No more details about her condition are known at the moment but Peter Davison, whose Doctor she appeared opposite as Tegan Jovanka, has won the support of other ex-Doctor actors to launch a charity fund-raising convention - Project MotorMouth - that aims to "not only raise money for a good cause but also keep Janet's spirits up."
Davison, Colin Baker, Sylvester McCoy, Paul McGann, and David Tennant are the first guests announced for the event, which will take place on Saturday 19th January 2013 at the Copthorne Hotel Slough-Windsor. All guests will be appearing subject to work commitments.
The profits from the convention will go to Project MotorHouse, which is seeking to convert a derelict building in Thanet into a mixed-use venue promoting sustainable technology and a place where youngsters can get help with starting their own businesses. Fielding is the project co-ordinator for the organisation as well as its community champion.
She first appeared in Doctor Who in 1981 in Tom Baker's final story, Logopolis, and left the TV series in the 1984 story Resurrection of the Daleks, but made a cameo reappearance two stories later in a regeneration dream sequence for Davison's swansong The Caves of Androzani.
She has also worked as a theatrical agent - a job that saw her representing McGann when he won the role of the Eighth Doctor - and has played the role of Tegan in a number of audio productions for Big Finish.
(With Thanks To Kenny Davidson)