Cervical cancer (CC) is a scourge that imposes a therapeutic emergency. This cancer is increasing steadily in sub-Saharan Africa, with more than 75,000 new cases and nearly 50,000 deaths a year (Steenbergen et al., 2005)(Mboumba et al., 2017). According to the World Health Organization, CC is the fourth most common affecting female population worldwide, and will kill more than 443,000 people worldwide by 2030, nearly 90% of them in sub-Saharan Africa. This high incidence may be justified by the lack of adequate structure for diagnosis, screening and treatment (Castellsague et al., 2007). In Senegal, CC is the first most common cancer of women (ICO/IARC HPV Information Center, 2019), and here we reported a pilot study exclusively dedicated to the distribution of HPV genotypes among Senegalese women with cervical cancerous lesions.
As expected, all cervical specimens collected in women with histologically confirmed ICC were HPVpositive with at least one genotype detected. The most commonly detected HPV types in women with single or multiple HPV infections were HPV16 (systematically detected in more than half of our patients), 18 (44%), 45 (33%), 33 (31%), 59 (28%), 35 (12%), 31 (11%), 58 (8%), 39 and 73 (4%), 44, 54 and 68 (3%) and the rest less than 1%. The high prevalence of HPV16 and HPV18 reported in our study was expected, since these types are the two most common HPV types across the world (de Sanjose et al, 2010; Li et al, 2011; de Oliveira et al, 2013; Deny et al, 2014; Lagheden et al, 2018; Liao et al, 2018). However in some studies (Mejia et al, 2015; Wang et al, 2018; Schisler et al, 2018; Long et al, 2018), other genotypes (HPV45, 58, 52) had been reported as the second commonest. This result agrees with that of Missaoui et al, 2010 had found that HPV16 is the most frequent virus among invasive squamous cell carcinomas (47.6%, p = 0.001) and adenocarcinomas (80%, p <0.001) in Africa from the north (Tunisia). On the other hand, in Central Africa more precisely in Cameroon, the prevalence of the HPV 16 and, HPV 18 genotypes represented 30.8% (Tebeu et al., 2018).
//Infections and cofactors //
we also noted that most women were infected with at least one high-risk HPV (70%). This high co-detection rate is especially due to the high sensitivity of the Chippron real-time PCR test which targeted a wide range of genotypes but also of the fact that the almost toltality of our patients were under polygamous regime. We know that being sexually active and having many sexual partners increases the risk of the most virulent papillomavirus infections. In Senegal, patients do not accept to tell you how many sexual partners they have, but we do have polygamy. the most frequent marital situation and that the majority of these patients were under this regime hence our assertion that polygamy is a risk factor. Indeed polygamy can involve the diversity of the noted genotypes as well as the high number of coinfection. Overall, it was noted that the proportion of HPV multiple infections increased in the last years from 4% to 15% (Li et al, 2011), reflecting the use of new tests more prone to detect multiple infections in recent studies.
Multiple HPV infections could, in part,explain the special aggressivity and the rapid progression of the cervical cancer disease noted in the Senegalese women as it was reported as an independent predictor of poorer survival another study (Genta et al, 2017). However the mechanism how multiple HPV infections affects patients survival is not fully understood. We also noted that co-infections with more than 2 HR-HPV types were especially prevalent in patients between 45 to 55 years age, probably due to viral persistence or reactivation of latent HPV (Simon and Poppe 2008; Dufit et al., 1991).
With regard to marital status, multiple HR-HPV co-infections were significantly more prevalent among polygamist. We also noted that women with more than six pregnancies were prone to multiple coinfections. Both results are in line with previous results which clearly indicated that multiple pregnancies and the high number of sexual partners increase the risk of HPV infection and persistence (IARC, 2016).
// Link with Vaccines //
Based on the new Gardasil-9® vaccine which operates against 9 HPV genotypes (6, 11, 16, 18, 31, 33, 45, 52 and 58), only 5 ICC cases were exclusively associated with non-vaccine types. So regarding the results obtained in the present study, the use of this nonavalent vaccine might provide an effective prevention outcomes for cervical cancer in Senegalese adolescent girls or young women, with the expectation to prevent up to 95% of ICC. However, further studies including more patients are needed for a better assesment of the real impact of this nonavalent vaccine.
Regarding the vaccination perpectives, the relatively high prevalence of the non vaccine types HPV59 (18.33%) and HPV35 (11.66%) could be a public health issue in Senegal, but once again additional studies are needed to confirm these findings.
However some limitations can be pointed out of this study. Firstly, the modest sample size included in this study. Indeed, infortenately only few cases were sampled and tested, and the HPV genotypes prevalence reported here should be considered as trends which need confirmation through additional more exhaustive studies. Secondly, the high prevalence of multiple infections, sometimes with more than 3 genotypes, complicates the establishment of the carcinogenic value of some HPV types or group of HPV types. Genotypes viral load determination by quantitative methods would probably help to have an idea about the more carcinogenic types or combinations ‘types' associated with (ICC) in Senegal.