Risk factors for rectal wall infiltration in hydrogel spacer placement: Influence of biopsy approach

Objectives: This study aimed to investigate the association between the type of prostate biopsy and the occurrence of rectal wall infiltration (RWI) with hydrogel spacer placement in patients undergoing radiotherapy for prostate cancer.

Methods: A retrospective study was conducted involving 175 patients who received hydrogel spacer placement before radiotherapy at the National Cancer Center East Hospital, between October 2021 and December 2023. The patients were categorized based on the type of prostate biopsy: transperineal and transrectal. Spacer placement was followed by MRI to confirm spacer position. Logistic regression analysis was employed to identify factors associated with significant RWI.

Results: Of the 175 patients analyzed, 115 underwent transperineal biopsy (TPB) and 60 underwent transrectal biopsy (TRB). The median age was 74 years, and the median prostate volume was 18.6 mL. RWI occurred in 44 (25.1%) of all cases. TRB was associated with a significantly higher occurrence of RWI grade ≥2 compared to TPB (23.3% vs. 4.3%, p < 0.001). Multivariate analysis identified TRB (OR = 5.81, 95% CI = 1.91-17.60, p = 0.002) and smaller prostate volume (≤18.0 mL) (OR = 4.23, 95% CI = 1.23-13.90, p = 0.018) as significant risk factors for RWI grade ≥2.

Conclusion: The study found that TRB significantly associated the risk of RWI following hydrogel spacer placement in prostate cancer radiotherapy. Smaller prostate volumes also heightened this risk. These findings highlight the importance of considering biopsy type and prostate size in planning spacer placement.