Just a few weeks after Shannen Doherty shaved her head, in anticipation of her breast cancer battle, Sarah Michelle Gellar has paid tribute to her friend.

Taking to Instagram, the 39-year-old posted a photo of herself alongside Charmed star Doherty, writing: “My #mondaymuse (and really every day #muse) is my brave friend @theshando."

The Buffy actress continued: "I've always said she is one of the most loyal friends I've ever known, and now while she is facing the toughest journey of her life, she is sharing it with friends she has never met in the hopes of helping other people who are going through the same struggle.

"That's a true friend #F**kCancer."

Doherty returned the sentiment, sharing the same photograph on her own Instagram page.

She wrote: “I'm starting #totaltuesday and dedicating it to @sarahmgellar. Why? Because she's the total package. Smart, funny, beautiful and a great friend.
 
“She's that friend that is always there when you need her no matter what. Loyal and loving to the bone.
 
“I am blessed for many reasons and she's one of them. Love you SMG.” 

The duo have been friends for years, with Doherty one of the few guests at the Cruel Intentions star’s intimate wedding to Freddie Prinze Jr. in 2002.

Doherty, who admitted that her “friends help cancer suck a little less”, was originally diagnosed with the disease in March 2015.

Last week, she told Entertainment Tonight that, despite undergoing a single mastectomy in May, her cancer had spread to her lymph nodes.

She said: “I had breast cancer that spread to the lymph nodes, and from one of my surgeries we discovered that some of the cancer cells might have gone out of the lymph nodes. So, for that reason, we are doing chemo, and after chemo, I’ll do radiotherapy.”

“The unknown is always the scariest part. Is the chemo going to work? Is the radiation going to work?” she continued.

“Everything else is manageable. Pain is manageable. You know, living without a breast is manageable. It’s the worry of your future and how your future is going to affect the people that you love.”

The actress has continued to share regular updates from her cancer journey on Instagram, sharing photographs of her shaving her head – and spending time with her friends.

She has also shared pictures of herself with her husband of five years, Kurt Iswarienko, whom she praised during her ET appearance for helping her through this difficult time.

"It's, you know, you're throwing up every single second. After my first treatment I lost 10 pounds, instantly. You're throwing up and the last thing you want to do is be in a car. You don't want to be moved, you can't eat.

“But my husband has to, you know, pick me up. He puts me in the car, he buckles me in, and he drives me to my oncologist and they hook me up to an IV and I get hydrated. ... There's nothing going in my body, it's all going out."

Sharing a snapshot of herself and Iswarienko on Instagram, she added: “He loves me with pink hair or no hair.

“I’m blessed to have such a strong support team starting with @kurtiswarienko who loves me more every second. Can’t imagine my life without him.”

Doherty continued, “Cancer is not pleasant but it can bring out the best in relationships or the worse. Thankfully, it has made our marriage stronger.”

Image: Rex Features