A High Court ruling is expected on whether a woman should be allowed the breast cancer drug Herceptin after she was refused it by her NHS trust.
Ann Marie Rogers' case was heard at the High Court last week
Ann Marie Rogers was denied the drug - which is not licensed for early stage breast cancer - by Swindon NHS bosses, who say they were following advice.
But the mother-of-three, 53, said the decision was a "death sentence".
The first case of its kind to reach court, it may have lasting implications for the way drugs are prescribed.
Herceptin has been licensed in England and Wales for the treatment of advanced breast cancer.
But pressure is mounting for the NHS to use it on patients with early stage cancer, as research has shown it is effective in fighting the disease.
It targets the HER-2 protein, which can fuel the growth of breast tumours
Herceptin prevents this process happening
Around a fifth of breast cancers are HER-2 positive
It is currently licensed for use in women with advanced breast cancer - where the disease has spread within the breast or to another organ
Early stage breast cancer refers to the first occurrence of the disease
The cost for one year's treatment with Herceptin is 20,000 pounds
Some trusts have been hesitant to fund the drug when asked, preferring to wait for it to be given a licence and approval by NHS adviser NICE, which rules on the cost-effectiveness of the treatment.
But previous legal actions by women have resulted in NHS trusts backing down and funding the drug, which costs around £20,000 for a year's treatment.
Last year, nurse Barbara Clarke, 49, threatened Somerset Coast Primary Care Trust with a judicial review, but the trust backed down before the case and provided her with the treatment.
And in November, Health Secretary Patricia Hewitt intervened when North Stoke Primary Care Trust refused to fund the drug for mother-of-four Elaine Barber.
Ms Hewitt said she wanted to see the evidence upon which health bosses had made their decision and within a day the trust had reversed the decision, citing Ms Barber's "particular exceptional circumstances".
Ms Rogers' legal team - which put forward her case during a High Court hearing last week - believes if the judgement goes her way it will set a precedent for future cases.
Matt Griffiths, prescribing adviser for the Royal College of Nursing, said such a decision could make it difficult for NHS trusts to stand their ground in the future, as well as raising question marks about NICE.
But he said: "What we also need to consider is that there are other groups, such as those with mental health problems, that are not able to lobby quite as hard as others.
"We do not want drug prescribing to be determined by people power alone, but need to look at the bigger picture to ensure equity in access to medicines for all patients.
"As individuals, we would all want access to the best treatment for ourselves and our families, but, taking a step back, NICE is the right body to be deciding about treatments, balancing greater issues such as cost and clinical effectiveness."
His warning comes as a survey of 168 NHS trust chief executives by the NHS Confederation revealed three quarters thought patient safety would be compromised if the drugs regulatory process was to be side-lined.
NHS Confederation chief executive Dr Gill Morgan said: "The licensing and regulatory processes for new drugs have been put in place to protect patients and to ensure that new drugs are both safe and effective.
"No-one would advocate a system in which decisions about drug safety and effectiveness are rushed through without careful consideration of their impact on patients".
NICE has refused to get involved in the debate, saying it will not comment before the judgement is given.
But cancer charities have argued trusts should not be with-holding treatment when doctors believe it is in the best interests of the patients, saying women should not be put through "unnecessary stress and anxiety to get access to a life-saving drug".