"Karthikeyan, who has been admitted to HCG Cancer Centre for the treatment of Hepato Cellular Cancer (liver cancer), is currently in a critical condition," hospital spokesman Shouvik Chakraborty told PTI.
In October last year, Karthikeyan sought expert treatment at the US-based Mayo Clinic and after a week he returned and was convalescing in Kerala. He had not taken part in the Kerala Assembly session held in December.
"Karthikeyan is due to undergo Cyberknife-Whole Body Robotic Radio Surgery, which will be performed by Dr P S Sridhar, who is radiation oncology consultant," Chakraborty said.
The 66-year-old veteran Congress leader has been in politics from his student days and was cabinet minister twice.