Internal mammary node irradiation fails to improve survival in women with node-positive breast cancer: JAMA
Korea: Findings from a phase III trial showed no difference in 7-year disease-free survival (DFS) between the internal mammary node irradiation (IMNI) and no IMNI groups in women with node-positive breast cancer. However, findings of an unprespecified subgroup analysis suggest that patients with medially or centrally located tumors may benefit from IMNI use.
The study was published in the journal JAMA Oncology on October 25, 2021.
Internal mammary node irradiation has been a subject of controversy since radiotherapy to the chest wall or breast and regional lymph nodes was shown to improve survival in patients with early-stage breast cancer. Yong Bae Kim, Yonsei University College of Medicine, Seoul, Korea, and colleagues, therefore, aimed to investigate whether the inclusion of IMNI in regional nodal irradiation improves disease-free survival in women with node-positive breast cancer.
For this purpose, the researchers conducted a multicenter, phase 3 randomized clinical trial from June 1, 2008, to February 29, 2020, at 13 hospitals in South Korea. It included women with pathologically confirmed, node-positive breast cancer after breast-conservation surgery or mastectomy with axillary lymph node dissection. Patients with distant metastasis and those who had received neoadjuvant treatment were excluded.
All patients underwent regional nodal irradiation along with breast or chest wall irradiation. They were randomized in the ratio of 1:1 to receive radiotherapy either with IMNI or without IMNI. The primary endpoint was the 7-year DFS.
A total of 735 women (mean age, 49.0 years) were included in the analyses, of whom 373 received regional nodal irradiation without IMNI and 362 received regional nodal irradiation with IMNI. Nearly all patients underwent taxane-based adjuvant systemic treatment. The median follow-up was 100.4 months.
Based on the study, the researchers found the following:
- The 7-year DFS rates did not significantly differ between the groups treated without IMNI and with IMNI (81.9% vs 85.3%; hazard ratio [HR], 0.80).
- However, an ad hoc subgroup analysis showed significantly higher DFS rates with IMNI among patients with mediocentrally located tumors.
- In this subgroup, the 7-year DFS rates were 81.6% without IMNI vs 91.8% with IMNI (HR, 0.42), and the 7-year breast cancer mortality rates were 10.2% without IMNI vs 4.9% with IMNI (HR, 0.41).
- No differences were found between the 2 groups in the incidence of adverse effects, including cardiac toxic effects and radiation pneumonitis.
"This randomized clinical trial found that including IMNI in regional nodal irradiation did not significantly improve the DFS in patients with node-positive breast cancer," wrote the authors. "However, patients with medially or centrally located tumors may benefit from the use of IMNI."
Reference:
Kim YB, Byun HK, Kim DY, et al. Effect of Elective Internal Mammary Node Irradiation on Disease-Free Survival in Women With Node-Positive Breast Cancer: A Randomized Phase 3 Clinical Trial. JAMA Oncol. Published online October 25, 2021. doi:10.1001/jamaoncol.2021.6036
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