Long term follow up (LTFU) of adjuvant zoledronic acid (ZOL) in high risk early stage breast cancer (ESBC) defined by bone marrow (BM) disseminated tumor cells (DTC).

e12001Background: BM DTC & peripheral blood CTC indicate metastatic potential. Adjuvant bisphosphonates in postmenopausal patients (pts) result in less bone metastases and better survival. We studied ZOL’s impact on DTC, CTC, and outcomes in ESBC (ASCO, 2010) and now report updated LTFU. Methods: Forty-five pts with ESBC and DTC > 4/mL BM were given ZOL every 4 weeks for 24 months (mo). DTC were quantified at baseline (BL), 12 and 24 mo of ZOL with immunomagnetic enrichment and flow cytometry (Clin Cancer Res, 2015). Serial CTC, survival, recurrence and toxicity were studied. Results: Forty-five pts received ZOL (56% HR+, 18% HER2+, 40% TN, 96% prior chemo). BL median DTC was 13.3/mL (range 4-333). Median DTC decreased from BL to 12 mo (median reduction 6.5/mL, range -57.2 to 23.6) and from BL to 24 mo (median reduction 4.6/mL, range -43.1 to 160.1). For 33 pts with BM at all 3 times, DTC decreased: BL median 11.5/mL (range 4-59.3), 12 mo median 6.8/mL (range 0-28.5), 24 mo median 6.5/mL (range 0.3-168.6)...