Determinants of Viral Oncogene E6-E7 mRNA Overexpression in a Population-Based Large Sample of Women Infected by High-Risk Human Papillomavirus Types

Abstract

Cervical cancer screening by human papillomavirus (HPV) DNA testing with cytology triage is more effective than cytology testing. Compared to cytology, the HPV DNA test's higher sensitivity, which allows better protection with longer intervals, makes it necessary to triage the women with a positive result to compensate its lower specificity. We are conducting a large randomized clinical trial (New Technologies for Cervical Cancer 2 [NTCC2]) within organized population-based screening programs in Italy using HPV DNA as the primary screening test to evaluate, by the Aptima HPV assay (Hologic), the use of HPV E6-E7 mRNA in a triage test in comparison to cytology. By the end of June 2016, data were available for 35,877 of 38,535 enrolled women, 2,651 (7.4%) of whom were HPV DNA positive. Among the samples obtained, 2,453 samples were tested also by Aptima, and 1,649 (67.2%) gave a positive result. The proportion of mRNA positivity was slightly higher among samples tested for HPV DNA by the Cobas 4800 HPV assay (Roche) than by the Hybrid Capture 2 (HC2) assay (Qiagen). In our setting, the observed E6-E7 mRNA positivity rate, if used as a triage test, would bring a rate of immediate referral to colposcopy of about 4 to 5%. This value is higher than that observed with cytology triage for both immediate and delayed referrals to colposcopy. By showing only a very high sensitivity and thus allowing a longer interval for HPV DNA-positive/HPV mRNA-negative women, a triage by this test might be more efficient than by cytology.

Keywords: HPV E6-E7 oncogene mRNA; biomarkers; cervical cancer screening; human papillomavirus.

FIG 1

Flow chart of the study. Pos, positive; Neg, negative.

FIG 2

Distribution of HPV E6-E7 mRNA test results reported as signal/cutoff (S/CO) values. All 2,449 HPV DNA-positive samples with a valid mRNA result are included. White bar, values below the positivity threshold of 0.5 S/CO.

FIG 3

Box plot reporting the distribution of the HPV E6-E7 mRNA test results expressed as S/CO values, by HPV type, with 942 cases positive for both HPV DNA and mRNA included (a), and by cytology, with 1,601 cases with HPV DNA and mRNA positive and available cytology results included (b). The line within the gray box represents the median, the limits of the box include 50% of the results, and the lines include 95% of the observations. HPV16 includes samples positive also for HPV18 or other high-risk HPV types. HPV18 includes samples positive also for other high-risk HPV types. Other high-risk HPV types included in the Cobas 4800 HPV DNA test are HPV31, -33, -35, -39, -45, -51, -52, -56, -58, -59, -66, and -68. Negative cytology includes also 14 inadequate samples; L-SIL includes 476 low-grade squamous intraepithelial lesions and 3 atypical glandular cells (AGC); no slides were classified as ASC-US; H-SIL includes 66 atypical squamous cells suggesting high-grade lesion (ASC-H), 86 high-grade squamous intraepithelial lesions (H-SIL), and 1 cancer.

FIG 4

Plot of the natural logarithms of the HPV DNA and HPV E6-E7 mRNA results reported as sample/control RLU ratios and S/CO values, respectively. All 1,183 Hybrid Capture 2 HPV DNA- and HPV mRNA-positive samples are included. The regression slope is 0.09 (95% CI, 0.07 to 0.11).