From early screening to early prevention of cervical cancer

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Wuhan Union Hospital obstetrics and Gynecology professor Wang HongboAt present, there is a clear relationship between cervical cancer and hu


Wuhan Union Hospital obstetrics and Gynecology professor Wang Hongbo

At present, there is a clear relationship between cervical cancer and human papillomavirus (HPV) infection. There is a long, reversible precancerous lesions in cervical cancer, and the treatment effect of early cervical lesions is much better than that of cervical cancer. It is reported that the five year survival rate of cervical invasive carcinoma is about 67%, and the early stage of cervical cancer is about 90%, while that of cervical carcinoma is almost up to 100%. Therefore, the screening and prevention of cervical cancer is of great significance.

New changes in ancient methods

Pap smear negative negative

Since the beginning of 1941, the Pap smear was born, all the countries in the world to the law as a means of screening for cervical cancer by clinical and as a routine screening project, and the incidence rate of cervical cancer screening in one fell swoop decreased by 70% to 90%, without major changes without the screening population morbidity level. Because of its simple method, patients without pain, and low cost, very suitable for a wide range of population census, is still used in some places.

Despite the overall success of Pap smear, there are still problems with its use. On the one hand, it is considerable infrastructure needed to build the project with cytology, especially the cytology and technical personnel, they need to go through long-term rigorous training and years of practice experience, to be more stable and accurate identification of Pap smear results. On the other hand, the accuracy of the Pap smear is affected by many factors, such as sampling method, smear smear making, dyeing skills, reading level, will inevitably lead to the false negative, false negative rate is about 15% ~ 40%.

Now, with the introduction of thinprep cytologic test, the false negative rate decreased. In 1998, a large scale survey was carried out on the site of high incidence of cervical cancer in Shanxi, China. The sensitivity and specificity of the identification of the lesions were 87% and 94%, respectively.

In addition, in view of the false negative problem of Pap smear, the automatic screening device has been developed and developed into the market, which is representative of PAPNET system and AutoPap system. PAPNET system is a kind of neural network interaction device, which is mainly used for cytological re screening. The detection rate and accuracy of PAPNET were significantly higher than that of the conventional methods for in situ and invasive carcinoma. The comparative study of AutoPap and routine screening showed that AutoPap was superior to conventional method in the diagnosis of atypical squamous cell carcinoma and low-grade squamous intraepithelial lesion. In addition, AutoPap can improve the specificity of diagnosis by reducing false positive cases.

HPV detection

Can improve the effectiveness of cervical cancer screening

Current epidemiological and biological data have demonstrated that HPV infection is the major cause of cervical cancer and precancerous lesions. Therefore, many scholars have proposed to detect HPV infection as a screening method for cervical cancer.

HPV infection can generally be divided into high-risk, low-risk, transient, delayed and sustained several types, the highest risk of sustained infection is the most important. Therefore, the clinical application of HPV detection includes screening, abnormal cytology and follow-up treatment of cervical lesions. For the detection of HPV as a screening content, although there are still some controversy, but in Europe, including a screening of 23890 patients showed that HPV test can significantly improve the screening effect.

HPV is the only human cancer incidence can be fully confirmed carcinogenic virus. Current research may even prove that prevention of HPV infection can prevent cervical cancer, without HPV infection can not suffer from cervical cancer. The detection method of HPV is very much, and now it is best to use hybrid capture technology (hC2), the sensitivity of detection is 88%~100%, the negative predictive value is as high as 99%, hC2 negative can be confirmed without HPV infection. The method can also report the amount of virus in order to follow the virus.

It is understood that HPV infection is very common, but only sustained HPV infection before the occurrence of precancerous lesions (CIN) or cervical cancer. The average duration of HPV infection was 8 to 24 months (CINI), CIN II and CIN III, with an average of 8 to 12 years.

It is very important to follow up after treatment of cervical precancerous lesions, because the recurrence rate of patients with precancerous lesions is 5 times higher than that of the normal population. Patients with precancerous lesions after treatment, in 4 to 6 months for the first time to review, including naked eye observation, cytology, HPV DNA test, or as appropriate, colposcopy.

hpv vaccine

The most promising means in the future

At present, human HPV is still lack of an exact solution, so more people will hope on the HPV vaccine.

There are 3 ways to develop HPV vaccine. The first is to prevent the infection of HPV vaccine, mainly in young women infected with HPV before the use of HPV infection has been infected with cervical precancerous lesions or cervical cancer. The second is a therapeutic vaccine for the treatment of patients who have been infected with HPV or cervical lesions. The third is a vaccine that has both preventive and therapeutic effects. Over the past ten years, the development of HPV vaccine has made considerable progress, a lot of products have been completed in the 1, phase 2 clinical trials. June 8, 2006, the United States Food and Drug Administration (FDA) formally approved the Gardasil cervical cancer preventive vaccine market, the use of the vaccine targets 9 to 26 year old women. This is the first cancer vaccine in the world.

Through efforts, our country in the development of HPV vaccine has been basically in line with international standards. The development of the vaccine in the prevention of HPV16, China completed the construction of HPV16 type L1 and L1/L2 recombinant baculovirus vaccine strains, and expressed in insect cells; to observe the formation of virus like particles in the electron microscope; the successful construction of the recombinant L1/L2 was expressed in replicating and non replicating vaccinia virus vaccine strain.

In the aspect of the development of HPV16 therapeutic vaccine, China has constructed a recombinant replication type expression of HPV16 E6/E7 protein and non replicating vaccinia virus vaccine strain. These strains have good immunogenicity, which can induce specific CTL reaction, and can protect C57 mice against TC-1 tumor cells. Compared with the control group, the time of subcutaneous tumor formation was delayed, and the survival time of tumor bearing mice was significantly prolonged. The researchers found that the vaccine was effective in preventing the recurrence of tumors in mice treated with the HPV vaccine. Especially in the residual or metastatic tumor cells after the operation of the tumor, and has certain application value in the prevention of tumor metastasis. These results laid the foundation for the development of genetic engineering HPV vaccine in china.

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