Distribution of human papillomavirus genotypes in cervical intraepithelial neoplasia and invasive cervical cancer in Canada.
Epidemiologic studies have reported the underrepresentation of cervical precancerous lesions caused by human papillomavirus (HPV) types 18 and 45 (HPV18/45) compared with the proportion of cervical cancers attributed to these HPV types. We investigated the timing of diagnosis of histologic cervical intraepithelial neoplasia grade 3 or worse (CIN3+) using data from the atypical squamous cells of undetermined significance-low-grade squamous intraepithelial lesion triage study (ALTS). Of the 2,725 women who underwent enrollment colposcopy, 412 of 472 (87.3%) diagnosed with histologic CIN3+ over the 2-year duration of ALTS could be assigned to a HPV type or group of types and were included in this analysis. Eighty-four percent of HPV16-positive CIN3+ were diagnosed at enrollment, compared with 57% of HPV18/45-positive CIN3+, and 58% of CIN3 positive for other carcinogenic HPV types at enrollment. In contrast, only 8% of HPV16-positive CIN3+ were diagnosed at exit, whereas 31% were HPV18/45 positive and 22% were positive for other carcinogenic types at study exit (P < 0.001). These results indicate the underrepresentation of HPV18/45 in precancers, whereas HPV16-associated CIN3+ is diagnosed much earlier. Whether the underrepresentation of 18/45 may be due to occult pathology needs further investigation.