Porter, the former CEO of the McGill University Health Centre, diagnosed himself with cancer in late 2012 in the Bahamas, where he runs a number of cancer clinics. That was just before he travelled to Panama and was arrested.
Sikora told CBC in an email dated May 6 that he visited Porter in the Santo Thomas Hospital last weekend.
"He has improved dramatically since being in hospital," Sikora said in the email.
"I arranged for him to see an excellent local oncologist and hopefully this will happen this week. He has an armed guard all the time but they are very pleasant."
Porter has been detained in a Panamanian prison since May 2013. He faces fraud charges in Canada related to the $1.3-billion MUHC hospital project in Montreal and is fighting extradition.
Sikora told CBC News on March 30 that, unless Porter was brought to hospital soon for tests and new drugs, he would likely die in prison within six to eight weeks.
Porter, a medical doctor, has been treating himself in prison.
His biographer, Jeff Todd, told CBC in an email Tuesday that members of Porter's family were travelling to Panama to be with him.
Pamela Porter, his wife, was sentenced in December to 33 months in jail after she pleaded guilty to two counts of money laundering in connection with her husband's case.
Sikora said the long-term outlook for Porter is still grim.
"The prognosis is still very poor as the chances of further response to new therapies is very limited. He is very realistic about this. It is truly amazing he is still alive as he has had no medical care at all in prison," Sikora said.
The doctor said that he's been doing his best to help Porter through what he called a "dreadful situation."
Sikora believes history will look favourably on Porter, despite the charges he is facing.
"When history is written, it was his persistence, drive and determination that gave Montreal its magnificent new hospital," Sikora said, referring to the new MUHC Glen site hospital which opened its doors a couple of weeks ago.
Sikora has come under scrutiny before over his cancer diagnosis of the Lockerbie bomber, Libyan Abdelbaset al-Megrahi.
A U.S. Senate committee questioned the medical diagnoses of Sikora and five other cancer specialists, whose opinions paved the way for al-Megrahi's early "compassionate release" from a Scottish prison in 2009.
Said to have only a few months to live, al-Megrahi survived for nearly another three years back in Libya.