Stereotactic Body Radiation Therapy (SBRT) delivers a much larger dose of radiation per patient visit than IMRT. SBRT technology is relatively new. Thus, there are fewer clinical trials comparing it with other therapies. Despite this, SBRT has become an accepted form of radiotherapy and meets the National Cancer Network “standard of care” guidelines for prostate cancer. The treatment course is one week as opposed to 9 weeks for IMRT. 

SBRT Technology

An average of five fractions of high-dose radiation are administered every other day, or sometimes on five consecutive days. The robotic system called CyberKnife is still the most commonly used form of SBRT, though there are now several different radiation platforms for the delivery of SBRT. 

Cure Rates and Side Effects

Five-years after therapy, the PSA relapse-free survival rates are 95 percent for Sky,* 84 percent for Teal, and 81 percent for Azure.  Preliminary studies indicate that cure rates are similar with or without hormone therapy. Side effects are similar to IMRT or seed implantation. Early side effects occur in the first 3 months and then dissipate. The most common early side effects are urinary issues such as increased frequency. Urinary and bowel incontinence are very rare with any form of radiotherapy. Rectal issues include occasionally loose bowel movements, more frequent movements, or occasional bleeding from pre-existing hemorrhoids. The risk of erectile dysfunction is roughly 5o percent, similar to other types of radiation. SBRT is becoming mainstream therapy due to its greater convenience and reduced cost. 

*The selection of treatment for prostate cancer is changing quickly. Ten years ago Sky was considered life-threatening and 100% of men were advised to have treatment. Back then, in 2008, practically no one was managed with active surveillance. Can treatment for Sky be justified in this modern era? Some argue for it as follows: “Since a well-performed, random, 12-core needle biopsy misses higher grade disease 20-30% of the time (when the initial Gleason grade is initially as 6), treatment is still indicated, “Just to be safe.” 

 


ABOUT THE AUTHOR

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Michael Steinberg, MD is Professor and Chair of the Department of Radiation Oncology at the David Geffen School of Medicine at UCLA. His professional career spans private, corporate and academic practice and is known for the development of multi-site radiation oncology care networks that are characterized by clinical excellence and community based clinical research. The UCLA Radiation Oncology network includes the department at Ronald Reagan Medical Center at UCLA, academically oriented community practices as well as Children's Hospital Los Angeles.

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