Sean P. Collins, MD, PhD, outlines the impact of rectal spacers for men with prostate cancer

A recent study presented at the 2025 American Society for Radiation Oncology Annual Meeting indicated that rectal spacer use is associated with reduced risk of prostate cancer recurrence. In this video, Sean P. Collins, MD, PhD, discusses the critical role of rectal spacers in modern prostate cancer radiation therapy, framing them as a necessary tool to safely achieve higher, more effective radiation doses.

Collins explains that for over 2 decades, increasing the radiation dose to the prostate has been shown to improve cancer control. However, many radiation oncologists were unwilling to perform this dose escalation due to fear of rectal toxicity. This toxicity, which includes rectal bleeding so severe it prevents patients from taking blood thinners like aspirin or Coumadin, or, worse, leads to debilitating bowel frequency and urgency.

He recounts seeing older patients who feel their lives were ruined by radiation, citing the need for 5 daily bowel movements, the inability to control the urge, and the consequent withdrawal from social activities like attending church or going to restaurants. He emphasizes that for a 70-year-old likely to die of a non-cancer cause, such a decline in quality of life is a "bad outcome.”

The availability of rectal spacers has fundamentally changed this dilemma. Spacers allow physicians to administer higher doses of radiation with a higher chance of local control. Collins stresses the oncological importance of local control, as local recurrences can lead to a "second wave of metastatic disease" that can ultimately cause death. Spacers also enable the safe boosting of small abnormal areas detected on MRI or PSMA scans, as the spacer prevents the boost margin from entering and damaging the rectum.

Collins outlines specific patient subgroups that benefit most from spacer placement:

• Patients on blood thinners (e.g., Coumadin): They are at a higher risk of late rectal bleeding and should "absolutely get a spacer.”

• Patients who have received prior radiation: A spacer is commonly used to protect the rectum if they are undergoing a second course of radiation.

• Patients with inflammatory bowel disease: Those with ulcerative colitis or Crohn disease are already prone to frequent bowel movements and are at a higher risk of increased bowel frequency/urgency after radiation.

• Unfavorable intermediate- and high-risk patients: These are the patients who truly need dose escalation to improve cancer control, making the spacer an essential tool to reduce side effects and improve the risk-benefit ratio.

REFERENCE

1. Collins SP, Tran E, Roane A, Morton R. Real-world data analysis of biochemical recurrence after primary radiotherapy for prostate cancer: Propensity matched comparison of patients with hydrogel rectal spacing vs no spacing. Int J Radiat Oncol Biol Phys. 2025;123(1S):e724-725. Abstract 3599