Abstract P1-08-35: Treatment across the four molecular types of breast cancer: Insight from the national cancer database, 2010–2014 (N=827,888)
Authors: Konduri SD , Singh M , Bobustuc GC , Rovin RA , Kassam AB 
Published: May 2019

Background: For patients diagnosed with breast cancer treatment plans are usually determined by biomarkers such as ER, PR and HER2, the absence or presence of which determines molecular subtype of the tumor (luminal A, luminal B, triple-negative, and HER2-enriched). However, it is unclear to what extent each treatment plan contributes to overall survival across these four molecular types of breast cancer (as determined by the presence or combination of biomarkers).

Objective: Assuming inherent heterogeneity among breast cancer patients, we sought to determine the benefit of any one or combination of treatment methods among surgery, chemotherapy, radiation, immunotherapy, and hormonal therapy and whether differences exist among various subgroups for predicting mortality risk.

Methods: A total of 827,888 patients diagnosed with breast cancer from the National Cancer Database were analyzed. The patient population was 99.1% female, 0.9% male, 75.5% white, 11.2% black, 0.8% Hispanic, and 12.5% other races. Most of the patients (97.1%) were diagnosed with invasive breast cancer; the remaining 2.9% were diagnosed with in situ and/or carcinoma in situ. For molecular subtypes, the distribution of patients was 72.7% with luminal A, 10.4% luminal B, 4.7% HER2-enriched and 12.2% triple-negative.

Results: Overall, patients who did not receive treatment were 6.9 times more likely to die (95% confidence interval [CI]: 6.7–7.0) than those who did. Within molecular subtypes, hazards ratios [HR] were for dying without treatment were7.0 (95% CI: 6.8–7.1) for luminal A, 7.8 (95% CI: 7.3–8.3) for luminal B, 6.9 (95% CI: 6.6–7.2) for triple-negative, and 8.9 (95% CI: 8.2–9.7) for HER2-enriched tumor. Overall survival was best for luminal A, followed by luminal B, HER2-enriched and triple-negative (p&lt;0.001). Multivariate Cox regression showed that the five most significant factors predicting mortality for luminal A were surgical treatment (HR: 0.4, p&lt;0.001), patient age (HR: 1.1 one year increment , p&lt;0.001), cancer stage (HR: 1.2, 2.1, 4.1, and 7.4 for stage I, II, III, and IV [all vs stage 0], respectively, p&lt;0.001), Charlson/Deyo score (HR: 1.4, 2.1, and 2.9 for score 1, 2, and ≥3 [all vs score 0], respectively, p&lt;0.001), and tumor grade (HR:0.8, 0.5, and 0.4 for poorly, moderately, and well-differentiated tumors [all vs undifferentiated], respectively). For luminal B, HER2-enriched molecular types, and for triple negative chemotherapy (HR: 0.5, 0.6, 0.5, respectively) replaced grade differentiation as one of the top five predictors.

Conclusion: Despite recent suggestions of over diagnoses and unnecessary treatment for certain types of tumor, this retrospective study suggested that treatment remains highly beneficial for breast cancer patients. Among treatments, surgery remains a strong predictor of survival across the board; however, for luminal B, HER2-enriched, and for triple negative subtype chemotherapy along with surgery provides additional survival benefit. Overall survival was better for luminal A, followed by luminal B, HER2 and triple negative breast cancer. These results can provide guidance for clinicians as well as for patients.

Citation Format: Konduri SD, Singh M, Bobustuc GC, Rovin RA, Kassam AB. Treatment across the four molecular types of breast cancer: Insight from the national cancer database, 2010–2014 (N=827,888) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P1-08-35.