Targeting DLL3 in Extrapulmonary Neuroendocrine Carcinoma: Bridging the Gap from Diagnosis to Emerging Biomarker-Driven Therapy
Dr. Jonathan Strosberg from Moffitt Cancer Center discussed the challenging landscape of extrapulmonary neuroendocrine carcinoma (NEC), a rare and aggressive malignancy distinct from well-differentiated neuroendocrine tumors. Through a case of a 64-year-old man with metastatic colonic NEC, Dr. Strosberg highlighted key diagnostic challenges and treatment limitations in this historically underappreciated disease. Poorly differentiated NECs demonstrate high Ki-67 proliferation indices (>55%), aggressive histology with necrosis and pleomorphism, and distinct mutational patterns including p53 and RB1 alterations similar to small cell lung cancer. Traditional platinum-based chemotherapy yields poor outcomes, with median progression-free survival of 2 to 6 months in second-line settings. DLL3 emerges as a promising therapeutic target, expressed in approximately 75% of extrapulmonary NECs. Bispecific T-cell engagers like tarlatamab targeting DLL3 show encouraging activity in patients with high DLL3 expression (>50%), achieving approximately 40% response rates versus 3% in low expressors.
Advertisement
Targeting DLL3 in Extrapulmonary Neuroendocrine Carcinoma: Bridging the Gap from Diagnosis to Emerging Biomarker-Driven Therapy
Dr. Strosberg introduces the case of James, a 64-year-old man with hypertension presenting with progressive abdominal pain, 12-pound unintentional weight loss, and fatigue over 6 weeks. Imaging reveals a 4.2-centimeter colonic mass with peritoneal lymph nodes and hepatic lesions. Colonoscopy-guided biopsy confirms poorly differentiated carcinoma of colonic origin, with positive chromogranin A and CK20 immunostaining, Ki-67 proliferation index of 82%, mitotic rate exceeding 20 per high-powered field, and confirmed metastatic disease. Somatostatin receptor expression is negative with mildly elevated chromogranin A levels.
Dr. Strosberg discusses clinical practice approaches when encountering patients like James with colonic masses demonstrating very high Ki-67 indices and neuroendocrine immunohistochemical markers. When pathologists confirm poorly differentiated carcinoma with characteristic Ki-67 exceeding 55% to 70% and appropriate morphology, metastatic disease typically requires medical oncology management with cytotoxic chemotherapy as the primary intervention.
Following multidisciplinary tumor board discussion, James initiates first-line carboplatin-etoposide therapy, achieving partial response after 3 cycles with shrinkage of hepatic metastases and the primary colonic mass.
Following first-line progression, James's tumor board recommends comprehensive biomarker evaluation. Tissue from the initial biopsy undergoes DLL3 immunohistochemistry testing, returning positive results with H-score of 180 and 85% of tumor cells demonstrating staining intensity of 1+ or greater. Case presentation at multidisciplinary conference raises questions about whether this biomarker result can guide therapeutic decision-making for a patient lacking currently approved targeted options.
Dr. Strosberg discusses tarlatamab, a bispecific T-cell engager targeting DLL3 on tumor cells and CD3 on T-cells, bringing cytotoxic T-lymphocytes into close proximity with cancer cells to induce targeted cell death. Although another DLL3-targeting antibody received approval for SCLC, tarlatamab has focused research efforts on both pulmonary and extrapulmonary NECs, making it particularly relevant for specialists managing rare extrapulmonary disease.
