One day cancer patients would receive treatment dependant on their genes.
With an increasing number of biological clues available to help predict cancer, doctors hope they will soon customize patients' treatments based on their genetic profiles.
In research presented at a meeting of the European Cancer Organization in Barcelona, experts said this week that these clues will help doctors determine not only which patients will probably develop cancer, but even those who will relapse, or be suitable for specific treatments.
"We are going to witness a revolution in cancer treatment," said Dr. Martine Piccart, head of medicine at the Institut Jules Bordet in Belgium.
"In a few years, we will be able to fully demonstrate how powerful these new technologies are."
Piccart and colleagues have been working to confirm the genetic sequences for women susceptible to breast cancer.
On Monday, German researchers said they had developed a test to identify cancer cells circulating in the blood of breast cancer patients.
That could potentially enable doctors to catch cancer cells en route to another location - and give them time to intervene to prevent a tumor.
Dr. Julia Juckstock and colleagues from the University of Munich analyzed blood samples from 1,767 women with breast cancer before they were treated, and compared them to samples taken from 852 of the same patients after they had finished chemotherapy.
In a small percentage of patients tested after chemotherapy, researchers found evidence of tumor cells in transport.
"This is a fascinating development," said Dr. John Smyth, a professor of medical oncology at the University of Edinburgh, who was unconnected to the Munich study.
Instead of a blanket approach to treatment, Smyth said that the test could help doctors pinpoint those women in whom breast cancer was likely to spread and needed extra care.
Tailoring treatment based on patients' genes is not new; experts have been deciding how to treat women with breast cancer depending on their tumor type for the last few years.
Doctors run a simple genetic test to see which 20 percent of women with breast cancer will actually benefit from chemotherapy, making the toxic side effects worthwhile.
But learning more about breast cancer has also given experts new tools to fight other cancers.
Another study at the Barcelona meeting presented on Tuesday found an unexpected twist: patients with a certain overactive breast cancer gene were also less likely to respond to chemotherapy for lung cancer.
"We know quite a bit about breast cancer genes, and now we're looking into the black box of what role they might play in other cancers," said Dr. Gordon McVie, a cancer expert at the European Institute of Oncology.
The breast cancer gene involved has several functions including helping with cell repairs. But if it is not acting properly it can contribute to a greater risk of breast cancer.
If a person has lung cancer, the malfunctioning gene makes the tumor especially aggressive, meaning that patient will probably not improve even if given chemotherapy. The patient will likely become sick from powerful medicine without benefit.
The problem, McVie said, is that even though researchers may understand a little about what a thousand of the genes involved in cancer do, there are about 31,000 others that they don't.
Several teams have already mapped out gene profiles that scientists suspect make women more likely to develop breast cancer, but have for the most part identified different genes.
Other studies presented in Barcelona on Tuesday identified genes that could triple a woman's risk of ovarian cancer, as well as molecular profiling to predict which colon cancer patients would benefit from chemotherapy.
Cancer is an incredibly complicated disease, and is influenced by other variables like diet and environmental exposure. Even if researchers can identify the genetic components responsible, many factors remain beyond doctors' control.
"We haven't had any big genetic hits," McVie said, explaining that while scientists have identified genes that predispose people to cancers including breast, bowel, ovarian and colon, those make up only a small amount of all cancers.
"Cracking the genetic code is still a very imprecise science," he said.
But because cancer is a biological problem that strikes when cells divide irrationally, some experts believe the ultimate solution will also be a biological one.
"We need to understand the genetic reasons behind cancer and what collides with the environment to make something go wrong in our bodies," Smyth said.
The real test, however, will be if doctors can then figure out what to do next. "It's never encouraging to say to a patient that she's going to do poorly because of her genes," Piccart said. "We need to be able to offer patients an effective treatment."