Prevalence of Human Papilloma Virus Sub Genotypes following Head and Neck Squamous Cell Carcinomas in Asian Continent, A Systematic Review Article

Objectives: In current era of blue brain intelligence and technology access at ease, standardization of disease etiology demands extensive research to drop-down human papilloma virus associated head and neck squamous cell carcinomas impact at large. Present retrospection aims to estimate comparative association of human papilloma virus sub-genotypes in head and neck squamous cell carcinomas, critical analysis of existing research gap, treatment progress, co-infection, gender association, national status and challenges following Human papilloma virus led head and neck squamous cell carcinomas among world largest continent. Background: Head and neck squamous cell carcinomas are not just like malignancies of uterine cervix, lymph nodes and breast cancers. Human papilloma virus led head and neck squamous cell carcinomas treatment directly impact Central nervous system in humans. Intriguingly, human papilloma virus mediated immune response increases patient survival, which indirectly transmit human papilloma virus in future generations and act as a potential threat developing neurogenic disorders. Methods: An objective based search strategy, following comprehensive and specific search approaches were made to retrieve recent 12 years research data from five different NCBI databases. Out of 300 shortlisted articles, only 24 principal studies met the inclusion criteria. Results: Highest human papilloma virus prevalence (10.42 %) was found in South Asia, 5.8 % in South East Asia, 5.7 % East Asia, 2.5% in west Asia and no relevant updated data was found from central Asian continent. Highest prevalence (10%) of HPV genotype-16 was recorded in Asia among 3, 710 enrolled cases including 2201 males, 1149 females and 360 cases of unknown gender. While undifferentiated multiple HPV genotype prevalence was 5.5 % (204 cases). Lowest percentage of HPV sub-types 68, 72, 57, 39 were recorded respectively. Pakistan ranked top reporting highest number of HPV-16 cases, Taiwan HPV-18, India HPV-31, Japan HPV-35 and Singapore in HPV-16 and HPV-18 co-infection rates respectively. Conclusions: Exact prevalence of HPV associated head and neck squamous cell carcinomas among Asian population is still debatable. Due to higher heterogeneity (P< 0.00001), I2 = 81-88% at 95 % confidence interval), non-availability and limitations of reported studies from Asian sub-continents especially central Asia, western Asia and from south and south east Asia demand large scale collaborative research culture to standardize head and neck squamous cell carcinomas aetiology.


Introduction
shortly reported from South Asia instead of entire Asian continent (Bhurgri et al., 2006). According to Faheem A et al study in 2009, HNSCC is considered second most prevalent type of cancer in Pakistani subjects alone with recorded incidence of 40.1% (Bhurgri et al., 2006;Faheem et al., 2009). Commencing comparative clinical aetiology of HNSCCs from Europe based case control studies. About (70-75%) HNSCCs cases are synergistically associated with tobacco and alcohol consumption accompanied by familial history (Hashibe et al., 2009;McKay et al., 2011). Whereas, (10-15%) HNSSCs cases are associated with decreased intake of fruit and vegetables (Chuang et al., 2012;De Feo et al., 2008). In contrast to European countries, betel-quid chewing also plays a major role in the development of malignant tumours focusing Asian subjects (Chen et al., 2008). Molecular biology of Head and neck carcinomas revealed that genetic mutations and chromosomal abnormalities, especially mutation of p53 gene involvement in development of head and neck cancers (Leemans et al., 2011). Recent progression in research trends indicated decline in alcohol and tobacco induced HNSCCs. Whereases, Prevalence of HPV induced HNSCCs is increasing. Another supporting evidence suggest higher chances of HPV transmission during sexual behaviour in comparison to tobacco and alcohol consumption (Chaturvedi et al., 2011;Gillison., et al 2012). Instead of HPV-genotypes independently, co-infection with Epstein Barr virus also errand development of nasopharyngeal carcinomas (Termine et al., 2008). Classical research reported 95% prevalence of HPV in cervical carcinomas and 12.8%-59.9 % association of HPV-Subtypes in HNSCCs, including HPV-35, HPV-33, HPV-31, HPV-18 and HPV-16. Which clearly highlights existing research gap focusing HPV subtype specific prevalence and exact role following HNSCCs zur et al., 2009;Westra et al., 2009;Liebertz et al., 2010;Nasman et al., 2009;Ha et al., 2009). HPV led HNSCCs require progressive and meticulous treatment measures. After critical care and monitoring only five-year survival rate of 68% was possibly achieved yet. While delayed tumour detection and improper treatment may impact nervous system in humans. Intriguingly, HPV mediated immune response increases patient survival, which indirectly transmit HPV in future generations and act as a potential threat developing neurogenic disorders (Pai et al., 2009;Howlader et al., 2009).
Present retrospection aims to estimate comparative association of HPV sub-genotypes in head and neck squamous cell carcinomas among world largest continent. The main objectives include to critically analyse existing research gap, epigenetic treatment progress, multiple genotype co-infection, gender association, national status and challenges following HPV related head and neck squamous cell carcinomas among Asian people.

Database search strategy
An objective based search strategy, following comprehensive and specific search approaches to retrieve recent 12.5-year research data from five different NCBI databases including PubMed, MeSH, PubMed Central, NLM Catalog and Bookshelf.

Inclusion and exclusion Criteria
The articles published in English language focusing human subject only were considered. Criteria followed include recent 12.5-year studies reported from five different geographic regions of Asia. Studies who had significantly explained the role of any sub-genotype of HPV in head and neck cancer. While, studies contradicting above mentioned inclusion criteria were considered ineligible and excluded. Detailed inclusion and exclusion criteria are mentioned in Table 1.

Studies Selection
By Specific approach overall, Principal author and third co-author shortlisted n = 300 abstracts from NCBI databases, including n = 236 duplicate and older than Jan-2009 were excluded for further analysis. From above mentioned 300 citations, only 64 full text articles were found. But, Due to irrelevance with inclusion criteria 40 full text articles were excluded. However, 24 principal studies were focussed and critically analyzed Table 2.

Data Retrieval and Risk Measures
Two co-investigators belonging from another country focused on data review and validation in collaboration with principal author for each included study. Country of study, first author, year of publication, type/site of lesion, number of cases included. Specific HPV type and overall prevalence of HPV in head and neck cancer infection was also studied. Prevalence estimation was done as total number of patient positive for specific HPV-subtype divided by total number of HNSCC patients. The accuracy of data search was counter checked by a second researcher, Further, Omissions; errors were resolved by sharing it with another co-investigator from another territory.

Statistical Analysis
Statistical analysis was done by using Revman 5.30, Prisma and Microsoft Excel 2010 multiple tools.

Characteristics of Meta-Analysis
Meta-analysis concentrating number of included studies from a country, patient selection, mean age, method followed, and relative outcomes as described in (Table 3) from 24 eligible studies. Khovidhunkit et al., (2008) reported only one patient with non-specific HPV out of 65 oral squamous cell carcinomas cases. Luo et al., (2007) examined 51 oral squamous cell carcinoma biopsies and reported 25 % high risk HPV positive cases. HPV-16 and HPV-18 were more prevalent than HPV-33 and HPV-52. Similar study carried by Li-Ang Lee et al., in (2012) reported increasing trend of high-risk HPV in Taiwan. Akhtar et al., (2013) examined 34 oral squamous cell carcinoma confirmed patients. author followed PCR method for detection of HPV subtypes highlighting no one person was affected by any specific high-risk HPV type among Bengali patients. Zhang et al., (2006) highlighted HPV association in oral squamous cell carcinomas including high risk HPV-16 and HPV-18 were positive studies and underdeveloped infrastructure only one recent study conducted by Jalouli et al., (2012) reported that 20% HPV were positive in oral squamous cell carcinomas.

Results
Based on purely two objective based search strategies including comprehensive and specific quality data retrieval approaches. overall 56,302 search results, 10,999 were reported from south Asia, 2,346 from middle East, 1,710 from central Asia, 1,229 from East Asia and only 17 search results from western Asia were found from recent eleven year published sources (Table 4). Our specific approach was based upon shortlisting relevant studies reported from each of five Asian regions.
Reflecting 24 principal studies, overall (9 %) prevalence of HPV was recorded in South Asia, 5.04 % in South East Asia,4.93 % East Asia, 2.21 % in west Asia, 0.32% from a bilateral Pak-Chinese study and no relevant updated patients' data was found from central Asian continent regarding HNSCC. From comparative point of regional HPV prevalence, highest prevalence of HPV was noted in south Asia, south East Asia and very less in central and west parts of Asian continent respectively ( Figure 1).

Assessment of risk bias and clinical heterogeneity
By following dichotomous data analysis random effect model at 95% CI. A significant clinical heterogeneity (Tau 2 = 1.14, P< 0.00001, I 2 = 87 %) was found between HPV positive HNSCCs and type specific HPV-16 led HNSCCs in Asian continent with an overall Odd ratio = 3. 41. (Figure 2A). Whereas, type specific HPV-18 clinical heterogeneity (Tau 2 = 1.87, P< 0.00001, I 2 = 81 %) with an Odd ratio of = 14.57 ( Figure 2B). clinical heterogeneity following HPV co-genotype 16-18 in HNSCCs and HPV multi-genotype led HNSCCs (Tau 2 = 5.43, P< 0.00001, I 2 = 85 %) with an Odd ratio = 0.47 ( Figure 2C). Comparing HPV-16 positive and HPV-18 positive genotype prevalence a significant heterogeneity was calculated (Tau 2 = 3.52, P< 0.00001, I 2 = 88 %). Greater heterogeneity in methodological aspect of included studies was also observed. Due to variable genotype testing methods including, PCR primers, ELIZA kits, ISH protocols and diversity in detection of HPV sub-genotypes followed by each individual study (Table 3). In parallel to determine the level of heterogeneity in our meta-analysis, we followed random effect model to estimate clear HPV type specific genotype prevalence in Asian continent (Table 5A-Table 5D).

South East Asia
HPV was (5.04 %) prevalent in south East Asia. However, 3.72 % multiple HPV genotypes were only reported from Singapore and overall HPV-16 was (1.24%) prevalent in South East Asia (Table 2).

West Asia
In western Asia 2.21% prevalence of HPV was estimated. Similarly, HPV-16 and HPV-18 genotypes were found most prevalent. Equal prevalence of HPV-16 was obtained from both Egypt and Turkey (Table 2).

Un-Categorized group
A collaborative study conducted by Mujtaba et al., (2018) enrolled 506 HNSCC patients both from china and Pakistan. HPV was prevalent in 12 cases (0.32%). Inclusion of Mujtaba et al., (2018) in a distinct category was done to highlight recent progress in collaborative research culture as well (Table 2).

Central Asia
Unfortunately, as per criteria set forth, not a single study from central Asian territories were found including Turkmenistan, Kazakhstan, Kyrgyzstan, Uzbekistan and Tajikistan.

Discussion
First time our review critically analyzed the available literature covering the whole Asian continent and reported 21.5% prevalence of HPV associated HNSCCs with clear heterogeneity insights. While prior to current study HPV association in HNSCCs was considered in the range of 12.8%-59.9 %, including HPV-35, HPV-33, HPV-31, HPV-18 and HPV-16 genotypes only. (zur et al., 2009;Westra et al., 2009;Liebertz et al., 2010;Nasman et al., 2009). However, our review was a collaborative research effort to minimize cancer research gap in Asian continent and focussed prevalence of more than fifteen HPV sub-genotypes. Similar large scale regional and worldwide studies covering whole Asia reported (33%) HPV prevalence in HNC-subsite (Oral cavity) among Asians, 16% in European and 16. 1% North American populations respectively (Kreimer et al., 2005) In 2014 another review reported by Abogunrin S et al focusing European population estimated 40 % prevalence of HPV in head and neck carcinomas. We accept exact prevalence of HPV associated HNSCCs among Asian population is still debateable and our study has certain limitations including non-availability of homogenise reported studies from Asian sub-continents especially central Asia, western Asia and even from south and south east Asia demand large scale collaborative research culture to standardize HPV led HNSCCs aetiology. Beside very potential outcomes, our review has certain limitations including a significant level of heterogeneity in comprised studies, Publication year, variable number of patients, specimen type and HPV detection methods. Similarly, the possibility of confounder cannot be ignoring, because some studies evaluated more then one type of HPV sub-genotype. while an included study detected HPV-16 genotype only as well.
In conclusion, highest priority should be given to initiate homogeneity cancer research programs among Asian countries especially; Afghanistan, Iraq, Nepal and Yemen to assess the tumour positivity rates of HPV in HNSCCs. While in countries like Pakistan, India, Bangladesh, Thailand, North Korea, Iran, Japan and Turkey more collaborative research is needed to standardize prevalence of HPV associated HNSCCs across Asian Continent.

Conflict of Interest
Nil.
Abbreviations P C R , P o l y m e r a s e c h a i n r e a c t i o n ; I S H , in-situ-hybridizations; ELIZA, Enzyme linked immunosorbent assay; HPV, human papilloma virus; HNC, head and neck cancer; CNS, Central Nervous System.