Optimal timing and interval of imaging for metastatic breast cancer.

1106 Background: Breast cancer is a family of diseases with varying disease trajectories based on intrinsic biology of the tumor. The time of progression varies across & within subtypes, and with increasing rates of drug resistance depending on prior therapeutic exposure. There is no strong consensus about optimal surveillance and routine imaging in patients with metastatic breast cancer (mBC), but many oncologists report that monitoring strategies are based on strategies used in clinical trials. Methods: We reviewed 17 prior Phase III studies that led to FDA approval in mBC. We reviewed 8 studies for ER+ mBC, 5 studies for HER2+ mBC, 2 studies for triple negative (TNBC) mBC, and 2 studies for BRCA+ mBC. We calculated rates of progression or death (POD) per month for the first year on therapy using data from survival analysis tables and compared them across the different types and lines of therapy. Results: Risk of progression in mBC varies based on receptor status and line of therapy (Table). There was a significant difference in POD rates between ER+ therapies compared with all other disease types (HER2+, TNBC, BRCA) (p = 0.012). Patients with TNBC or receiving PARP inhibitors or later line HER2 therapies had higher POD rates than those with ER+ breast cancer or receiving first line HER2 therapy (6.9% vs 4.1% per month; p = 0.0004). No significant difference was seen in the monitoring frequency between ER+ and HER2+ disease (p = 0.39). Conclusions: These data suggest that shorter interval imaging should be performed for patients with TNBC or receiving PARP inhibitors or later line HER2 therapies. Surveillance imaging for patients with mBC should be based on disease biology, number of prior regimens, time since initiation of therapy, and regimen efficacy. Current imaging recommendations are not data-based and do not adjust for new agents that have been approved. Oncologists should integrate these into individualized estimates to determine optimum frequency of imaging in clinical practice and research. [Table: see text]