The use of image-guided radiation therapy (IGRT) may be more successful than traditional external beam radiation therapy (EBRT) in treating moderately to severely obese prostate cancer patients, according to a study in the Sept. 1 issue of the International Journal of Radiation Oncology*Biology*Physics.
The reason, according to James R. Wong, MD, chair of radiation oncology at Morristown Memorial Hospital in Morristown, N.J., and colleagues is that IGRT is able to correct for prostate shifts, which if not planned for can lead to incorrect radiation doses to the diseased area.
Studies have shown that obesity can lead to higher rates of biochemical failure rates in prostate cancer patients who undergo EBRT. The authors used data from 117 patients who received IGRT for prostate cancer between January 2005 and April 2007. Of those, 26.5 percent were considered to be normal weight, 48.7 percent overweight, 17.9 percent mildly obese and 6.9 percent moderately to severely obese.
The authors determined that moderately to severely obese patients (body mass index of more than 35) have larger prostate shifts during treatment, which means radiation might not be delivered to the same spot each day of the treatment. The authors found that the percentage of moderately to severely obese patients with a left to right shift greater than 10 ml was 21.2 percent, compared to just 1.3 percent among patients of average weight, 1.5 percent for overweight patients and 2 percent for mildly obese patients.
The advantage of IGRT, the authors said, is that doctors are able to compare images taken earlier in the treatment process with those taken before the patient receives his daily radiation treatment and then adjust radiation doses if necessary.
"With the results of this study, we now know that obese patients have a unique complication when it comes to planning their treatment, but we can try to correct it simply by using IGRT instead of EBRT," said Wong.