HPV and Cervical Cancer

The Human Papilloma Virus

The Human Papilloma Virus (HPV) is one of the most common sexually transmitted infections (STI) in the world. It is estimated that 5.5 million people worldwide are infected annually. Sexually active individuals have an 80 to 85% chance of being infected at some time in their life.

The virus invades human epithelial cells (a type of skin cell), including the oral mucosa, esophagus (throat), larynx (voice box), trachea (airway), conjunctiva of the eye, and the anal and genital areas. The time between exposure to the virus and having any symptoms can be 3 to 4 months, yet the virus can be transmitted to someone else during this time (unbeknownst to either person). Although HPV is considered a sexually transmitted infection, this can be misleading. It is transmitted by skin to skin contact, therefore traditional methods of protecting oneself against an STI, such as condoms can reduce, but not eliminate the risk of HPV infection. Infection can occur through skin to skin genital contact without intercourse.

Persons at higher risk for HPV infection include those with numerous lifetime sexual partners (the higher the number, the higher the risk), early age of first intercourse, history of other STIs, alcohol and drug use related to sexual behaviors, and partner's number of sexual partners.

The infection is most prevalent in women in the 20-24 year old age group, with 15-19 year olds being the second largest group. Prevalence decreases with age, dropping significantly after age 30. It is thought that the younger, developing cervix is more likely to be infected, but these infections tend to be short-lived and are usually cleared by the immune system. Cases of cervical cancer are extremely rare under age 30.

Researchers have identified 100 different strains of HPV, 40 of which can infect the anal and genital areas. These strains have been further divided into low and high risk strains, which we will address later. Many people think of HPV as the virus that causes genital warts, yet only a few of the 100 strains actually cause warts.

There is no treatment to rid the body of HPV, but 80% of infections are cleared by the body's immune system. For the 20% who develop chronic infection with HPV, the risk of cervical cancer is higher. If the HPV strain is one that causes genital warts, they can be treated by topical methods such as freezing, acid application or imiquimod (a medication used to boost local immune response). Surgical treatments include laser, excision, or CUSA (ultrasound).

Cervical Cancer and the Pap test

Cervical cancer is the second most common cancer in women worldwide. Approximately 500,000 new cases are diagnosed annually worldwide, 83% of which will be in developing countries (estimated 10,370 new cases in the US in 2005). There will be an estimated 273,000 deaths due to the disease annually, three-fourths of these in developing countries. Higher income nations have the Papanicolaou (pap) test to thank for a 75% decrease in cervical cancer cases over the past 50 years. Unfortunately, this test has not been successful in lower income nations due to cost, ability to get the test to women and once available, to get the results back to them. The Pap test has made great strides in catching cervical changes early, but it is not without problems. The traditional Pap test is not very sensitive (55-60% sensitivity), which means that up to 40-45% of the time that the test is read as normal, there is actually cervical dysplasia (abnormality) present. By performing the test annually, along with a manual exam, we increase the chance of detecting a cancer. Newer liquid based cytology tests, called Thin Prep ® and Sure Path ® , reportedly have a sensitivity of 84%, which is better, but still not great.

Cervical cancer is further broken down into 3 types: squamous cell carcinoma (about 75% of cases), adenocarcinoma (15-25% of cases), and rarely, adenosquamous (a combination of the two). It is recommended that women start screening with Pap smears within 3 years of becoming sexually active, but no later than 21 years old. Then annual testing with traditional Pap methods, or every 2 years with the liquid based cytology. Women who have had a hysterectomy should clarify with their surgeon whether or not they still have a cervix and whether they should continue screening.

Pap Test Results

Pap test results in the U.S. are reported in the “2001 Bethesda System”. The system is quite detailed, but some of the common results include the following (and common follow-up):

Mild dysplasia (also called CIN 1 or Low grade squamous intraepithelial lesions (LSIL)): most resolve spontaneously, so follow with Pap every 4-6 months, if it lasts more than 2 years an excisional biopsy may be needed.
Moderate or severe dysplasia (also called CIN 2 or CIN 3 or high grade squamous intraepithelial lesions (HSIL)): should be confirmed by colposcopy and treated for the abnormality.
Atypical squamous cells of unknown significance (ASCUS): Repeat Pap in 6 months, if still abnormal, colposcopy to test further. Alternatively, test for high risk HPV strains, if positive, colposcopy to further evaluate, if HPV negative, can repeat Pap in 1 year.

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