Ann Marie Rogers, 54, has been refused access to the drug, despite evidence it could halve the chances of her cancer returning.
She accused local health service managers of leaving her "on death row" because of budgetary restraints on the £21,000-a-year cancer treatment.
If she wins, the case could have wide-ranging implications for the NHS budget and for thousands of patients who claim they are being prevented from receiving the best treatments because of where they live.
Lawyers for Mrs Rogers claim that the denial of treatment went against guidance from the Health Secretary, Patricia Hewitt, and also breached Mrs Rogers' human rights.
Mrs Rogers, a divorcee who has three children and two grandchildren, was diagnosed with breast cancer in late 2004 and in January last year underwent a mastectomy.
She was given chemotherapy and radiotherapy but doctors warned her that there was a 57 per cent chance of the cancer recurring within 10 years.
Herceptin is currently only licensed in the UK for advanced breast cancer, despite the latest research showing that it is also highly beneficial for early stage forms of the disease - like that suffered by Mrs Rogers.
Roche, the company that manufactures Herceptin, is applying for a licence that covers early stage breast cancer and the National Institute for Health and Clinical Excellence has pledged to fast-track the submission, with a decision expected in May.
Mrs Rogers' fight for the right to Herceptin is the first to reach the courts.
She borrowed £5,000 to fund the prescription costs of Herceptin for herself last year, but says she cannot afford further treatments.
In a statement, she told the court that "waiting for the cancer to return is like waiting on death row. I know that if it comes back, it will be terminal."
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