Gastrointestinal stromal tumors and second primary malignancies: a retrospective monocentric analysis

In the post-Imatinib era, the median survival of patients diagnosed with GIST has reached almost 5 years. Prolonging GIST-specific survival, GIST patients have an increased incidence of secondary neoplasia. Data on the prognostic impact of second tumors in GIST patients are very poor with few and small retrospective analyses available in the literature. We conducted a retrospective monocentric analysis on 145 patients diagnosed with GIST between April 2001 and October 2018. Kaplan-Meier and Cox hazard methods were used for survival analysis. A total of 154 GIST patients were included and 31 patients of them (21%) were diagnosed with at least one additional malignancy. The most common second tumors associated with GIST were gastrointestinal tumors. GIST patients with additional malignancies showed to have lower size (>5 cm: 35% vs 45%; p=0.75), higher mitotic rate (>5/50 HPFs: 42% vs 29%; p=0.24), higher presence of c-KIT mutation (85% vs 69%), a lower presence of PDGFRα mutation (8% vs 17%; p=0.05) and shorter survival (mOS: 9.6 vs 15.5 years; p=0.30). In conclusion, our study did not find any significant correlation between clinicopathological characteristics and the development of a second tumor in GIST patients. Further analyses and strict follow up protocols are needed in order to early diagnose and promptly treat a second primary tumor in the GIST population.