EXCLUSIVE: Shannen Doherty reacts to Michael Buble's son's 'devastating' cancer diagnosis

Shannen Doherty feels for Michael Buble.

ET caught up with the 45-year-old actress at the American Cancer Society's Inaugural Giants of Science Gala at the Four Seasons Hotel in Beverly Hills, California, on Saturday, where she reacted to Buble's son Noah's recent cancer diagnosis.

WATCH: Michael Buble's Three-Year-Old Son Has Cancer, Singer Puts Career 'On Hold'

"I can't even begin to touch that one to be honest, because it's a 3-year-old," she said. "I would imagine your child having cancer is devastating as a parent."

See photos of Michael Buble's son and family:

Doherty -- who was diagnosed with breast cancer in February 2015, and revealed she was "nearly finished" with her chemotherapy treatments in September -- said the best thing Buble and his family can do is "stay positive" and trust in their doctors.

"Just trust in your doctors. Make sure you have amazing doctors, a great team and know that organizations like the American Cancer Society, Stand Up to Cancer, they are doing so much good for cancer," she continued. "And [there is] so much research that we have much better chances now. Stay positive."

"That positivity, that outlook on life that you can get through something, it actually does get you through," she added.

Buble revealed on Friday that Noah has been diagnosed with cancer, and that he and his wife, Luisana Lopilato, would be taking time off to care for their son.

See photos of Shannen Doherty:

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"We are devastated about the recent cancer diagnosis of our oldest son Noah who is currently undergoing treatment in the U.S.," the 41-year-old singer said in a statement on his Facebook page. "We have always been very vocal about the importance of family and the love we have for our children."

"At this difficult time, we ask only for your prayers and respect for our privacy," the statement continued. "We have a long journey in front of us and hope that with the support of family, friends and fans around the world, we will win this battle, God willing."

ET recently spoke with Buble about how he's changed since becoming a father to Noah and 9-month-old son, Elias.

"I love them more than I'll ever love anything, or anyone in the whole universe," he said. "You're scared all the time because you love them so much that you can't ever, ever think of a world without them. You try not to even think about it."

EXCLUSIVE: Michael Buble Says Fatherhood 'Makes Me Better at Everything'

Additional reporting by Brendon Geoffrion.

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