Vaccines Do Not Cover Most Common HPV Types in Black Women

The HPV subtypes that are most common in black women in the United States are not targeted by the currently available vaccines Gardasil and Cervarix, according to new research.

The findings suggest that current HPV vaccination will be less beneficial for black women in the US than for their white counterparts, said study coauthor Catherine Hoyo, PhD, MPH, of Duke University, in Durham, North Carolina.

She spoke at a press briefing today at the annual International Conference on Frontiers in Cancer Prevention Research, in National Harbor, Maryland. The meeting is sponsored by the American Association for Cancer Research.

"The approved cervical cancer vaccines are effective but may not be effective for everyone," said Paul Limburg, MD, from the Mayo Clinic, in Rochester, Minnesota, who moderated the press briefing. He was not involved with the study.

Persistent infection with HPV 16 and/or HPV 18 accounts for about 70% of all cervical cancers, said Dr. Hoyo. These are the subtypes targeted by Gardasil and Cervarix. Gardasil also targets HPV 6 and HPV 11.

Some black women in the new study did, in fact, have infections with HPV 16 and/or HPV 18. But much less often — their rate was about half of that of white women.

"Since African-American women don’t seem to be getting the same subtypes of HPV with the same frequency, the vaccines aren't helping all women equally," said study coauthor Adriana Vidal, PhD, in a press statement. She is also from Duke University.

The investigators prospectively looked at 572 women at 10 Duke-affiliated clinics with abnormal Pap tests who then underwent colposcopy; the group was about evenly divided among blacks (n = 280) and whites (n = 292). And just about even numbers of the respective racial groups subsequently had evidence of cervical intraepithelial neoplasia 1 (CIN1; 112 vs 118).

For whites with CIN1, the most frequent HPV subtypes were 16, 18, 56, 39, and 66.

But for blacks with CIN1, the most frequent HPV subtypes were 33, 35, 58, and 68.

Thus, in blacks, the most common genotypes were not HPV 16 and 18, which defies conventional wisdom about HPV infection.

There were no data on Hispanics in the new presentation because their numbers were too small at this point to be included, said Dr. Hoyo.

Without HPV 16/18, Are Some Black Women "Getting Dropped"?

The study findings may help explain why black women in the US are harder hit by cervical cancer than white women, said Dr. Hoyo.

She pointed out that both the incidence of invasive cervical cancer and related mortality rates are higher in blacks than in whites.

"We don't know what is causing the disparity," Dr. Hoyo told Medscape Medical News in a phone interview after the press conference.

"The problem is not likely detection," she said, explaining that screening rates for precancerous lesions are comparable for black and white women.

The new data, however, suggest that, if clinicians are strongly focusing on HPV 16 and 18 for more careful follow-up in their black patients, then they may be missing some eventual cervical cancers, Dr. Hoyo said.

"Somewhere along the line, some black women may be getting dropped because they don’t have the HPV subtypes that are considered to be most aggressive," she summarized.

Her advice to clinicians with black females who HPV infection and CIN is: "Broaden the subtypes that you look at."

Currently, there is a vaccine in phase 3 clinical trials that targets 9 HPV subtypes (6, 11, 16, 18, 31, 45, 52, and 58). That means that 2 of the 4 most common subtypes in blacks are targeted by the experimental vaccine. "We need more African American women to enroll in trials like this to see how beneficial this new vaccine will be for them," Dr. Hoyo said.

The new study is not the first to indicate that black women have lower rates of HPV 16 and 18.

A recent report found that black race was a predictor of lower HPV 16 and 18 positivity among women with high-grade cervical lesions (Cancer. 2013;119(16):3052-3058).

However, the new study from the Duke team is the first to indicate that this race-influenced distribution of HPV subtypes also occurs in lower-grade cervical lesions.

The Duke investigators also looked at high-grade lesions (CIN2/3).

In CIN2/3, HPV 16, 18, 33, 39, and 59 were the most common genotypes detected in white women, whereas HPV 31, 35, 45, 56, 58, 66, and 68 were the most prevalent in African American women.

12th annual International Conference on Frontiers in Cancer Prevention Research: Abstract B11, presented October 28.

The study was supported by the National Institute of Health.

The authors have disclosed no relevant financial relationships.

Fonte: www.medscape.com