Radiation Therapy Basics (IMRT And SBRT/SABR)

Dr. Brian Lawenda briefly discusses the treatment of prostate cancer using external beam photon radiation therapy (intensity modulated radiation therapy “IMRT” and stereotactic body radiation therapy “SBRT” also known as stereotactic ablative radiation therapy “SABR”).


A recently published study of over 6000 prostate cancer patients treated with only 5 sessions of a non-invasive, highly-focused radiation technique called stereotactic body radiation therapy (SBRT) reported cancer control rates of 95% (5 years) and 94% (7 years)! Furthermore, the risks of significant longterm bowel and bladder side effects are remarkably low (less than 2%).

Data from over 40 prospective studies have established that SBRT is a new standard treatment for the vast majority of patients with the most common prostate cancers (low and intermediate risk) can be treated with a fast 5-session course of stereotactic body radiation therapy (SBRT). Even higher risk prostate cancers (unfavorable intermediate and high-risk) can be treated with a shorter course treatment using a combination of 5-weeks of IMRT followed by 3-days of SBRT, instead of 9-weeks of IMRT.

In the last few years, radiation oncologists have been using a dissolvable gel (SpaceOAR) to further improve side effect profiles.

Many patients also hear about the “seed implant” or catheter-based implant technique (called brachytherapy). While these are also established short-course alternatives for treating the prostate, SBRT has some obvious advantages over brachytherapy:

  • It is non-invasive
  • No anesthesia is required
  • There is no needle-induced trauma (brachytherapy uses many needles to deliver radiation into the prostate)
  • There is a lower risk of urinary obstruction after treatment

There are also significant advantages of SBRT over other external beam radiation regimens:

  • SBRT is a significantly shorter radiation course (5-sessions vs 20-45 sessions)
  • SBRT is less expensive

Reference: https://www.redjournal.org/article/S0360-3016(19)30612-1/abstract