Kerryn McCann Plans A Hard Fight Against Cancer

Champion marathon runner Kerryn McCann has spoken publicly for the first time since being diagnosed with breast cancer, saying there's a tough battle ahead but she's determined to fight.

The two-time Commonwealth Games champion and three-time Olympian, 40, is pregnant and was diagnosed with the disease two weeks ago.

She has already had surgery to remove a lump from her breast and is due to start 18 weeks of chemotherapy after the birth of her third child, which is expected to be induced on September 5, Fairfax has reported.

"It's worth fighting for another little baby," she told Fairfax.

"I plan on fighting the cancer and other women have been through it so I can do it too."

McCann said the diagnosis had been a shock.

She said she had no family history of the disease she didn't think fit and healthy people would ever get cancer.

"It has all happened so quickly but I think the good news is it is treatable," she said.

"It's a rough road ahead."

McCann, who has been going to breast cancer fundraisers, said she was inspired by fellow runner and cancer survivor Raelene Boyle.

"I'll be back," she said.

"Not at an international level, but I plan on coming back and running races around Australia."

McCann provided the highlight of last year's Commonwealth Games, when she edged out Kenyan Hellen Cherono by just two seconds to successfully defend her marathon title.

The lead changed several times in the final two kilometres of an unforgettable race before McCann triumphed, receiving a huge ovation from the packed MCG crowd.