Introduction:

Hydrogel placement is recommended for men with prostate cancer undergoing definitive radiation therapy. However, risk factors for inadequate hydrogel placement are not well understood. Our goal was to examine whether type of prostate biopsy effects spacer placement quality using a large sample of patients treated in the ambulatory setting.

Methods:

A retrospective cohort study was conducted on patients diagnosed with prostate cancer who underwent hydrogel spacer placement before primary radiation treatment between 2018 to 2023 after transperineal (TP) or transrectal (TR) prostate biopsy. Study outcomes were Spacer Quality Score (SQS) (0-2, with greater values indicating better placement), Rectal Wall Invasion (RWI) (0-3, with lower values indicating lack of RWI), and the occurrence of other hydrogel complications. Prophylactic antibiotics were not routinely used. 

Results:

A total of 394 patients were included. A pre-hydrogel TR biopsy was performed in 273 patients (69.1%), while a TP biopsy occurred in 122 (30.9%). A SQS ≥ 1 occurred in 308 (77.9%) patients. A greater proportion of TP patients had a SQS ≥ 1 compared to those who underwent TR (87.7 vs. 73.5%, p<0.002). A RWI score ≥ 2 was found in 180 (45.6%) patients. The proportion of patients with a RWI score ≥ 2 did not differ significantly by type of biopsy performed. Patients who had an interval of > 70 days between biopsy and hydrogel placement had significantly decreased odds of a RWI score ≥ 2 (OR = 0.42, 95% CI: 0.21 – 0.83). Only one infection was found after hydrogel placement. Figure 1 displays the quality of hydrogel placement overall and by type of biopsy. 

Conclusion:

The quality of hydrogel placement was significantly better in men who had undergone TP biopsy. Rectal wall invasion was more common than previously reported and did not differ between TP and TR biopsy. 

Funding: N/A