The drug-maker says it will undertake further study to establish which patients will benefit from the drug

US drug regulators have rescinded approval of a breast cancer drug, saying it is not effective enough to justify the risks of taking it.

The drug, Avastin, was approved for US use in 2008, but UK officials have also rejected claims that it prolongs life.

Further research showed it did not help patients live longer or improve quality of life, Food and Drug Administration commissioner Margaret Hamburg said.

Avastin will still be used to treat other kinds of cancer.

The drug is used to treat breast cancer that has spread to other parts of the body. It works by starving cancer cells of a blood supply.

However, its side-effects include severe high blood pressure, massive bleeding, heart attack or heart failure and tears in the stomach and intestines, FDA studies have found.

FDA approval of the drug had initially been given under a special programme that allows patients to start using promising treatments while the manufacturer finishes the studies to prove the medicine works as well as expected.

The decision to withdraw the approval - which can happen if results of the research do not match predictions - was not easy, the FDA said.

"With so much at stake, patients and their doctors count on the FDA to ensure the drugs they use have been shown to be safe and effective for their intended use. Sometimes, the results of rigorous testing can be disappointing," Ms Hamburg told the Associated Press news agency.

US health insurance companies could remove the drug, which can cost as much as $100,000 (£63,342) per year, from their coverage - although doctors would still be permitted to administer the drug.

But the government-backed Medicaid programme has said it has no immediate plans to change its policy of paying for it.

Some advocates of the drug disagree with the watchdog's decision.

"The bottom line is that they are throwing out the baby with the bathwater. There absolutely may be subsets of carefully chosen breast cancer patients who benefit from Avastin," said Dr Elisa Port, co-director of the Dubin Breast Center of Mount Sinai Hospital in New York.

Roche, the Swiss manufacturer of the drug, has said it will undertake further study of the treatment, especially with the chemotherapy drug paclitaxel, to try to identify which patients might be best suited to benefit from use of the drug.

The company says it expects the medicine will generate $7.6bn (£4.8m) of revenue annually, despite the FDA decision.

The drug was approved on the basis of a study that showed Avastin was able to stall the growth of breast cancer by five-and-a-half months, when used together with a standard chemotherapy treatment.

But subsequent studies revised the period of delay to between one and three months, and there was no evidence to show that the drug extended patients' lives.

The US decision comes after Avastin fell foul of health authorities in the UK and in Europe.

In February 2011, the UK's National Institute for Health and Clinical Excellence (NICE), the NHS drugs advisory body, said Avastin should not be used to treat secondary breast cancers.

NICE, which issues guidance for NHS in England and Wales, said there was insufficient evidence that the drug prolonged life.

This guidance followed a recommendation by the European Medicines Agency (EMA) that doctors only prescribe the drug in combination with the taxane drug, paclitaxel.

Engineers say the material is less dense than aerogels and metallic foams

A team of engineers claims to have created the world's lightest material.

The substance is made out of tiny hollow metallic tubes arranged into a micro-lattice - a criss-crossing diagonal pattern with small open spaces between the tubes.

The researchers say the material is 100 times lighter than Styrofoam and has "extraordinarily high energy absorption" properties.

Potential uses include next-generation batteries and shock absorbers.

The research was carried out at the University of California, Irvine, HRL Laboratories and the California Institute of Technology and is published in the latest edition of Science.

"The trick is to fabricate a lattice of interconnected hollow tubes with a wall thickness 1,000 times thinner than a human hair," said lead author Dr Tobias Schaedler.

The resulting material has a density of 0.9 milligrams per cubic centimetre.

By comparison the density of silica aerogels - the world's lightest solid materials - is only as low as 1.0mg per cubic cm.

The metallic micro-lattices have the edge because they consist of 99.99% air and of 0.01% solids.

The engineers say the material's strength derives from the ordered nature of its lattice design.

By contrast, other ultralight substances, including aerogels and metallic foams, have random cellular structures. This means they are less stiff, strong, energy absorptive or conductive than the bulk of the raw materials that they are made out of.

William Carter, manager of architected materials at HRL, compared the new material to larger low-density structures.

"Modern buildings, exemplified by the Eiffel Tower or the Golden Gate Bridge are incredibly light and weight-efficient by virtue of their architecture," he said.

"We are revolutionising lightweight materials by bringing this concept to the nano and micro scales."

To study the strength of the metallic micro-lattices the team compressed them until they were half as thick.

After removing the load the substance recovered 98% of its original height and resumed its original shape.

The first time the stress test was carried out and repeated the material became less stiff and strong, but the team says that further compressions made very little difference.

"Materials actually get stronger as the dimensions are reduced to the nanoscale," said team member Lorenzo Valdevit.

"Combine this with the possibility of tailoring the architecture of the micro-lattice and you have a unique cellular material."

The engineers suggest practical uses for the substance include thermal insulation, battery electrodes and products that need to dampen sound, vibration and shock energy.