Evaluation of FDG uptake by renal malignancies (primary tumor or metastases) using a coincidence detection gamma camera

The aim of this study was to evaluate the usefulness of FDG scanning using an ordinary gamma camera equipped with coincidence detection (CDET) for 2 r enal cancer indications: characterization and staging of renal masses befor e nephrectomy and search for recurrence after nephrectomy. Methods: Between September 1997 and June 1998, a whole-body scan and at least 1 tomoscintig ram were obtained on 23 occasions in 22 patients (fasting for at least 6 h) using a Prism-XP 2000 CDET gamma camera;scanning was begun 45 min after in travenous injection of 150-250 MBq FDG. Results: Postoperative histologic e vidence was obtained from 13 of 16 patients who underwent FDG using a CDET gamma camera before renal surgery; 4 renal masses did not accumulate FDG (3 true negatives, 1 false-negative), whereas 9 renal tumors accumulated FDG (8 true-positives, 1 false-positive). In the other 3 patients, only 1 extra renal site of FDG uptake was checked and confirmed on histologic ex-aminati on: a bone metastasis from renal cell carcinoma in 2 cases and lymph node m etastasis from a squamous cell carcinoma (3 true-positives). The primary lo cal and regional staging of the malignant renal tumors was accurate in the 9 patients who underwent nephrectomy (8 true-negatives, 1 true-positive). T he primary distant staging was positive In 1 case (focus in the chest corre sponding to a probable true-positive on follow-up). In the 7 examinations p erformed because of suspected recurrence of renal cell carcinoma several mo nths after nephrectomy, metastases were visualized by FDG In 4 patients, co nfirmed by biopsy in 2 patients, and confirmed by conventional imaging or f ollow-up (or both) in 2 patients, The other 3 patients had negative FDG sca ns, corresponding to probable true-negative results on follow-up. Conclusio n: FDG using a CDET gamma camera can be used effectively for the staging an d restaging of renal tumors and might be useful for characterization of the primary renal tumor in doubtful cases.