using the Kaplan-Meier method, and Cox regression was used to assess prognostic factors.

Results:

With a median follow-up of 90 months (range: 11–219 months) after INR diagnosis, 1 patient (9.1%) experienced local recurrence (at 87 months), 1 (9.1%) had regional recurrence (at 16 months), and 5 (45.5%) developed distant metastases (at 5, 9, 23, 59, and 69 months). 4 patients (36.4%) died, all from breast cancer (at 11, 15, 32, and 150 months). At 5 years, the locoregional recurrence-free survival (LRFS) was 100%, the locoregional recurrence-free survival (LRRFS) was 88.9% (95% CI: 70.6–100), the metastasis-free survival (MFS) was 62.3% (95% CI: 38.9–99.9), and both the overall survival (OS) and cancer-specific survival (CSS) were 71.6% (95% CI: 48.8–100).

Negative prognostic factors for OS and CSS included TNBC status (p=0.04) and absence of IMC irradiation during regional radiotherapy (p<0.01). Absence of IMC irradiation was also significantly associated with reduced MFS (p<0.01), while TNBC status showed a trend towards poorer MFS (p=0.06). At 18 months, OS, CSS, and MFS were all 50% (95% CI: 18.8–100) without IMC irradiation, compared to 100% with IMC irradiation.

Acute grade 2 toxicities included radiodermatitis (36.4%), and late grade 2 toxicities were limited to fibrosis (18.2%). No cardiac, pulmonary, or grade 3 or higher toxicities were reported.

Conclusion:

This study highlights the favorable survival outcomes and safety profile of contemporary curative strategies for INRs following localized breast cancer, with a 5-year OS rate exceeding historical benchmarks. Internal mammary chain irradiation appears to improve survival without increased toxicity. However, the poor prognosis associated with TNBC INR underscores the need for effective systemic therapies. Prospective multicenter trials are essential to validate these findings and optimize treatment protocols.