GISTs are rare digestive tumors [1]. Fifteen cases were identified during the study period. Similar trends were seen in other African series. Only 19 cases of gastric GIST were identified in Cairo, Egypt over a 6 year period at the National Cancer Institute; and 10 cases of GIST (all localizations included) over a 8 year period at the main hospital of Dakar, Senegal [6, 7].
The median age at diagnosis was 52 years. Similar data are reported by other series from Africa [6, 7]. The median age in western series seems higher than our, ranging from 65,8 to 69 years [12, 13, 14]. This could be explained by the higher age of the western population as well as their better life expectancy.
We noted in our series a male preponderance. However, GISTs usually affect both genders without predilection [3]. Other studies from Africa with small sample size reported similar results [3, 7, 15].
Delay in care seeking after onset of symptoms ranged from 24 hours to 15 years. In case of non-emergency, patients seek health care late, probably because of their low income status. This leads to late diagnosis which involve a higher risk of recurrence.
All patients were symptomatic, and the most frequent symptoms were abdominal pain and abdominal mass. Others African studies have reported similar symptoms [6, 7]. Most of authors described GISTs as asymptomatic tumor until they reach a large size and main symptoms are the pain and gastrointestinal bleeding [2]. The delay in diagnosis in Africa probably made tumors become larger and palpable, and the patients symptomatic.
The stomach was the most common site for GISTs with 8 cases followed by the large bowel. Given the size of our sample, the interpretation of the frequency of locations could be biased. For instance, the second most frequent location in many studies is the small intestine [2, 3, 12, 14].
In our series, endoscopy contributed to diagnosis in few cases (n=5). The typical endoscopic appearance of GIST is usually a nonspecific smooth bulge covered by normal mucosa [16]. The endoscopic lesions (ulcerating and ulcerative-budding lesions) in our series were probably due to tumor size. But the intraluminal lesion isn’t always correlated with tumor size. Figure 4A is an example of large gastric GIST associated with a small intraluminal lesion.
In our study, all endoscopic biopsies were conclusive. In contrast, according to many authors, the endoscopic biopsy used to be negative because it does not often reach the submucosa where the tumor is located [3, 17]. Our biopsies were conclusive probably because of endoscopic appearance of the tumors which were large with a relatively large intraluminal portion.
Laparoscopy was performed on two patients for diagnostic purpose. This allowed for adequate neoadjuvant treatment to be put in place. However, in western studies, it is most often performed for therapeutic purpose [18, 19]. In our series, the size of the tumors did not allow laparoscopic resection.
Most of the tumors resected in the study were larger than 10 cm (n = 6) with a median size of 11 cm. Similar data have been reported from other low-income countries of Africa and south America [6, 20, 21]. In contrast, studies in Iceland, Korea and Japan have found a median size about 4 cm [14, 22]. The large tumor size is the evidence of the impact of delayed diagnosis in low-income countries like Benin. Such locally advanced tumors led to complex resection in our setting (figure 4B).
We noted a strong predominance of the fusiform cells type and the expression of KIT. In fact, GISTs are often spindle-shaped type and almost always express the KIT [2, 3, 16]. Almost half of the tumors (n = 7) expressed DOG1. DOG1 is a sensitive and specific biomarker that can contribute to the diagnosis of GIST [23]. It is important to point out that the low income of patients contributes to diagnosis delay due to the high cost of immunohistochemistry in our country. Moreover, exams such as molecular biology are required to improve treatment. Unfortunately, these diagnostic methods are not available in most sub-Saharan African countries such as Benin.
Most of our patients were at high risk of recurrence according to Joensuu's modified NIH scoring system. Our data are similar to those of Egypt [6]. In Iceland, Korea and Japan, few patients presented a high risk of recurrence [14, 22]. This could be explained by the large size of the tumors in the African series due to delay in diagnosis. .
Access to imatinib was difficult in Africa especially in Benin [7, 10]. The high cost of targeted therapies for GIST creates a significant barrier to providing cancer patients in low- and middle-income countries [11]. Until 2010 imatinib was not available in Benin [10]. A high risk of recurrence was associated to poor outcomes. But for the past five years, the GIPAP program has enabled patients with GIST to obtain imatinib free of charge. This has greatly improved the outcome of GIST in our country. However, an effort must be made to make second-line treatment such as sunitinib and sorafenib available [3]. In fact, patients currently on treatment may need it if they develop resistance to imatinib.
This study highlights the difficulty of managing GIST in low-income countries such as Benin. Its particularity lies in the diagnostic methods including histology but also immunohistochemistry. Its weaknesses are essentially the small sample size and the retrospective data collection.