Postmastectomy Radiation Therapy for Intermediate-Risk Breast Cancer Patients With 0-3 Positive Axillary Lymph Nodes:...

Area of Science:

• Oncology
• Radiotherapy Research
• Clinical Trial Emulation

Background:

• Intermediate-risk breast cancer requires careful consideration of adjuvant therapies.
• Postmastectomy radiation therapy (PMRT) is a standard treatment, but its benefit in specific risk groups is debated.
• The Selective Use of Postoperative Radiotherapy After Mastectomy (SUPREMO) trial provides a framework for evaluating PMRT.

Purpose of the Study:

• To emulate the SUPREMO trial using real-world data.
• To assess the impact of PMRT on overall survival (OS) in intermediate-risk breast cancer patients.
• To identify subgroups that may benefit from PMRT.

Main Methods:

• Utilized the National Cancer Database (2006-2013) for patient selection.
• Included women with intermediate-risk breast cancer matching SUPREMO criteria (pT1-2N1, pT3N0, or pT2N0 with grade III/LVI, 0-3 positive nodes).
• Employed multivariable logistic regression, Cox proportional hazards regression, and stabilized inverse probability of treatment weighting.

Main Results:

• 49,335 patients were analyzed; 13.9% received PMRT.
• PMRT was more common in patients with T3N0, 1-3 positive nodes, or positive margins.
• Overall, PMRT showed no significant OS improvement (HR 0.98, 95% CI 0.92-1.04).

Conclusions:

• PMRT did not confer a significant OS benefit for the overall intermediate-risk cohort.
• A notable survival advantage was observed in the T3N0 subgroup receiving PMRT (HR 0.72, 95% CI 0.58-0.89).
• Retrospective analysis suggests T3N0 patients may benefit from PMRT, aligning with preliminary SUPREMO findings.