HPV-SAVE_Merck_Sub-Study for Preventing Recurrence of HSIL

Advances in the treatment of HIV-infected individuals with the advent of the combination antiretroviral therapy (cART) era has led to dramatic reductions in mortality and morbidity. These dramatic strides in survival within HIV-positive populations have led to a focus on longer-term morbidities in these individuals, including malignancies. Indeed, an increase in a variety of malignancies in HIV-infected individuals has been noted in the cART era. Amongst these are cancers associated with HPV, responsible for the vast majority of cervical cancers (itself a well-established acquired immune deficiency syndrome (AIDS)-defining illness), and 40-90% of anal, vulvar, vaginal, penile, and oropharyngeal cancers. More specifically, a recent meta-analysis indicates that the overall prevalence of HPV in anal carcinoma is approximately 84%, with HPV type 16 being isolated in 73% of all cases, making it the most prevalent type implicated in anal carcinoma.

Though infrequent at a rate of one per 100 000, squamous cell anal carcinoma is on the rise in the general population. It occurs at significantly higher rates in HIV-positive men - particularly among MSM - with an estimated rate of 60 to 160 per 100 000. A recent study of thirteen North American AIDS Cohort Collaboration on Research and Design (NA-ACCORD) with over 34,000 HIV-infected patients, found that anal cancer rates were highest in HIV-infected MSM, with a rate of 131 per 100,000 person years. In fact, rates of anal cancer among HIV-infected MSM are comparable to rates of cervical cancer in women prior to the adoption of routine screening for cervical dysplasia. In addition to its etiologic association with HPV, anal cancer shares many similarities with cervical cancer. Both are squamous cell cancers occurring at the squamo-columnar junction, and both likely arise from histologically-similar, dysplastic precursor lesions. It is postulated that a critical step in anal cancer carcinogenesis is the establishment of persistent infection (conventionally defined as greater than six or twelve months) with oncogenic HPV in the anal canal. Though the majority of HPV infections are considered transient and will eventually clear even in HIV-positive individuals, HIV-positive individuals have higher rates of persistent infection, especially with oncogenic HPV types.

Of the greater than 170 HPV types, over 30 favour the anogenital area, and on the basis of epidemiologic and phylogenetic data, these have been classified by the International Agency for Research on Cancer (IARC).

The vast majority of anal cancers (as well as cervical cancers) are caused by two high-risk HPV types: HPV type 16 and HPV type 18, felt to be responsible for 66% and 5% of anal cancers, respectively. However, a recent study from France examining the distribution of HPV types in cases of anal cancer found even more dramatic results: HPV was found in 96.7% of all cases, with HPV-16 being the most prevalent type (75%), with other high risk types (HPV-18, -52, -33, and -51) found in 4% to 6% of cases. Further, HPV-16 and -18 - either alone or in combination - were found in over 78% of cases. HPV lesions caused by low-risk types include condylomata (or commonly known as 'genital warts'), of which 90% are caused by HPV types 6 and 11.

Prevention strategies for anal cancers have emerged that are analogous to strategies used in cervical cancer screening, that rely on a combination of cytology (Papanicolaou, or Pap smear) and high-resolution anoscopy (HRA; analogous to colposcopy), both of which screen for high-grade anal intraepithelial neoplasia (HGAIN; typically graded as anal intraepithelial neoplasia (AIN) AIN-2 or -3). Despite the clear evidence indicating the benefit of screening and treatment procedures in cervical cancer screening, no large rigorous studies have been performed to assess the performance of such strategies in anal cancer screening in either men or women.

In addition to the scant literature on the efficacy of screening programs for anal cancer and HPV in all men - but particularly those who are HIV-positive - there remains an even greater paucity of data on issues surrounding primary prevention of HPV. The HPV quadrivalent recombinant vaccine, or Gardasil®, protects against HPV types 6 and 11, which are the most common types implicated in condylomata acuminata (anogenital warts), as well as the most common oncogenic strains, types 16 and 18. The use of this vaccine has been shown to prevent persistent cervical HPV infection caused by vaccine types in women, as well as preventing nearly all high grade genital lesions in women - the latter of which are considered precursor lesions to invasive cancers. Additionally, a retrospective pooled analysis of two large efficacy trials of quadrivalent HPV vaccine has also demonstrated a treatment effect from HPV vaccine in preventing recurrences of previously treated high grade cervical disease.

Few studies have been done on the use of the quadrivalent HPV vaccine in men; there has only been one study examining the use of the HPV vaccine in HIV-positive men, and this study found the vaccine to be safe and immunogenic. Overall, these studies have shown promise, demonstrating a reduction in vaccine-type genital lesions in young men who were vaccinated versus those receiving placebo, evidence of protection against HGAIN in MSM, and a 50% reduction rate in HGAIN recurrence in MSM previously treated for dysplastic lesions. This latter study lays the foundation of the currently proposed study. However, the role of the HPV vaccine in secondary prevention of HGAIN has not been examined in a systematic, prospective way. Given the unacceptably high rates of HGAIN recurrence in those having undergone ablative therapy (from 62% to 91% within two years in HIV-positive MSM), exploring this potentially novel benefit of the HPV vaccine is certainly warranted and could potentially change the way clinicians address HPV-related disease in this high-risk group.

Until recently there existed no standard recommendation for the use of HPV vaccinations in males, regardless of HIV serostatus; however, these studies have prompted the Centres for Disease Control and Prevention's (CDC) Advisory Committee on Immunization Practices (ACIP) to recommend that boys be routinely vaccinated for HPV beginning at age 11 or 12. Canada's National Advisory Committee on Immunizations (NACI) went further, recommending vaccination in all males between 9 and 26 years of age, as well as any MSM 9 years of age or older.

Gardasil-9 is a novel, 9-valent HPV recombinant vaccine, which expands the coverage of oncogenic HPV types, with the addition of HPV types 31, 33, 45, 52, and 58 to the existing quadrivalent vaccine types. The addition of these five oncogenic types is estimated to improve cancer coverage to 90% (versus 70% for the quadrivalent vaccine). With its expanded coverage of oncogenic HPV types, its proven efficacy in primary prevention and its potential role in mitigating HGAIN recurrences - all coupled with the disproportionate burden of HPV-related anal cancers borne by HIV-positive MSM - it is critical that its use be comprehensively assessed in this very high risk population