Researchers say new experimental cancer drugs developed through the latest advances in biopharmaceutical technology are starting to prevent cancer reoccurrence while prolonging some cancer patient life spans.

Cancer specialists attending the annual American Society of Clinical Oncology conference in Orlando, Florida said Friday that new biotechnology drugs - called "targeted therapies" - are working.

Researchers say targeted therapies work by aiming at the underlying molecular activity that cause tumor growth. They say these new drugs work by stopping blood supply to tumors and blocking specific proteins that trigger tumor development without killing healthy cells around the cancer.

While some of these drugs are not new, scientists say the supporting evidence from clinical trials is new and mounting, giving oncologists cause for optimism.

Major gains in the fight against cancer are still considered far from cures. Side effects from the biotech drugs exist for small percentages of patients, but still outweigh the eventual outcome of the disease without treatment.