Challenges and opportunities in the management of non-urothelial bladder cancers

Urothelial carcinoma accounts for approximately 90% of all bladder cancer diagnoses. Localized, muscle-invasive disease is often managed with a multidisciplinary approach including either neoadjuvant chemotherapy (NAC) followed by radical cystectomy or concurrent chemoradiation, whereas multiple immunotherapies and novel antibody drug conjugates have recently joined platinum-based chemotherapy as standard of care therapy for metastatic disease. However, the clinical trials leading to these standards often require majority if not complete urothelial histology for eligibility. As many as one quarter of patients diagnosed with bladder cancer will have either divergent differentiation of their urothelial carcinoma or an alternate epithelial tumor such as squamous cell carcinoma, adenocarcinoma, or small cell carcinoma; even more rare are non-epithelial tumors such as sarcoma. The rarity of these diseases and their general exclusion from treatment within prospective clinical trials has created a challenging situation where treatment plans are often derived from case series or extrapolated from other disease types and outcomes are poor compared to pure urothelial carcinoma. In this review, we summarize the existing data on the diagnosis and treatment of epithelial, non-urothelial bladder cancers including adenocarcinoma, squamous cell carcinoma, and small cell carcinoma in their localized and advances stages. We will also review the current clinical trial landscape investigating novel approaches to these diseases.

Results of a multicenter, phase 2 study of nivolumab and ipilimumab for patients with advanced rare genitourinary malignancies

BACKGROUND

In this multicenter, single-arm, multicohort, phase 2 trial, the efficacy of nivolumab and ipilimumab was evaluated in patients with advanced rare genitourinary cancers, including bladder and upper tract carcinoma of variant histology (BUTCVH), adrenal tumors, platinum-refractory germ cell tumors, penile carcinoma, and prostate cancer of variant histology (NCT03333616).

METHODS

Patients with rare genitourinary malignancies and no prior immune checkpoint inhibitor exposure were enrolled. Patients received nivolumab at 3 mg/kg and ipilimumab at 1 mg/kg intravenously every 3 weeks for 4 doses, and this was followed by 480 mg of nivolumab intravenously every 4 weeks. The primary endpoint was the objective response rate (ORR) by the Response Evaluation Criteria in Solid Tumors (version 1.1).

RESULTS

Fifty-five patients were enrolled at 6 institutions between April 2018 and July 2019 in 3 cohorts: BUTCVH (n = 19), adrenal tumors (n = 18), and other tumors (n = 18). The median follow-up was 9.9 months (range, 1 to 21 months). Twenty-eight patients (51%) received 4 doses of nivolumab and ipilimumab; 25 patients received nivolumab maintenance for a median of 4 cycles (range, 1-18 cycles). The ORR for the entire study was 16% (80% confidence interval, 10%-25%); the ORR in the BUTCVH cohort, including 2 complete responses, was 37%, and it was 6% in the other 2 cohorts. Twenty-two patients (40%) developed treatment-related grade 3 or higher toxicities; 24% (n = 13) required high-dose steroids (≥40 mg of prednisone or the equivalent). Grade 5 events occurred in 3 patients; 1 death was treatment related.

CONCLUSIONS

Nivolumab and ipilimumab resulted in objective responses in a subset of patients with rare genitourinary malignancies, especially those with BUTCVH. An additional cohort exploring their activity in genitourinary tumors with neuroendocrine differentiation is ongoing.

LAY SUMMARY

Patients with rare cancers are often excluded from studies and have limited treatment options. Fifty-five patients with rare tumors of the genitourinary system were enrolled from multiple sites and were treated with nivolumab and ipilimumab, a regimen used for kidney cancer. The regimen showed activity in some patients, particularly those with bladder or upper tract cancers of unusual or variant histology; 37% of those patients responded to therapy. Additional studies are ongoing to better determine who benefits the most from this combination.