HPV DNA test predicts cancer risk for 18 years

A single clinical human papillomavirus DNA test can predict a woman’s cervical cancer risk for at least the next 18 years, identify women who already have invasive cervical cancer and if those HPV infections will develop into disease in the future, a study has shown.

In contrast, Pap smears cannot predict clinically important disease beyond 1 to 2 years, said the American Society for Clinical Pathology, Washington.

“An HPV test provides greater reassurance against cervical intraepithelial neoplasia grade 3 and cervical cancer than Pap testing and thus might be used as the screen to rule out disease in healthy women. Whereas Pap is useful as a secondary diagnostic test to identify HPV-positive women at immediate risk of “invasive cervical cancer, colleagues analyzed data from a Portland, Ore., cohort of 19,512 women who underwent routine cytologic screening when they aged 16-94 years at baseline in 1989-1990. Cervicovaginal lavages were retrospectively tested for HPV DNA through a commercially available diagnostic test used routinely in clinical practice.

The study subjects were followed thoroughly 18 years with annual Pap smears. A total of 199 cases of invasive cervical cancer (cervical intraepithelial neoplasia grade 3+) were diagnosed during this time; 396 cases of CIN2+ were detected.

A positive Pap smear at baseline predicted cervical cancer within 2 years, but not beyond that point. A positive HPV DNA test continued to predict cervical cancer until the end of the study.

A one-time negative HPV test at enrollment “provided greater reassurance over the 18-year follow-up” than a one-time negative Pap smear against CIN2+ (1.85% vs. 2.47%) and ClN3+ (0.90% vs. 1.27%) more cases of CIN2+ (215 vs.136 cases) and CIN3+ (112 vs. 65 cases) developed after an HPV-positive result than after a positive Pap result. And among women who were positive for HPV DNA at baseline and who went on to develop ClN2+ orCIN3+, only half had positive Pap smear results.

These findings “provide additional support for the use of HPV testing in routine screening” in women 30 and older. Moreover, the results of other studies have suggested that HPV testing also may help identify women at risk for cervical adenocarcinoma — two disorders that ”are poorly detected by cytology-based screening alone.”