[Positron emission tomography. Introduction of a new procedure in diagnosis of urologic tumors and initial clinical results].

Correct preoperative staging of malignant tumors is a prerequisite for an adequate therapy. This is not always possible with the imaging techniques available. Often, only an exploratory laparotomy can give the final diagnosis. Therefore, the search is on for a non-invasive technique for staging. Positron emission tomography (PET) is a new method in nuclear medicine; it is used for the diagnosis of primary tumors, for staging, and for follow-up after therapy. With PET, biochemical pathways and physiological functions are studied, in contrast to CT and MRI, with which anatomy and morphology are examined. In our department PET was used in 26 patients with invasive bladder cancer, in 11 patients with renal cell carcinoma and in 1 patient for follow-up after testicular cancer. The primary bladder tumor was found in 85% of cases; in 4 a non-organ-confined tumor was diagnosed preoperatively. Specificity in staging of lymph nodes was 86% (18/21); in 3 patients lymph nodes were false-positive on PET. However, in 5 patients all lymph node metastases were found by PET. Renal cell carcinoma were found in 8 out of 9 patients; in 2 patients with high-grade tumors an FDG-uptake defect was found. Lymph node staging was accurate in 9 patients without metastases and in 2 with metastases. One patient had a slightly enlarged retroperitoneal lymph node in the follow-up of a non-seminomatous germ cell tumor, which was positive on PET. Histology confirmed that it was the only positive lymph node within the whole specimen after retroperitoneal lymphadenectomy. PET gives new insights in uro-oncology by examination of the metabolism. Our initial results are promising and warrant further studies.