Cervical cancer is the second most common cancer among women in the world. Despite a decline of up to 70% in its incidence and prevalence through screening programs, it is still the most common gynecological cancer worldwide. Since the human papilloma virus (HPV) was conclusively identified as the etiological factor inducing cervical cancer, investigations during the last two decades have been concentrating on producing a vaccine against HPV virus.
Thus prevention of HPV infection has been the main purpose and vaccination is expected to reduce up to 70% of related cervical cancer and prevent precancerous and cancerous lesions of the genitalia. However, screening programs are still essential for those who have already been exposed to the high risk forms of the virus and educational and information programs continue to play important roles to increase the success rate of screening, by whichever of the modalities is most appropriate for the local conditions.
Cervical cancer is the second most common
Cervical cancer is the second most common cause of death among women with various cancers. In 2006, about 500,000 new cases of cervical cancer were reported and it was predicted that 280,000 of them led to death. Most of these cases have been reported from developing countries in Africa, Central America, and South America in which there is no organized programs for screening and early diagnosis (Society of Gynecologic Oncologists statement on cervix cancer vaccine, 2006).
Cervical cancer is the most common gynecological cancer in Iran (Behtash et al.,2005), where various methods of screening, diagnosis, and treatment hav been reported (Behtash et al., 2003; 2005; 2006; Nazari et al., 2006; Mousavi and Karimi Zarchi , 2007; Ghaemmaghami et al.,2008; Mousavi et al., 2008). However, since there is no lucid system to document the data on cancers, there are no clear reports of incidence and prevalence of cervical cancer in Iran.
The Cancer institute has reported a 6-7/ 100,000 prevalence for cervical and endometrial cancers with a peak at 30-55 years of age, although there have been several reports of younger age involvement. During the last 50 years in the Westrn world there has been a decline of 70% in prevalence and incidence and also mortality of this cancer owing to the screening programs and regular Pap smear testing.
Like other genitalia infections, is only a predisposing factor for cervical cancer. However, after 2000, the virus was confimed as the main etiological factor, which makes cervical cancer the only cancer in women with a clear viral etiology. HPV viruses act via inhibition of apoptosis (programmed cell death) and producing proteins to restrain P53 and retinoblastoma (cell growth inhibition) genes (Behtash et al.,).
More than 40 types of HPV viruses has been indentified which are able to infect vaginal mucosa, but only 15 of them are high risk and cause cancer or precancerous lesions such as CIN III. The most common types of HPV virus which cause cervical cancer are types 16 and 18 which have been detected in 60% and 10-20% of cervical cancers respectively (Munoz et al.,; Castellsague et al.).
It is important to note that HPV has also been detected in 30% of oropharynx cancers, 45-95% of anal cancers, 60-65% of vaginal cancers, and 40-60% of vulvar cancers (Schiffman et al., 2003; Daling et al.). Independent factors which increase the risk of cervical cancer are: starting sexual activity at young age, multi-parity, multi partners, cigarettes, and HIV (human immunodeficiency virus) infection (Daling et al., 2004).
HPV infection is well known to be a sexually transmitted disease and therefore its rate is higher among individuals with multiple partners. Women with permanent HPV infections are at higher risk of developing precancerous lesions or cervical cancers (Munoz et al., ; Castellsague et al., ). Therefore, factors like smoking which impact on the immune system can influence the likelihood of cancer development.