The "Beverly Hills, 90210" star shared videos of her undergoing a CT scan and finding out her cancer had spread. Doherty's doctors found metastases, which she called mets, on her brain on Jan. 5 and the actress began radiation on Jan. 12.
"My fear is obvious. I am extremely claustrophobic and there was a lot going on in my life," Doherty captioned the post. "I am fortunate as I have great doctors like Dr Amin Mirahdi and the amazing techs at cedar sinai. But that fear…. The turmoil….. the timing of it all…. This is what cancer can look like."
In March, Doherty seemed to be doing well.
She was part of a panel at 90s Con for the show "Charmed" and when the moderator asked how she was feeling, the actress replied, "I'm feeling great, thank you! … This crowd is amazing," according to People.
Doherty was first diagnosed with breast cancer in 2015. The actress underwent eight rounds of chemotherapy and radiation treatments along with a single mastectomy before entering remission in 2017.
In 2018, Doherty revealed her tumor markers were "elevated."
She wrote on Instagram: "Test and results. One Tumor marker test came back good. Other... elevated. Just means I get monitored and another test."
"But even after that call, I’m staying positive and taking stock of my life. It certainly helps put things in perspective and reminds you of what you learned thru the cancer journey. And I sometimes, need a refresher. (sic)"
By 2020, the "Charmed" actress' cancer was back and in stage four, spreading beyond its original location.
"I definitely have days where I say, ‘Why me?’ And then I go, ‘Well, why not me? Who else? Who else besides me deserves this?’ None of us do," Doherty said on "Good Morning America" at the time. "I don’t think I’ve processed it. It’s a bitter pill to swallow in a lot of ways."
Doherty continued to work after the cancer came back. She appears in "List of a Lifetime," "Dying to Belong," "Fortress" and "Hot Seat."
"I want people to not hear stage 4 cancer and think of the person that is gray and falling over and they can't move and they're going into hospice and they can't work," she previously said in an interview with "Entertainment Tonight." "You get written off so quickly, even though you're vital and healthy and happy and wanting to go out there and work."
Doherty launched her career at the age of 11 when she appeared in "Little House on the Prairie." She also starred alongside Sarah Jessica Parker in "Girls Just Want to Have Fun."
However, the young actress shot to stardom in the '90s with her role on "Beverly Hills, 90210."
The Associated Press contributed to this report.