Speaking to Entertainment Tonight, the 45-year-old admitted that the scariest part is not knowing what the future holds.
"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 said. "So for that reason, we are doing chemo, and then after chemo, I'll do radiation."
Shannen Doherty revealed that she will have more chemo and radiation
"The unknown is always the scariest part," said Shannen, who had a single mastectomy in May. "Is the chemo going to work? Is the radiation going to work? You know, am I going to have to go through this again, or am I going to get secondary cancer?
"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."
The 90210 star can count on her husband-of-five-years Kurt Iswarienko for support. She also has her mum Rosa and her close friends to lean on.
With their help Shannen went through the emotional process of shaving all her hair off, and she took to Instagram to post photos last month. She has also explained that despite feeling self-conscious about her appearance at first, she wanted to share the experience with her followers to inspire other cancer victims.
The actress can count on her husband Kurt Iswarienko for support
"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," said Shannen. "I just remember holding onto huge clumps of my hair in my hands, and just running to my mum crying, like, 'My hair, my hair, my hair, my hair.'
"It was just shedding and it was driving me crazy. It was just clumps, and I was like, 'Just grab the kitchen scissors.' And my mum's like, 'Wait, wait, wait.' I'm just, like, 'Grab it.'"
"We did stages," she added. "We did a pixie. And then we did a mohawk, which was my favourite look. And then finally, we had to get the shaver thing and just buzz it off."