Predictive value of molecular subtyping for loco-regional recurrence in early breast cancer patients with one to three positive axillary lymph nodes / 中华放射肿瘤学杂志

ABSTRACT

Objective To investigate the relationship between molecular subtypes of breast cancer and postoperative loco-regional recurrence (LR) in early breast cancer patients with 1-3 positive axillary lymph nodes (pN1) and to improve the individualized indications for post-mastectomy radiotherapy (PMRT)in these patients.Methods A total of 547 patients with pT1-2 N1M0 breast cancer,who received mastectomy between December 1998 and December 2009 in Sun Yat-sen University Cancer Center,were retrospectively analyzed.None of them received adjuvant radiotherapy after mastectomy.The patients were divided into luminal A group,luminal B group,HER-2-overexpressing group,and triple-negative group according to the molecular subtypes of breast cancer determined by immunohistochemistry and fluorescence in situ hybridization.The patients in different groups were compared in terms of LR rate (LRR) and LR-free survival (LRFS),and the risk factors for LR were analyzed in combination with clinical and pathological features.The Kaplan-Meier method was adopted to calculate LRR and LRFS;the Logrank test was used for survival difference analysis and univariate prognostic analysis.The Cox proportional hazards model was used for multivariate prognostic analysis.Results The luminal A group,luminal B group,HER-2-overexpressing group,and triple-negative group accounted for 30.0％,48.6％,9.3％,and 12.1％,respectively,of all the patients.The follow-up rate was 97.1％ ;334 patients were followed up for at least 5 years,and 127 were followed up for at least 10 years.Univariate analysis showed that,compared with the luminal A group,the HER-2-overexpressing group and triple-negative group had significantly higher 5-year LRRs (19.0％ vs 5.3％,x2 =4.28,P =0.026; 14.9％ vs 5.3％,x2 =5.02,P =0.015) and significantly lower LRFSs (73.5％ vs 91.1％,x2=7.27,P=0.005;80.6％ vs 91.1％,x2=4.77,P=0.021).Multivariate analysis revealed that HER-2 overexpression,triple-negative phenotype,age of ≤ 35 years,and stage pT2 were poor prognostic factors for survival (LRR and LRFS) (x2 =2.29,2.08,18.22,and 6.86,P =0.020,0.016,0.001,and 0.005;x2 =1.90,1.41,8.58,and 3.94,P=0.006,0.025,0.002,and 0.039).The 10-year LRRs of patients with 0,1,and ≥2 of the above risk factors were 4.3％,14.1％,and 31.9％,respectively (x2 =28.03,P =0.000).Conclusions Molecular subtyping is helpful for individualized evaluation of LR risk in early breast cancer patients with 1-3 positive axillary lymph nodes (pN1).PMRT should be recommended for the patients with 2 or more risk factors for LR.