Prostate cancer is the most common cancer in Singaporean men. Radiotherapy is a treatment for prostate cancer with known rectal toxicity in up to 30% of patients. The utilisation of rectal spacers has emerged as a promising strategy to reduce rectal toxicity. In this case series, we demonstrate the early learning curve of rectal spacer implantation, investigate factors affecting procedural difficulty and report our outcomes.

We retrospectively analysed consecutive patients treated with radiotherapy following hydrogel rectal spacer insertion between May 2024 and March 2025 at Sengkang General Hospital. Spacer placement was performed transperineally under ultrasound guidance as day surgery. All patients had a Magnetic resonance imaging (MRI) done post-procedure to confirm spacer position and for treatment planning. Data including demographics, prior benign prostate hyperplasia surgeries (BPH), pathological features (extra-prostatic extension (EPE) status, tumour (T stage)), procedural details (operation time, deployment success), post-procedure MRI findings including optimal placement, post-spacer prostate to rectal wall distance (PRWD) and radiation-related toxicities (Common Terminology Criteria for Adverse Events v5.0). Statistical comparisons (Mann-Whitney U test) assessed associations between prior BPH surgeries, EPE and difficulty of the procedure.

The cohort comprised 18 patients (median age 70 years). Gleason Grade Group distribution included 13 patients in Groups 2-3 and 5 in Group ≥4. All patients underwent successful spacer deployment with a mean operative time of 14 minutes 53 seconds. Post-procedure MRI revealed a mean PRWD of 13.04mm (range: 6.33mm to 18.45mm). 3 patients had prior BPH procedures, and 6 patients had EPE. In both instances, there were no significant differences in operation time or deployment failures. Post-procedure MRI confirmed optimal spacer positioning in 17 of the cases and in 1 case there was intra-prostatic capsular injection of the spacer. Grade 2 rectal toxicity occurred in 1 patient. No other rectal toxicities were reported.

The early learning curve of rectal spacer injection is both feasible and safe. Neither did prior BPH procedures nor EPE affect the procedural difficulty. The high rate of optimal spacer positioning and low incidence of significant radiation side effects support the increased use of rectal spacers.