Preventive measures are being sought for cervical and ovarian cancers.
AN ALARMING 38 PERCENT of women will develop cancer in their lifetimes, a statistic that has remained unchanged since the 1990s. Fortunately, the number of women who will die from cancer has decreased 19 percent over the same time frame. This decline is partly attributed to increased usage of screening tests that can detect some cancers at early stages, when treatments are more effective. For example, since the introduction of the Pap smear in the 1950s, more precancerous changes of the cervix are being detected early, and rates of cervical cancer have been steadily declining as a result.
In 2006, there was another major breakthrough in cervical cancer prevention with the introduction of a vaccine against the human papillomavirus (HPV), a sexually transmitted infection that causes the majority of cervical cancers as well as cancers of other male and female genital organs; it has recently surpassed tobacco use as a main cause of cancers of the oropharynx. The vaccine is highly effective at preventing HPV infection when administered before initial exposure to the virus during sexual contact. It is recommended that all girls and boys receive their first dose of the vaccine at age 11 or 12 years, and get a second dose at least six months later. These vaccines do not treat existing infections, but adolescents who have already been exposed to HPV through sexual contact can still receive it and have some protection against future infections.
Rates of HPV vaccination have been slowly increasing, but only about 50 percent of adolescent boys and 63 percent of girls in the U.S. have started the vaccine series, and only about 30 percent of countries worldwide include the HPV vaccine in their immunization programs. Some of this slow uptake in vaccine administration is due to safety concerns among parents. However, the vaccine has proven very safe, with most side effects being mild and transient, and studies have shown that adolescents who get the vaccine are no more likely to start having sex at a younger age. We are fortunate to have the technology to prevent and potentially eradicate a devastating and lethal disease, but rates of HPV vaccination must increase in the U.S. and worldwide if we are to achieve this goal.
While significant strides in preventing cervical cancer have been made, protecting women against ovarian cancancer remains a major challenge. Ovarian cancer is the ninth most common cancer affecting U.S. women, but the fifth leading cause of cancer deaths in that population. It is often diagnosed at an advanced stage, when symptoms become more apparent but treatments are less effective. A screening test is urgently needed if we are going to decrease ovarian cancer mortality. To date, efforts to discover a suitable screening test have been unsuccessful.
The most promising of these was thought to be for a protein called CA125. It is found at high levels in the blood of over 80 percent of women with advanced ovarian cancer, but in only 50 percent of women with early-stage disease. It is also present at abnormally high levels in about 1 percent of healthy women due to benign conditions. Therefore, measuring CA125 levels in healthy women results in a significant number of incorrect and missed diagnoses. Combining annual CA125 measurements with a pelvic ultrasound that directly visualizes the ovaries has also been evaluated as a screening test, but has not been found to decrease ovarian cancer mortality rates, and false positives may result in women undergoing unnecessary surgeries.
A more reliable strategy may be to track serial CA125 levels over time, and to perform a pelvic ultrasound if the level is increasing. This screening method was tested in over 200,000 women in the United Kingdom. More ovarian cancers were diagnosed at early stages in the group undergoing screening compared with women who received no screening, and while there was a suggestion that mortality rates were lower in those who were screened, the difference was not statistically significant, making the method not effective enough — at least for now — to adopt for widespread screening. Studies combining tests for CA125 with other tests for other substances in the blood known to be elevated in women with ovarian cancer are also ongoing, but, so far, no panel of tests has proven sufficiently accurate as a screening method. Because of the disappointing results of these studies, various national organizations agree that there are currently no recommended screening tests for ovarian cancer.
Until an ovarian cancer screening test is further refined, annual gynecologic exams and recognition of early symptoms are important strategies for diagnosing this disease. These symptoms include pelvic or abdominal pain, bloating, increasing abdominal size or becoming full quickly while eating. While other causes may explain many of these symptoms, they should not be ignored if they are new and persistent, and should be discussed with a doctor to determine if other tests are warranted. Women may also consult with their doctors about the potential value of more invasive methods of helping to prevent ovarian cancer: using birth control pills for at least five years or undergoing hysterectomy after completing childbearing.
Laurie Brunette, M.D., is a gynecologic oncologist at the University of Southern California, in Los Angeles.Agustin C. Garcia, M.D., is hematology/oncology section chief, a professor of medicine and the Charles W. McMillin and Richard Paul Grace Chair in Cancer Research at Louisiana State University Healthcare Network Clinic, in New Orleans. His primary clinical and research interests focus on women’s cancers, particularly breast and ovarian, and drug development.