Hydrogel Spacer Efficacy Shows 50% Reduction in Treatment Failure

Watch the first part of the interview with Dr Collins here.

The initial challenge facing the researchers was the lack of definitive, long-term evidence supporting the use of rectal spacers to improve cancer cure rates. While the spacers were already proven to reduce rectal toxicity, no randomized controlled study with sufficient follow-up had conclusively established that they also enhanced biochemical disease-free survival (bDFS).

To address this critical knowledge gap, the team initiated a comprehensive retrospective analysis utilizing an extensive electronic medical record database. This database contained information on 36,000 men who underwent treatment for prostate cancer between 2016 and 2022. Within this large cohort, approximately 2,000 to 3,000 men had received a rectal spacer, while the remaining 30,000 served as the control group.

Factors Influencing Spacer Use

The first phase of the study involved determining the clinical rationale used by treating physicians when selecting patients for the spacer procedure. The analysis revealed distinct patterns in patient selection. Doctors were most likely to recommend rectal spacers for men with localized disease, meaning the cancer had not yet spread beyond the prostate. Conversely, men with metastatic disease were less likely to receive the spacer. This caution was rooted in early concerns that placing the hydrogel might inadvertently separate potential cancer cells located in the fat between the prostate and the rectum, theoretically hindering the effectiveness of the radiation treatment.

Furthermore, the data showed a strong correlation between spacer placement and the use of dose escalation, specifically involving an internal radiation boost called brachytherapy. Physicians were also more inclined to use the spacer in patients who had significant comorbidities, such as diabetes and hypertension. This decision was clinically sound, as these underlying conditions are well-known to increase a patient's inherent susceptibility to radiation-induced tissue damage and subsequent toxicity.

Matched Comparison and Key Findings

To establish a scientifically robust comparison, the research team meticulously employed a patient-matching technique to create two highly comparable groups. This process resulted in a cohort of 250 men who received a spacer and 500 men who did not. The patients in both groups were closely matched based on factors known to influence outcomes, ensuring that any difference in results could be reliably attributed to the spacer.

The primary endpoint for comparison was cancer control, measured by bDFS. This measure tracks the percentage of men who maintain a low, stable prostate-specific antigen (PSA) level after treatment, as a rising PSA is the definitive indicator of treatment failure. The results of the comparison were significant: in the first few years following treatment, the men who had received the rectal spacer experienced a 50% reduction in treatment failure. Specifically, the rate of biochemical failure dropped from 11% in the non-spacer group to just 5.5% in the group that received the hydrogel spacer. This dramatic difference strongly suggested that the rectal spacer not only offered crucial protection to the rectum but also served as a powerful tool for improving the probability of a cure.