"The exponential increase in oropharynx cancer incidence in young white US men has ebbed," say the authors of a new study, who also report that "modest increases are occurring/anticipated in cohorts born after 1955."
The new data come from a study published online April 26 in the Journal of Clinical Oncology.
The last two decades have seen an "epidemic" increase in the incidence of oropharynx cancers in young white men related to infection with the human papilloma virus (HPV), as previously reported by Medscape Medical News.
The study suggests that age demographics are shifting.
Led by Joseph E. Tota, PhD, of the National Cancer Institute, the authors comment this the first study, to their knowledge, that has identified "a substantial attenuation of the increase in oropharynx cancer incidence" in younger white men — those born from 1955 to 1969 and currently aged 46 to 60 years — with those born from 1939 to 1955 and currently aged 61 to 76 years.
As this was a registry-based study, the reasons remain unclear, they comment. However, the likely explanation is "changes in sexual behaviors in recent birth cohorts, given the presumed correlation between sexual behaviors and the course of the oropharynx cancer epidemic."
To support this hypothesis, there are data to show a steady increase in the average number of recent sexual partners (used as a surrogate for high-risk lifetime sexual behavior) through the 1960 birth cohort and then a significant moderation/decline thereafter, they note.
As previously reported by Medscape Medical News, there has been speculationthat the rising incidence of HPV-related oropharyngeal carcinoma was the result of the "sexual revolution" of the 1960s, at least for men, with oral sex being the main risk factor for oral HPV infection.
Trending Differences Noted
The study used incidence data for HPV oropharyngeal cancer from 1992 to 2015 from the US National Cancer Institute's SEER program.
The team found that from 1992 to 2015, oropharynx cancer incidence increased significantly in white men (estimated annual percentage change [EAPC], 3.8%), Hispanic men (EAPC, 1.2%), and men of other races/ethnicities (EAPC, 1.0%) but significantly declined among black men (EAPC, 21.4%).
Among women, rates also significantly increased in white women (EAPC, 0.7%), declined in black women (EAPC, 22.0%), and remained stable in Hispanics and other races.
In both white men and women, an increasing incidence was observed in each successive age group, but this varied by age and birth cohort. The incidence in white men, for example, increased 1.5% for successive 2-year birth cohort from 1909 to 1927 but accelerated to 3.5% per 2-year birth cohort from 1927 to 1939, and then continued to accelerate to 5.3% from 1939 to 1955.
Increases slowed, however, to 1.7% per 2-year birth cohort, among white men born from 1955 to 1969 and continued to stabilize in individuals born until 1981. The authors note that data were limited among those born after 1969.
For white women, the incidence remained stable for those born from 1909 to 1945, and then increased by 1.2% for each 2-year birth cohort from 1945 to 1981. In contrast, the incidence of oropharynx cancers substantially declined among successive birth cohorts in blacks (men and women, all cohorts), Hispanics (1959 to 1981 birth cohorts in men, all cohorts in women), and other races (women only, all cohorts).
Tota and colleagues note that if these trends continue, they forecast that from 2016 to 2029 incidence will dramatically rise in white men aged 65 to 74 years (from 40.7 to 71.2 per 100,000) and 75 to 84 years (from 25.7 to 50.1 per 100,000).
Conversely, there will only be a moderate increase in white men 55 to 64 years of age (from 40.3 to 52.0 per 100,000), and rates will remain stable among those 45 to 54 years of age (approximately 18 per 100,000).
Clinical Implications
Commenting on the article, Richard Bakst, MD, an associate professor of radiation oncology at the Icahn School of Medicine at Mount Sinai in New York City, reiterated that some years ago, physicians had begun seeing healthy young men with oropharyngeal cancers who lacked the traditional risk factors. "Subsequently, we found that they were related to HPV infection," he said. "And now we are seeing an increasing incidence in older men."
The younger cohort has stabilized, Bakst noted. "There may be a latency right now in the younger age group, and then we may see it rise again among those born in the 1980s."
However, the rise in incidence among older men has important implications in the clinical setting. "This study is making us more aware of the growing incidence in an older population who were not initially described," he said. "And this has implications of who should be screened."
"When a patient comes into the office, you may think smoking or drinking — the classic risk factors of this cancer," said Bakst. "And HPV may not come to mind, so the patient may not be screened."
The demographics will change going forward because of the HPV vaccine, he predicts. Right now, the HPV vaccine is recommended for women through to aged 26 years, and the Gardasil 9 vaccine is approved for use in men aged 9 to 26 years, but indications for the vaccine are evolving, he added. "That may be a moving target, as indications may change and the age limit is likely to expand."
The study was supported by the Intramural Research Program of the US National Institutes of Health/National Cancer Institute. Several of the authors have reported relationships with industry. Bakst has reported no relevant financial relationships.
J Clin Oncol. Published online April 26, 2019. Full text
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