Background: Decrease of circulating tumor cells (CTC) during treatment is an independent prognostic factor in metastatic breast cancer (MBC). We specifically evaluated the impact of CTC on brain metastasis outcome.
Methods: HER2-positive MBC with brain metastasis not previously treated with whole-brain radiotherapy received first-line combination of lapatinib and capecitabine in a phase II study. CTC were detected at baseline and day 21 (CellSearch).
Results: Median follow-up of the 44 analyzed patients was 21.2 months. The central nervous system objective response (CNS-OR) rate was 66%. At baseline, 20 of 41 assessable patients for CTC (49%) had ≥1 CTC (range 1-301, median 3) and 9 (22%) had ≥5 CTC. At day 21, 7 of 38 patients (18%) had ≥1 CTC (P = 0.006, versus baseline), and CTC had disappeared in 11 patients. CNS-OR rate was significantly higher in patients with no CTC at day 21 [25 of 31 (80%) versus 2 of 7 (29%), P = 0.01]. The 1-year overall survival rate was 83.9% in patients with no CTC at day 21 versus 42.9% in patients with ≥1 CTC (P = 0.02).
Conclusions: This is the first report showing a correlation between CNS metastasis response, outcome and early CTC clearance under targeted treatment of HER2+ MBC.
Clinical trials number: NCT00967031.
Keywords: HER2; brain metastasis; breast cancer; capecitabine; circulating tumor cells; lapatinib.