Epidemiological profile of brain tumors in Cameroon: a retrospective study

Brain tumors represent group of neoplasms originating from intracranial tissues and the meninges. The aim of this study was to determine the epidemiological profile of brain tumors seen in a referral health center in Cameroon. We carried out a 10-year retrospective study in the neurosurgical, neurology, pathology, oncology and radiotherapy units of our hospital. We found 150 complete case files accounting for 0.7% of total admissions in the various units. Males accounted for 50.7% of the cases. Children less than 14 years represented 12.7% of cases (n = 19). Primary brain tumors constituted 92% (n = 138). Most patients with primary brain tumors were between 25 and 54 years of age, making up 57% of cases (n = 79). The most prevalent histological type of brain tumor was meningioma (26%, n = 39), followed by astrocytoma (24.7%, n = 37), and pituitary adenomas (18%, n = 27). The majority of cases presented with signs of raised intracranial pressure with headache being the most frequent symptom (88%). Some patients presented with seizures (34%), neurological deficit (13%), visual disturbances (10%), and cognitive disorders (7%). Young adults represent the most affected age group. Meningioma, astrocytoma and pituitary adenomas were the most frequent brain tumors in adults. Further studies are needed to assess the long-term outcome of patients with BTs.


Background
Brain tumors (BT) refer to a mixed group of neoplasms originating from intracranial tissues [1,2]. There are two basic types of brain tumors: primary and metastatic brain tumors. Primary brain tumors originate and remain in the brain. Metastatic brain tumors originate from other organs in the body and spread to the brain. Primary BTs could equally be termed benign or malignant, depending on their ability to invade surrounding tissue. In 2015, the world annual incidence of primary BTs was estimated at 3.7 and 2.6 per 100,000 men and women, respectively, with a higher rate in developed (5.1/100,000) than developing countries (3.0/100,000) [3]. In African countries, little research has been conducted on the incidence of BTs. Davies in 1965 estimated central nervous system (CNS) tumors to represent 1.1% of all cancers registered in Uganda [4]. A higher incidence was reported in a hospital-based cancer registry from 2009 to 2010 in Nigeria, where brain cancer represented 3.9% of total cancers [5].
Clinical presentation of BTs ranges from headaches to more serious states like neurological deficits, seizures and blindness, depending on the characteristics of the tumor (histology, anatomical location) [6,7]. Diagnosis of BTs has evolved over the years, from the use of gamma encephalography in the past to modern methods like CT scan, MRI, and brain biopsy [8]. The management is multidisciplinary, involving neurosurgeons, neurologists, oncologists, pathologists, radiologists, radiotherapists, and other health care providers depending on the  [9]. The estimated the annual BTs incidence in Cameroon from 2006 to 2010 was 8 per 100,000 with a male:female ratio of 1:1.5. The commonest histological types were astrocytomas, meningiomas, and ependymomas [10]. This study aimed to determine the epidemiological features of BTs in a referral health center in Cameroon.

Study design
This was a hospital-based retrospective study conducted in the oncology, neurosurgical, pathology, radiotherapy, intensive care and neurology units of a referral hospital in the economic capital of Cameroon. We carefully reviewed medical files of patients from January 2007 to December 2016. We included in this study, all patients admitted for the diagnosis of BT during the study period in our study site. Incomplete files were excluded. This study was conducted with strict respect of ethical consideration, and was submitted and approved by the institutional ethical committee for research in human health of the University of Douala N° CEI-UDo/804/02/2017/T of the 13th of February 2017.

Data collection
After identifying the patients from the registers (hospitalization and outpatient registers), their files were retrieved from the hospital records department and examined individually. Data collection was done with the aid of structured forms designed for this study.
The diagnosis of BT was based on clinical and paraclinical evaluation. The patient's complete information was obtained from these files. Further data obtained from these case files included: the clinical presentation of each tumor type and means of diagnosis. We recorded in this study: • Socio-demographic data: gender, age, and occupation. • Patient history: comorbidities, and risk factors of BT. • Clinical presentation: neurological and extra-neurological signs. • Investigation results (brain CT scans, MRI, and biopsy).

Statistical analysis
Data were analyzed using SPSS 23.0. Categorical variables were presented as frequency (n) and percentage (%).
Continuous variables were expressed as mean ± standard deviation (SD).

Results
A total of 200 patients were managed in this hospital for BTs. This accounts for about 1% of the total number of patients managed within the study period. Of these, 150 patients (75%) had complete. There were 76 males (50.70%). BTs were most common in age groups: 25-54 years (54.66%) and > 55 years (22.68%). Patients in whom no risk factor was identified accounted for 84.68% ( Table 1). The most common histological types found in our study were meningioma (26.60%), astrocytoma (24.70%), pituitary adenomas (18%), and metastases (8%) ( Table 2).  Meningioma was found to be most frequent (64%) in patients within the ages of 25-54 years. There was a slight female predominance (51.3%) as opposed to 48.7% in males. WHO grade I was the most common histological subtype. Astrocytoma was the most frequent tumor type in children between 0 and 14 years of age. WHO grade IV tumors were the most common subtypes. Pituitary adenomas commonly affected females. Lung and breast cancers were the most frequent sources of brain metastases (Table 3).

Prevalence and socio-demographic characteristics
The aim of this study was to determine the epidemiological profile of BTs in a referral hospital in Cameroon. A total of 150 cases were recorded during this period giving an annual frequency of 15 cases per year. In Nigeria,  [10] obtained from the cancer registry in Yaoundé and pathological unit of Buea Regional Hospital. They reported a female predominance 62.5%. Literature reports a slight male predominance [10].
Most of patients in this study were young adults (24-54 years). Olasode et al. observed that the peak age group for intracranial tumors in adults was 25-30 years and Soyemi et al. had similar findings (21-30 years) [5,11]. All of these findings are quite similar to our results. This age group represents the active population of our study area.

Histological types of brain tumors
Primary BTs were the most common types in our patients. Olasode et al. found similar results with primary tumors making up 77% of the cases and metastases 23% of intracranial neoplasms [5].
Meningiomas were found to be most frequent in patients within the ages of 25-54 years. WHO grade I were the most common histological subtype in our series. Eyenga et al. and Mwangombe et al. [9,12] found similar findings. Other studies reported astrocytomas to be more frequent [10,13]. The slight female predominance among cases of meningioma is similar to the results of Mwangombe et al. in Kenya [12].
Gliomas accounted for about one-third of cases in this study. This is very similar to the 33% reported by Olasode et al. in 2000 [5]. Astrocytomas were the most common type, followed by oligodendromas, and ependymomas. More than half of astrocytomas were grade IV. Similarly, Mwangombe et al. [12] reported 22 cases of glioblastomas (55%) in 2006. Andrews et al. found high-grade astrocytoma to be the most common intracranial neoplasm in their study (23%) [13]. Literature reports that astrocytomas make up 50% of brain tumors and glioblastomas are the most frequent form of astrocytoma [5,12,13]. Oligodendromas are far less frequent than astrocytomas in this study. Very similar findings were reported by some authors [5,14].
Ependymomas represented 2% of all intracranial neoplasms in this study which is comparable to the 1.1% in a Caucasian series [15]. In USA, ependymoma is more common in children than adults [16]. We found ependymoma only in adults. Medulloblastoma is the commonest intracranial neoplasm in American children [17]. In the present study, it was the second most common neoplasm after astrocytoma. Three adult cases of medulloblastoma were recorded, which is similar to the reports in USA [7].
Pituitary adenomas were the third most common type in this series. This is comparable to the 17.8% obtained by Cushing et al. [15]. Lower frequency of pituitary adenomas (9.86%) has been observed by Mwangombe et al. [12]. Tumors of the pineal region accounted for 5.3% namely pineoblastomas, pineal carcinomas, and pineocytomas. A study done in Japan indicates that these tumors represent 3.5% of intracranial tumors [18]. Acoustic neuromas were one of the least frequent tumor types in our population. With only two cases found, the annual incidence is far less than the 1 to 20 per 100,000 reported by Edward et al. in 2006 [19].
About two-thirds of brain metastases were above 55 years; no case of brain metastases was reported by Soyemi et al. in Nigeria [11]. Half of brain metastasis originated from lung cancers. One-third of cases were breast cancers. These results differ from the report of Olasode et al. [5] who found choriocarcinomas as main source of metastases followed by Burkitt's lymphoma. This difference may be related to the increasing trends in incidence and prevalence of lung and breast cancers over the years [20,21].
Burkitt's lymphoma is mainly a pediatric tumor and this study does not show pediatric involvement in brain metastases [22].

Clinical manifestations
Commonest clinical features were signs of raised ICP including: headache, blurred vision, vertigo and vomiting. These signs can be associated with mass effect on the brain by tumor. Other signs included seizures, motor deficits, and cognitive deficits. These could be attributed to direct effect on critical brain areas by the tumor, mass effect, leptomeningeal spread and compromise of vascular flow to these areas [23]. These proportions agree with literature reports which indicate signs of raised intracranial pressure as most common clinical presentations of brain tumors [2,9,10,15,24].

Conclusion
BTs are serious conditions with an annual incidence of 15 cases per year. Young adults are mainly affected with a slight male predominance. Primary BTs represent the