OPTimizing Irradiation through Molecular Assessment of Lymph node (OPTIMAL): a randomized open label trial

Area of Science:

• Oncology
• Radiation Oncology
• Surgical Oncology

Background:

• Standard treatment for early breast cancer (BC) with ≥4 positive lymph nodes involves surgery and irradiation.
• Treatment strategies for BC with fewer positive lymph nodes, especially without lymphadenectomy, are not well-defined.
• The One-Step Nucleic Acid Amplification (OSNA) assay offers sensitive molecular assessment of lymph node metastasis.

Purpose of the Study:

• To assess the feasibility of incidental axillary node irradiation in early-stage BC patients with limited sentinel lymph node (SLN) metastasis.
• To demonstrate non-inferiority of incidental irradiation compared to intentional irradiation regarding 5-year disease-free survival.
• To standardize treatment for BC patients with limited nodal involvement using OSNA-guided strategies.

Main Methods:

• Randomized trial of early BC patients with SLN tumor load (OSNA assay) between 250-15,000 copies/µL.
• Intentional arm: irradiation of breast, tumor bed, axillary, and supraclavicular nodes.
• Incidental arm: irradiation of breast and tumor bed only; all nodal areas contoured for dose assessment.

Main Results:

• Primary endpoint: Non-inferiority of 5-year disease-free survival between incidental and intentional axillary node irradiation.
• Secondary endpoints: Comparison of acute/chronic toxicity and loco-regional/distant recurrence rates.
• Dose received in all contoured volumes (including internal mammary chain) will be calculated.

Conclusions:

• Standardization of BC treatment for patients with limited nodal metastasis is crucial due to current lack of consensus.
• OSNA assay's quantitative metastatic burden score aids in identifying BC patients who may benefit from incidental radiation.
• This study aims to define a more precise adjuvant treatment strategy for early-stage BC.