Senator Sinodinos, the Minister for Industry, Innovation and Science, is currently on leave and believes the prognosis is very positive and that the cancer is eminently treatable.

The minister announced two weeks ago that he was taking a period of medical leave and said he expected to be back as soon as practicable.

At the time, Senator Sinodinos requested privacy and did not disclose the nature of his illness.

The NSW senator, who served as chief of staff to former prime minister John Howard for a decade and is one of the most respected figures in the Federal Parliament, confirmed to Fairfax Media he has been undergoing treatment for cancer for the last two weeks.

Senator Sinodinos has not disclosed the type of cancer he is fighting.

Senator Sinodinos chose to reveal his fight to Fairfax Media to put to bed suggestions he may not return to work, and to make clear that he fully expects to return to politics fighting fit.

Senator Sinodinos' recent weight loss has not gone unnoticed by parliamentary friends and colleagues, some of whom have been concerned that he may step down from the ministry or even leave the Parliament.

There has also been speculation among some Coalition MPs that he may choose to leave the Parliament and take up a diplomatic posting.

But in a sign of his determination to return to politics as soon as possible, the cabinet minister said he wanted to return to work on delivering policy reform through Mr Turnbull's National Innovation and Science Agenda (NISA).

"I am taking this period of leave in order to focus on my health and to get the treatment that I need," he told Fairfax Media in a statement.

"I was pleased that I could work with my colleagues Michaelia Cash and Simon Birmingham on announcing our commitment to an Australian space agency last month, something which I look forward to reviewing and implementing early next year."

Mr Turnbull threw his support behind his friend and political ally, telling Fairfax Media: "Arthur is and remains a valued member of the cabinet, he has a good prognosis and I look forward to having Arthur back as soon as he is ready".

The senator played a key behind-the-scenes role in the Liberal Party's decision to dump former prime minister Tony Abbott and switch to Mr Turnbull back in September 2015 and Senator Sinodinos remains a trusted adviser to the Prime Minister.

Assistant Minister Craig Laundy, another friend of Senator Sinodinos, has taken stewardship of the $3.5 billion R&D Tax Incentive review during his colleague's leave of absence.

Mr Laundy said: "Arthur's continuing advice and counsel in managing this critical piece of the NISA agenda has been invaluable and I look forward to him returning to work when he is ready."

Senator Cash and Mr Laundy have stepped in to help with Senator Sinodinos' portfolio responsibilities while he receives treatment, but colleagues say that despite his illness the senator is still in regular contact by phone about his portfolio.

Senator Sinodinos is the son of Greek immigrants and was selected to fill a casual Senate vacancy in 2011 and re-elected in 2013 and 2016. He is married with children. Early in his career as a minister in the Abbott government, Senator Sinodinos stood aside as assistant treasurer when he was called to give evidence to the NSW Independent Commission Against Corruption. The agency subsequently cleared him.

Another Coalition senator, Special Minister of State Scott Ryan, returned to work this week after more than two months' absence with an undisclosed illness.

The federal government announced plans to establish a new national agency to grow Australia's domestic space industry last month, with former CSIRO chief Megan Clark to chair a working group that will provide advice on how to establish the agency by the end of March next year.