Shannen Doherty's doctor explains what the 'hardest thing' about watching her final moments really was

Dr Lawrence D. Piro - the oncologist who treated US actress Shannen Doherty prior to her tragic death at the weekend - has lifted the lid on the star's final moments.

The Beverley Hills, 90210 actress had been receiving treatment from the Hollywood doctor when necessary since 2015, when she was first diagnosed with breast cancer.

Shannen died on Saturday 13 July. (Jon Kopaloff/Getty Images)

In the years that followed, her cancer initially went into remission, leaving fans overjoyed, before returning at a heartbreaking stage 4 level after spreading to her brain and bones, marking her condition as terminal.

Despite her devastating prognosis, Shannen ceaselessly remained composed about her health battle when updating her fanbase in her weekly podcasts.

Prior to her passing - which was announced on Sunday 14 by her publicist and agent Leslie Sloan - Shannen told People magazine that she was no longer afraid to say her final goodbyes.

"I'm not afraid of death because I know where I'm going," she told the publication. "I know the people that I'm going to see.

"I think I would be afraid of death if I wasn't a good person, but I am."

She continued: "I don't want to die - that's the difference. I'm not afraid of dying, I just don't want to die, like ever."

Shannen's doctor has recalled her final moments. (Amanda Edwards/WireImage)

And speaking to the news outlet in the hours since Shannen's death, Dr Lawrence says it was the star's knowledge that she still had something to live for that was the most difficult aspect of watching her take her final breaths.

"The hardest thing about this was that she wasn’t ready to leave because she loved life," he said.

"In the last few hours, she was in a place where she was very comfortable and sleeping and transitioning, and she was surrounded by some of her very close friends.

"The room was surrounded by a select group of friends that were giving her a lot of care and support.

"It was somber and sad, but beautiful and loving."

Dr Lawrence also recalled his final conversation with the star, adding: "We kept going until we couldn’t go any more.

"The last conversation that we had, she was in the process of realising that things had taken a pretty significant turn.

Shannen has been praised for her drive to survive. (Neilson Barnard/Getty Images for Hallmark Channel)

"The conversation was about love and support and caring and still fighting through.

"She wanted to continue to take treatment and fight through, even though her physical condition had taken a bit of a downturn. And so we did."

He went on to explain that he never believed that the 'emotional challenge' that came with Shannen's ceaseless health hurdles affected her drive to survive.

"It certainly made it more challenging, but she’s such a winner that I feel like she pulled all the resources necessary to give the best fight against cancer, even though she was being very emotionally challenged," he said.

"She fought so hard and she didn’t believe that it would ever be over, which kind of makes everybody around you believe that, too, because you want to believe that."