Atezolizumab, lurbinectedin, tarlatamab, and FOLFIRNOX in a patient with metastatic small cell carcinoma of the anal canal: A case report and review of the literature.

Small cell carcinoma (SCC) of the anal canal is a rare and highly aggressive neuroendocrine malignancy, and its infrequency has limited the development of evidence-based treatment approaches. As a result, management of extrapulmonary SCC (EPSCC) is often extrapolated from small cell lung cancer (SCLC), given the similar disease biology and the lack of formal approval for many SCLC-directed agents. We report the case of a 60-year-old woman who presented with metastatic SCC of the anal canal and whose disease course illustrates both the challenges and therapeutic uncertainties inherent in treating this diagnosis. Given the absence of established standards, she was treated with SCLC-based regimens and achieved a partial radiographic and clinical response to platinum-based chemotherapy in combination with the immune checkpoint inhibitor atezolizumab.

Upon subsequent progression, she was treated with lurbinectedin and tarlatamab, a bispecific T-cell engager targeting delta-like ligand 3 (DLL3), reflecting evolving treatment paradigms in SCLC. Her response suggests that novel therapies developed for pulmonary small cell disease may offer benefit in select extrapulmonary cases. This case highlights the need for continued reporting of clinical experiences and prospective investigation to better define the role of emerging therapies in rare and aggressive extrapulmonary neuroendocrine malignancies.