A phony cancer doctor who sexually assaulted his vulnerable patients was sentenced yesterday to six years in prison — but not before he tried to withdraw his plea, claiming that he thought he was getting six months.

Michail Sorodsky, 63, who advertised in Russian-language newspapers, pleaded guilty this month to 20 counts, including first-degree rape, to avoid prosecution on more than 100 others. He agreed to the six years, half of which he’d done while held on $11 million cash bond.

But he told Brooklyn Supreme Court Justice Guy Mangano via an interpreter that he was tricked into “taking a cop-out plea.”

Mangano quickly rejected the motion, calling it “dilatory and disruptive” and Sorodsky “crazy like a fox.”

“While six years is not enough, the disposition was swift, it was definite and it is final,” the judge ruled.