Do We Screen Too Much for Cervical Cancer?
People may assume that frequent testing improves health outcomes, but recent studies show that isn’t always the case. However, waiting too long in between screenings can also be detrimental. What does the science say?
Cancer screenings have become controversial. That’s because research has shown that annual screenings often lead to overdiagnosis. That’s why the once-recommended annual Pap smear has been changed to co-testing for human papillomavirus (HPV) along with an updated version of the Pap smear called “liquid-based cytology” every five years. For cytology alone, the recommendation is for every three years. While reduced screenings can be beneficial, University of New Mexico researchers recently discovered that some women are waiting far too long between screenings. So why does this happen and how should women approach these new guidelines?
Cervical Cancer Screenings Can Save Lives
Cancer occurs when damaged cells continue to divide and multiply rather than dying off. Cervical cancer begins when cells inside the cervix begin to change. This change, called dysplasia, is when abnormal cells begin to grow. Although these cells are not cancerous, over time they can develop into cancer. However, when the abnormal cell growth occurs in the cervix, which is located at the lower end of the uterus and leads to the birth canal, the abnormal progression is generally quite slow. Because it can take years to become cancerous (if ever), early detection through screenings has been extremely successful.
Since its introduction over 70 years ago, the Pap smear has become a cancer success story. Today around 14,000 women in the U.S. are diagnosed with cervical cancer every year. Over 4,000 will die from the disease. However, it was once a leading cause of cancer death for women–––the mortality rate from the disease has plummeted by more than 70% since the 1950s.
The procedure uses a tiny brush that collects cells from the cervix and surrounding area which are then examined under a microscope. Invented by Dr. Georgios Papanikolaou in 1941, it became part of the annual check-up for most women throughout the later 20th century and an uncomfortable right of passage for teenage girls. “Among one of the great success stories in cancer was the development of a simple swab of the cervix and a smear on a slide to detect changes associated with precancer of the cervix,” explained Dr. Robert Wenham, chair and research director for Gynecologic Oncology at Moffitt Cancer Center. “It led to a dramatic decline in a terrible cancer that affects some of the youngest women with gynecologic cancer.”
Because the human papillomavirus (HPV) infection is a major risk factor for cervical cancer, screening for HPV along with the arrival of a vaccine to prevent its infection has also contributed to a drop in deaths. However, the news about these screenings is not completely positive––in part because of false positives. Inaccurate detection can drive overdiagnosis.
Almost unrecognized until the 21st century, “overdiagnosis” means that a patient is treated for a condition that, left alone, was unlikely to progress. Because people who were not at risk were often included in cancer statistics, survival rates were inflated. People assumed that frequent testing improved health outcomes. Recent studies show that isn’t always the case.
Changing Screening Schedules Create Confusion
To prevent overdiagnosis, screenings have been modified. Although young women often undergo Pap smears, very few under the age of 21 get cervical cancer. Abnormal cells often go away on their own. Women who have undergone a total hysterectomy for a non-cancerous reason along with those over 65 who have had a Pap smear that did not detect abnormal cells do not need to undergo screenings either.
Because the screenings can be pricey and the cells so slow growing, the recommendation is that women between the ages of 30 and 64 have a liquid-based cytology test (the 21st century version of the Pap smear) every three years. If they combine this with the HPV test, they can do a screening every five. Unfortunately, annual check-ups are easier to remember––a fact borne out by a study examining New Mexico’s HPV Pap Registry. It showed that some 65% of the women in the registry for 2019 who had a normal prior co-test were re-screened within three years. This is far too often.
Yet the study also found that some 6.5% of women screened with a prior negative co-test and 14.9% of women with a prior negative cytology alone were not re-tested for over five years. The researchers pointed out that just having a negative cytology is not the same as a negative co-test which means the woman is at risk for developing cervical cancer during the lengthy period between screenings.
“We not only show the overuse of cervical cancer screening, but we also show that more and more women are not coming back for more than five years,” explained research leader Cosette Wheeler, PhD, Regent’s Professor in the UNM Department of Pathology and director of the Center for HPV Protection at the UNM Comprehensive Cancer Center. “Alarmingly, as recommendations for intervals between cervical screening have become longer and therefore less frequent, more women are falling out of screening within reasonable and recommended intervals. They are not coming back until five or more years, which is too long to have protection from prior screening.” While scheduling an appointment years in advance may be difficult, it’s important to contact your health care provider to make sure you haven’t waited too long.
- Cervical Cancer Screening (PDQ®)–Patient Version
- Cervical Cancer Prevention – Cervical Screening: Science in Evolution
- Georgios Papanikolaou: Inventor of the Pap Smear Test
- Overdiagnosis: causes and consequences in primary health care
- Adherence to National Guidelines on Cervical Screening: A Population-Based Evaluation From a Statewide Registry