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As Shannen Doherty continues her ongoing battle with breast cancer, the Beverly Hills, 90210 alum has revealed the disease may have spread.

“I had breast cancer that spread to the lymph nodes, and from one of my surgeries we discovered that some of the cancer cells might have actually gone out of the lymph nodes,” she told Entertainment Tonight in an interview airing Monday. “So for that reason, we are doing chemo, and then after chemo, I’ll do radiation.”

Since being diagnosed in February 2015, Doherty underwent a single mastectomy in May, though she says the treatment isn’t what she finds most difficult.

“The unknown is always the scariest part. Is the chemo going to work? Is the radiation going to work?” she continued. “Everything else is manageable. Pain is manageable. You know, living without a breast is manageable. It’s the worry of your future and how your future is going to affect the people that you love.”

Earlier this month, she shared a heartfelt update via Instagram, thanking her family and friends for their support after she shaved her head.

“After my second treatment, my hair was really matted, like in dreadlocks. And I went to try and brush it out, and it just fell out… I just remember holding onto huge clumps of my hair in my hands and just running to my mom crying,” she said of losing her hair. “We did stages. We did a pixie. And then we did a mohawk, which was my favorite look. And then finally we had to get the shaver thing and just buzz it off.”

During a three-part interview to air on ET beginning Monday night, the actress will further detail the toll her fight with cancer has taken.

“I started thinking that I wasn’t going to live. I don’t look past today, [and] I don’t know if I’ll ever look like me again,” she said in a preview for the episode. “I want to believe that if I fight I’m going to be okay.”

Watch a clip from Doherty’s interview below and check local listings for air times.