Image guided radiotherapy (IGRT) and intensity modulated radiotherapy (IMRT) are two new techniques that allow the radiotherapy beams to target the prostate and spare the surrounding normal tissues. IMRT and IGRT provide cure rates considered equivalent to those of surgery and brachytherapy, with very low risks of complications. IMRT and IGRT suit both younger and older men, says Dr. Sapna Nangia.

The radiation beam used to treat the tumor is created by a medical linear accelerator. Utilizing IMRT this beam is shaped by a multi-leaf collimator, which “paints” the area to be treated. The machine is outfitted with a pair of robotic arms and/or a portal imaging device, which produce low-dose, high-resolution X-ray images for pinpointing the exact position of the tumor immediately prior to treatment. These images provide the radiation oncologist with precise information about the tumor and surrounding anatomy. When compared with existing images from a MRI, CT or other kinds of scans, they reveal changes in tumor position over a multi-week course of treatment. The fiducial markers allow the linacs to see where the prostate is, and the machine is moved before each treatment to ensure the prostate is targeted and normal tissues are avoided.

IMRT and IGRT are able to give high doses of radiotherapy, called dose-escalation. Dose-escalation with IMRT and IGRT can deliver doses similar to those given with brachytherapy, yet also spare surrounding normal tissues.

From a patient’s perspective, the advantages of IMRT and IGRT are that they provide cure rates equivalent to surgery and brachytherapy, without patients having to undergo significant invasive procedures. IMRT and IGRT offer very low rates of complications again similar to the low rates seen with surgery and brachytherapy.

IMRT/IGRT treatment involves three basic steps: diagnosis, treatment planning and delivery. As part of the diagnosis, physicians generate three-dimensional diagnostic images (usually CT or MRI) of the patient’s anatomy and use these to specify the dose of radiation each area will receive. In some cases, treatment planning includes a simulation session to further localize the cancer and finalize the radiation treatment plan.

The main disadvantage of IMRT and IGRT is that the treatment goes over an 8 week period, compared to high-dose rate brachytherapy which typically takes 6-7 weeks. The types of side-effects are similar to those seen with EBRT, but the risks are much lower. The risks of significant complications are around 1-2%. After treatment you will have further PSA tests to monitor developments. Your PSA should gradually reduce over about 12 months to between 0 and 2. If the PSA rises again, it is often 10 years or longer before problems arise. There are several treatment options available if the PSA rises (“salvage treatments”). Salvage treatments after IMRT and IGRT are the same as for EBRT, and include radical prostatectomy, cryotherapy, high-frequency ultrasound (HI-FU), hormone therapy and chemotherapy.