Shannen Doherty Shares Emotional Pic From First Day of 'Frightening' Radiation Treatment

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Shannen Doherty continued her fight against breast cancer on Monday, starting her first round of radiation treatment.

The outspoken star took to Instagram to post a snapshot from the doctor's office, in which she got very candid about her fear of the procedure.

WATCH: Shannen Doherty Shares Update on Radiation Plan: 'Sometimes You Just Get Sick of Being Poked'

"I look like I'm about to make a run for it which is accurate," the 45-year-old star shared in the caption. "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."

PHOTOS: Stars Post Pics From Hospitals and Doctors' Offices

"I'm sure I'll get used to it but right now.... I hate it. #radiation #radiationmondaysucks #stillfightinglikeagirl," Doherty added.

The actress has been very open regarding her fight against cancer, sharing frequent health updates with followers and fans on Instagram.

WATCH: Shannen Doherty Gives Update on Cancer Battle, Her Doctor Says She's 'Nearly Finished' With Chemotherapy

Earlier this year, Doherty shared a video of herself getting her head shaved in anticipation of her various treatments for the aggressive ailment, a process that she said was "impossibly tough."

Check out the video below to hear more about the former Beverly Hills, 90210 star's valiant battle and her gamut of grueling cancer treatments.

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