Last year scientists wre hailing the discovery of a method to cultivate human embryonic stem cells for its potential to help fight many diseases, included, for example, is the possibility that the process could someday create bone marrow for cancer patients. These cultivated cells come from human embryos... Yes there is some controversy.
Everyone wants good news on cancer. The preceeding year seemed to bring plenty, with stories on advances in cancer research and treatment that have given hope to millions living with the disease and millions more living in fear of it.
Yet some stories come with reader beware clauses. Look behind the headlines of 1998. Experiments shrink tumors in mice, unfortunately that doesn't mean they'll do so in humans, new drugs may prevent breast cancer but has frightening side effects; the horizon shows glimmers of new test procedures that detect prostrate cancer, but are they reliable enough to screen all men?
"We're a huge way down the path in understanding the genesis of cancer," remarks Dr. Harmon Eyre, M.D., with the American Cancer Society, "and understanding how the cancer cell behaves."
Unquetionably, progress has come throgh earlier diagnoses, healthier lifestyles and better cancer care. But where are the real medical breakthroughs?
Still, the main treatments for cancer remain surgery, radiation, and chemotherapy. The latter two are meant to stop the disease from spreading, but are often so toxic and imprecise as they kill healthy cells as well as cancerous ones.
Yet those 50 years and billions of dollars spent on research has fueled one huge advance. We now know what cancer is and how it spreads. Even allowing for the optimism of scientists - and their need to justify the investment - it's clear that the top researchers do believe the payoff is just over the horizon.
The goal is to find ways to prevent cancers from erupting in the first place and if they do take hold, to reduce them to chronic but survivable conditions. How? With six new promising approaches.
Cancers can take years to develop. Chemoprevention aims to slow or halt the many changes in cells that result in malignancy.
Last spring, early results of the first large-scale breast cancer prevetion study brought dramatic evidence that such an aproach might work.
Testing the drug tamoxifen on 13,000 women judged at high risk for the disease proved so successful (a reduction of 49 percent of invasive breast cancers) that the study was stopped earlier than planned.
"The results are remarkable," says National Cancer Institute Director Richard D. Klausner, M.D."They tell us that breast cancer can be prevented." The food and drug Administration in October of 1998, approved tamoxifen as apreventive drug for woman who have not had breast cancer. But tamoxifen is far from ideal. Side effects include increased risks of blood clots and uterine cancer.
Another drug, raloxifene, approved recently by the FDA to prevent osteoporosis, may work at preventing breast cancer with fewer side effects. While the drug finasteride is already used to treat men for benign prostrate tumors and for baldness. Further, research is underway to see if finasteride can prevent prostrate cancer.
The earlier caner is found, the better a person's chances of survival. But many cancers can take up to fifteen years before symptoms show. Screenings can catch some. Such as early mammograms for breast cancer; PAP smears for ceverical cancer; Prostrate-Specific Antigen (PSA) blood tests for prostrate cancer. Unfortunately, the tests aren't always reliable and they don't even exist for most tumors.
One promising idea in the search for simple, cheap and accurate tests is molecular detection.
In 1991 researchers at the Jojn Hopkins School of Medicine in Baltimore detected abnormal DNA in the urine of a patient with bladder cancer. The next year they found DNA mutations in the stools of patients with colorectal cancer. Since then they've analyzed saliva to detect head and neck cancers and sputum for lung cancer.
The urine testy for bladder cancer (which is tough to diagnose) has been tried on 44o people. Early results, says David Sidransky, M.D., head of the project, has shown a 95 percent detection rate and 100 percent "specificity" (meaning that every participant who tested positive proved to have the disease or developed it soon afterwards.
If that rate holds up, and if the current price tag of $150 per test can be reduced, Sidransky reckons, the bladder test could be in use in two years, with similar tests for cancer close behind.
Traditional vaccines are designed to prevent disease from developing in the first place. Cancer researchers are looking for therapeutic vaccines that fire up the immune system to seek and destroy any cancerous cells left in the body after surgery has removed the main tumor.
Some research teams are looking for vaccines that would work on anyone, while others are trying a custimize the aproach by injecting each patient with cells from their own individual tumor.
Knowledge of how the immune system recognizes tumors is so new that many researchers believe that it's going to take a long time to translate that information into an effective therapeutic.
A tumor, like all cells, needs needs a blood supply. A tumor makes its own blood vessels to feed itself, a process called angiogenesis. Thus, prevent angiogenesis and the tumor will starve.
The beauty of the concept is that it would, in theory, work against any type of tumor. Two protiens; angiostantin, and endostantin had cuased tumors to shrink or even disapear, in mice. Though trials begin this year on humans, "Three to five years would be warp speed," Says James Pluda, M.D., and senior researcher at the National Cancer Institute, but even if the tumors didn't wither and die, continued Pluda, "you can live forever with microscopic tumors. It's not until cancer grows that it causes problems."
So anti-angiogenesis, if it works, has the potential to reduce cancer from a fatal to a less severe, chronic disease; something a person can live with.
In normal cells, a protien called p53 calls the immune system into action, and the attack begins. But the alarm system of most tumors has been deactivated as most lack p53. Scientists are trying to take advantage of this flaw in tumor by engineering a virus that will infect and kill tuumor cells but not healthy ones (a problem of current treatments is that they do too kill both healthy and cancer cells).
The longest used virus in clinical trials is an engineered version of a cold virus developed by Onyx Pharmaceuticals in California. Injected into a tumor, the virus multiplies without activating immune defences there and healthy tissues are unharmed.
The Onyx team has tested the virus mainly on advanced head and neck tumors, with limited work on ovarian, colon, and pancreatic cancers. In some patients the tumors did shrink. But the virus seems most effective when combined with chemotherapy.
Normally, science identifies disease targets, then drugs are desinged to target them. This approach has met little success with cancers. The exception is monoclonal antibodies.
The antibodies are designed to kick the immune system into action so it can target the growth-factor receptors that cause cancer cell to multiply. It seems that when cancer growth is disrupted, the cancer cells shrink and die.
Last September the FDA approved Herceptin, a monoclonal antibody drug for women with advanced breast cancer that targets a protien associated with a fast spreading form of the disease. In late 1997 the FDA aproved Rituxan to treat an incurable type of non-Hodgkins lymphoma, a cancer that kills white blood cells.
"This is the most exciting time I've seen in thirty years", says Eyre of the ACS. The new approaches, and their early success, have generated much hope.
Produced By: Michael E. Hall, R.N., and
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