Outcomes related to delayed initiation of anti-HER 2 therapy in pregnant HER2 positive breast cancer patients.

Abstract

e12059 Background: Overexpression of HER2 is associated with aggressive breast cancers. In non-pregnant HER2+ breast cancer patients, anti-HER2 therapy is usually initiated after surgery or in the neoadjuvant setting. However, for pregnant HER2+ breast cancer patients, anti-HER2 therapy must be delayed until after delivery due to fetal toxicity. We describe here the outcomes of pregnant patients with HER2+ breast cancer at a single center. Methods: Twenty-three pregnant HER2+ breast cancer patients were treated between November 1989 to October 2016. Median age at diagnosis was 31.8. (Table 1) We report Kaplan-Meier estimates of OS from diagnosis and PFS from surgery. The effect of time from diagnosis to anti-HER2 therapy (TTH) on OS and PFS from HER2 therapy initiation was assessed using Cox proportional hazards regression models. Results: Seventeen patients received anti-HER2 therapy after delivery, 6 did not – 4 were treated prior to the use of HER2 therapies, and 2 were lost to follow-up. Median TTH was 181 days. All but 3 patients started HER2 treatment within 2 months of delivery. Twenty-one received anthracycline-based chemotherapy during pregnancy. Three patients have died, with all 3 receiving HER2 therapy, but one only at relapse due to diagnosis before routine trastuzumab use. Median follow-up was 3.4 years (range 0.2-16.2 years), and 5-year OS was 80% (95%CI 41-95%). Five patients progressed. Median PFS was 3.1 years (range 0.3-14.2 years), and 5-year PFS was 75% (95%CI 46-90%). Delay of initiation of HER-2 therapy did not appear to be associated with OS or PFS from date of HER-2 therapy initiation (both n = 17, HR 1.01, 95%CI 0.97-1.06, P= 0.52). Conclusions: In this small case series, we did not detect adverse outcomes associated with delaying initiation of anti-HER2 therapy in pregnant patients with HER2+ breast cancer. Larger series are needed to further evaluate this concern. [Table: see text]