Comparison of survival in non-metastatic inflammatory and other T4 breast cancers: a SEER population-based analysis

BACKGROUND: Previous studies have reported poor survival rates in inflammatory breast cancer (IBC) patients than non-inflammatory local advanced breast cancer (non-IBC) patients. However, until now, the survival rate of IBC and other T4 non-IBC (T4-non-IBC) patients remains unexplored. METHODS: Surveillance, Epidemiology, and End Results (SEER) database was searched to identify cases with confirmed non-metastatic IBC and T4-non-IBC who had received surgery, chemotherapy, and radiotherapy between 2010 and 2015. IBC was defined as per the American Joint Committee on Cancer (AJCC) 7th edition. Breast Cancer-Specific Survival (BCSS) was estimated by plotting the Kaplan-Meier curve and compared across groups by using the log-rank test. Cox model was constructed to determine the association between IBC and BCSS after adjusting for age, race, stage of disease, tumor grade and surgery type. RESULTS: Out of a total of 1986 patients, 37.1% had IBC and mean age was 56.6 ± 12.4. After a median follow-up time of 28 months, 3-year BCSS rate for IBC and T4-non-IBC patients was 81.4 and 81.9%, respectively (log-rank p = 0.398). The 3-year BCSS rate in HR−/HER2+ cohort was higher for IBC patients than T4-non-IBC patients (89.5% vs. 80.8%; log-rank p = 0.028), and in HR−/HER2- cohort it was significantly lower for IBC patients than T4-non-IBC patients (57.4% vs. 67.5%; log-rank p = 0.010). However, it was identical between IBC and T4-non-IBC patients in both HR+/HER2- (85.0% vs. 85.3%; log-rank p = 0.567) and HR+/HER2+ (93.6% vs. 91.0%, log-rank p = 0.510) cohorts. After adjusting for potential confounding variables, we observed that IBC is a significant independent predictor for survival of HR−/HER2+ cohort (hazards ratio [HR] = 0.442; 95% CI: 0.216–0.902; P = 0.025) and HR−/HER2- cohort (HR = 1.738; 95% CI: 1.192–2.534; P = 0.004). CONCLUSIONS: Patients with IBC and T4-non-IBC had a similar BCSS in the era of modern systemic treatment. In IBC patients, the HR−/HER2+ subtype is associated with a better outcome, and HR−/HER2- subtype is associated with poorer outcomes as compared to the T4-non-IBC patients.