SEATTLE (FRONTLINE MEDICAL NEWS) – Aggressive screening and treatment of HPV anal dysplasia probably doesn’t decrease the incidence of anal cancer, even in high-risk groups, according to investigators from Kaiser Permanente of Southern California.

The increase in anal squamous cell carcinoma (SCC) over the past 20 years has led to surveillance programs for anal dysplasia in many institutions, based on the assumption that finding and destroying the lesions will prevent anal cancer, similar to the reason why polyps are removed during colonoscopy to prevent colon cancer, said lead investigator Marco Tomassi, MD, a general surgeon with Kaiser in San Diego.

However, the rate of malignant transition from anal dysplasia to SCC is not well understood, and dysplasia recurs in perhaps up to 90% of treated patients. In short, it’s been unclear if intensive surveillance truly decreases the risk of anal cancer.

Kaiser in Southern California doesn’t have an intensive surveillance program for anal HPV. Instead, high risk patients – those with HIV, past cervical cancer, anogenital warts, among others – are screened with digital rectal exams and anoscopy every 3-12 months, and only anal warts and other grossly abnormal growths are removed.

Physicians there do not routinely use high resolution anoscopy (HRA), Pap smears, and other techniques to identify and destroy microscopic foci of dysplasia, as in more intensive programs.

To see how the approach has worked, Dr. Tomassi and his colleagues reviewed the incidence of anal SCC among almost 6 million Kaiser patients from 2005 through 2015.

The cumulative incidence in all groups of patients, even those at risk for the disease, was less than 1%; 425 of the 460 anal cancers (92%) were in the general population, among patients who would not have been part of a high risk surveillance program.

Even without an aggressive surveillance program, high grade anal dysplasia was identified in 377 patients; their incidence of anal SCC was 0.8%, the highest found in the study.

There were no incident cases of SCC among the 133 HIV patients with anal dysplasia. Among over 5,000 HIV patients in the study, the anal SCC incidence was 0.09%. In the general population of 5.86 million, it was 0.01%.

“The cumulative incidence in our group, despite not performing ablative techniques for dysplasia, was comparable to those institutions that routinely perform high resolution anoscopy and destruction of dysplasia. The low rate of malignant conversion suggests that aggressive surveillance regimens, such as HRA, may lead to unnecessary procedures even in high risk patients,” Dr. Tomassi said.

Intensive surveillance doesn’t seem to make much difference because “the incidence of anal cancer is very low even in very high risk populations,” and “most SCC cases develop in the general population,” so “regimens dedicated to identifying cancer in high risk groups will ultimate miss the majority of patients who will succumb to this disease,” he said.

“It’s rare that I come to a meeting and hear a paper that’s going to change my practice. Thank you for that,” an audience member said after Dr. Tomassi presented his findings at the American Society of Colon and Rectal Surgeons annual meeting.

Dr. Tomassi did not have any disclosures.