Case Report: Third-line QL1706, a bifunctional PD-1/CTLA-4 MabPair product, plus chemotherapy for primary small-cell neuroendocrine carcinoma of the ureter

Background Primary small-cell neuroendocrine carcinoma of the ureter is an extremely rare and aggressive malignancy with no established standard treatment strategy, particularly after progression on prior systemic therapy. Case presentation A 52-year-old man with primary ureteral small-cell neuroendocrine carcinoma underwent non-radical surgery followed by six cycles of etoposide, nedaplatin, and tislelizumab, without subsequent maintenance immunotherapy. The postoperative progression-free interval (PFS1) was approximately 39 months. Following recurrence, second-line etoposide and carboplatin were initiated, with tislelizumab reintroduced in the second cycle; the second-line progression-free survival (PFS2) was approximately 7 weeks. Third-line treatment consisted of QL1706, a bifunctional PD-1/CTLA-4 MabPair product comprising iparomlimab and tuvonralimab, combined with nab-paclitaxel and lobaplatin. QL1706 was administered for two cycles and discontinued because the patient declined further QL1706 treatment, whereas chemotherapy was administered for five cycles. Subsequent imaging showed tumor shrinkage, with the response assessed as stable disease. The third-line progression-free survival (PFS3), measured from treatment initiation to documented progression, was approximately 8 months. Treatment-related adverse events were tolerable. Conclusion This case illustrates that progression after prior PD-1-containing chemoimmunotherapy did not preclude subsequent disease control with a QL1706-containing chemotherapy regimen. The observed outcome supports further investigation of this combination as a potential salvage strategy for recurrent or refractory ureteral small-cell neuroendocrine carcinoma. However, the individual contribution of QL1706 cannot be distinguished from that of concomitant chemotherapy in this single case.