If widely adopted, the treatment would be similar to what doctors already do to prevent cervical cancer. But until now, there has been little evidence that the therapy would be effective against anal cancer.
In a randomized trial including 4,459 volunteers, after a median follow-up of 25.8 months, nine people developed anal cancer (a rate of 173 per 100,000 person-years) in the group whose lesions were treated with ablation in the office, ablation or excision under anesthesia, or topical fluorouracil or imiquimod.
In contrast, 21 patients who didn't receive the aggressive therapy developed anal cancer (a rate of 402 per 100,000 person-years).
The reduction in incidence was 57% (P=0.03).
All of the participants were infected with HIV, a group whose risk of anal cancer is 12 to 22 times higher than in the general population.
The results appear in the New England Journal of Medicine.
"We now have a tool to prevent anal cancer in at least one very high-risk group: people with HIV," chief author Dr. Joel Palefsky of the University of California, San Francisco, told Reuters Health by phone.
"We hope these data can be developed into standard-of-care guidelines so it becomes routine to look for and treat patients in this population," he said. "It should be considered in other groups as well."
Dr. Palefsky speculated that the therapy might be even more effective in non-HIV populations.
"But whether policy makers are okay in taking these results and applying them to other groups, I don't know for sure. People can be uncomfortable with extrapolation from one group to another," he said.
Anal cancer is caused by a human papillomavirus infection. Its incidence has been increasing over the last half-century.
The study, begun in 2014, was done at 25 U.S. sites.
The initial therapy to treat the lesions was office-based electrocautery ablation in 84% of the volunteers, all of whom were age 35 or older.
"Not all anal cancers were prevented through HSIL treatment. Similarly, treatment of cervical HSIL or colon polyps does not completely eliminate the risk of progression to cervical cancer or colon cancer, respectively," the researchers note.
"In the cervix, larger lesion size and positive margins are associated with an increased risk of recurrent HSIL after treatment, particularly among women living with HIV, and progression to cervical cancer. Similarly, a larger lesion size was associated with an increased risk of progression to anal cancer in our trial," they write.
A logistical limitation to wide implementation of the findings is that "to find these high-grade lesions and treat them requires competence in a technique known as high-resolution anoscopy (HRA)," said Dr. Palefsky. "Right now there is a serious shortage of people in the United States who know how to do that. So, we have to ramp up training programs to meet the demand we anticipate."
He said it would also be beneficial to have the anal equivalent of a Pap smear to help determine who needs an HRA exam.
For now, the team writes, "Our data provide support for the use of screening and treatment for anal HSIL as the standard of care for persons living with HIV who are 35 years of age or older."
And until HRA becomes more available, "we've been telling providers that everybody who is living with HIV should have a digital anorectal exam" to feel for abnormalities, said Dr. Palefsky.
The study, known as ANCHOR, was funded by the National Cancer Institute.
SOURCE: https://bit.ly/3zsiKAJ The New England Journal of Medicine, online June 10, 2022.
By Gene Emery
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