Voluminous Gastric Stromal Tumors: Place of Surgery about 5 Cases at the Dakar Cancer Institute

Objectives: To describe the surgical and prognostic aspects of voluminous gastric stromal tumors at Joliot Curie Cancer Institute. Methods: This was a retrospective study of patients with voluminous stromal tumors from January 2010 to December 2015. Patients had a bulky gastric mass at the clinical examination and CT and had positive CD117 marker. Local stage and extension was evaluated and surgical treatment studied. Prognosis was also analyzed according to surgery and adjuvant treatment. Results: Five large GISTs were found. Most are women with a mean age of 39. The tumor was palpable in all patients. Other symptoms are pain and vomiting. Gastroscopy found a burgeoning tumor in 4 patients with external compression in 1 patient. Biopsy showed stromal tumor with fusiform cells in 3 patients and epithelioid cells in 2 patients. CD117 and CD34 were positive in all patients. Abdominal and thoracic CT showed a sus mesocolic mass voluminous with multi viscerl involvement without distant metastasis. Surgery consisted in all cases of total gastrectomy extended to the spleen, the tail of the pancreas, the colon and the liver. One patient died of postoperative peritonitis at day five. There was none other immediate post-operative complications. All patients received adjuvant treatment with Imatinib. After a 23-month follow-up, 1 patient experience important sarcopenia while 1 patient recurred to the liver and brain with resistance to Imatinib and second line Sunitinib and died. Conclusion: voluminous gastric GIST in Africa is characterized by young age and involvement of sus mesocolic organs. Surgery with Imatinib as first line adjuvant treatment showed good results.


Introduction
Gastrointestinal Stromal Tumors (GIST) are related to the group of soft tissue sarcomas, of which they constitute about 20% [1]. The prognosis of GIST improved with the advent of Imatinib. The best treatment remains surgery which represents the only potentially curative treatment [2]. Their most frequent primary sites are the stomach (about 60% of cases) and the small intestine (25%) [3]. The main discussion in the literature is about laparoscopic versus open approches. The size of GIST in the stomach can be very large, involve other organs. In this cases surgery and the following treatments represent a great challenge. The objective of this work was to describe the therapeutic and prognostic aspects of volumeous gastric stromal tumors at Joliot Curie Cancer Institute.

Methods
This was a retrospective study of patients with voluminous gastric stromal tumors from January 2010 to December 2015. Patients had a bulky gastric mass at the clinical examination and CT and had positive CD117 marker. Local stage and extension was evaluated and surgical treatment studied. Prognosis was also analysed according to surgery and adjuvant treatment.

Results
Five large GISTs were found. They were 3 women and 2 men. The mean age was 39.5 with extremes of 21 and 56. Pain was found in 3 patients. Vomiting occurred in 2 patients. Mass was palpable in all patients. Gastroscopy found a burgeoning tumor in 4 patients with external compression in 1 patient. Biopsy showed stromal tumor with fusiform cells in 3 patients and epithelioid cells in 2 patients. CD117 and CD34 were positive in all patients. Abdominal and thoracic CT showed a sus mesocolic mass with large necrosis suggestive of GIST with multi visceral invasion in 2 cases ( Figure 1).
There was no distant metastasis. Pancreatic tail, spleen and transverse colon invasion were seen in 1 patient while invasion of the left liver occurred in 1 patient. Surgical exploration showed involvement of the gastric curvatures ( Figure 2). Surgery consisted in all cases of total gastrectomy. It was extended to the spleen, the tail of the pancreas, the transverse colon in 1 patient and to the left liver in 1 other patient ( Figure 3).
One patient died of postoperative peritonitis at day five. There was none other immediate post-operative complications. All patients received adjuvant treatment with Imatinib. Evaluation of quality of life showed in 3 patients acceptable behaviour and in 1 patient important sarcopenia. After a 23-month follow-up, one patient recurred to the liver and brain with resistance to Imatinib and second line Sunitinib and died.

Discussion
GIST account for 5.6% of gastric tumors at Joliot Curie Cancer Institute in Dakar.
The exact incidence of GIST is still difficult to evaluate due to recent changes in their definition [3]. These tumors account for less than 3% of gastrointestinal tumors [4]. The incidence seems to be the same in the other african series [5,6]. Male predominance is not really confirmed [7,8]. Stromal tumors can occur at any age but are infrequent before 40 years [9-11]. GISTs are often asymptomatic. They may be revealed by nonspecific symptoms such as occult digestive bleeding, pain or abdominal mass [12][13][14]. Bleeding and pain are the most frequent symptoms. In african series, mass is the first symptom [7,15]. The frequency of stromal lesions under the gastric epithelial during gastroscopy makes it necessary to use echo endoscopy. It makes it possible to distinguish the GIST from an extrinsic compression [16,17]. The mean size after CT is 10 cm [18]. This examination allows to evoke the diagnosis in more than 80% of the cases and to predict the prognosis. The pejorative prognosis arguments for survival are a diameter greater than 11 cm, an irregular surface, blurred borders, invasion of the wall of the digestive segment or mesentery, heterogeneous contrast, hepatic metastases and peritoneal dissemination [19]. Surgical treatment is the cornerstone of the treatment. The quality of the surgical procedure (R0 versus R1) has a prognostic impact. The best surgical results are obtained after complete surgery without tumor split with a five-year survival of 50% [20]. If surgery is macroscopically incomplete or in case of preoperative rupture of the tumor, overall survival at five years drops to less than 10%. The resectability rate of non-metastatic primary tumors oscillates between 60 and 90% [21]. Although the conventional route is preferred over laparoscopy, the feasibility of laparoscopic resection of GIST has been demonstrated for tumors of less than 5 cm with an advantage in terms of operative time, hospital stay, blood transfusion [22,23]. Tumor size plays an important role in resecability and choice of approach. Locally advanced GIST are less frequent in the literature. The quality of the resection partially compensates for the disadvantage of size [24]. Immediate post-operative complications are related to the type of surgery. In case of resection of numerous organs, complications such as infections, fistulas are more frequent [11]. Delayed comlications are characterised by post gastrectomy insuffisciency such as dumping syndrom and particularly sarcopenia [25]. It is related to the extension of the underlying neoplasm and the gastrectomy [26]. The efficacy of Imatinib as adjuvant treatment and in metastatic situation is established [27]. Neo-adjuvant treatment is not recommended outside of a clinical trial. Its effectiveness remains to be defined in the residual lesions as well as in surgery for metastatic lesions [28]. The resectability of the tumor is an important prognostic factor. The overall survival at twelve months and sixty months is 80% and 45% respectively [29,30].

Conclusion
GISTs of the stomach are characterized by younger age and large sizes at diagnosis in Africa. Factors of poor prognosis are closely related to tumor size. The surgical treatment is essential for prognosis often consists of multi-visceral excision. Resection is difficult to complete. The use of tyrosine kinase inhibitors and more recently of the anti-angiogenic agents improves the results of the surgery in adjuvant and metastatic situation. Their efficacy is doubtful in case of multiple metastases.