Fluorodeoxyglucose (FDG) positron emission tomography (PET) as an indicator of disease progression for patients with castration-resistant metastatic prostate cancer (CRMPC).

Abstract

e15193 Background: We have preliminarily shown that FDG PET can be used to demonstrate post-treatment responses to taxane based chemotherapy (Morris, et. al. CCR, 2005). However, it is uncertain how patients who are progressing on treatment will manifest on FDG PET. In this study of FDG PET, we examined patients undergoing treatment with either novel ligand inhibitors or anti-androgens to determine patterns of relapse at the point of biochemical, clinical, or radiographic progression by standard measures. Methods: Under the auspices of an imaging clinical trial and co-registered to clinical trials using either a CYP17 inhibitor or novel anti-androgen, patients with CRMPC were prospectively serially scanned with FDG PET in addition to standard protocol-driven outcome measures. Patients were included in this analysis if they had an FDG PET within 12 weeks of coming off study for progressive disease by the protocol-defined criteria. Using the Prostate Cancer Clinical Trials Consortium (PCCTC) molecular imaging data capture toolset, the FDG PET recorded at progression was compared with baseline and interim PETs and analyzed by any increase in SUVMAXAVG from nadir or the presence of new lesions. Results: Seventy-two patients were scanned, 33 of whom fulfilled the requirements for this analysis. Of this cohort, four patients progressed by a single new or existing lesion, 22 patients progressed by multiple new or existing lesions, and seven patients did not progress by PET. Of the 15 patients who developed new lesions, two patients developed asingle new lesion and 13 developed multiple new lesions. Of the patients who progressed by existing lesions, the median DSUVMAXAVG was 34.38% (4.18-124.29%). Conclusions: The results of this preliminary analysis suggest that progression by PET appears to be manifest by the emergence of multiple resistant target lesions. A minority of patients progress by virtue of a single lesion. Further study will assess whether PET, PSA, standard scans, or clinical criteria is the most relevant measure for predicting survival.