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Sir Michael Parkinson said the cancer is contained to his prostate, and that he should be "completely free" of the disease by August.
And he urged men to pay greater attention to their health in order to catch potential diseases early - with a simple test to check for prostate cancer.
Sir Michael added: "I'm 78 and I have had a good life. When you get involved in this, you begin to understand the extraordinary work of those involved in treating cancer.
"You just sit and look at them in wonder. They do the most extraordinary things, and I am very grateful.
"I shall be around for a while yet, to the delight of my friends and the dismay of my enemies."
Sir Michael Parkinson was diagnosed with prostate cancer in May after a routine health check and doctors immediately began organising his treatment, which involves five sessions of radiotherapy a week.
The renowned journalist and interviewer said he was left in shock by the diagnosis, but said he was "in wonder" at the "marvelous" work of medical staff after initial thoughts of his own mortality.
The 78-year-old said: "I had to start calling a few of my social engagements to tell them I couldn't do it - what do you say to them?
"When you are told you have something like cancer, it is a shock. But the cancer specialist said: 'I will assure you, you will not die of this.'
"I am concerned about it, of course, but I am not frightened of it."
Chat show host Sir Michael Parkinson has revealed he has cancer.
The television legend, 78, is currently undergoing radiotherapy for prostate cancer but said he confident of fighting the disease and returning to full health.
Sir Michael said: "It was a great shock, but I have been told to expect to make a full recovery."