Scientists from the Barbara Ann Karmanos Cancer Institute in Detroit will present data that suggests low levels of pre-treatment radiation mimicking the doses delivered by CT scans for image guidance pose no risk to the efficacy of radiotherapy in patients with prostate carcinoma and non-small cell lung carcinoma. The findings will be formally announced on Sunday, Oct. 31, during the American Society of Therapeutic Radiology and Oncology (ASTRO) Annual Meeting.
Iftekhar U. Ahmad, M.D., M.S., a former radiation oncology resident at Karmanos and the Wayne State University School of Medicine (WSU SOM), is lead author of the study titled, "Effect of Pre-Treatment Imaging Dose on the Radiosensitivity of Tumor Cells" and will present the findings at ASTRO. Dr. Ahmad is now a staff radiation oncologist at OSF Saint Anthony Medical Center in Rockford, Ill.
Fellow authors from Karmanos and WSU SOM include Vinita Singh-Gupta, Ph.D., member of the Department of Radiation Oncology; Christopher Yunker, B.S., research assistant with Karmanos; Jay Burmeister, Ph.D., chief of Physics; Michael C. Joiner, Ph.D., professor and program leader of Radiation Oncology; and Gilda G. Hillman, Ph.D., associate professor in Radiation Oncology.
Dr. Ahmad said that imaging of patient anatomy using CT scans is routinely performed immediately prior to radiation therapy to provide information on soft tissue differentiation and to confirm localization of external beam radiation delivery to the tumor. Karmanos' study built upon the findings of a recent University of Virginia study that suggested that such pre-treatment doses of radiation caused the cancer cells to have higher survival rates.
"Our question was, is this real?" he said. "The doses they used to mimic their CT scan doses were higher than image guided dose data published in the literature. Our dose was less than half of what they used. We felt this was more realistic as to what is delivered in routine clinical care of patients with prostate and lung cancer.
"The goal of this study was to determine whether these low doses of radiation used for image guidance prior to therapeutic doses affects radiation therapy efficacy for prostate carcinoma (PCa) and non-small cell lung carcinoma (NSCLC) cells and to determine the influence of the time gap between image guidance and treatment."
Karmanos researchers used the PC-3 PCa and A549 NSCLC human tumor cell lines for the study, similar to cell lines used in University of Virginia's study. All radiation was delivered using a Pantak orthovoltage unit. Karmanos researchers used a dose of two centigray units of absorbed radiation to mimic a CT scan and doses were administered at intervals of two, five and eight minutes.
After simulated CT doses were given, researchers then used increased levels of radiation therapy doses in the prostate and lung cancer cell lines.
Control groups included non-irradiated cells and cells irradiated only with radiation therapy doses between two and eight gray units. Treated cells were tested in triplicate. Plating efficiency (PE) – the measure of the number of colonies originating from single cells – was determined for each sample and the surviving fraction was calculated by normalizing each test PE and control PE for non-irradiated cells. Researchers also assessed damage to the cells on a molecular level.
Based on results, the study suggests that low doses of radiation for daily pre-treatment positioning prior to radiation therapy do not affect the human prostate carcinoma and non-small cell lung carcinoma cell lines.
"If we're giving between 30-40 treatments to a patient and imaging them prior to treatment every day, we wanted to know how this is affecting how well we treat the cancer and how much extra radiation is being delivered to the patient," said Dr. Ahmad. "Any time you irradiate at any dose, there is going to be some response by the cell.
"In this study, we didn't see any changes in the cancer cell survival rate due to the administration of doses typical for pre-treatment imaging. We also didn't see any changes whether you quickly treat the patient after the pre-treatment dose or if you wait, for example, eight minutes."
The Karmanos Cancer Institute and WSU SOM recently took delivery of three new top-of-the-line Varian linear accelerators, located at the Institute's sites in Detroit, Rochester Hills and Farmington Hills. Andre Konski, M.D., MBA, MA FACR, chairman of the Department of Radiation Oncology, says that radiation technology is improving so rapidly that staff must remain highly trained to ensure accuracy.
"Doing research is only one part of establishing best practices when using sophisticated radiotherapy equipment," said Dr. Konski. "It isn't enough to have the most advanced technology at our disposal. Through these in-depth, retrospective studies, we are able to determine the safest and most effective methods in treating our patients."
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