INTRODUCTION
Urinary bladder is an extremely rare site of extrapulmonary small cell cancer (EPSCC). Unlike small cell lung cancer (SCLC), there is no clear guideline for prophylactic cranial irradiation (PCI) for EPSCC. In this case report and literature review, we discuss small cell cancer of urinary bladder (SCCUB) and the role of PCI in SCCUB.
CASE PRESENTATION
A 74-year-old male presented with gross hematuria and an unremarkable physical examination. CT showed 1.7 cm right anterolateral bladder wall thickening. Cystoscopy revealed a 2-3 cm high-grade bladder lesion. Pathology from transurethral resection of the tumor was consistent with T1N0M0 small cell carcinoma. MRI brain and FDG-PET showed no extravesical disease. Patient received four cycles of neoadjuvant carboplatin/etoposide per his preference as he wanted to protect his hearing due to his profession followed by radical cystoprostatectomy. Post-op pathology showed clear margins. We decided to forego PCI in favor of interval surveillance with MRI and follow- up images remain negative for distant metastases.
DISCUSSION
EPSCC accounts for 2.5-5% of all SCC, very rare in male genitourinary tract. Treatment approach is derived from SCLC, guided by extent of disease and patient’s functional status. Role of PCI in EPSCC has not been clearly described, and even less evidence is available for SCCUB. From a review of eleven studies in PubMed for the role of PCI in SCCUB or EPSCC, we found that SCCUB has lower incidence of brain metastases than SCLC. One study suggested that SCCUB arises from totipotent cells in the submucosa, unlike Kulchitsky cell origin of SCLC. This difference might explain the difference in their metastatic behavior. With this background, PCI is not routinely recommended for limited- stage SCCUB. There might still be a role for PCI in extensive SCCUB with high metastatic burden. More studies are needed to update the guidelines for the role of PCI for these tumors.
CONCLUSIONS
Per this literature review, PCI is not routinely recommended for SCCUB, likely due to different cells of origin compared to SCLC. Future studies should focus on characterizing differences in their metastatic behavior and updating guidelines for PCI for SCCUB.