Purpose: Apply measurability criteria based on the response evaluation criteria in solid tumors (RECIST) to lesions found on (18)F-choline positron emission tomography (PET)/computerized tomography (CT) in patients with hormone refractory prostate cancer.
Methods: Whole-body PET followed by CT or in-line PET/CT using 3.3-4 MBq/kg of (18)F-choline was performed prospectively on 30 patients with prostate cancer, castrate testosterone levels, and rising post-treatment prostate specific antigen (PSA) levels. Lesions demonstrating increased (18)F-choline uptake were classified as measurable or non-measureable based on RECIST.
Results: Three patients were known previously to have RECIST measurable lesions, 10 patients had metastatic findings on radionuclide bone scan, and 17 patients had elevated serum PSA level as the only evidence of disease. Lesions demonstrating increased (18)F-choline uptake were found in 28 (93%) patients. Thirty-eight PET/CT lesions from 14 patients were measurable by RECIST. Lymph node maximum standardized uptake value (SUV(max)) correlated with lymph node diameter (Pearson r = 0.44, p < 0. 001). RECIST measurable lymph node SUV(max) was significantly higher than that of non-measurable nodes (8.1 vs. 3.7, p < 0.0001). Detection of skeletal, prostatic, or RECIST-compatible lesions was more likely with a PSA level greater than 4.0 ng/ml (Fisher exact p = 0.0005).
Conclusion: Lesions detected with (18)F-choline PET/CT are frequently measurable by RECIST at baseline. Therefore, it may be feasible to include comparisons to RECIST in evaluations of (18)F-choline as a therapeutic response marker for hormone refractory prostate cancer.