The NHS's drugs watchdog says people with early stage breast cancer should be able to get the drug Herceptin.
The Appeal Court said Ann Marie Rogers should be given Herceptin
The draft guidance from the National Institute for Health and Clinical Excellence (NICE) comes two weeks after the drug received its European licence.
Cancer experts say hundreds of lives will be saved by making Herceptin available across the UK.
But doctors have questioned whether the NHS can afford to fund the drug, without making cutbacks elsewhere.
Campaigners have fought a high profile, and at times emotional battle to make the drug more widely available on the NHS.
Once final guidance is published in July, local health bosses will be given a three-month period of grace to implement it.
They will then face legal proceedings if they fail to offer eligible patients Herceptin.
In addition to NICE's guidance - which applies to England and Wales - the Scottish Medicines Consortium is also putting out its own final guidance recommending Herceptin should be available on the NHS.
Women in Northern Ireland have had access to the drug, where clinically appropriate, since November 2005.
Herceptin has been shown to benefit women with HER2 positive breast cancer - around 20% of all breast cancer cases.
However, up to 10% of that group will not be able to take the drug because of concerns it could exacerbate heart problems.
More than 5,000 women - and possibly hundreds of men - in the UK would be suitable to use Herceptin.
Previous estimates put the cost to the NHS at around £100m a year.
The NHS Confederation warned that with finite resources for the NHS, the ruling could see cutbacks elsewhere.
And Dr Jonathan Fielden, deputy chairman of the BMA¿s Consultants Committee said: "The NHS will now have to find the money to fund this treatment.
"We have already heard this week how huge amounts are being wasted on management consultants.
"The government needs to rethink its strategy and spend money that has been earmarked for the NHS on benefits to patients not pie in the sky political ideas."
However, Professor Mike Richards, the government's national cancer director, said: "The health service is getting more money each year.
"This is a major step forward. It's is good news for women because it may mean more actually get cured of their breast cancer.
"Because of that it is an absolutely appropriate use of the new funds that are going into the health service."
A trial of the drug has shown it can increase the chance a woman treated for early stage breast cancer will still be disease-free after three years by 6%.
NICE's recommendations, produced after a fast-track appraisal, recommend a year's course of Herceptin.
However, it says heart function must be assessed before therapy begins, and Herceptin should not be given to patients at risk of with heart failure.
It should also not be given to patients with certain heart problems including heart failure and severe chest pain, and uncontrolled high blood pressure.
NICE also recommends women who are prescribed Herceptin should have heart checks every three months.
It has also called for more research into the drug's effects, including long-term studies.
Uncertainty 'at an end'
Andrew Dillon, chief executive of NICE, said: "These proposals are very good news for women with HER2 positive breast cancer.
"Herceptin, for these women, is clinically and cost effective in the early stage of the disease and we look forward to being able to issue final guidance, subject to any appeal against our recommendations, in a few weeks time."
Ann Marie Rogers from Swindon, who won her legal fight to be given the drug, said: "I hope this means an end to the battle for others who are still fighting their PCTs [NHS Primary care Trusts] for the drug.
"No one should have to suffer like I did and have to fight in the courts for a drug a doctor prescribes you."
But Kate Law of Cancer Research UK, said: "We must remember that Herceptin is only suitable in about one in five cases of breast cancer.
"So it's essential not to create a climate of false hope for women, where Herceptin is seen as a miracle cure suitable for everyone with breast cancer."
Jeremy Hughes, chief executive of Breakthrough Breast Cancer said a year of uncertainty and post-code lottery was "at last coming to an end".
"But this will only be the case if women are sure they can be tested to see if Herceptin is suitable for them.
"Nationwide, HER2 testing is being put in place and all women diagnosed with breast cancer need to know this test will be available quickly."
Doctor Ian Smith, head of the Breast Unit at the Royal Marsden Hospital in London, said the development of the drug heralded similar treatments for other types of cancer.
"It's the first of a type of targeted therapy, where you pick up a specific molecular abnormality in the cancer cell and you hit it. And there are other drugs already in the pipeline.
"I think Herceptin will be looked back on in breast cancer as a historic drug, the first of a whole new generation."