Therapy Analysis - Human papillomavirus
Associated diseases
HPV infection is responsible for a variety of diseases, depending on the strain involved. Many strains of HPV are low risk, and are responsible for common manifestations of HPV. However, other high risk strains are known to be associated with the development of cancer.
Perhaps the most commonly recognisable HPV-associated condition is skin warts, or verrucae. Warts present as rough epithelial tumours, typically on the hands and feet, and are usually caused by HPV strains 2 and 7. Warts can also occur on the plantar regions of the foot, with HPV strains 1, 2, 4, and 63 implicated in their development.
Anogenital warts is a sexually-transmitted infection, and is caused by HPV strains 6, 11, 42, 43, 44, and 55, amongst others. Genital warts occur in clusters at anal and genital regions, and can form large masses. Virus particles are able to penetrate the mucosal surfaces through abrasions during sexual contact, making genital warts highly contagious. In the US, prevalence of genital HPV infection is estimated at 10-20%, with clinical symptoms in 1% of the sexually active population. Surgical treatments are available to remove the warts; however, the remaining HPV infection remains, resulting in recurrence of symptoms in over 50% of cases.
Perhaps the most infamous consequence of HPV infection is its implication in the development of cervical cancer, a malignant neoplasm of the cervix. Infection with certain strains of HPV can lead to pre-malignant changes, leading to a condition known as cervical intraepithelial neoplasia (CIN) which can potentially cause malignant changes in the cells of the cervix. Of the high risk strains of HPV, strains 16 and 18 are thought to account for about 70% of cervical cancer cases, while HPV DNA is found in 90% of clinical samples of cervical cancer.
There are two main types of cervical cancer. Squamous cell carcinomas arise from the flat squamous cells of the cervix, and account for around 80-85% of cervical cancer cases. Most other cases are adenocarcinomas, arising from glandular cells. Cervical cancer develops on the surface of the cervix, and can invade nearby tissues such as the vagina. Cancer cells entering the blood and lymphatic system give rise to invasive metastatic disease. Prognosis often depends on the stage of the cancer. Survival data shows a 5-year survival rate of 80-90% at Stage I, whereas Stage IV cervical cancer carries a significantly poorer prognosis, with 5-year survival at just 15%. Furthermore, there may be no symptoms in the early stages of the disease, and until recently, detection by clinical examination was the mainstay of therapy for cervical cancer.
In the US, it is estimated that 2010 will see around 11,000 new cases of cervical cancer, along with around 4,000 deaths. Due to the lack of symptoms at the early stages and the invasive potential, cervical cancer remains a major global problem. While the adoption of screening programmes has reduced fatalities, the prevention and treatment of HPV infection by therapeutic intervention may offer a better alternative in the fight against HPV-associated diseases.
