Association Between Gastrointestinal Stromal Tumors and Other Malignancies: It Is Only a Matter of Time? A Case Series and an Overview of Systematic Reviews

Purpose: Little is known about the sporadic coincidence of gastrointestinal stromal tumors (GISTs) with second primary tumors (SPTs). The aim of this study is to clarify if there is a clinicopathologic correlation responsible for the synchronous or metachronous occurrence of SPTs in GIST patients. Methods: We carried out a single-center, retrospective analysis on patients with GISTs surgically treated at our institution from January 2019 to June 2019. Two groups of patients were identified: isolated GIST (group A) and GIST associated with SPT (group B). A meta-review was conducted with the aim to examine the published systematic reviews that included studies assessing the SPT risk in GIST patients. Results: Thirty-nine patients were surgically treated for GIST during the study period, with seven (17.9%) of them having other SPTs. SPTs were most frequent in the colon. Group A patients had a lower mean age at initial diagnosis (56.8 ± 15.2 vs. 73.4 ± 16.6, P = 0.012). No statistically significant difference was found between the two groups in terms of tumor location, mitotic index, Ki-67 expression, risk classification, and imatinib therapy. The overview showed that the cumulative prevalence rate of SPTs ranged from 9.3 to 18.0%. SPTs were more frequent in the gastrointestinal tract (37.9–95.0%), followed by the genitourinary tract. Conclusion: GIST patients under our care experienced a 17.9% overall risk of developing SPTs with different histology. When comparing patients with isolated GIST and patients with GIST and SPT, age was the only variable significantly related to the development of other neoplasms. However, the potential non-random association and causal relationship between GISTs and SPTs remain to be investigated.