A new paper by a team of scientists from across the U.S. provides quantifiable data that can be used by national groups seeking to create guidelines for anal cancer screening.
MUSC Hollings Cancer Center researcher Ashish Deshmukh, Ph.D., co-leader of the Cancer Prevention and Control Research Program at Hollings, is first author on the paper published in the Annals of Internal Medicine, which is the result of nearly a decade of work.
There are two types of anal cancer screening tests – cytology, which looks at cells under a microscope, and HPV testing, which looks for strains of the human papillomavirus that are known to cause cancer.
The tests are similar to those performed for cervical cancer.
"Anal cancer is preventable," Deshmukh said. "Our study shows that screening for anal cancer has the potential to reduce incidence and death rates by 65% over the lifetime – that's substantial."
The U.S. Preventive Services Task Force, however, hasn't set guidelines for doctors to follow, citing a lack of evidence on harms versus benefits or cost-effectiveness.
"That was the major knowledge gap, and our objective was to address that," Deshmukh said.
Deshmukh noted that once you take into account the two types of screening, the various ages at which screening might start and the different groups that could be considered for screening, there are dozens of possible combinations.
This work builds off of guidelines written by the International Anal Neoplasia Society, which Deshmukh also helped to write. Those guidelines offer five screening modalities but no specific recommendations on which of those are superior options.
The new paper considered cost-effectiveness and harm versus benefit – in other words, the number of tests that would need to be performed to prevent one case of cancer or to extend one life year.
It focused on men who have sex with men with HIV, the group at highest risk of anal cancer.
"Screening is associated with a lot of anxiety and false positives. So what we're doing is identifying certain strategies that are associated with a substantial number of false positives over an individual's lifetime versus certain strategies that may not cause as much harm and anxiety and identifying specific strategies that reduce those harms but maintain the cancer prevention benefit."Ashish Deshmukh, Ph.D.
The study found that cytology screening every three years among members of this group currently over the age of 35 plus cytology screening every two years for those who become newly eligible for screening at age 35 provide the highest value.
The cost-effectiveness and harm-versus-benefit ratio would likely be different for other groups, Deshmukh noted. In addition, this recommendation could change in the future as more young adults get the HPV vaccine, since the human papillomavirus is responsible for the majority of anal cancers.
"Screening is associated with a lot of anxiety and false positives," Deshmukh said. "So what we're doing is identifying certain strategies that are associated with a substantial number of false positives over an individual's lifetime versus certain strategies that may not cause as much harm and anxiety and identifying specific strategies that reduce those harms but maintain the cancer prevention benefit."
This paper used U.S. dollars and U.S.-based assumptions to develop its recommendations. However, it also provides an "efficiency frontier," a graphical approach that illustrates the number of screening procedures against the number of cancers prevented, which guideline-writing bodies in other countries could use to write their own guidelines.
"Every country has different screening infrastructure," Deshmukh said. "So based on their screening infrastructures, they can identify what's optimal and where it falls on the efficiency frontier, given their resources."
The paper was a collaborative effort, reflecting the work of several academic medical centers, the National Cancer Institute and the International Agency for Research on Cancer.
