The one-size-fits-all approach to radiation treatment of lung cancer patients may become a thing of the past.
A team of Duke Comprehensive Cancer Center scientists discovered a correlation between a protein called TGF-beta and risk levels of patients developing lung damage as a result of radiation treatment. The team presented its findings last Monday at the annual meeting of American Society for Therapeutic Radiology and Oncology.
"Our basic finding is that you can combine data on blood protein changes with [data on] the volume of the irradiated lung to determine risk groups for patients," said Dr. Mitchell Anscher, professor of radiation oncology and principal investigator. This study will allow doctors to predict whether any such post-procedure complications of the lung will occur.
In the 78-patient study, TGF-beta tests placed 27 percent of patients in the low-risk group, 50 percent of patients in the intermediate group and 23 percent of patients in the high-risk group. Anscher explained that low-risk patients can be given higher doses of radiation.
"Currently, the most sensitive patients determine the maximum dose [of radiation]," he said, explaining that doctors now treat all lung cancer patients with the dose best fit for high-risk patients.
Randy Jirtle, professor of radiation oncology and associate professor of pathology, likened the situation to the risk of getting a sunburn. Those with a developed tan can expose their skin to the sun for a long time before getting a sunburn. Others, especially those who have particularly pale skin, can get a sunburn easily-usually after spending only 30 minutes in the sun. If doctors' advice on sun exposure functioned like current lung cancer treatment, they would tell everyone to stay out for only 30 minutes, even though a significant portion of the population could withstand the sun's rays much longer.
This limitation of the use of higher radiation levels can be of crucial importance when the reduced treatment does not get rid of the cancer completely. Anscher said he believes an increased dose of radiation would boost the effectiveness of the treatment not only by getting rid of a greater portion of the cancer, but also by slowing the rate at which the cancer spreads to other parts of the body. He added that several studies have supported this link between radiation levels and higher cure-rates for cancer.
TGF-beta is heavily involved in wound-healing, scar tissue formation and control of epithelial cell growth, so it is a good indicator of the healing-run-amock that causes post-radiation complications. As cancers in epithelial cells replicate unchecked, TGF-beta attempts to counter this growth by building up scar tissue. Researchers believe that this is what causes the lung damage.
Additionally, while TGF-beta is usually in its inactive form, radiation can activate it. Hence, higher levels of TGF-beta predispose patients to injury during radiation treatment.
The next step in improving treatment, said Anscher, will be developing drugs and chemicals that could regulate patients' TGF-beta levels, thus reducing damage from radiation treatments. In a related study, also presented at the ASTRO conference, the researchers reported that a drug called amifostine does just that.
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