* Madoff moved to medical wing Dec. 18

* Bureau of Prisons declines comment on reason for move (Adds background)

WASHINGTON, Dec 23 (Reuters) - Convicted swindler Bernard Madoff was moved last week to the medical center within a federal prison for undisclosed reasons, a spokeswoman for the Federal Bureau of Prisons said on Wednesday.

Spokeswoman Traci Billingsley said he had been transferred on Dec. 18, but she declined to comment on the reason, citing privacy rules.

Madoff, 71, is serving a 150-year prison term after pleading guilty to a $65 billion fraud. He has been imprisoned at the Butner Federal Correctional Complex in North Carolina.

A lawyer for Madoff was not immediately available for comment.

In late August, prison officials denied a published report that Madoff had been diagnosed with cancer and was terminally ill.

The New York Post reported that Madoff had cancer and that he had told other inmates that he did not have long to live. The newspaper cited unnamed prison sources.

Madoff pleaded guilty in March to orchestrating a worldwide Ponzi scheme that bilked thousands of investors. (Reporting by Jeremy Pelofsky; Editing by Toni Reinhold)