Bone scan with technetium 99m-methyl diphosphonate, the missing link in the initial staging of muscle-invasive bladder carcinoma

Background Accurate staging is crucial to determine the type of treatment for patients with bladder cancer (BCa), especially in high-risk cases. We aimed to assess the role of bone scan in the initial staging of muscle-invasive bladder carcinoma (MIBC). Material and methods Forty-five patients with MIBC were referred to our tertiary clinic to perform a technetium 99m-methyl diphosphonate (Tc99m-MDP) bone scan from January 2019 to March 2020. The patients underwent bone scintigraphy with pelvic SPECT/CT before radical cystectomy. Whole-body scanning was performed 4 hours after Tc99m-MDP injection in both anterior and posterior views. Since the most common bone involvement site in these patients is the pelvic bones and the spine, pelvic SPECT/CT was performed in all patients. Results Frequency of skeletal metastasis was 26.7%. Only 19% of the metastases were detected by previous pelvic CT/MRI images performed for routine staging. All the reported skeletal metastases by previous anatomical imaging methods were detected in the bone scan. There was no statistically significant correlation between bone metastasis and the patient's age, lymph nodes metastasis (LNM), hydronephrosis, and muscle-invasive type. The mean serum calcium level was 8.7 +/- 0.57 in patients with bone metastasis and 8.87 +/- 0.99 in patients without bone metastasis, which was not statistically significant. Conclusion Bone scan has higher diagnostic performance than conventional imaging methods for detecting bone metastases. It changed the management plan in 8.8% of our patients, so we conclude that performing a whole-body bone scan in the initial staging of MIBC would be helpful.