EP1010 - Patterns of initial presentation, treatment and outcomes of rectal small cell carcinoma: A nationwide study

Purpose/Background: Extrapulmonary small cell carcinomas (EP-SCCs) of the GI tract are rare diseases, where approximately 0.1-1.0% of cases arise from the gastrointestinal tract. The most common site for EP-SCC is the esophagus, followed by the colon and rectum, accounting for 0.2-0.8% of all colorectal neoplasms. There is minimal information on the management of EP-SCC in the rectum (R-SCC), with the primary source being case reports or case series. In this study, we aimed to assess the patterns of patient presentation and treatment using the National Cancer Database (NCDB).

Methods/Interventions: The NCDB was queried for adult patients diagnosed with R-SCC from 2004 to 2022. Patients with carcinoma in situ and unknown stage were excluded. Variables analyzed included patient demographics, stage at diagnosis, and treatment modalities. Overall survival (OS) was assessed using Kaplan-Meier analysis and compared across stages and treatment modalities using the log-rank test.

Results/Outcomes: A total of 921 patients met the inclusion criteria. Mean age at diagnosis was 62.0 ± 14.1 years and 52.1% were male. More than 60% of the patients had stage IV disease at the time of diagnosis whereas early diagnosis (Stage I and Stage II) was only made in less than 15%. Approximately 80% of the patients were treated with chemotherapy and 43% underwent radiation therapy. Surgical resection was performed in12% patients. Median OS was 10.9 months. The patient who underwent chemotherapy had significantly improved OS compared to those who did not in stage III and stage IV disease (p < 0.05). Ones treated with radiation therapy had better OS in stage IV disease (p < 0.05) and tendency to have improved OS stage III (p=0.05) while surgical resection added no difference in survival.

Conclusion/Discussion: R-SCC is a rare and aggressive malignancy with poor OS across all stages. In this national cohort, chemotherapy and radiation therapy were associated with improved survival, particularly in stage III and stage IV disease. The lack of statistical difference in OS with surgical treatment may be due to a small sample size in early-stage R-SCC. Surgical resection should be considered judiciously in locally advanced R-SCC. Overall prognosis remains poor, emphasizing the need for earlier diagnosis and prospective evaluation of combination regimens.