Predictive value of prostate-specific antigen, tumour stage and tumour grade for the outcome of bone scintigraphy in patients with newly diagnosed prostate cancer.

OBJECTIVE: In order to evaluate the negative predictive value of a low prostate-specific antigen (PSA) for a positive bone scan, we performed a retrospective study in a patient material from the Umea region in Northern Sweden. We also evaluated whether different tumour grades could influence this predictive value. MATERIAL AND METHODS: Four-hundred-and-forty-six patients of newly diagnosed prostate cancer were reviewed. We analysed different levels of PSA, tumour grade, tumour stage and combinations of these parameters for their use in making a positive bone scintigraphy (BS) prediction. RESULTS: Among 214 patients with PSA <20 ng/ml, 9 showed a positive BS. When tumours of grades 2 and 3 were excluded, the number of positive BS predictions decreased to 6. For 350 of these 446 patients, a classification according to TNM was available; 162 of these 350 had a PSA value <20 ng/ml, and when this group comprised only small and well-differentiated tumours (T1-2, G1), only one of the remaining 81 patients had a positive BS result. CONCLUSIONS: We conclude that in most patients with small and well-differentiated tumours (T1-2, G1) and PSA <20, BS staging need not be carried out.