RECIST measurability of 18F-choline PET/CT detected lesions in androgen insensitive prostate cancer

Objectives Apply measurability criteria based on the Response Evaluation Criteria in Solid Tumors (RECIST) to lesions found on 18F-choline PET/CT in patients with androgen insensitive prostate cancer (AIPC).

Methods Whole-body PET followed by CT or in-line PET/CT using 4 Mbq/kg of 18F-choline was performed on 30 patients with prostate cancer, castrate testosterone levels, and rising post-treatment prostate specific antigen (PSA) levels. PET/CT images were interpreted visually to identify lesions with increased 18F-choline uptake. Lesions were assessed for measurability based on RECIST.

Results Lesions showing increased 18F-choline uptake were found in 28/30 (93%) of patients. Thirty-eight of 55 (69%) lesions (from 14 patients) were measurable by RECIST. Three patients were known previously to have RECIST measurable lesions, 17 patients previously had elevated serum PSA level as sole evidence of disease, and 10 patients had metastases noted on prior radionuclide bone scans. 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). Lymph node maximum standardized uptake value (SUVmax) correlated with node diameter (Pearson r = 0.44, p< 0. 001).

Conclusions PET/CT with 18F-choline may allow whole-body detection of RECIST measurable lesions in AIPC, while also detecting skeletal and prostate lesions that may be measurable by other criteria. Therefore, comparisons with conventional response criteria such as RECIST may aid in the evaluation of 18F-choline PET/CT for gauging therapeutic response in AIPC.

Research Support This work was supported by U.S. Army Medical Research and Materiel Command grant W81XWH-05-1-0056 (PCRP PC04130).