Diagnostic and cost-effectiveness of axial skeleton MRI in staging high-risk prostate cancer

Current literature suggests that axial skeleton magnetic resonance imaging (AS-MRI) is more sensitive than Tc 99m bone scintigraphy (BS) for detecting bone metastases (BM) in high-risk prostate cancer (PCa). However, BS is still widely performed. Its diagnostic accuracy has been studied; however, its feasibility and cost implications are yet to be examined.

We reviewed all patients with high risk PCa undergoing AS-MRI over a 5-year period. AS-MRI was performed on patients with histologically confirmed PCa and either PSA > 20 ng/ml, Gleason ≥8, or TNM Stage ≥T3 or N1 disease. All AS-MRI studies were obtained using a 1.5-T AchievaPhilips™MRI scanner. We compared the AS-MRI positivity and equivocal rate with that of BS. Data were analysed according to Gleason score, T-stage and PSA. Multivariate logistic regression analyses were used to quantify the strength of association between positive scans and clinical variables. Feasibility and burden of expenditure was also evaluated.

Five hundred three patients with a median age of 72 and a mean PSA of 34.8 ng/ml were analysed. Eighty-eight patients (17.5%) were positive for BM on AS-MRI (mean PSA 99 [95% CI 69.1-129.9]). Comparatively 409 patients (81.3%) were negative for BM on AS-MRI (mean PSA 24.7 (95% CI [21.7-27.7]) (p = 0.007); 1.2% (n = 6) of patients had equivocal results (mean PSA 33.4 [95% CI 10.5-56.3]). There was no significant difference in age (p = 0.122) between this group and patients with a positive scan, but there was a significant difference in PSA (p = 0.028), T stage (p = 0.006) and Gleason score (p = 0.023). In comparison with BS, AS-MRI detection rate was equivalent or higher compared with the literature. Based on NHS tariff calculations, there would be a minimum cost saving of £8406.89. All patients underwent AS-MRI within 14 days.

The use of AS-MRI to stage BM in high-risk PCa is both feasible and results in a reduced burden of expenditure.