There are lots of celebrities, but few icons, yet when one thinks of Farrah Fawcett, instantly that iconic image comes to mind: the dazzling smile, sparkling eyes, flawless skin, and of course the colossal hairstyle that launched millions of copycat trips to salons across the world. It is this image that broke poster sales records in the late '70s, and the one that will always be evoked when the actress's name is mentioned. It's that memory of health and youth that is now in marked contrast with Fawcett's current reality as she battles valiantly against cancer.

In 2006, the Charlie's Angels actress was diagnosed with cancer, but just a few months later, when turning 60, was given the all clear. The cancer has since returned and through April and May of this year Fawcett has been reported to be in various states of critical. She has taken what can only be described as a 'Jade Goody approach' to her illness, filming everything from the doctor's second diagnosis of her cancer, to different stages of her treatment. Some of that footage was broadcast as a two-hour documentary entitled Farrah's Story on US TV station NBC last week.

Farrah was born 'Ferrah' (her name was later changed to the Arabic word for 'joy') to Pauline, a housewife, and William, an oil contractor, who lived in oil territory in Corpus Christi in Texas. Studying at the University of Texas where she was also a sorority sister, she was named as one of the 10 most beautiful students. A Hollywood agent spotted her potential, urging her to move to Los Angeles. Fawcett took the risk, dropping out of university three years in and heading west.

Seven years after her move to LA, after dabbling in commercials and a few bit parts on TV, and three years after marrying Lee Majors, otherwise known as the Six Million Dollar Man, the first episode of Charlie's Angels aired. Fawcett was in the final year of her 20s when she stepped into the character of Jill Munroe. Simultaneously, accidental or not, the famous poster of Fawcett in a swimsuit went on sale. It was an unprecedented smash, selling 12 million copies to teenage boys and college students around the US and beyond. Her image was beginning to be set in the fickle stone of popular culture, so it was just as well Charlie's Angels saw ratings rocket.

The programme was an instant hit, capitalising on the fun and ridiculous atmosphere of the late '70s, which saw three female detectives (Kate Jackson and Jaclyn Smith played the other two) caper around utilising their sex appeal and martial-arts skills to get the baddies. "When the show was number three, I thought it was our acting," Fawcett remarked as the first series grew into a monster. "When we got to be number one, I decided it could only be because none of us wears a bra," she added, wryly. Fawcett may be the enduring image of Charlie's Angels, but she in fact left the show after just one year, while the series continued for another four. The legacy of Charlie's Angels endured, reworked twice as a film starring Drew Barrymore, Lucy Liu and Cameron Diaz.

Despite being attached to the show for such a short amount of time, Fawcett found it difficult to shake off the Charlie's tag. She starred in off-Broadway shows, for which she won acclaim, and TV movies – the most notable perhaps being The Burning Bed in 1984 which was the first film on television to be accompanied by a helpline number for callers affected by its subject of domestic abuse. Abuse became a common theme in Fawcett's choice of roles; she played a rape victim in both the stage and film version of Extremities.

Abuse has itself always been lurking in the background. Her relationship with fellow actor Ryan O'Neal has been as tumultuous as it has lengthy, although they have never married. Allegations of abuse, break-ups, make-ups, fights and a lack of commitment have dogged them. Now, O'Neal finally says he wants to marry Fawcett, although she is reluctant to change their "good thing" which stretches back almost 30 years.

In a throwback to her bestselling poster, the December 1995 issue of Playboy, in which Fawcett posed nude, became the biggest-selling of the '90s, shifting four million copies. She returned to the centrefold in 1997 aged 50, in an issue which also became a huge seller. Fawcett made a disastrous appearance on The Late Show With David Letterman that same year. In an addled state, she rambled incoherently and shifted uncomfortably. She appeared baffled by Letterman's conversation, leading the host to call it the worst interview of his life.

Fawcett's vacant demeanour on that show led to intense speculation about whether she was under the influence of drugs or alcohol. Sadly, the influence of drugs has tormented her life – not her's personally, but her and O'Neal's son Redmond's. Redmond has spent much of his young life in and out of rehab and correctional facilities and was arrested again last month for drug possession while out on parole after being picked up driving under the influence.

With trademark upbeat ballsiness, Fawcett has aggressively fought her illness, flying to Germany for alternative treatments (this was filmed for the documentary On a Wing and a Prayer: Farrah's Fight for Life) and constantly speaking out about her experience. Her doctor and best friend, and Charlie's Angels star Kate Jackson, who survived breast cancer, have recently appeared on television on her behalf, saying that she's staying strong. Touchingly, they spoke about her losing "the most famous hair in the world" during her cancer treatment. The hair may be gone, but the iconic image endures.

Curriculum Vitae

Name: Farrah Fawcett
Born: 2 February, 1947, in Texas
Career: Actress who became a 1970s icon after rocketing to fame as Jill Munroe in the television series Charlie's Angels
Personal life: Separated from actor Lee Majors, she is in a relationship with Ryan O'Neal, and has one son, Redmond
In the news: Near to death with cancer. Her experience of treatment was filmed by Alana Stewart (Rod Stewart's former wife) and the documentary was watched last week by nine million Americans