Elevated Long-Term Risk of Invasive Cancer Seen After CIN3 Treatment

By Anthony J. Brown, MD

NEW YORK OCT 25, 2007 (Reuters Health) - Women who have been treated for cervical intraepithelial neoplasia grade 3 (CIN3) are more than twice as likely as other women to develop invasive vaginal or cervical cancer on long-term follow-up, new research shows.

"The most important finding was that the risk after treatment hardly decreases at all ... and is still sustained after more than 25 years," lead author Dr. Bjorn Strander, from Sahlgren"s University Hospital in Gothenburg, Sweden, told Reuters Health. No other studies have had this long a follow-up period, he added.

Knowing the long-term risks of invasive cancer in such women is important in creating appropriate follow-up programs, the researchers note. Even with the introduction of vaccines designed to prevent cervical cancer, follow-up after treatment for high-grade lesions will likely be needed for the foreseeable future.

In their study, Dr. Strander"s team analyzed data from the Swedish cancer registry covering more than four decades. The study included all women with severe dysplasia/cervical carcinoma in situ (equivalent to CIN3) who were treated between 1958 and 2002. A total of 132,493 women with 2,315,724 woman-years of follow-up were included in the analysis.

The researchers report their findings in the October 26th Online First issue of the British Medical Journal.

Compared with the general population, women who had been treated for CIN3 were 2.34-times more likely to develop invasive cervical cancer. Although the risk tends to decrease as the time from CIN3 treatment increases, it is still apparent 25 years later.

As for invasive vaginal cancer, the standardized incidence ratio was initially 6.82, but fell to 2.65 after 25 years, the researchers report. These ratios changed little on multivariate analysis.

The key point for clinicians, Dr. Strander said, is that "while well-screened women after 50 - 60 years of age are very well protected from cervical cancer and have little, if any, further use of screening, this does not apply to women who have been treated for CIN3. They need, and should have, long-term follow up, perhaps lifelong."

Regarding clinical recommendations that could be derived from these findings, Dr. Guglielmo Ronco, from the Centre for Cancer Prevention in Torino, Italy, and colleagues comment that "the important question is how different follow-up schedules compare in terms of effectiveness and cost in preventing the excess risk of cancer. Unfortunately, we have direct evidence to answer this question, as no large study of the risk of cancer has also reported women"s individual follow-up history."

SOURCE:

• BMJ Online First 2007