Small cell bladder cancer (SCBC) is aggressive and very rare; it accounts for less than 1 percent of bladder cancers. “Because it is so rare, very few trials have ever been done to determine the best way to treat it,” says medical oncologist Jean Hoffman-Censits, M.D.

SCBC has more in common – in its behavior as well as its appearance under the microscope – with other small cell cancers than it does with other bladder cancers, says Hoffman-Censits. In fact, “recommended chemotherapy for SCBC is different than the standard chemotherapy for the more common urothelial bladder cancer, and is instead borrowed from the treatment approach to small cell lung cancer. Furthermore, our team and others have shown that mutations or changes that drive tumor development and growth, assessed by tumor genetic sequencing, look more similar between small cell lung cancer and SCBC, than do the changes comparing SCBC and urothelial bladder cancers.”

Several studies have shown that combination chemotherapy with immunotherapy – checkpoint-inhibiting drugs – “is a safe and effective approach, leading to better outcomes than chemotherapy alone,” says Hoffman-Censits. Checkpoint inhibitor therapy is FDA-approved for urothelial bladder cancer, although less is known about the effectiveness of these drugs in SCBC.

Hoffman-Censits and Hopkins colleagues are testing the combination of the FDA-approved checkpoint inhibitor, Atezolizumab, and standard chemotherapy in patients with newly diagnosed, localized SCBC. “Patients in this trial will begin therapy with intravenous chemotherapy and Atezolizumab, followed by surgical removal of the bladder. Ongoing postoperative atezolizumab treatment is planned to continue for a year to maximize the potential benefit of this approach.” This important trial is enrolling patients in Baltimore and at Sibley Hospital. (NCT05312671).