Radiotherapy Boost to Clinically Positive Internal Mammary Lymph Nodes: An Effective Non-Surgical Alternative?

Area of Science:

• Oncology
• Radiation Oncology
• Breast Cancer Treatment

Background:

• Internal mammary lymph node (IMLN) involvement is a critical prognostic factor in breast cancer.
• Optimizing radiation therapy (RT) boost strategies for IMLNs is essential for improving patient outcomes.
• Understanding the impact of different RT boost sequences and doses on oncologic control and toxicity is crucial.

Purpose of the Study:

• To evaluate the impact of radiation therapy (RT) boost sequences and doses to internal mammary (IM) lymph nodes (LNs) on oncologic outcomes.
• To assess the toxicity profiles associated with different RT boost strategies in clinically IMLN-positive breast cancer patients.
• To identify prognostic factors influencing outcomes in patients with IMLN-positive breast cancer receiving RT boost.

Main Methods:

• Retrospective evaluation of 26 patients with positive IMLNs treated between 2013 and 2022.
• RT delivered to the whole breast/chest wall, including axillary, supraclavicular, and IM lymphatics post-systemic therapy and surgery.
• Comparison of sequential vs. simultaneous integrated boost (SIB) for IMLN RT, analyzing outcomes and toxicity.

Main Results:

• High response rates (CR/PR) in metastatic IMLNs post-systemic therapy (84.6%).
• Excellent 5-year survival rates: OS 86.7%, DFS 76.4%, with low rates of recurrence/metastasis.
• Absence of extracapsular extension in axillary LNs correlated with improved OS/DFS; boost sequence did not significantly affect outcomes or toxicity.

Conclusions:

• RT boost to IMLNs without surgical resection yields excellent oncologic outcomes and acceptable toxicity.
• SIB technique, while reducing fractions, did not show superior oncologic results compared to sequential boost.
• Further prospective studies are warranted to define optimal RT boost sequencing for IMLNs.