Real-World Evidence Evaluating The Use Of Single Versus Combination Chemotherapy In Salvage Therapy For Metastatic Breast Cancer.

e12600 Background: Metastatic breast cancer (mBC) patients often receive multiple lines of systemic chemotherapy (Chemo) to extend life, manage disease symptoms and improve quality of life. Combination chemotherapy (cChemo) provides no survival advantage over single agent sequential chemotherapy (sasChemo) in mBC, but it may increase the risk of toxicity and adverse events while decreasing quality of life. The National Comprehensive Cancer Network guideline states that sasChemo is preferred for recurrent or stage IV mBC. This study aimed to explore adherence to this recommendation by evaluating contemporary real-world treatment patterns in mBC. Methods: Patients were identified from a third-party, administrative claims database. Using medical and pharmacy claims, any female with mBC (both BC and metastatic ICD9/10 codes) diagnosed between 01-Jan-2013 and 31-Dec-2017, followed for at least 6 months, and who had initiated systemic therapy was selected. Patients who received any HER2 targeted therapy, any oral or infused hormonal therapy, and/or had other malignant diagnoses were excluded. The proportion of patients receiving each line of chemotherapy was calculated in addition to the proportion of sasChemo and cChemo. Results: 10,342 patients met the selection criteria. Mean age at initiation of treatment was 61.7 years (SD = 12.12), 35.7% of patients had Medicare/Medicare advantage insurance coverage. All patients received first line (1L) systemic chemotherapy, 59% received 2L, 39% 3L, 25% 4L, 16% 5L, and 12% 6L respectively. 4 patients received ≥ 7L. The distribution between sasChemo vs cChemo was 50%/50% in 1L, 42%/58% 2L, 43%/57% in 3L, 44%/56% in 4L, 45%/55% in 5L and 46%/57% in 6L. Conclusions: Despite medical evidence which resulted in clinical guideline preference for sasChemo, cChemo use continues to have significant use in the salvage treatment of mBC. Research is warranted to understand and lessen this low value practice.