Richard G. Stock, MD, presented “Prevention and Management of Rectal Toxicity” during the 23rd Annual Southwest Prostate Cancer Update on April 15, 2018 in Scottsdale, Arizona

How to cite: Stock, Richard G. “Prevention and Management of Rectal Toxicity” April 15, 2018. Accessed [date today].

Prevention and Management of Rectal Toxicity – Summary:

Radiation Dose Volume Effects

Prostate brachytherapy became common in clinical practice from about 1993 to 1998. Over that period of time, the incidence of rectal bleeding following brachytherapy increased.  However, there was no centralized guidelines regarding the proper radiation dosage to the rectum.

In response to these conditions, Dr. Stock and a research group published a paper in 2001. They created a dose-response analysis of brachytherapy implants and proctitis, and found a relationship between the volume of rectal wall receiving doses, dosage amount, and the likeliness of developing intermittent, persistent rectal bleeding. Additionally, the study defined various cutpoints of doses and rectal volume that marked increases in rectal bleeding

In this presentation, Dr. Stock reviews ample studies confirming a correlation between dosimetric findings of implants and rectal bleeding.

The Effect of Prostate Swelling on Rectal Dosage

Dr. Juanita Crook published a paper finding that immediately following implantation, the prostate swells significantly near the locations of the needles. This creates edema, therefore separating the prostate from the rectum. While edema is present, the radiation dose to the rectum is is low. However, over time, that edema recedes, and rectal doses become much higher.

Are There Factors We Cannot Control?

Clinicians cannot control some conditions while using brachytherapy, including are the exact seed distribution, genetically based dose volume, individual patients’ location of the prostate compared to the rectal muscles, and shifting of seeds.

The image to the left illustrates a shift of brachytherapy seeds from the insertion location.

Methods for Decreasing Rectal Toxicity

In the management of rectal bleeding, studies comparing brachytherapy alone or brachytherapy with hormone therapy, patients experience less rectal bleeding with ADT treatment. This indicates ADT is protective against rectal bleeding.

Utilizing rectal balloons or hydrogel spacers can also decrease rectal toxicity. These methods move the prostate during implantation in order to spare the rectum from higher doses.