Table of Contents

Chapter 2: Initial Treatment: Weighing the Pros and Cons of Each Option

d. Radiation Therapy

Unlike prostatectomy, which uses surgery to remove the disease entirely from the body, the goal of radiation therapy is to kill the prostate cancer cells where they live. To accomplish this, very high doses of x-rays are delivered to the prostate, concentrated on the small clusters of tumor cells that comprise the cancer within the prostate gland.

The most common type of radiation therapy is external beam radiotherapy. Radiation oncologists and technicians use CT scans and MRIs to map out the location of the tumor cells, and x-rays are targeted to those areas. With 3-D conformal radiotherapy, a computerized program maps out the exact location of the prostate tumors so that the highest dose of radiation can reach the cancer cells within the gland. Because the treatment planning with this type of radiation therapy is far more precise, higher—and more effective—doses can be used with less chance of damaging surrounding tissue.

Intensity-modulated radiation therapy (IMRT) takes the dose planning one step further. Studies have clearly shown that delivery of higher doses of radiation results in better outcomes. However, if you remember from the anatomy lesson above, the prostate lies right next to two rather important internal structures: the bladder and the rectum. Radiation damage to either of those organs can result in significant urinary and bowel problems that are not only unlikely to improve over time, but that have been shown to worsen over time as the effects of the radiation accumulate. To avoid these problems, oncologists might be tempted to opt for delivering lower doses of radiation—at the expense of decreasing the chances for cure.

IMRT does exactly as its name suggests—it allows oncologists to modulate, or change, the intensity of the doses and radiation beams to better target the radiation delivered to the prostate, while at the same time delivering lower doses to the tumor cells that are immediately adjacent to the bladder and rectal tissue.With this approach, the local side effect rate is lowered further while keeping the cure rates as high as possible.

Regardless of the form of external radiation therapy, treatment courses usually run five days a week for about seven or eight weeks, and are typically done on an outpatient basis.