Significance of increased scrotal Tc-99m MDP uptake in patients with prostate cancer

Abstract

We observed an unusually increased scrotal uptake as an interesting finding in some patients with prostate cancer who were scanned for any possible metastatic disease. This study was designed to investigate the significance of this incidental finding in the technetium-99m methylene diphosphonate scintigraphies. The study population consisted of 104 patients with biopsy-proven prostate cancer (group I), 55 male patients with other cancers (group II), 30 male patients with nonmalignant diseases (group III) and finally 15 patients with benign prostate hypertrophy (group IV). The square-shaped regions of interest are placed centrally on the scrotum and then on the lateral femoral soft tissue. Then the simple ratios of the scrotal and femoral soft tissue mean counts (S/Bg) were calculated. The statistical significance of differences among the groups in terms of scrotal uptake was determined. Group I showed increased scrotal uptake relative to the other groups. The mean uptake ratios (S/Bg±standard deviation) were 3.49±1.42 in group I, 2.89±0.70 in group II, 2.87±0.75 in group III, and 2.91±0.60 in group IV. This ratio was significantly higher in patients with prostate cancer than the normal group (P=0.024), the group with benign prostate hypertrophy (P=0.004), and the patients with other cancers (P=0.004). Our results showed that technetium-99m methylene diphosphonate bone scintigraphy, as a routine for detecting metastatic disease or performed for other purposes, could give clues for a hidden prostate cancer. Then, in elderly male patients, we strongly recommend that it is wise to keep one's eye on scrotal activity when bone scans are read and where there is any doubt, take appropriate regions of interest to make quantitative evaluations.