Despite the tremendous progress made in health care, cervical cancer continues to be the leading cause of cancer mortality among women worldwide. Cervical cancer has an unequal geographic distribution with the highest global disease burden confined to the developing countries, where the facilities to combat the disease are clearly insufficient. A decline in the incidence and mortality of cervical cancer has been observed in most of the western countries since the third decade of the past century. It stands now at one-two per cent of women'scancer. This may be partly due to improved hygienic and living conditions and the significant role of Pap test developed by George Papanicolaou in 1940s. However, this is most common cancer occurring in women in India. Almost 35 to 40 per cent cancers in women in India are situated in cervix. Nearly one lakh new cases are diagnosed each year.
Now it is fully established that cervical cancer is caused by a human papiloma virus infection. But the link between HPV and cervical cancer, discovered only 30 years ago, is yet to be broken in India, to the benefit of women and public health alike. Medical bodies and GoI should also create IEC material to wake up women about their risk of cancer.
Role of HPV in Carcinogenesis
It is estimated that the cumulative risk of HPV infection in 70 years of life of an average woman is more than 70 per cent. Only very few women will ever develop a persistent infection that may last for longer than 6-12 months and pose a significant increased risk of subsequent development of cancer.
Natural history of HPV infection
Seven out of 10 women are exposed at least once to HPV during their lifetime. Without treatment, one in five women exposed to HPV can develop cervical cancer. Exposure to these viruses occurs during sexual intercourse often with the first partner. Prevalence of HPV before the age of 30 years is 30 per cent, between 30 and 50 years is 10 per cent, whereas in women more than of 50 years of age the increase is five per cent only of cervical lesions.
Present recommendations for primary screening
Western world has shown that preventive screening has paid rich dividends in decreasing cervical cancer to as low as one-two per cent of all cancers in women. Somehow GoI is faced with so many other problems that is has no policy as yet to reach out to masses for prevention of cancers in women. However the public must know how much is their life time risk of developing problem of cervical cancer and HPV infection (the causative agent to carcinoma cervix).
Method valuable for screening
FDA approved the use of HC2 for primary screening with HPV testing combined with cytology (Pap smear) for women aged 30 and above. HPV testing is very expensive. Test itself cost Rs 1000 to 1500. Because HPV testing is more sensitive than cervical cytology in detecting CIN 2 and CIN 3, (precancerous lesions). Women with negative concurrent test result can be reassured by doctor that their risk of unidentified precancerous lesion or cervical cancer is approximately 1/1000. Studies using combined HPV tests with cervical cytology have reported a negative predictive value for precancerous lesion of 99-100 per cent.
Initiation of screening
Both American College of Obstetrician and Gynaecologists and American Cancer Society (ACOG and ACS) guidelines concur with the fact that cytological screening should be initiated three years after the first sexual activity but no later than 21 years. In France, the recommendation to start cytology screening is at 25 years. For HPV testing American societies recommend not to start it before the age of 30 years. Cuzik'sgroup proposed to use HPV alone as the primary test for women above 25 years. There are no guideline issued by FOGSI, our gynaecologists association or GoI.
If combined cytology and HPV are used screening should be done every three years. In women above 30 years with a negative cytology result with positive high risk HPV DNA test result should have both tests repeated every 6-12 months. Those with persistent high-risk HPV should undergo colposcopy regardless of the cytological results. This test of colposcopy is a routine test, available with leading gynaecologists of all metros, big hospitals and medical colleges.
When to stop screening
Experts state that evidence is inconclusive to establish an upper age limit for cervical cancer screening.
However international cancer society guidelines recommend that if the patient had three or more documented technically normal cytology and had no abnormal results within the past 10 years, one can stop screening.
Immunocompromised patients, HIV positive patients, women with a former history of precancerous lesion or cervical cancer require frequent (annual or biannual) screening.
HPV vaccination in primary prevention of cervical cancer
The fact that cervical cancer is caused by a viral infection raises the possibility of preventing the disease by vaccination against this known etiological agent, simulating a hepatitis B vaccination in prevention of cancer liver.
HPV vaccination would probably have different impact on cervical cancer in different countries. Industrialised countries would probably see a rapid reduction in the number of precancerous lesions detected by screening, while developing countries like India would have to wait longer to be able to see an impact on the incidence and mortality of cervical cancer.
Prophylactic HPV vaccine should be administered ideally between 9 and 12 years of age and a target population of 13-26 years of women have to be given vaccine by parental route. Two types of vaccines of Merk (quadrivalent) and GSK (bivalent) are expected to be available commercially in India by next year. Duration of protection of vaccinated women has shown effective immunity for 5.5 years. The role and timing of boosters is not yet defined.
In USA, Merk vaccine is available for 200 dollars; GoI has to fix the price in India. The fact remains that it is expensive, but people must know about it and availability should be made in India.
In socio-cultural scenario of this country, many parents would not be willing to spend money for vaccine against future cancer in their girl child. But seeing 80 per cent population who seek private care will probably spend on their daughters, if they are spending for routine vaccination given in childhood.