Human Papillomavirus Genotype Prevalence in Invasive Vaginal Cancer From a Registry-Based Population

Sinno, Abdulrahman K. MD; Saraiya, Mona MD, MPH; Thompson, Trevor D. BS; Hernandez, Brenda Y. PhD, MPH; Goodman, Marc T. PhD, MPH; Steinau, Martin PhD; Lynch, Charles F. PhD, MD; Cozen, Wendy DO, MPH; Saber, Maria Sibug MD; Peters, Edward S. ScD, DMD; Wilkinson, Edward J. MD; Copeland, Glenn MBA; Hopenhayn, Claudia PhD, MPH; Watson, Meg MPH; Lyu, Christopher MPA; Unger, Elizabeth R. PhD, MD

Obstetrics & Gynecology:
doi: 10.1097/AOG.0000000000000171
Contents: Original Research

OBJECTIVE: To describe the human papillomavirus (HPV) genotype distribution in invasive vaginal cancers diagnosed before the introduction of the HPV vaccine and evaluate if survival differed by HPV status.

METHODS: Four population-based registries and three residual tissue repositories provided formalin-fixed, paraffin-embedded tissue from microscopically confirmed primary vaginal cancer cases diagnosed between 1994 and 2005 that were tested by L1 consensus polymerase chain reaction with type-specific hybridization in a central laboratory. Clinical, demographic, and all-cause survival data were assessed by HPV status.

RESULTS: Sixty cases of invasive vaginal cancer were included. Human papillomavirus was detected in 75% (45) and 25% (15) were HPV-negative. HPV 16 was most frequently detected (55% [33/60]) followed by HPV 33 (18.3% [11/60]). Only one case was positive for HPV 18 (1.7%) Multiple types were detected in 15% of the cases. Vaginal cancers in women younger than 60 years were more likely to be HPV 16– or HPV 18–positive (HPV 16 and 18) than older women, 77.3% compared with 44.7% (P=.038). The median age at diagnosis was younger in the HPV 16 and 18 (59 years) group compared with other HPV-positive (68 years) and no HPV (77 years) (P=.003). The HPV distribution did not significantly vary by race or ethnicity or place of residence. The 5-year unadjusted all-cause survival was 57.4% for women with HPV-positive vaginal cancers compared with 35.7% among those with HPV-negative tumors (P=.243).

CONCLUSION: Three fourths of all vaginal cancers in the United States had HPV detected, much higher than previously found, and 57% could be prevented by current HPV vaccines.


In Brief

Human papillomavirus (HPV) 16 and 33, not HPV 18, are the most prevalent HPV types found in invasive vaginal cancers from a multicenter registry-based U.S. population of 60 patients.

Author Information

Kelly Gynecologic Oncology Service, Department of Gynecology and Obstetrics, Johns Hopkins University, Baltimore, Maryland; the Division of Gynecologic Oncology, Emory University, Department of Gynecology and Obstetrics, and the Division of Cancer Prevention and Control, National Center for Chronic Disease Prevention and Health Promotion, and the Division of High-Consequence Pathogens and Pathology, National Center for Emerging and Zoonotic Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia; the University of Hawaii Cancer Center, University of Hawaii, Honolulu, Hawaii; the Department of Epidemiology, College of Public Health, The University of Iowa, Iowa City, Iowa; the Norris Comprehensive Cancer Center and Department of Pathology, Keck School of Medicine, University of Southern California, Los Angeles, California; the Department of Epidemiology, School of Public Health, Louisiana State University Health Sciences Center, New Orleans, Louisiana; the Department of Pathology, Immunology, and Laboratory Medicine, College of Medicine, University of Florida, Gainesville, and the Florida Department of Health, Tallahassee, Florida; the Michigan Department of Community Health, Lansing, Michigan; the Department of Epidemiology, College of Public Health, University of Kentucky, Lexington, Kentucky; and the Battelle Memorial Institute, Durham, North Carolina.

Corresponding author: Mona Saraiya, MD, MPH, Mona Saraiya, 4770 Buford Highway, Mailstop K76, Atlanta, GA 30341; e-mail:

Supported in part by the Centers for Disease Control and Prevention grants NO. 5U58DP000810-5 (Kentucky), 5U58DP000844-5 (Florida), 5U58DP000812-5 (Michigan), and 5U58DP000769-5 (Louisiana) and from the Surveillance, Epidemiology, and End Results (SEER) Program, National Institutes of Health,

Department of Health and Human Services under Contracts N01-PC-35139 (Los Angeles), N01-PC-35143 (Iowa), and N01-PC-35137 (Hawaii). The support for collection of specimens from Kentucky, Florida, Michigan, and Louisiana coordination of genotyping data from both SEER and National Program for Cancer Registries and genotyping were largely supported by the Centers for Disease Control and Prevention (CDC) intramural funds and Vaccine for Children Funds. The collection of data from California was largely supported by the California Department of Health Services as part of the statewide cancer reporting program mandated by California Health and Safety Code Section 103885; by the National Cancer Institute, National Institutes of Health, Department of Health and Human Services under Contract N01-PC-2010-00035; and grant number 1U58DP000807-3 from the CDC.

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the CDC.

Financial Disclosure Dr. Hernandez has received consultation and speaker fees from Merck and Co, Inc. The other authors did not report any potential conflicts of interest.

Article Outline

Vaginal cancer accounts for less than 2% of all gynecologic malignancies with an annual incidence rate of 0.7 per 100,000 and 1,178 new cases per year for 2005–2009.1,2 The 5-year relative survival rate for squamous cell carcinoma of the vagina is 54%.3,4 The etiology of vaginal cancer varies by histology. Squamous cell carcinoma accounts for 80–90% of all cases and is associated with a history of cervical carcinoma, prior irradiation for anogenital cancer, and human papillomavirus (HPV) 16.5 Some of the risk factors for vaginal carcinoma are also indicators of either increasing acquisition or decreasing clearance of HPV (multiple lifetime sexual partners, age at first intercourse, immunosuppression, cigarette smoking). Others are non-HPV-related risk factors such as chronic pessary use, surgical menopause, or prior hysterectomy.6,7

Human papillomavirus DNA has been detected in 55–64% of invasive vaginal cancers8–10; however, these studies have been limited by small sample sizes as a result of low numbers of vaginal cancers or HPV testing that is limited to HPV 16 or HPV 18 detection. Furthermore, these samples were convenience samples from single institutions and not population-based studies. Human papillomavirus vaccines provide immunity to HPV 16 and HPV 18 and cross-immunity to other HPV types11 and are expected to reduce the incidence of HPV-associated cancers such as vaginal cancer. The HPV type distribution in these cancers should also shift after vaccine introduction. The aims of our study were to describe the HPV genotype distribution in invasive vaginal cancers diagnosed before the introduction of the vaccine and evaluate if survival differed by HPV status.

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The Centers for Disease Control and Prevention Central Cancer Registries study was designed to provide a baseline prevalence of HPV types in HPV-associated cancer cases from participating population-based cancer registries. Four population-based registries and three residual tissue repositories provided formalin-fixed, paraffin-embedded tissue from microscopically confirmed primary vaginal cancer cases diagnosed between 1994 and 2005. One formalin-fixed, paraffin-embedded tissue block from each case was provided.

Sample processing, extraction, and HPV testing have been previously described.12,13 Briefly, serial sections were cut using precautions to prevent contamination between cases. Hematoxylin and eosin staining of first and last section was used to confirm presence of representative material. DNA extracts were tested with the Linear Array HPV Genotyping Test. Samples with negative or inadequate linear array results were retested with the INNO-LiPA HPV Genotyping Assay. Samples failing both assays were considered inadequate and were not, therefore, included in the final analysis.

Deidentified demographic (age, sex, population size), clinical (year of diagnosis, history of other cancers), pathologic (subsite, stage, grade), and survival data for cancer cases were available from each registry and tabulated. The Pearson χ2 test or Fisher’s exact test was used for discrete variables and the Kruskal-Wallis rank sum test for continuous variables. Deidentified demographic (age, sex, population size), clinical (year of diagnosis, history of other cancers), pathologic (subsite, stage, grade), and survival data for cancer cases were available from each registry. Five-year all-cause survival estimates are presented as Kaplan-Meier estimates with statistical testing performed using the log-rank test. A Cox proportional hazards model was used to determine the effect of HPV positivity on 5-year all-cause survival after adjusting for age. As a result of the small number of events (26 deaths), additional covariates such as stage and treatment were not included to avoid overfitting the model. The statistical analyses were performed using SAS 9.2 and R 2.15.2. The Centers for Disease Control and Prevention and each participating state received approval for the institutional review board for the study.

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One block from each of the 71 cases was cut and submitted. Of these, 60 cases had representative tissue and were successfully tested and 11 blocks did not contain representative tissue. The median age at diagnosis was 65 years, with 63% being 60 years of age or older (Table 1). At 76%, whites were the largest group in the sample. Human papillomavirus DNA was found in 75% (45/60) of cases. Human papillomavirus 16 was the most common type detected (55% [33/60]). The second most common was HPV 33 with 18% (11/60) of cases positive. Only one case was positive for HPV 18 (1.7%). In 15% of cases (9/60), multiple types were detected (Fig. 1) but for eight of nine of those cases, HPV 16 was also detected and among five of nine of those cases, both HPV 16 and 33 were found.

Ninety-one percent of women younger than 60 years of age were HPV-positive with most HPV types being HPV 16 and 18 (77.3%). Among the vaginal cancer cases in women 60 years of age and older, approximately two-thirds were positive for HPV, and the proportion of HPV 16 and 18 was lower (44.7%; P=.038). The median age at diagnosis was younger in the HPV 16 and 18 group (59 years of age) compared with other HPV-positive (68 years) and no HPV (77 years; P=.003). The HPV distribution did not significantly vary by race or ethnicity or rural or urban residence (Table 1).

Among all cases, 86% (49/57) were found to be squamous cell carcinomas, whereas 14% (8/57) were adenocarcinomas. Of the squamous cell carcinomas, 31 cases (63.3%) were positive for HPV 16 and 18 as opposed to only 25% of adenocarcinomas (P=.08). Stage at diagnosis was not statistically different among the HPV subtypes.

The unadjusted all-cause survival for all patients with vaginal cancer who were positive for any HPV was 57.4% compared with 35.7% for patients who were HPV-negative (P=.243). The unadjusted hazard ratio comparing HPV-positive with HPV-negative was 0.62 (95% confidence interval [CI] 0.28–1.39). However, after adjusting for age, the hazard ratio was 1.57 (95% CI 0.63–3.91) (Fig. 2).

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In this multicenter study, which spanned 11 years, of the 60 samples examined, 75% were HPV-positive, much higher than most previously published results.8,10,14–16 Ostrow et al8 found HPV in 21% of 14 patients by using in situ hybridization. Using Southern blot hybridization, Ikenberg et al10 found 55% of 18 patients positive for HPV. Koyamatsu et al15 and Ferreira et al16 both used polymerase chain reaction for detection and found HPV in 53% and 81% of 40 and 21 patients, respectively.

It is possible that our HPV detection rate, which is on the higher end of the reported spectrum, is secondary to careful tissue selection, optimized extraction, and the inclusion of a second polymerase chain reaction assay if the first assay was unsatisfactory.13,17

Human papillomavirus 16 was the most commonly detected type with 33 of 60 of the samples positive. Human papillomavirus 33 was detected in 11 of 60 cases and HPV 18 was only detected in 1 of 60 cases. Of note, 45% of cases positive for HPV 33 were also coinfected with HPV 16. Human papillomavirus 33 has not been previously reported to have such a high prevalence in vaginal cancer. The currently licensed HPV vaccines protect against HPV 16 and 18 and our study found that 57% of vaginal cancers could theoretically be prevented. These vaccines do not provide primary coverage for HPV 33, the second most common HPV genotype found in our study. However, Wheeler et al18 showed vaccination with the quadrivalent vaccine despite only including four HPV types reduced the infection rate of related HPV types 31, 33, 45, 52, and 58 by 17.7% (95% CI 5.1–28.7%) in preinvasive cervical lesions. Cross-immunity secondary shared characteristics between the HPV subtypes have been proposed as the mechanism behind this reduction. These results could theoretically be extrapolated to vaginal cancer but further studies are needed.

Previous studies have attributed a longer overall survival for vaginal cancer cases that were HPV-positive.9,19 Our study did not show a statistically significant longer unadjusted survival. The median age in our population for HPV 16– or 18–positive cancers was 18 years younger than those who were HPV-negative. After adjusting for age, the survival hazard ratio for HPV positivity changed from 0.62 to 1.57 but this remained statistically insignificant. This could be partially explained by the younger age at diagnosis of women with HPV-positive tumors. Younger patients are likely to tolerate more aggressive treatment and have better functional status and less comorbidity. These results, if validated by larger sample sizes, could show that age-adjusted HPV positivity in vaginal cancer is a poorer prognostic marker and a marker of more aggressive cancers. However, ideally, we would have a larger sample size to control for additional variables such as stage and treatment.

We acknowledge several limitations to our study, one of which is the small sample size, which is attributable to the rarity of the disease. This small sample size yields low statistical power and limits the ability to interpret the data. Vaginal cancer is, however, an extremely rare disease and this is the cumulative data of seven centers over 10 years. Another limitation in these data are that variables were missing from some cases such as stage and residence (12 and 6 samples, respectively). This is an unfortunate problem with retrospectively collected data.

Similar to other reports,20,21 76% of the samples were obtained from white patients, which potentially limits the generalizability of these data to other races. Like with all studies based on extracted DNA, the detection of HPV DNA does not necessarily prove its involvement in malignant transformation compared with its incidental presence. Another limitation is the use of formalin-fixed tissue blocks, which could potentially underestimate the HPV prevalence rate.

This study describes the prevalence of HPV in vaginal cancer. Given that the majority of vaginal cancers are positive for HPV 16, it is expected that if girls are vaccinated as recommended and coverage is high, we may anticipate a decrease in vaginal cancers by up to 57%.21,20

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© 2014 by The American College of Obstetricians and Gynecologists. Published by Wolters Kluwer Health, Inc. All rights reserved.