Born in South Africa, she was best known for her role of barmaid Dawn in BBC series Howards' Way.
She also hit the headlines in 1999 when details of an affair with Jeffrey Archer became public.
Novelist Archer said in a statement: "After Sally's brave struggle against this terrible disease, I was saddened to hear the news of her death."
In later years, Farmiloe raised money for cancer charities, while her book My Left Boob detailed her experiences with the disease.
Farmiloe also had roles in Steptoe and Son and Bergerac on TV, and Absent Friends and When the Lilac Blooms on stage.