P-251 Multidisciplinary challenge for the oncologist and surgeon: Gastrointestinal stromal tumors. Follow-up of a tertiary surgical department

Abstract

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in gastrointestinal system with most found in stomach. With the characteristic of being mostly c-KIT positive (CD117) as a mutation carrier, genetics is a part of the management of GIST, helping both the surgeon and the oncologist. The diagnosis and the definition of the characteristics of tumor will help to define the response to treatment procedures, which is fundamental for oncologists and surgeons to create an algorithm for their patients. The follow-up should be done both with oncologists and surgeons in order to define early recurrences and metastasis. This study is based on the follow-up of GIST patients operated in a tertiary general surgery department. 43 patients have been operated on between January 2017-December 2018. Routine preoperative diagnostic findings and postoperative pathological evaluations are identified and noted. In our hospital, routine management of GIST is as follows: In case of high grade GISTs, postoperative adjuvant imatinib therapy is routinely given for three years, and if there is metastasis or locally unresectable tumor, neoadjuvant imatinib treatment is given for shrinking the primary tumor and curing the systemic disease before the surgery. As the primary and golden treatment of GIST is surgery, surgery is always an option for even metastatic disease. Of 43 patients, 23 patients had a mitosis rate under 5/50, whereas 5 patients had a mitosis rate between 5/50 – 10/50, and 15 patients had a mitosis rate over 10/50. According to the size of the tumor, 3 patients had a single tumor under 2 cm. All of these three patients had lesions in the prepiloric area, and got operated with the symptoms of gastric outlet syndrome. 17 patients had a tumor between 2-5 cm, whereas 14 patients had a tumor between 5-10 cm. 9 patients had GIST tumors over 10 cm in diameter. Interestingly, all patients with liver metastasis had liver lesions over 10 cm. One patient with a tumor bigger than 10 cm had an extragastrointestinal stromal tumor, arising from the mesentery. The pathological results of the specimens were as follows: 29 spindle cell histologic subtype, 3 epitheloid cell subtype, and 11 mixed cell subtype. The focal necrosis was present in 14 patients. From 43 patients, three patients got reoperated. The first patient was reoperated at the fifth month postoperatively because of mechanical obstruction. The second patient got reoperated at the ninth month postoperatively because of incisional hernia. The third reoperated patient was reoperated because of the first pathological specimen was found out to be surgical borders millimetrically positive. The reoperation rate for our patients in three years of follow up was 6.97%. All reoperated patients had a pathological finding of spindle-cell type of morphology, with mitosis rates over 10/50. There needs to be more studies based on reoperation rates after GIST surgeries, but this study evaluated that complications after GIST surgery should be followed both by the oncologist and the surgeon.