Because of the size of the rectum and the proximity of other organs, is radiation less targeted than for other types of cancer? Is there a danger that other organs will be harmed by this treatment?
The radiation therapy for rectal cancer is targeted using 3-dimensional radiation therapy. When treating rectal cancer, the tumor, adjacent rectum and lymph node regions at risk need to be treated. The radiation dose used, is less than for other tumors, such as prostate or head and neck cancer, where very targeted radiation called intensity modulated radiation therapy (IMRT) is used. If the treating physician thinks it will be beneficial for organ sparing, IMRT can also be used for rectal cancer. Currently there is no strong data supporting the use of IMRT routinely for rectal cancer. The main organs at risk include the bladder, small bowel, hips, and residual rectum. With careful treatment planning, the long term side effects can be minimized. Although any type of therapy has risks of side effects, the benefits of treatment typically outweigh the risks.