Cervical cancer is the leading cause of cancer-related death among women in sub-Saharan Africa (SSA) but it can be prevented by vaccination. But, due to financial and logistical obstacles, their implementation is difficult in SSA. Although current vaccines can only prevent up to 9 different genotypes, it affords cross-protection between the genotypes targeted by the vaccine and non-target genotypes. However, the effectiveness of these campaigns also depends on a better understanding of the distribution of different HPV genotypes in women with high-grade lesions. Although many studies have been conducted over the past few decades in SSA countries, their comparison is difficult because of the lack of standardization in the methodologies used in pathology and virology. Although screening by molecular testing for HPV genomic DNA is more efficient than screening by cytology, histological confirmation of cases remains the cornerstone of clinical diagnosis. However, pathology laboratories are rare in low-income countries [14]. For example, to date in Gabon, there are only four laboratories all located in the capital city and the most recent of which became operational in 2020. However, two of these laboratories located at the CHUA and the HIA OBO have biobanks that can be used to assess the prevalence of different HPV genotypes in cervical cancer according to clinical stage. However, screening based on smears associated with cytological analysis has a low coverage rate due to the insufficient infrastructures and the lack of trained personne; HPV screening covers a greater proportion of the population, but is difficult to set up due to the need fo specific infrastructures unavailable on a large scale in Gabon. The global health situation due to COVID-19 has led to a large deployment of thermal cyclers in hospitals in the capital of Gabon as well as in the provinces [15]. Thus, the implementation of molecular screening now seems possible throughout the country.
To determine the prevalence of the different HPV genotypes associated with CIN3 + in the Gabonese population according to methodologies standardized with other French-speaking African countries belonging to the COFAC-Col consortium [7], they were screened on the FFPE samples. The proportions of HPV detected were lower than those reported in studies performed on smears or biopsies in the same Gabonese population [9–11]. There are two main reasons behind this absence of HPV detection in a small proportion of cancer biopsies [16, 17]. First, the DNA extracted from FFPE samples may be partially degraded, making HPV detection more difficult for technical reasons. Second,the target region of the PCR/qPCR used may have been deleted during the process of integration of the viral genome into that of the host. A metanalysis reported viral integration of HPV into the host genome in more than 80% of cervical cancers [18]. This proportion is similar to that obtained in a recent study performed in Gabon, in which the viral genome was found integrated in 85.7% of cervical cancer cases [19].
The diversity of HPV genotypes detected in this study is lower than that obtained in other studies conducted in other SSA countries. Indeed, only six genotypes were detected: HPV16, 18, 33, 35, 45 and 58. Previous studies conducted in Gabon reported between 11 and 24 different genotypes including the six high-risk genotypes in this study [9–11]. However, these studies were based on total DNA extracted from either cervical smears or non-paraffin biopsies, in contrast to this study where only high-grade tumor tissues were specifically collected from paraffin slides. This preselection decreases the probability of finding HPV genotypes not associated with cancer or high-grade lesions. For example, high-grade CIN is primarily caused by a single HPV type [20]. The diversity observed in Gabon is also lower than that observed in Senegal (HPV16, 18, 31, 33, 35, 39, 45, 56 and 58) and Cameroon (HPV16, 18, 33, 35, 39, 45, 51, 56 and 82) in FFPE samples, where nine genotypes were detected [21, 22]. Although diversity varies among SSA countries, the two main genotypes are still HPV16 and HPV18, with more than 75% of cases in Gabon. Finally, the clinical data for cervical cancer in our study are consistent with previous studies conducted in Africa, and particularly in SSA [23, 24]. Cervical cancer in Gabon mainly affects young women under 50 years of age and a large number of cervical cancer cases is diagnosed at a late stage, with 87.3% of patients at stage II or higher.