Abstract
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Objectives PARP inhibitors are a novel class of drugs targeting cancers with specific DNA-repair defects, as seen in BRCA-deficient tumors. Olaparib (AZD2281) is an orally active PARP inhibitor that has shown encouraging results in pts with advanced ovarian cancer. This study assessed the ability of early FDG PET to predict the later RECIST and/or CA-125 response to olaparib of advanced refractory breast and ovarian cancers.
Methods In a non-randomized, open-label, single group, phase II efficacy study (NCT00679783), 90 pts received continuous oral olaparib 400 mg bid as a single agent in 28-day cycles. Pts were tested for BRCA1/2 mutations. A FDG PET scan was acquired before and after the first cycle, on days 1 and 29. PET response was assessed by EORTC-PET criteria using SUVmax data for the most active lesion at baseline.
Results Of 21 pts evaluable for PET scan response (median age 59 yrs), 14 had tubo-ovarian carcinoma (67%) and 7 had breast carcinoma (33%). 6/21 pts (29%) had a PET scan response (≥25% reduction in tumor FDG uptake from baseline) at 4 wks and 3/19 (16%) had a RECIST response at 8 wks; 2 pts had no RECIST evaluation at 8 wks. Concordance between wk 4 PET response and wk 8 RECIST response was 14/19 (74%). 2/6 (33%) PET responders at wk 4 had RECIST responses at wk 8 and 12/13 (92%) PET non-responders at wk 4 were RECIST non-responders at wk 8. Concordance for wk 4 PET response and wk 8 CA-125 response (ovarian pts only) was 11/13 (85%); 1 pt had no CA-125 evaluation.
Conclusions FDG PET is a promising tool for evaluating response after one cycle of olaparib in pts with advanced breast and tubo-ovarian cancers. There was a strong correlation for non-response: all but one PET non-responder also failed to respond by RECIST. This should be validated in larger trials to assess correlation with clinical outcome and potential impact on pt management.
Research Support AstraZenec
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