Addition of Pembrolizumab to the Standard of Care Chemotherapy in Patient With SCCOHT

This study tests whether adding the immunotherapy drug pembrolizumab to standard chemotherapy improves outcomes for patients with small cell carcinoma of the ovary, hypercalcemic type (SCCOHT) — an extremely rare and aggressive ovarian cancer that primarily affects young women and has very few effective treatments. **You may be eligible if...** - You are at least 12 years old - You have been recently diagnosed with SCCOHT (small cell carcinoma of the ovary) at any stage (I–IV), confirmed by pathology - You have not yet received treatment, or have received only one cycle of chemotherapy - Your overall health/functional status is good (ECOG 0 or 1) - Your blood counts, liver, and kidney function meet required levels **You may NOT be eligible if...** - You have received more than one prior cycle of chemotherapy for this cancer - Your blood counts or organ function do not meet requirements - You are pregnant or breastfeeding - You have severe immune system problems or take high-dose steroids Talk to your doctor to see if this trial is right for you.