Tailor-made treatment
The one thing Kevin Carlberg refused to face after his diagnosis with brain cancer in 2002 was anyone’s estimate for how long he might live.
His doctors and his family all knew the number: six to 18 months.
“I understand the averages,” says Carlberg, a rock musician who had just released a CD and was two months from his wedding date when he was told he had the worst stage of the worst kind of brain cancer, glioblastoma. “But every person is different.”
Those words could serve as the new mantra in medicine. After having his tumor removed and undergoing chemotherapy and radiation, he received a novel treatment that was designed using his own white blood cells and proteins taken from his tumor to prod his immune system into recognizing and attacking more cancer in his body. It’s an example of a growing healthcare strategy known as personalized medicine.
In the traditional medical model, patients diagnosed with cancer in a particular organ receive the same medications -- usually chemotherapy -- delivered in an average dose. But some estimates suggest that as many as 70% of cancer patients don’t respond to this standard approach. The treatment fails and then doctors go back to the drawing board.
Personalized medicine aims to minimize that one-size-fits-all approach by matching each patient to a specific treatment based on the genetic and molecular characteristics of that person’s tumor. Doctors can use genetic information gleaned from the tumor itself to choose -- or avoid -- certain medications for that patient or, as in Carlberg’s case, create a treatment specifically for that person.
Not so long ago, “most lung cancers were treated the same way; colon cancer the same way. Breast cancer was treated one of two ways,” says Dr. Dennis Slamon, director of clinical and translational research at UCLA’s Jonsson Comprehensive Cancer Center and a pioneer of personalized cancer care. “But that was as sophisticated as it got, and we had huge variations in patients’ outcomes. That should have told us we were dealing with different diseases.”
Personalized medicine is gaining momentum in many areas of treatment. But its greatest application may be in the complex field of cancer, says Dr. Robert Figlin, director of the City of Hope Comprehensive Cancer Center in Duarte.
“Cancer is a disease which has been misnamed,” Figlin says. “It’s not a disease. It’s hundreds of diseases.”
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Molecular ‘revolution’
Personalized medical care is a practical benefit from the Human Genome Project, the 13-year project, completed in 2003, that gave scientists a precision map of the genetic information of humans. Completion of the genome project allowed them to easily locate genetic differences between individuals, including gene variations that cause disease, as well as molecular changes that sometimes turn cells rogue.
“This revolution in molecular biology has translated to understanding . . . the reasons why cancer grows,” says Dr. Roy S. Herbst, chief of the section of thoracic medical oncology at the M.D. Anderson Cancer Center in Houston.
For example, he says, in traditional practice, doctors removing a tumor send it to a lab to be categorized by size and shape.
But now in some cancers -- not yet all -- doctors can examine the tissue for specific genes and molecular processes that suggest the cause of a cancer, its potential to grow and what it might take to subdue it.
Personalized medicine -- luckily -- doesn’t mean that every cancer is unique and must be treated in a unique way, Slamon says. In a group of 1 million people with breast cancer, for example, there are not 1 million types of cancer. Rather, “There may be seven or eight different subgroups,” he says, each with a different molecular cause that warrants a different approach to treatment.
To identify these sub-types of cancer, doctors search for biomarkers, molecular indicators of how that tumor will respond to various drugs. Slamon, for example, worked for more than a decade trying to understand a protein biomarker called HER2.
About 25% of women with breast cancer carry a gene mutation that triggers an excess production of HER2. This protein makes the cancer more aggressive and difficult to treat. The discovery led to a drug called Herceptin, approved in 1998, which specifically targets HER2 and decreases cancer recurrences in these women by as much as 50%.
“The science is in its infancy,” Slamon says. “Breast cancer is about seven to 10 years ahead in terms of appreciating the diversity of the disease. But those lessons are being applied to other cancers now.”
Targeted therapies are now in use for certain types of colon, lung and ovarian cancers, and research is underway in many other types.
Drugs tailored to a particular genetic or molecular mechanism are called targeted therapies because they home in on the biological signature of that tumor. They are often less harsh than standard chemotherapy because they target only the cancer cells without harming healthy cells. For example, therapeutic cancer vaccines, which are being used now to treat several types of cancer, are designed to activate the immune system to recognize and kill only cancer cells.
Carlberg’s treatment at the UCLA Jonsson Comprehensive Cancer Center, involved just such a vaccine. To make it, Dr. Linda Liau, director of UCLA’s brain tumor program, isolated proteins from his tumor, mixed it with immune cells from his blood and injected the mixture. The vaccine was designed to prime the body’s immune system to recognize and attack cancer cells.
After six years in remission, Carlberg, now 31, recently had another small tumor removed and began receiving chemotherapy and the personalized vaccine therapy again.
Although he had never heard of a cancer vaccine, Carlberg thought the idea sounded brilliant. “It made perfect sense to me,” he says. “Forty years from now I hope I can say I was among the first people to conquer this cancer because of the vaccine. That would be amazing.”
Cancer vaccines have the potential to do more than shrink an already-grown tumor, says Liau, a professor of neurosurgery at the David Geffen School of Medicine at UCLA. “Once we are able to prolong life through molecular targeted cocktails of treatment, I think the next step is to cure it, by giving something like a vaccine that really tries to get rid of the microscopic cancer cells and prevent the cancer from coming back.”
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A ripple effect
Personalized cancer treatments are being tested in many types of cancers, particularly those most difficult to cure.
Lung cancer, which strikes 215,000 Americans a year and kills almost 162,000, is one area of rapid advancement. Doctors are now looking at several biomarkers that can dictate the course of treatment, says Dr. Karen Reckamp, assistant professor of medical oncology and hematology at City of Hope.
Tarceva is a targeted therapeutic drug that has extended the lives of many people with advanced non-small cell lung cancer. But about 25% of people with such lung cancer have mutations in a gene called KRAS. In people with this mutation, Tarceva is ineffective.
“In the last five years, we understand the biology of lung cancer significantly better than we ever did,” Reckamp says. “This means that we can give the appropriate drug or treatment to the appropriate person at the right time.”
At M.D. Anderson Cancer Center in Houston, Herbst is overseeing a cutting-edge clinical trial, which goes by the acronym BATTLE, that is attempting to match specific lung cancer patients to the most suitable therapies.
The patients, all of whom have not been helped by standard therapies, undergo tumor biopsies and have their biomarkers typed. They are then assigned to one of four clinical trials studying different drugs or drug combinations. After the treatment cycle, the patient’s disease is reassessed. If the disease has not progressed, patients remain on that treatment. If the cancer has grown or spread, they are able to enter one of the other three trials.
By seeing how patients with certain biomarkers fare with different drug regimens, the scientists hope to learn how to fine-tune their treatment for different cancer types.
“It’s more targeted,” Herbst says. “We put them on a drug we think is best for them. Our hope is we’ll learn about the biology of the tumors and we’ll be able to show that by using this approach we can target the right tumor with the right drug.”
Patient safety is another bonus of personalized therapy. For example, researchers have found that some children with acute lymphoblastic leukemia carry a gene mutation that causes a standard drug used to treat the disease to build up in the body and cause dangerous side effects. These children are identified before treatment begins and receive smaller doses to prevent toxicity.
As cancer specialists learn more about the variability of tumors, some of the news they give patients isn’t good. Personal cancer care sometimes means that patients are told a particular drug -- often promising for some people -- will not work for them.
“People think of personalized medicine as ‘If my doctor knew what I had, the results of the treatment would be better.’ That is our hope as well,” Figlin says. “But the reality is we also identify genetic abnormalities in cancer that predict why a certain treatment may not work.”
Nonetheless, after a slow start, the field of personalized medicine is now gathering steam as researchers and drug companies focus more on drugs to target subsets of patients instead of blockbuster medications aimed at treating all of them. According to the research firm Datamonitor, sales of targeted cancer therapies grew 33% worldwide last year. Since 2005, 10 targeted drugs have come on the market.
Slamon spent years trying to persuade others that targeting HER2 would cure some women of breast cancer. Eventually, the drug company Genentech developed Herceptin.
“Once Genentech understood that the drug was going to work, the fact that the market was a subset of breast cancer patients didn’t deter them at all,” he says.
“Drug development is becoming more complex and more challenging as we understand more. But that is how it has to be if we’re going to treat cancer more effectively.”
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On the Web
Personalized medicine may be the new wave in cancer care, but it can be difficult for patients to access. For more information on your options, go to latimes.com/cancer extra.
