Invasive Cervical Cancer Audit: Why Cancers Developed in a High-Risk Population With an Organized Screening Programme

Abstract

In the United Kingdom, routine screening of all women for cervical cancer is conducted at defined intervals (3 or 5 years). Interval cervical Neoplasias have been diagnosed during the screening interval preceding diagnosis, and some of these are invasive cancers. It is unclear whether the cancers were diagnosed as a result of the investigation of symptoms or investigation of an abnormal cytology test during routine screening in asymptomatic women. The primary aim of this observational study was to investigate why invasive cervical interval cancers developed in a high-risk urban population with an established screening program, to look for reasons why they were not prevented, and for preventable causes. Precancerous cervical intraepithelial neoplasia CIN2 + CGIN, CIN2, CIN3 lesions and invasive cervical cancers were diagnosed at Guy's and St. Thomas' National Health Service (NHS) Foundation Trust in 1999-2001, 2002-2004, and 2005-2007. The NHS Screening program audit of screening histories of all women diagnosed with invasive cervical cancer provided data on route to diagnosis, histological type, and International Federation of Obstetrics and Gynecology stage. A period of 5 years was chosen to define interval cancers. During the 9-year study period, 133 invasive cervical cancers were diagnosed, and there were 1472 biopsy diagnoses of CIN2, 1502 diagnoses of CIN3, and 53 diagnoses of CGIN. About 49% of the cancers identified were screen-detected cancers in asymptomatic women; these were successively more likely to occur in younger age groups (P = 0.03), and with one exception, all were stage IA or IB1. Screen-detected IA cancers were significantly more likely (P < 0.001) to be interval cancers (80.5%) than screen-detected fully invasive cancers (58.3%) or symptomatic cancers (35.5%). Cytology tests had been performed in routine screening during the 5 years before diagnosis in 53.4% (71/133) of all cancers. Among these 71, negative cytology had been reported within 5 years of diagnosis in 11 women who had been screened within 3.5 years and 2 women had negative tests within 10 years. Negative tests had occurred less frequently in the other 60 women, or they had previous abnormal cytology, colposcopy, or treatment. A number of potentially avoidable factors were identified, including false-negative cytology, high-grade cytology misidentified as low-grade, and poor compliance in attendance either for routine or repeat screening or for colposcopy or treatment. These findings show that interval cancers diagnosed in previously screened women tend to be early-stage tumors detected by cytology, which are rare in comparison with high-grade CIN and often are potentially avoidable.