by Won Kyung Cho, Jee Suk Chang, Seung Gyu Park, Nalee Kim,
Doo Ho Choi, Haeyoung Kim, Yong Bae Kim, Won Park, Chang Ok Suh
The Breast: VOLUME 59, P37-43, OCTOBER
01, 2021
Background
It is important to continually reevaluate the risk/benefit
calculus of internal mammary node irradiation (IMNI) in the era of modern
systemic therapy. We aimed to investigate the effect of IMNI on survival in
node-positive breast cancer treated with mastectomy and anthracycline plus
taxane-based chemotherapy.
Methods
We analyzed 348 patients who underwent mastectomy and
anthracycline plus taxane-based chemotherapy for node-positive breast cancer
between January 2006 and December 2011. All patients received postoperative
radiation therapy (RT) with IMNI (n = 105, 30.2%) or without IMNI (n = 243,
69.8%). The benefit of IMNI for disease-free survival (DFS) and overall
survival (OS) was evaluated using multivariate analysis and inverse probability
of treatment weighting (IPTW) to adjust for unbalanced covariates between the
groups.
Results
After a median follow-up of 95 months, the 10-year
locoregional recurrence-free survival rate, DFS, and OS in all patients were
94.8%, 77.4%, and 86.2%, respectively. The IPTW-adjusted hazard ratio (HR) for
the association of IMNI (vs. no IMNI) with DFS and OS was 0.208 (95% confidence
intervals (CI) 0.045–0.966) and 0.460 (95% CI, 0.220–0.962), respectively. In multivariate
analysis, IMNI was a favorable factor for DFS (HR, 0.458; P = 0.021)
and OS (HR 0.233, P = 0.018).
Conclusions
IMNI was associated with improved DFS and OS in
node-positive patients treated with mastectomy, post-mastectomy RT, and
taxane-based chemotherapy, although the rate of locoregional recurrence was
low.
