Bone Scan with Tc99m-MDP, the Missing Link in the Initial Staging of Muscle-Invasive Bladder Carcinoma

Introduction: Background: Accurate staging is crucial to determine the type of treatment for patients with bladder cancer, especially in high-risk cases. We aimed to assess the role of bone scan in the initial staging of muscle-invasive bladder carcinoma

Methods: 45 patients with muscle-invasive bladder cancer were referred to our tertiary clinic to perform a 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 four hours after injection of Technetium 99m-methyl diphosphonate (MDP) 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/MRIimages 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, 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. Serum ALP levels in patients with and without bone metastasis were 271.4±11 and 276.7±98.9, respectively. Bilateral hydronephrosis was significantly associated with lymph node metastasis.

Conclusions: 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 weconclude that performing a whole-body bone scan in the initial staging of muscle-invasive bladder carcinoma would be helpful.