"I reached out to her yesterday when the news broke," Priestley told People magazine at the Monte Carlo Television Festival 60th Anniversary Celebration on Wednesday.
“She’s overwhelmed with well wishers and with people reaching out to her. I haven’t heard back from her yet, but I’m sure that I will very soon," he added.
Doherty, 48, and Priestley, 50, played close-knit twins Brandon and Brenda Walsh on the hit '90s series and reunited for last year's "BH90210" reboot.
“Shannen was a big part of my life,” the actor shared. “Shannen and I will always have a bond that is very meaningful. I’m very heartbroken about the news and I wish her and her family the best in this very difficult time.”
Doherty opened up about her health on Tuesday, nearly three years after announcing she was in remission from the disease. She was first diagnosed with breast cancer in 2015.
The former "Charmed" star said she went public with her latest diagnosis so fans would learn about it from her and not from court documents from her ongoing lawsuit against insurance company State Farm. The documents state the actress "is "dying of stage 4 terminal cancer."
"I'd rather people hear it from me,'' Doherty told ABC News. "I don't want it to be twisted. I don't want it to be a court document. I want it to be real and authentic. And I want to control the narrative. I want people to know from me, I just didn't want them to know yet."