Nelson Mandela has begun radiation therapy after being diagnosed with prostate cancer.
The cancer is not expected to pose a threat to his life, his spokeswoman said.
The seven week radiation regime will require the former South African president to have treatment for about 10 minutes every day.
"I think it's a thing that he'll approach positively and hopefully the doctors will do the rest," said spokeswoman, Zelda la Grange.
Last November, Mandela's doctors said they had discovered high protein levels in his blood, a possible indicator of prostate cancer. They discovered the cancer in a subsequent examination.
The cancer was found three to four years before it would have started causing trouble, said his urologist, Dr Louis Gecelter. Mr Mandela, 83, is not currently sick and he is not experiencing any symptoms.
"It's a very early case of cancer of the prostate, and he should be cured," he said. "This isn't going to impact on his life expectancy. He's going to live until one hundred and plenty years."
Prostate cancer is generally less aggressive in men Mr Mandela's age, and many choose not to undergo treatment, said Dr Michael Cohen, a urologist in private practice, who is not involved in treating Mr Mandela.
Unlike more aggressive forms of cancer treatment, the radiation therapy will not make Mandela sick, Dr Gecelter said.
Since retiring from the presidency in 1999, Mr Mandela, a Nobel Peace Prize winner, has maintained an extremely active schedule, regularly travelling overseas and mediating peace efforts in Burundi. He is also writing a second autobiography.