Shannen Doherty says she's living longer than expected after her stage 4 cancer diagnosis, and her work is giving her a renewed sense of purpose

Stage four is the most advanced stage of breast cancer, and means the cancer has spread to other parts of the body outside of the breast, like the lymph nodes, bones, and, in some cases, organs including the lungs, liver, or brain.
Treating a recurring cancer is also different than treating the disease the first time since cancer can become resistant to to chemotherapy and doubling up on treatments can make its long-term side effects like nerve damage worse.
On "Nightline," Doherty said she's on her "first protocol," or treatment plan, which "is a very, very big thing.".
"So it's kind of like you just want to last on your protocols as long as possible so that you don't run out of protocols," she said.
It's unclear what her protocol involves, but it's allowing her to live in the moment rather than checking off bucket-list items, a concept she's said she doesn't believe in.
"I like to say that those are goals," she told Chang.
"I just want to operate as I don't have things to check off because I'm going to keep fighting to stay alive.".
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