A novel nomogram for predicting treatment and prognosis in primary gastric squamous cell carcinoma (PGSCC).

e16092 Background: PGSCC is an aggressive tumor that accounts for 0.5% of all gastric cancer cases. Its poor prognosis and lack of management guidelines make it challenging. A prognostic index for estimating the clinical outcomes of PGSCC would be attractive in the current clinical practice. We aimed to develop and validate an effective nomogram to predict the survival of patients with PGSCC. Methods: We analyzed data from the SEER database of patients diagnosed with PGSCC between 2004 and 2021. Patients who were not diagnosed based on histology, previous history of cancer or other concurrent malignancies, or unknown data were excluded. The clinicopathological features of each group were compared using the chi-square test. Kaplan-Meier estimation, log-rank tests, and Cox regression analyses were used to identify the prognostic factors for OS and CSS. A nomogram was developed to predict 5-year OS, and a calibration curve was plotted to evaluate the agreement between the actual (observed) outcomes and expected probabilities. Results: A total of 938 patients were included, most of whom were male (71.2%) and predominantly White (73.7%), followed by Black (14.5%). The median patient age was 66 years, and the median tumor size was 5.3 cm. Most tumors were in the cardia (75.5%), followed by the gastric antrum (3.7%), and lesser curvature (3.2%). Most patients were classified as T4 (22.5%) and T3 (20.9%), with 35.7% having N0 and 47.8% having no metastasis. Only 34.4% of patients underwent surgery, with gastrectomy involving esophageal removal being the most common type (16.6%). Most patients did not receive radiation (55.7%), whereas 57.1% received chemotherapy. Patients who received radiation had better 5-year survival rates (OS, 23.6%; CSS, 28.45%) than those who did not (OS, 14.97%; CSS, 19.9%). Chemotherapy had a minimal impact on survival (OS: 19.5%, CSS: 23.76%) compared with those who did not receive chemotherapy (OS: 17.23%, CSS: 23.87%). Surgery significantly improved survival outcomes (OS, 37.31%; CSS, 47.4%) compared to no surgery (OS, 8.67%; CSS, 10.56%). Patients without metastasis had markedly better 1-year survival rates (OS: 56.7%, CSS: 62.87%) than those with metastasis (OS: 14.68%, CSS: 15.29%). We developed a prognostic nomogram that integrated significant variables, including metastasis, surgery, chemotherapy, and radiation. The model assigned the highest weight to the metastatic status, followed by surgery and chemotherapy. The AUC was 0.73 (95% CI: 0.69–0.77), and the calibration curves exhibited a mean error of 0.048. Conclusions: This study underscores the potential use of a nomogram as a tool for personalized medicine in treating PGSCC. Although radiotherapy showed limited survival benefits and the least impact within the nomogram, its precise role remains underexplored, warranting further research to better understand its effectiveness in managing this rare cancer.