Cervical cancer has a major impact on women's lives and is the leading cause of cancer mortality in India, accounting for 17% of all cancer deaths among women aged 30 to 69 years of age. Carcinoma of the uterine cervix is the most frequent gynecological malignancy affecting women in developing countries despite being a potentially preventable disease. Globally, it is the second most frequent cancer affecting women with a steady rise in incidence among younger women..
Each year more than 5,00,000 women are diagnosed with cervical cancer and approximately 2,70,000 of them die from it. The implementation of cytology-based screening programs, or Pap smears, has greatly reduced the incidence and mortality of cervical cancer in the developed countries. In the absence of such a program and the fact that only 15% of cytologically dysplastic lesions progress to cancer, there is a need to develop markers to identify women who will progress to cervical cancer.
HPV detection was considered relevant for assessing cases that are likely to progress to cancer since it was established that cervical cancers are associated with persistent HPV infection with "high-risk" strains like HPV 16, 18, 31, etc. However, 90% of HPV infections resolve spontaneously and hence it is important to identify individuals who will develop this cancer.
Chromosomal abnormalities such as gains, losses and rearrangements of whole or parts of chromosomes are a hallmark of cancer and have been described in many tumor types, including cervical cancer. The most commonly described abnormality in cervical cancer is gain of the 3q26 where two genes important for carcinogenesis are located:the RNA component of human telomerase (TERC), and phosphatidylinositol-4,5- bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA). Genomic gain of the 3q26 locus has been associated with the progression from high-grade cervical disease to cancer. In addition to 3q26, amplification at 5p15 and 20q13 has also been frequently described in cervical cancer. Hence, a new Fluorescent insitu Hybridization (FISH) based diagnostic test to identify multiple markers like 3q26, 5p15, 20q13 has been developed.
FISH is a sensitive and accurate technique that allows the detection of chromosome aberrations. In this method, a single-stranded fluorescent-labeled nucleic acid sequence (probe) complementary to a target genomic sequence is hybridized to metaphase chromosomal and interphase nuclei to detect the presence and absence of a given abnormality. The chief advantage of FISH is that it can be applied to non-dividing cells and a variety of specimen types, including pap smears.