Nuanced View of Oral Sex, HPV+ Oropharyngeal Cancer

Age at initiation of oral sex and intensity (number of partners per 10 years), in addition to number of oral sex partners, had significant associations with human papillomavirus (HPV)-positive oropharyngeal cancer, a multicenter case-control study showed.

Consistent with existing data on HPV infection and other related cancers, number of lifetime partners significantly increased the odds of HPV-positive oropharyngeal cancer, quadrupling the risk among people with 10 or more partners. After adjusting for number of oral sex partners and smoking history, younger age at first oral sex almost doubled the odds ratio (OR), and increased oral sex intensity (more than five partners/10 years) almost tripled the likelihood.

Certain characteristics of oral sex behavior, such as older partners and extramarital partners, also significantly increased the odds of developing HPV-positive oropharyngeal cancer, reported Gypsyamber D’Souza, PhD, of the Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues in Cancer.

“This study provides the most comprehensive behavioral picture of HPV-related oropharyngeal cancer to date,” the authors concluded. “Ever performing oral sex and number of partners remain strong risk factors for HPV-oropharyngeal cancer. Measures of sexual behavior, including timing of oral sex and intensity of exposure, are independent risk factors for HPV-OPC (oropharyngeal cancer), suggesting that these behaviors may explain additional nuances of how and why some people develop HPV-OPC.”

HPV-OPC Background

HPV infection accounts for about 70% of new diagnoses of oropharyngeal cancer in the U.S. Case-control studies showed a strong associations between oral sex behavior and risk of HPV-related oropharyngeal cancer, but most studies focused primarily on number of oral sex partners, the authors noted.

Some investigators have hypothesized that sexual behaviors at the beginning of a person’s sexual experience may predispose an individual to HPV infection. Moreover, serologic response might differ by initial mucosal site of exposure. For example, initial HPV exposure by vaginal sex might induce a more robust immune response that decreases subsequent acquisition of oral acquisition of HPV, whereas oral exposure without initial anogenital exposure may increase the risk of oral acquisition, the authors continued.

Limited data support hypotheses regarding associations between early sexual behaviors and subsequent risk of HPV-OPC. D’Souza and colleagues undertook a study to examine differences in sexual behaviors, relationship dynamics, and serologic response to HPV.

The study included 163 patients with newly diagnosed HPV-OPC at three cancer centers during 2013-2018. They were matched with 345 individuals who were evaluated at otolaryngology clinics for symptoms unrelated to cancer.

All study participants completed a medical and behavioral risk survey and provided blood samples, and tumor samples were obtained from the patients with OPC. Tumors were tested for presence of HPV p16, and all serum samples were tested for eight HPV types associated with cancer.

Men accounted for more than 80% of study participants. About 70% of participants were ages 50-69, three-fourths were married or living with a partner, and about 95% identified as heterosexual. A majority of study participants were college graduates. Patients with OPC were significantly more likely to have a history of sexually transmitted infections (26.7% vs 15.5%, P=0.003).

Key Behavioral Differences

Oral sex behaviors differed significantly between cases and controls, including:

• Ever perform oral sex: 98.8% vs 90.4%, OR 1.8 (P<0.001)
• Performed oral sex at sexual debut: 33.3% vs 21.4%, OR 1.8 (P=0.004)
• Age at first performed oral sex: <18 vs >20 – 37.4% vs 22.6%, OR 3.1 (P<0.001)
• >10 lifetime oral sex partners: 44.8% vs 19.1%, OR 4.3 (P<0.001)
• Intensity (partners/10 years [sex-years] >5): 30.8% vs 11.1%, OR 5.6 (P<0.001)

After adjustment for number of oral sex partners and smoking history, significant differences remained for ever perform oral sex (OR 4.4, 95% CI 1.1-18.9), younger age at first oral sex encounter (OR 1.8, 95% CI 1.1-3.2), and oral sex intensity >5 sex-years (OR 2.8, 95% CI 1.1-7.5).

The patients with HPV-OPC had significantly more lifetime vaginal sex partners, deep-kissing partners, and vaginal sex-years (P<0.001). They also were significantly more likely to report having >10 casual sex partners (37.5% vs 24.6%, P<0.001) and having extramarital sex partners (43.9% vs 36.0%, P=0.002). Finally, the patients were more likely to report having an oral sex partner who was at least 10 years older when they were younger than 23 (30% vs 20%, P=0.01).

The study confirmed the association between number of prior oral sex partners and HPV-OPC and delved more deeply into the specific oral sex behaviors associated with HPV-OPC, said Debbie Saslow, PhD, of the American Cancer Society. The new data have messages for clinicians and the general public.

“The main message for clinicians is that researchers continue to search for more nuanced understanding of risk factors and behaviors leading to HPV-related throat cancer,” Saslow told MedPage Today via email. “For both clinicians and the public, the message continues to be that both men and women are at risk for throat cancers caused by HPV. These cancers have been on the increase and, while we cannot screen for throat cancer, we can prevent over 90% of them by vaccinating girls and boys. Vaccination at ages 9-12 will prevent the most HPV cancers.”