25P Risk of second primary head and neck cancer in patients with head and neck soft tissue sarcoma

Head and neck soft tissue sarcoma carries poor prognosis. They are also known for their high recurrence rate however, the possibility of a second primary is still unclear. So, we aim to assess the risk of developing a second primary cancer in the head and neck region to highlight the association with head and neck soft tissue sarcoma and for better quality of life. We extracted the data of 5935 patients from Surveillance, Epidemiology, and End Results (SEER) database diagnosed from 2000-2019. Using MP-SIR seer session, the standardized incident ratio (SIR) was assessed as Observed/Expected (O/E) ratio and Excess Absolute Risk (EAR) is per 10000. Confidence intervals are 95% and P value is significant P<0.05. The overall 5-year relative survival of head and neck soft tissue sarcoma was 66.9%. It had an overall EAR of 30.67 and O/E of 37.4 (P<0.05, 95%CI: 29.5-46.8). The nasal cavity was the most site to have a risk for a second primary cancer with EAR of 19.4, and O/E= 444.2 (P<0.05, 95%CI: 326.4-590.7). The larynx had the second highest risk of a second primary tumor with EAR=10.4 and O/E= 28.3 (P<0.05, 95%CI: 18.5-41.5). The gum of the mouth demonstrated the third highest risk with EAR= 6.5 and O/E= 16.1 (P<0.05, 95%CI: 6.9-31.8). Salivary glands had an EAR of 6.1 and O/E of 57.0 (P<0.05, 95%CI: 31.9-94.0). Nasopharynx had an EAR=4.1 and O/E= 83.48 (P<0.05, 95%CI: 40.03-153.52). These results show a 30-fold increase in the risk of developing a second primary cancer in the head and neck region. Nasal cavity had the highest fold risk increase by 19 folds followed by larynx by 10 folds. The gum and salivary glands both had around 6-fold rise in the risk of a second primary tumor. Nasopharynx showed the least risk by 4 folds. We recommend follow up screening of the nasal cavity and the larynx as most sites at risk of a second primary especially cancers at these sites only manifest at later stages making it hard to treat.