With an alarming rise in the number of oral cancer cases among males in the city, doctors and scientists suspect that Human Papiloma Virus transmitted during unhygienic oral sex is the main culprit.
"Oral cancer is on the rise in Bengal. Although tobacco consumption is the main reason, there are high chances that unhygienic oral sex can lead to oral cancer due to the presence of HPV virus in human genitals," said Jaydip Biswas, Director, Chittaranjan National Cancer Institute (CNCI).
If the HPV passes from a genital organ to oral cavity, it leads to oral cancer, Biswas said, adding "it is one of the agents of oral cancer".
According to a survey carried out in 2008-09 by the CNCI, which will be published by the end of this year, the prevalence of oral cancer is among the top three most common cancers affecting Kolkatans.
The oral cancer did not find place among top five cancers prevalent among males in a survey conducted by the CNCI in 2006-07.
The survey report has billed the lung and prostate cancer as the top two cancers affecting the people of Kolkata.
The prevalence of lung, prostate and oral cancer is around 18 per cent with the last two taking up seven per cent each of the pie.
"The HPV is found in human genitals, both male and female. The virus is transmitted from one person to another only through sexually-transmitted infection. So when you get such virus in the mouth leading to oral cancer, it can be said that it had passed during oral sex," Biswas said.
"We also know that syphilis is one of the main reasons behind oral cancer or tongue cancer," said Biswas.
According, to experts, this virus is found in sexual passages, genitals, and sexual organs of male and female.
"There are various types of HPV virus, but the HPV 16 and 18 are the cancer causing type. HPV virus can lead to cancers of the cervix, vagina, vulva, penis and anus. So it is suspected that the passage of this virus during unhygienic oral sex may lead to oral cancer," said Partha Basu, head, gynaecological oncology, CNCI.
In the study involving 310 samples of oral cancer, both malignant and pre-malignant, comprising both males and females, more than 60 per cent of the nearly 197 samples reported the presence of HPV virus in oral cavity.
"This study was conducted by collecting either oral swabs or biopsy reports of the 310 patients who had reported either malignant stage or pre-malignant stage of oral cancer. We had found the presence of HPV virus in 197 patients," C K Panda, head of the research team, CNCI, said.
Out of these 197 patients which reported presence of HPV virus, HPV 16 virus was found in 180 patients and the rest of the patients are reported to have HPV 18 virus in oral cavity.
Panda noted that in a micro study of the 155 samples of 197 samples which reported the presence of HPV virus, it has been found that HPV constitutes the sole carcinogenic agent in 26 per cent of cases.
Tobacco comes out the sole cancer causing agent in 32 per cent cases, said Panda.
Genital and oral hygiene is the best way to avoid transmission of HPV virus, Basu said.