*This post was originally published on April 13th, 2020. 

All women know the drill.

That dreaded moment when your physician says, “Well, it looks like you’re due for a pap.”

Let’s just say it. Most cancer screening tests suck. We’ve already discussed colonoscopies, the prep for which everyone has heard about.

January is Cervical Cancer Awareness Month. Hence, today’s cancer screening edition: cervical cancer and the pap smear.

What is Cervical Cancer and How Does it Develop?

Cervical cancer is a cancer of the cervix, a part of the female reproductive system located at the junction of the uterus (womb) and the birth canal (vagina). In the US, it is estimated that around 14,480 women will be diagnosed with invasive cervical cancer in 2021 and that 4,290 will die of the disease.

Like all cancers, cervical cancer is a disease in which normal cells become abnormal, in a process called transformation. However, this process does not happen overnight – over time, cells acquire pre-cancerous changes, which eventually take over, resulting in cells becoming cancerous. In addition to finding full-blown cancer, finding those pre-cancerous changes is what cancer screening is designed to do.

In particular, unlike some other cancer types, cervical cancer does have one known causative factor: human papilloma virus, or HPV. HPV is a sexually transmitted virus that almost all sexually active men and women will get during their lifetime. The majority of people clear the infection without a problem, but a small proportion of infections can lead to more serious conditions like cancer.

Human papillomavirus Virus, HPV is the most common sexually transmitted infection globally. HPV infection is caused by human papillomavirus, a DNA virus from the papillomavirus family.

There are over 100 types of HPV, and 9 are known to cause cancer or other serious diseases (called high-risk types). Even so, not everyone with a high-risk HPV infection will develop cancer and the reasons behind this are unclear. Ongoing research in this field is trying to determine the factors that result in this seemingly random chance of progression.

What is the Pap Test and How Often Should I be Screened?

The pap test is the major cervical cancer screening method. During a pap test, a doctor collects cells from the cervix to look at under a microscope. By visual inspection with the aid of cell staining methods, a pathologist can determine whether all cells look normal or can identify cells that look abnormal.

If cells do look abnormal, additional tests may be required, such as a colposcopic biopsy, which involves taking a larger tissue sample of abnormal areas to confirm whether cancer is present, and if so, how far it has progressed.

Cervical Cancer (Squamous cell carcinoma) under light microscopy zoom

Not all women with pre-cancerous changes will develop cervical cancer. As with any cancer type, however, the sooner cervical cancer is found and identified, the better the chances of survival. In fact, thanks to increased screening, cervical cancer has gone from one of the most common causes of cancer-related deaths to below the top ten.

According to the American Cancer Society, women aged 21 years and older should be screened for cervical cancer. From ages 21 to 29,  a pap test should be performed every 3 years (HPV testing only if abnormal results are found), and after age 30, every 5 years (in combination with HPV testing) until age 65. If abnormal results are found, screening may occur within 6 months to a year after the first abnormal result.

Like many cancer screening methods, the pap test is not perfect. It relies on visual inspection of the cervical cells collected and thus, it’s subject to human error. While improvements to the test are being investigated, sticking to the recommended screening schedule helps reduce some of this error.

Can Cervical Cancer be Prevented? 

You may have seen the commercials for an HPV vaccine called Gardasil 9®. Gardasil 9® is a vaccine against the 9 strains of HPV known to cause cancer or other serious disease, and is recommended for males and females starting at the age of 9. Since the vaccine only works before exposure (it does not protect against existing infection), it is important to ensure it is given before the onset of sexual activity. A recent study showed that Gardasil 4 (a vaccine that protects against 4 HPV strains) is associated with a lower risk of developing cervical cancer.

It is also important that both males and females get the vaccine. Although men cannot get cervical cancer, they can get other types of cancer caused by HPV, like oral cancer, and can spread the virus if exposed.

Importantly, if enough of the population continues to be vaccinated and if screening continues to catch cervical cancer early, hundreds of deaths due to cervical cancer may be prevented.