title: FDG-PET as a predictive biomarker for therapy with everolimus in metastatic renal cell cancer.
abstract: The mTOR (mammalian target of rapamycin) inhibitor, everolimus, affects tumor growth by targeting cellular metabolic proliferation pathways and delays renal cell carcinoma (RCC) progression. Preclinical evidence suggests that baseline elevated tumor glucose metabolism as quantified by FDG-PET ([(18)F] fluorodeoxy-glucose positron emission tomography) may predict antitumor activity. Metastatic RCC (mRCC) patients refractory to vascular endothelial growth factor (VEGF) pathway inhibition were treated with standard dose everolimus. FDG-PET scans were obtained at baseline and 2 weeks; serial computed tomography (CT) scans were obtained at baseline and every 8 weeks. Maximum standardized uptake value (SUVmax) of the most FDG avid lesion, average SUVmax of all measured lesions and their corresponding 2-week relative changes were examined for association with 8-week change in tumor size. A total of 63 patients were enrolled; 50 were evaluable for the primary endpoint of which 48 had both PET scans. Patient characteristics included the following: 36 (72%) clear cell histology and median age 59 (range: 37-80). Median pre- and 2-week treatment average SUVmax were 6.6 (1-17.9) and 4.2 (1-13.9), respectively. Response evaluation criteria in solid tumors (RECIST)-based measurements demonstrated an average change in tumor burden of 0.2% (-32.7% to 35.9%) at 8 weeks. Relative change in average SUVmax was the best predictor of change in tumor burden (all evaluable P = 0.01; clear cell subtype P = 0.02), with modest correlation. Baseline average SUVmax was correlated with overall survival and progression-free survival (PFS) (P = 0.023; 0.020), but not with change in tumor burden. Everolimus therapy decreased SUVs on follow-up PET scans in mRCC patients, but changes were only modestly correlated with changes in tumor size. Thus, clinical use of FDG-PET-based biomarkers is challenged by high variability.
authors.affiliation: Departments of Biomedical Informatics and Internal Medicine, The Ohio State University Columbus, Ohio.
authors.forename: James L
authors.initials: JL
authors.lastname: Chen
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Appelbaum
authors.forename: Masha
authors.initials: M
authors.lastname: Kocherginsky
authors.forename: Charles L
authors.initials: CL
authors.lastname: Cowey
authors.forename: Wendy Kimryn
authors.initials: WK
authors.lastname: Rathmell
authors.forename: David F
authors.initials: DF
authors.lastname: McDermott
authors.forename: Walter M
authors.initials: WM
authors.lastname: Stadler
mesh_terms: D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D015415:Biomarkers; D002292:Carcinoma, Renal Cell / Q000175:diagnosis* / Q000188:drug therapy* / Q000401:mortality; D000068338:Everolimus; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007680:Kidney Neoplasms / Q000175:diagnosis* / Q000188:drug therapy* / Q000401:mortality; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D049268:Positron-Emission Tomography; D020123:Sirolimus / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000627:therapeutic use; D016896:Treatment Outcome; D047368:Tumor Burden
chemical_list: D000970:Antineoplastic Agents; D015415:Biomarkers; D019788:Fluorodeoxyglucose F18; D000068338:Everolimus; D020123:Sirolimus
keywords: Kidney carcinoma; mTOR protein; pharmacological biomarkers; positron emission tomography