|The State of Cervical Cancer|
January is cervical cancer awareness month and although the incidence of the disease has dropped off over the last 40 to 50 decades largely due to screening, the disease remains a serious health threat worldwide.
Akinso: Well January is cervical cancer awareness month and although the incidence of the disease has dropped off over the last 40 to 50 decades largely due to screening, the disease remains a serious health threat worldwide. Dr. Diane Solomon a senior investigator in the Division of Cancer Prevention at the National Cancer Institute discusses the screening and testing process involved with this disease.
Solomon: Over the last four to five decades, cervical cancer screening has largely been the pap test, cervical cytology where cells are scraped from the cervix. They're spread on a slide and looked at under the microscope. Over the past several years, there have been a number of advances on many fronts. In terms of cervical cytology, we now have new techniques whereby instead of spreading cells on a glass slide, now the sampling instruments can be rinsed in fixative. And that collects more of the cells that were obtained from the cervix. There also are techniques to use computers to help the laboratory personnel, cyto-technologists who are scanning the slides for abnormal cells. The computer can assist in locating potentially abnormal areas on the slide and focus their attention to those areas. In addition we have new testing modalities such as HPV testing, where we're actually looking for the DNA of the human papillomavirus in the cell material from the cervix.
Akinso: Cervical cancer can be caused by several types of a virus called human papillomaviruses known as HPV. HPVs are a group of more than 100 viruses. They are called papillomaviruses because certain types may cause warts, or papillomas, which are benign noncancerous tumors. During a presentation, Dr. Allan Hildesheim, Senior Investigator for the Division of Cancer Epidemiology and Genetics at the National Cancer Institute talked about the history of HPV.
Dr. Hildesheim: We know that HPV infection is common and that it often occurs shortly after initiation of sexual activity that's a very important point for when you want target vaccination we'll come back to that. We now know that the vast majority of these infections clear and that they usually clear within 1 to 2 years with no sequela. That it's the women with persistent HPV infection that have a higher risk of progression to pre-cancer. And that there's a group of 15-18 oncogenic HPV types which are necessary for the development of cervical cancer and of those, HPV 16 and 18 infections are the most worrisome, the most likely to persist and to progress. And they together account for up to 70% of all cervical cancer cases worldwide.
Akinso: The HPVs that cause the common warts which grow on hands and feet are different from those that cause growths in the throat or genital area. Some types of HPV are associated with certain types of cancer. These are called oncogenic or carcinogenic HPVs. Dr. Solomon and Dr. Hildesheim explained the importance of the HPV vaccine and the screening process.
Hildesheim:Just to point out, this is what people countries have done in the developed world where pap smear screening has been effective at reducing rates of cervical cancer. They've screened over and over starting at the age of 18 over and over and over again for decades. And it works because of this intense screening. Now we have a vaccine that prevents infection with two of the most important types that cause cervical cancer. It is meant to prevent infection. It is meant to be given to young individuals before sexual debut. And now we can have HPV tests that are very sensitive as I showed you. And in one round of testing can accomplish what usually takes multiple rounds of pap smear screening. So now we may be able to instead of cytology screening to use HPV testing at much more limited time points, and this combination of vaccinating the young and limited screening in older women targeting the age where the prevalence of infection has gone down and the rates of cancer are beginning to go up. This is the time to begin to screen right here, so you can prevent all of the cancers by testing for HPV without picking up all of these infections that happen early on that are inconsequential.
Solomon: We now have a vaccine against two of the carcinogenic, oncogenic HPV types, 16 and 18. The vaccine has been shown to be very effective for women who have not previously been exposed to 16 and 18 in protecting them against infection and subsequent cell abnormalities that might have derived from an infection with 16, 18. So this is very, very promising.
Akinso: Types 16 and 18 are the most common HPV types which can cause cervical cancer. Dr. Solomon said that it's important to emphasize that the vaccine does not have any affect on women who have or have been infected.
Solomon: The vaccine is very important for young girls, who should be vaccinated before sexual exposure. It's important to emphasize however that screening is still the mainstay of cervical cancer prevention. It's very important for women who are beyond the recommended age range for vaccination, they should continue with the recommended cervical screening. And it's also important to understand that even if girls and women have been vaccinated, they still need to continue with cervical screening because the vaccine protects against only two of the cancer-causing HPV types. There are several other HPV types that can cause cervical cancer that are not covered by the vaccine.
Akinso: Dr. Solomon lends some advice to women about screening.
Solomon: Women should be screened for cervical abnormalities, depending on their age. Women who begin sexual activity should be screened about three years after they first start having sex, or at the latest by age 21. For women 30 and over, in addition to pap testing, in addition to cervical cytology, we have the option of doing a dual test, of cervical pap smear screening plus HPV test. And that combination of dual testing provides greater sensitivity and therefore the test can actually be done less often.
Akinso: This is Wally Akinso at the National Institutes of Health, Bethesda, Maryland.