Shannen Doherty Begins Radiation Therapy: 'I Hate It'

— -- Shannen Doherty has begun radiation therapy.

On Monday, the former "Beverly Hills, 90210" actress shared a photo of herself online and updated her followers about her treatment.

The treatment, she wrote, was unpleasant.

"First day of radiation treatment. I look like I'm about to make a run for it which is accurate," she wrote. "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. I'm sure I'll get used to it but right now.... I hate it. #radiation #radiationmondaysucks #stillfightinglikeagirl"

Doherty, 45, has been very open about her battle with breast cancer, which was revealed last year. At the time, she sued her former business managers for allowing her health insurance to lapse. That case was settled this past summer, according to reports.

Since her diagnosis, the actress has undergone a mastectomy and chemotherapy.

“I think what’s beautiful and hard and interesting about cancer is that it tears you down and builds you, and tears you down and builds you and it remakes you so many different times," Doherty told Chelsea Handler on Netflix's "Chelsea" last month. "So the person I thought I was supposed to be or was going to be or who I thought I was six months ago is now somebody completely different. And I realize, 'Wow, I really thought that I was so brave and so gracious this entire time and really I was just hiding.'"