HPV infections increase prostate cancer risk by 2.3 times, study finds

In a recent study published in the journal Prostate Cancer and Prostatic Diseases, researchers investigated the potential associations between human papillomavirus (HPV) infections and prostate cancers. They used a large cohort case-control study comprising 5,137 Taiwanese patients with prostate cancer as cases and 15,411 patients without the disease as controls. Multiple logistic regression analyses revealed that 14.5% of prostate cancer patients had been clinically diagnosed with HPV prior to the onset of the cancer. These findings further revealed that HPV patients have a 2.3-fold increased risk of subsequently developing prostate cancer compared to individuals without a history of HPV infections. This research contributes to a growing body of evidence that these highly morbid conditions are closely associated.

Study: Association of prostate cancer with human papillomavirus infections: a case-control study. Image Credit: Julien Tromeur / Shutterstock

HPV and prostate cancer

Human papillomavirus (HPV) is the most common sexually transmitted disease (STI) currently known, with an estimated one in every three adult men (31%) infected with the condition. Alarmingly, research hypothesizes that more than 90% of all sexually active men and 80% of all sexually active women will experience at least one HPV infection during their lifetimes.

Despite being symptomatically invisible in most patients, HPV can sometimes be ‘high-risk’, causing the development of genital warts and potentially increasing the subsequent risk of cervical, throat, head, neck, and prostate cancers. In China, 36,714 deaths were attributed to the virus in 2015, making it one of the foremost contributors to oncogenicity known. While HPV has been proven to directly increase the risk of throat, anal, and cervical cancers, its association with lung, breast, and prostate cancers remains contentious.

Prostate cancers are malignancies of the male prostate gland, a small walnut-sized gland responsible for the production of seminal fluid. Many phenotypes of prostate cancer exist, collectively making the disease one of the most common extant male malignancies. The association between HPV and prostate cancer remains debated because, while some studies have linked HPV infections to the cancer, others have found no such association.

Research establishing the association (or lack thereof) between HPV and malignancy would help shape future prevention policy and clinical interventions for both conditions. Given the high prevalence of both HPV and prostate cancers, this research is imperative to prevent HPV spread and improve the quality of life (QoL) for patients worldwide.

About the study

In the present study, researchers used a case-control study design to elucidate the associations between HPV infections and subsequent prostate cancer risk in Taiwanese patients. Data was obtained from the Longitudinal Health Insurance Database 2010 (LHID2010), a database that catalogs all health insurance claims in Taiwan and is assumed to represent 99% (more than 2 million) of the country’s population.

Inclusion criteria comprised age (>40 years), health (clinically/biopsy confirmed prostate cancer), and the availability of an index date (date on which prostate cancer was initially diagnosed) for cases. Controls (patients devoid of prostate cancer) comprised age- and propensity-score-matched individuals (within 0.2 SD of the respective case individual) to those identified as cases in a 3:1 ratio. This resulted in a final sample cohort of 5,137 cases and 15,411 controls.

“The propensity score for each enrollee and sampled patient with prostate cancer was calculated based on demographics such as age, monthly income category, geographic location and urbanization level of the patient’s residence, along with medical conditions that have been linked to an increased risk of prostate cancer such as hyperlipidemia, diabetes, hypertension, chronic prostatitis, tobacco use disorder and alcohol abuse/alcohol dependence syndrome if they were present before the index date.”

Given the nonobligatory utility of the polymerase chain reaction (PCR) test in all transmissible diseases in Taiwan, PCR test results (genetic) were included in the analyzed data variables. Since HPV is an umbrella term comprising more than 100 known viral strains, and only a few patients underwent screening for the specific strain involved, associations between HPV strain and prostate cancer risk were excluded.

Statistical analyses consisted of Chi-square tests to evaluate the contributions of demographic and medical comorbidities in measured outcomes (cancer risk), and multiple logistic regressions to compute the associations between prior HPV infections and current prostate cancer prevalence/risk. The regression models were adjusted for age, monthly income, geographic pin code location, degree of urbanization, and patients’ health and behaviors (tobacco/alcohol consumption, diabetes, and chronic prostatitis).

Study findings

The present study found no case-control differences in prostate cancer risk based on age, income, geographic location, urbanization, hypertension, hyperlipidemia, diabetes, chronic prostatitis, tobacco/alcohol use, other STIs (not including HPV), or prior cancer history. However, 8.8% of prostate cancer patients (1,812) were found to have been previously diagnosed with HPV, with the chi-square test confirming the significance of this association – HPV patients had a higher probability of subsequently developing prostate cancer than expected by chance alone (p < 0.001).

Regression analyses assigned odds ratios (ORs) to these observations, suggesting that HPV patients had a 2.269 higher OR of prostate cancer compared to their non-HPV counterparts. Adjusting for demographic and medical variables strengthens this association to an OR of 2.321.

“Notably, individuals diagnosed with chronic prostatitis were also more likely to be subsequently diagnosed with prostate cancer (adjusted OR = 1.586; 95% CI = 1.338–1.879), which aligns with expectations in this context.”

Conclusions

The present study evaluated the associations between HPV and prostate cancer in a large cohort comprising more than 20,000 Taiwanese patients. Their findings revealed that HPV infections significantly increase the odds of subsequently developing prostate cancer by more than 2-fold compared to never having had the STI. Given the almost ubiquitous prevalence of HPV in men (90% of all sexually active men will contract an HPV infection at least once in their lives), these findings call for urgent measures to curb the spread of the disease, thereby reducing the burden of prostate cancer (and other malignancies) that present comorbidities far more severe than HPV infections themselves.

“Nevertheless, due to incongruous outcomes in the current literature, additional research is imperative to authenticate this association and examine its clinical ramifications.”