With the recent licensure of a vaccine that protects against human papillomavirus (HPV) types 16 and 18, US women are expected to experience lower rates of cervical cancer. However, surveillance systems must be in place in the US to measure the real-world effectiveness of vaccination programs. Although population-based registries will provide invasive cervical cancer (ICC) incidence and burden data, the impact of HPV vaccine on cervical cancer will not be measurable for several decades. Cervical carcinoma in situ (CIS), a cervical precancer and the immediate precursor to ICC, is an earlier presentation of HPV-related cervical disease that affects a much larger number of women, and monitoring trends in CIS could provide an earlier measure of HPV vaccine effectiveness. Currently, registries do not collect data on CIS except for the state cancer registry in Michigan, which has been continually collecting CIS data since 1985.
All cases of CIS and ICC diagnosed from 1985 through 2003 in the Michigan registry were identified. Available data include age at diagnosis, race, morphologic tumor type, and tumor behavior.
There were 58,144 cases of CIS and ICC, of which 48,272 (83.0%) were CIS and 9872 (17.0%) were ICC. There were 2928 CIS cases and 413 ICC cases diagnosed in Michigan during 2003, compared with 1577 CIS and 516 ICC cases reported in 1985. Age-adjusted CIS rates increased from 1985 (31.7 per 100,000) to 2003 (59.2 per 100,000); rates of CIS were highest among women age <40 years. Age-adjusted rates of ICC have declined since 1990, when the rate was 14 per 100,000 females; the rate is currently down to 7.8 per 100,000 females in 2003.
The rising rates of CIS in women age <40 years, coupled with declining rates of ICC, suggests the important role of early CIS detection in the prevention of ICC. The CIS trend data, used in conjunction with ICC trend data, help to provide a more thorough picture of cervical disease in the state and also provide baseline data regarding CIS burden in a prevaccine era. The experiences of the Michigan registry can inform the development of CIS surveillance in other registries, an important potential registry role relative to monitoring cervical cancer prevention efforts. Cancer 2008;113(10 suppl):2946–54. Published 2008 by the American Cancer Society.