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Raditaion Therapy and Obesity

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Last Modified: June 15, 2007

Dear OncoLink "Ask The Experts,"

I am a 60 year old female diagnosed with breast cancer, for which I underwent lumpectomy. I am 300 pounds and have been turned down by several radiation facilities due to my weight and the ability of the machine to support me. Am I destined for a mastectomy or is there somewhere that can treat me?

Neha Vapiwala , MD, Senior Editor of OncoLink and Chief Resident in the Department of Radiation Oncology at the Hospital of the University of Pennsylvania, responds:

The issue of weight and not only radiation machines, but radiology as well, is likely to become more common with how common obesity has become in our society. The linear accelerators we use at the University of Pennsylvania can support up to 350 pounds. Varian Medical Systems has developed newer machines that can support up to 450 pounds. You may be able to visit the Varian website to find an institution in your area that uses their machines.

While not an issue in breast cancer because the affected tissues are located near the surface, but for deeper tumors, there may be an issue of effectiveness. A patient's body size, as in the case of prostate cancer, the size of the pelvis, helps to determine the energy of the radiation beams that are used (i.e.: need higher energy beams for greater depth of penetration, because the larger a patient is, the further away the prostate is from the skin surface). Furthermore, the dosimetry (dose distribution and tumor coverage) achieved with the radiation treatment plan may be suboptimal if a patient is too big, depending on the distribution of the weight.