In a groundbreaking study, the SUPREMO trial explored the necessity of chest wall irradiation for women with intermediate-risk breast cancer following mastectomy. Conducted with 1,607 participants, the trial aimed to determine whether postmastectomy radiation could be safely omitted without compromising survival rates. The results showed no significant difference in disease-free, metastasis-free, or overall survival after 10 years between those who received irradiation and those who did not.
The trial recorded a 10-year overall survival rate of 81.4% for patients undergoing irradiation, compared to 82% for those who skipped the treatment. While chest wall irradiation reduced locoregional recurrences—20 cases without radiation versus 9 with radiation (hazard ratio, 0.45)—the recurrence-free survival probabilities were remarkably similar: 98.8% for those with radiation and 97.1% for those without at median follow-up.
The SUPREMO trial utilized contemporary systemic therapies such as taxanes, trastuzumab, anthracyclines, and endocrine therapy. The trial defined intermediate-risk tumors as those no larger than 50 mm with one to three positive axillary lymph nodes, tumors over 50 mm with no positive nodes, or node-negative tumors measuring 20 mm to 50 mm (T2) with grade 3 histology and/or lymphovascular invasion. Notably, 12% of participants had three positive nodes.
Ian Kunkler, MBBS, the trial's lead investigator and a clinical breast oncologist at The University of Edinburgh, emphasized the significance of these findings. However, he cautioned that ongoing subgroup analyses might reveal unknown variables affecting women not well represented in the trial.
“for shared decision-making conversations between patients and clinicians, as many patients eligible for post mastectomy chest wall irradiation may not require the treatment” – Ian Kunkler, MBBS
Kunkler also noted that these findings could lead to reconsideration of current treatment guidelines, which were influenced by earlier trials from the 1990s showing a survival benefit of chest wall irradiation for intermediate-risk breast cancer patients.
The trial received funding from the UK Medical Research Council, the European Organisation for Research and Treatment of Cancer, among others. Additionally, study discussant Elinor Sawyer, MBBS, PhD, disclosed funding from Pfizer, Seagen, and IQIVIA. Sawyer mirrored Kunkler's caution regarding generalizing these outcomes to all patients with one to three positive nodes.
“But I don’t think this can be generalized to all patients with one to three positive nodes, especially as only 12% of the patients in the trial had three positive nodes.” – Elinor Sawyer, MBBS, PhD
While the SUPREMO trial suggests a shift in treatment approach might be warranted, thorough review and validation by guideline groups will precede any official changes. Kunkler remarked that these findings could significantly influence future clinical decisions.
“adjuvant chest wall irradiation should be omitted in most patients meeting the eligibility of the SUPREOMO trial” – Ian Kunkler, MBBS
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