Table 1 Inclusion and exclusion criteria

Histologically or cytologically confirmed unresectable, incompletely resected, recurrent, or metastatic squamous cell carcinoma of the vulva. Patients with unresectable disease are defined as T2 or T3 primary tumors (N0-3, M0) not amenable to surgical resection by standard radical vulvectomy

Patients who in the opinion of the investigator cannot safely receive a minimum of 30 Gy in 10 fractions are not eligible for the trial

Participants must have measurable disease based on RECIST 1.1. Lesions situated in a previously irradiated area are considered measurable if progression has been demonstrated in such lesions

Participants who have received prior systemic anti-cancer therapy including investigational agents within 4 weeks prior to first dose of study treatment

Documented Microsatellite stability status by routine methods including MMR IHC, MSI PCR or MSI by Next Generation Sequencing (NGS)

Participants who have received a live vaccine within 30 days prior to the first dose of study drug

Participants with no prior therapy are eligible and patients with recurrent disease must not have had more than two lines of cytotoxic therapy

Participants with a history of gastrointestinal or colovesicular fistulae

ECOG performance status of 0 or 1

Has active autoimmune disease that has required systemic treatment in the past 2 years (i.e. with use of disease modifying agents, corticosteroids or immunosuppressive drugs)

Absolute neutrophil count (ANC): ≥ 1500/µL

Platelets: ≥ 100,000/µL

Hemoglobin: ≥ 9.0 g/dL or ≥ 5.6 mmol/L

Creatinine: ≤ 1.5 × ULN

AST (SGOT) and ALT (SGPT): ≤ 2.5 × ULN

Total bilirubin: ≤ 1.5 × ULN

Has known active CNS metastases and/or carcinomatous meningitis