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Unexpected Consequences Of Talc Pleurodesis
University of Florida researchers reported that talc has the ability to stunt cancer growth by cutting the flow of blood to metastatic lung tumors. Their study, published in the European Respiratory Journal, revealed that talc stimulates healthy cells to produce endostatin, a hormone considered the magic bullet for treating metastatic lung cancer. The researchers say talc is an exciting new therapeutic agent for a cancer largely considered incurable.
Talc causes tumor growth to slow down and actually decreases the tumor bulk. Talc is able to prevent the formation of blood vessels, thereby killing the tumor and choking off its growth. The tumors appeared to grow much slower and in some cases completely disappeared.
Scientists have only recently discovered that talc stunts tumor growth, though the mineral has been used for almost 70 years to treat the respiratory problems that accompany metastatic lung cancer. about half of all patients accumulate fluid around the surface of the lungs, a condition known as malignant pleural effusion. That fluid can press down upon the lung, impair the breathing of the patient and cause the patient to feel very short of breath.
Pleural effusions indicate that the cancer, which might have started in the breast, lung, or gastrointestinal tract, has spread throughout the body. The prognosis for the roughly 200,000 patients afflicted with this condition is poor: Many die within six months.
To make life more bearable for these patients, doctors close the extra space between the lung and the chest wall, where the troublesome fluid collects. The trick is gluing the two surfaces together. Talc is blown into the patients' chest cavity to irritate the tissue and create tiny abrasions. When the lung tissue heals, it becomes permanently adhered to the chest wall without impairing the patients' breathing. The effects of the procedure, called medical thoracoscopy with talc pleurodesis, are immediate and last a lifetime.
The procedure has been used very extensively in Europe but it's had slower acceptance in the United States, perhaps because of the need to learn a new technology. The Food and Drug Administration approved talc for use in medical thoracoscopy in 2003, but UF is one of just a handful of U.S. institutions that perform the outpatient procedure on a routine basis.
Doctors have noticed that patients who undergo medical thoracoscopy with talc live up to 18 months longer than expected. The UF researchers were surprised to find that talc has added benefits besides causing scarring and taking away the fluid that surrounds the lung. The cells that cover the lining of the lung are stimulated by the presence of talc to produce a factor that inhibits the growth of blood vessels and kills the tumor cells themselves.
Less than one day after treatment with talc, patients began producing 10-fold higher levels of endostatin, a hormone released by healthy lung cells. Endostatin prevents new blood vessels from forming, slows cell growth and movement, and even induces nearby tumor cells to commit suicide. All of these make it hard for tumors to grow and spread into healthy lung tissue.
When endostatin was first discovered in 1997, doctors hoped its tumor-fighting properties would lead to a cure for cancer. But clinical trials have been disappointing, possibly because most clinicians have injected the hormone directly into patients. The hormone breaks down in the body before it has a chance to slow the spread of cancer.
What they've done is caused the normal pleural mesothelial cells to continue to produce endostatin. Talc doesn't go away. Talc stays in the chest cavity, constantly causing the normal cells to produce this factor that inhibits the growth of the tumor. The antitumor effects of talc appear to be long-lasting, and they are continuing to investigate the long-term outcomes of patients who have undergone talc pleurodesis.
I can understand the disbelief that endostatin clinical trials had been disappointing, possibly because most clinicians had injected the hormone directly into patients, where the hormone broke down in the body before it had a chance to slow the spread of cancer. But researchers like Dr. Veena Antony "rethought" the situation by understanding that by allowing talc in the chest cavity, thus constantly causing the normal cells to produce endostatin, may inhibit the growth of tumors.
Thanks to scientists like Dr. Antony that took the time to think through "whiz bang" science that often gets a pass without much thought. The problem is that few scientific discoveries work the way we think and few physicians/scientists take the time to think through what it is they're discovered. I genuinely believe that there is more to Talc than is commonly recognized. Perhaps because it is easily available and cheap, and it has not had the press it deserves.
SOURCE: University of Florida
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