Real--world evidence of gastrointestinal stromal tumors (GIST) patients with second primary malignant tumors (SPMT)

GISTs are rare; constituting 1% of all sarcomas and 3–5% of gastrointestinal tumors1. Most frequently originated from the stomach and small intestine2. There are several tumours associated with GISTs but only 5% of them occur within the context of a family syndrome. GISTs patients have a twofold risk of developing a second tumor than general population3. We present the frequency and type of SPMT in patients diagnosed of GISTs from our experience.

We included a total of 116 patients who were diagnosed with GIST and admitted to the University Hospital Reina Sofía Medical Oncology Unit (Spain) between 2013 and 2022. Patient information was retrospectively obtained from the medical history. Patients’ and tumor characteristics, as well as follow-up and survival data were analyzed. Logistic regression was used to determine Progression Free Survival (PFS) and Overall Survival (OS), using SPSS.

The median age was 71 years old. Forty-eight percent were females and 52% males. The majority were located in the stomach (54%) and small intestine (32%). Eighty percent with localized disease and 20% metastatic. KIT mutations were found in 60% (48% exon 11 and 12% exon 9) and 34% were Wild Type. Eighty-eight percent were found to be CD117 positive and 65% CD34 positive and 40% DOG 1 positive. The mean follow-up was 85 months. Median OS was 67 months. Median PFS was 22 months for patients receiving first-line treatment. And 8 months in second line. The incidence of SPMT was 18’7%. The most common was prostate cancer followed by colorectal, kidney and breast cancer. We also found association with lung, bladder, gastric, endometrium, melanoma or schwannoma. Thirty-five percent were synchronous 35% and 65% metachronous. Being 70% localized and 15% metastatic. The median OS for patients with SPMT was 81 months. When comparing GISTs patients with SPMT and the others, the difference was not statistically significant (p= 0’7).

GISTs patients in this study reached a similar OS as reported in literature. In large cohorts, the association between GISTs and SPMT has been reported to be 14– 19%, similar tan in our cohort; 18,7%4,5. Most incident tumours associated with GIST are gastrointestinal and genitourinary tumours, as in our experience. It is believed that patients with second tumours have a worse survival rate than those without second tumours, what we have not been able to confirm. More exhaustive study of these patients at higher risk of developing second malignancies is needed.

The authors.

Has not received any funding.

All authors have declared no conflicts of interest.