The patient, a 61-year-old woman, arrived at the gynecology department in August 2024 after five months of progressive abdominal distension. Examination revealed fluid shifting within her abdomen, and laboratory tests told an alarming story: her CA-125 tumor marker stood at 562 units per milliliter and her HE4 level at 303 picomoles per liter, both dramatically elevated. Transvaginal ultrasound identified complex masses in both adnexal regions—the right ovary harboring a mass of roughly 9.2 by 9.3 by 6.5 centimeters and the left 7.5 by 7.1 by 5.6 centimeters—along with multiple hypoechoic nodules studding the omentum and bowel surfaces and five centimeters of free pelvic fluid. PET-CT imaging confirmed the grim picture: hypermetabolic bilateral adnexal lesions, diffuse peritoneal, mesenteric, and omental implants, and massive ascites, all consistent with advanced ovarian cancer and peritoneal carcinomatosis. Cytology of the ascitic fluid confirmed malignancy.

Immunohistochemistry helped pin down the diagnosis. The tumor cells stained positive for CK7, WT-1, and Pax-8—a classic Müllerian immunophenotype pointing to an ovarian primary rather than a gastrointestinal metastasis—while showing mutant-type P53, partial P16 positivity, and a Ki-67 proliferation index of approximately 70 percent, hallmarks of a high-grade serous carcinoma. The differential diagnosis had included primary peritoneal carcinoma and metastatic gastrointestinal adenocarcinoma, but the distribution of disease and the staining pattern settled the question. Beginning on August 27, 2024, the patient received three cycles of the standard paclitaxel-plus-carboplatin regimen, the platinum–taxane backbone that constitutes first-line therapy for most advanced ovarian cancers worldwide.

The response was disappointing. Assessed by the Response Evaluation Criteria in Solid Tumors, version 1.1—the international standard for measuring tumor shrinkage on imaging—the disease showed no significant regression after three cycles. A multidisciplinary team spanning gynecologic oncology, medical oncology, radiology, and surgery concluded that proceeding directly to surgery would almost certainly leave behind macroscopic tumor, dooming the operation to a suboptimal result. Instead, the team recommended an individualized escalation: adding sintilimab, a PD-1 checkpoint inhibitor developed in China, to the existing chemotherapy backbone. Notably, they deliberately withheld bevacizumab, the anti-angiogenic antibody often combined with chemotherapy in this setting, because the anticipated surgery would involve extensive bowel-surface dissection, and bevacizumab’s effects on wound healing raise the risks of bleeding, gastrointestinal perforation, and fistula formation.

From November 9, 2024, to February 1, 2025, the patient received four cycles of sintilimab combined with paclitaxel and carboplatin. The change was striking. Follow-up ultrasound on February 14, 2025, showed the right adnexal mass reduced to 5.4 by 4.9 by 3.7 centimeters and the left lesion to just 2.8 by 2.0 by 1.2 centimeters, with the pelvic effusion that had filled her abdomen now undetectable. On February 17, 2025, surgeons performed a total hysterectomy with bilateral salpingo-oophorectomy, pelvic and para-aortic lymphadenectomy, presacral lymph node dissection, omentectomy, and excision of bowel-surface nodules. Intraoperatively they found a six-centimeter right ovarian mass and omental nodules up to two centimeters across—and they achieved a complete R0 resection. Final pathology confirmed poorly differentiated serous adenocarcinoma in the left ovary, with no residual tumor in the right ovary, uterus, omentum, or any of the resected lymph nodes.

The biology behind this strategy is worth unpacking. PD-1 is a coinhibitory receptor expressed on T cells that normally restrains immune activation and prevents autoimmunity. Its ligand, PD-L1, is displayed on tumor cells and immune cells within the tumor microenvironment, and when the two engage, cytotoxic T-cell activity is dampened—allowing tumors to evade immune surveillance. Blocking the interaction with an antibody such as sintilimab releases that brake, restoring the ability of T cells to recognize and kill tumor cells. Chemotherapy, meanwhile, is not merely cytotoxic; it can potentiate immunotherapy by releasing tumor antigens, reversing immunosuppressive signaling in the tumor microenvironment, and promoting the infiltration of effector T cells. The rationale for giving checkpoint blockade before surgery rather than after is particularly compelling: preoperative delivery coincides with an intact primary tumor, maximizing antigen release and CD8-positive T-cell priming, and animal and clinical studies in melanoma, triple-negative breast cancer, and non-small-cell lung cancer suggest neoadjuvant immunotherapy generates broader and more durable antitumor immunity than the same drugs given after resection.

Yet the authors of the report are careful to temper enthusiasm, and rightly so. Ovarian cancer has historically been a poor responder to checkpoint inhibition. In the KEYNOTE-100 trial, pembrolizumab monotherapy showed only modest activity in recurrent disease. More sobering still, the phase III IMagyn050/GOG 3015/ENGOT-OV39 trial failed to demonstrate a meaningful progression-free survival benefit when atezolizumab was added to frontline chemotherapy plus bevacizumab in newly diagnosed stage III or IV ovarian cancer. Checkpoint blockade, in other words, cannot be presumed effective in this disease; its utility depends on treatment setting, combination partners, tumor biology, and patient selection. The favorable outcome in this single case cannot be attributed to sintilimab alone, since chemotherapy, radical surgery, bevacizumab, and PARP inhibitor maintenance all contributed to the result. The report is explicitly hypothesis-generating rather than practice-changing.

The surgical decisions in the case also illustrate the tension between evidence and individualized judgment. Randomized trial data, including the landmark study published in the New England Journal of Medicine by Harter and colleagues, show that systematic lymphadenectomy confers no survival benefit for advanced ovarian cancer patients who achieve macroscopic complete resection with clinically negative lymph nodes—and may increase perioperative complications. Although this patient’s preoperative PET-CT showed no suspicious nodal involvement, the surgical team performed pelvic, para-aortic, and presacral lymphadenectomy anyway, reasoning that high-grade serous carcinoma carries substantial risk of occult micrometastatic spread even without radiologic lymphadenopathy. All resected nodes proved negative, but the choice reflects a deliberate balancing of population-level trial evidence against the biologic behavior of an individual tumor—a reminder that personalized operative planning remains central to this disease.

After surgery, the patient received three further cycles of paclitaxel, carboplatin, and bevacizumab. Genetic testing revealed wild-type BRCA1/2 genes but homologous recombination deficiency positivity—a DNA repair defect that, like BRCA mutation, renders tumor cells vulnerable to PARP inhibitors. Under the 2025 edition of the Chinese Guidelines for Gynecologic Cancer, she was started on maintenance therapy with olaparib, 300 milligrams twice daily, combined with bevacizumab. At her most recent follow-up on January 4, 2026, ten months after surgery, CT imaging and tumor markers showed no evidence of recurrence, and she remains clinically disease-free and asymptomatic, though longer observation is clearly required before any durable conclusions can be drawn.

What does this case mean for the wider field? It suggests that for carefully selected patients with advanced high-grade serous ovarian cancer who respond suboptimally to upfront platinum–taxane chemotherapy, adding a PD-1 inhibitor as a neoadjuvant adjunct may convert an inoperable situation into one permitting complete cytoreduction—an outcome that correlates strongly with survival. It also highlights the mechanistic logic of chemo-immunotherapy synergy and the potential advantages of delivering immunotherapy before, rather than after, surgery. But the authors are unambiguous about the limits of a single observation: extended follow-up, expanded case series, and prospective randomized trials are necessary to define the regimen’s true efficacy, its safety profile, and the criteria that should guide patient selection. Until such trials report, sintilimab before surgery in ovarian cancer remains an intriguing, cautiously promising idea rather than a new standard of care.

Subject of Research: Neoadjuvant PD-1 inhibitor sintilimab combined with chemotherapy for advanced high-grade serous ovarian cancer

Article Title: PD‐1 Inhibitor (Sintilimab) Combined With Chemotherapy as Neoadjuvant Therapy in Advanced Ovarian Cancer: A Case Report

Article References: Zhenyan, W., & Yan, W. (2026). PD ‐1 Inhibitor (Sintilimab) Combined With Chemotherapy as Neoadjuvant Therapy in Advanced Ovarian Cancer: A Case Report. Clinical Case Reports, 14(10), Article e73598. https://doi.org/10.1002/ccr3.73598

Image Credits: AI Generated

DOI: 10.1002/ccr3.73598

Keywords: ovarian cancer, sintilimab, PD-1 inhibitor, neoadjuvant therapy, immunotherapy, chemotherapy, R0 resection, PARP inhibitor, olaparib, bevacizumab, high-grade serous carcinoma, case report