Does Obesity Affect Radiation Treatments?

Last Modified: April 2, 2006


Dear OncoLink "Ask The Experts,"

I had a biopsy of my prostate, Gleason 7 [4+3], after a digital rectal examination (DRE) revealed a nodule on the left side of my prostate. I think I am a stage T2a or b, not sure. I'm 51 years old and obese, 6'1" and about 400 pounds with a 58-inch waist. How does my size affect the choice of radiation as a treatment?


Neha Vapiwala , MD, Senior Editor of OncoLink from the Department of Radiation Oncology at the Hospital of the University of Pennsylvania, responds:

A patient's body size, and specifically the size of the pelvis in the case of prostate cancer, helps to determine the energy of the radiation beams that are used (i.e.: need higher energy beams for greater depth of penetration, because in general, the larger a patient is, the further away the prostate and other targets are from the skin surface). Furthermore, the radiation dosimetry (distribution of high, uniform dose to the target but minimal dose to normal tissues) may be suboptimal if a patient is too heavy or the surface anatomy is too irregular, depending on the distribution of the weight.

Maybe most problematic of all is that a patient with excessive weight simply may not be able to lie on the treatment table (couch) of the radiation treatment machine. Depending on the machine, there is a limit to how much weight the remote-controlled, movable couch can tolerate.