Shannen Doherty Undergoes ‘Frightening’ First Day of Radiation: ‘I Hate It’

Shannen Doherty is “still fighting like a girl” in her brave battle against breast cancer.

The 45-year-old Charmed actress began her first day of radiation on Monday and documented the next step in her treatment process on Instagram.

“First day of radiation treatment. I look like I’m about to make a run for it which is accurate. Radiation is frightening to me. Something about not being able to see the laser, see the treatment and having this machine moving around you just scares me,” Doherty captioned a photo of herself sitting in the doctor’s office in a hospital gown.

“I’m sure I’ll get used to it but right now…. I hate it. #radiation #radiationmondaysucks #stillfightiglikeagirl,” the post continued.

Doherty first opened up about her battle with cancer to PEOPLE in August 2015. “Yes, I have breast cancer, and I am currently undergoing treatment,” the actress said in an exclusive statement to PEOPLE. “I am continuing to eat right, exercise and stay very positive about my life,” she continued. “I am thankful to my family, friends and doctors for their support and, of course, my fans who have stood by me.”

But in the year-and-a-half since she revealed her diagnosis, the actress has openly shared her journey, documenting her hair shavesharing photos and videos of her cancer treatment on social media and attending cancer awareness events. In October, she documented her experience with yet another round of chemotherapy, and shared an Instagram video of herself receiving an injection from her nurse.

“Chemo day. I’m lucky to have such a great team!!!” she captioned the post. “Dawn has been taking care of me pretty from much the start along with Dr. Piro, Joyce, Rosie, Kathy and everyone else at the clinic.”

“I don’t enjoy chemo day or needle like things in my chest or my port but, at least with this crew it’s not so bad,” she continued, before urging her followers: “Make sure you connect not only with your oncologist but also the person administering your chemo. Thank you to the Los Angeles Clinic.”

Shannen Doherty attends Stand Up To Cancer 2016. (Photo: Steve Granitz/WireImage)