A decision not to fund Herceptin for a breast cancer patient was "arbitrary in the extreme", a lawyer representing the woman has told the Court of Appeal.
Treatment with Herceptin costs around £20,000 a year
Ann Marie Rogers, 54, from Swindon, Wiltshire, lost a landmark legal case in the High Court last month.
The judge ruled Swindon Primary Care Trust was right not to allow Ms Rogers the drug, which is not licensed for the early stage breast cancer she has.
Lawyers for the trust told the court its decision was a "considered one".
Counsel for Ms Rogers, David Pannick QC, said the trust's decision was unreasonable and a breach of her right to life under the Human Rights Act.
"We say that where you have, as you do here, undisputed clinical need, the absence of any alternative treatment offering as good - far less better - prospects for her, her clinician prescribing the drug and no suggestion by the PCT that cost is a factor to be weighed in the balance, it is arbitrary in the extreme then to say to the patient 'you can't have this drug'."
He added: "One searches in vain for a cogent reason why the PCT refuses to provide Herceptin in the circumstances of this case."
Mr Pannick also argued that not all the arguments had been taken into account when the decision was made.
He said there was undisputed clinical trials had shown that Herceptin reduced by 50% the risk of recurrence for patients like Ms Rogers.
The cancer specialist treating her had prescribed it and there was no suggestion that any other drug or treatment offered as good a chance of survival, Mr Pannick said.
He argued that the Swindon trust had relied entirely on an editorial in medical journal the Lancet in which caution about the drug had been expressed.
The argument that Herceptin was not licensed was "simply irrelevant" to the case, he added.
But Philip Havers, QC, for the trust, said the decision had been taken after advice was sought from the local cancer network and that it was in line with the advice of the strategic health authority.
He stressed that Herceptin had not yet been licensed or appraised by drugs body the National Institute of Health and Clinical Excellence.
A question mark remained over the drug, which had been raised not just in the Lancet, but also in a paper in the New England Journal of Medicine.
Mr Havers also argued that Health Secretary Patricia Hewitt had deliberately not stated that Herceptin should be routinely provided or funded but had left it up to individual trusts to decide.
If she had considered that Herceptin would be routinely provided for the treatment of early stage breast cancer, then she would "surely" have said so, he added.
Swindon Primary Care Trust had followed the minister's guidance and its policy was wholly consistent with it, he said.
He said if an exception was made in Ms Rogers' case, then the trust would have to prescribe Herceptin to all those with early stage breast cancer.
Herceptin targets the HER-2 protein, which fuels the growth of breast tumours in about a fifth of cases.
The treatment is currently licensed for the treatment of advanced breast cancer, but not for those in the early stages of the disease.
Swindon Primary Care Trust said during the High Court case that it could not prescribe the drug until the safety implications and possible benefits had been checked.
But Ms Rogers, who is to receive the drug until the Appeal Court makes its decision, said: "I am facing a death sentence if I cannot receive Herceptin."
Makers Roche submitted their application for a licence to European drug authorities in February.
Once that has been granted, the NHS drugs watchdog, the National Institute for Health and Clinical Excellence (NICE), said it will fast-track its appraisal if Herceptin is cost-effective
That process is set to be complete later this year.