FEASIBILITY OF INTEGRATING RECTAL HYDROGEL SPACER FOR SALVAGE TREATMENT USING STEREOTACTIC ABLATIVE BODY RADIOTHERAPY FOR LOCALLY RECURRENT PROSTATE CANCER

Purpose:

Salvage stereotactic ablative body radiotherapy (SBRT) is an emerging option for radio-recurrent prostate cancer (PCa). To mitigate the increased risk of rectal toxicity, the use of a rectal spacer is an attractive option. However, increased fibrosis in previously irradiated tissue can make spacer placement a challenge. We aimed to assess the feasibility of successful rectal spacer placement in patients receiving SBRT for radio-recurrent PCa.

Materials and Methods:

This is a single institution Phase-I/II feasibility study. All patients had histologically confirmed locally recurrent PCa without any evidence of distant metastasis. All patients received 25 Gy to the whole gland and 35 Gy to the recurrent lesion in 5 weekly fractions following placement of a rectal spacer. The primary endpoint was the feasibility of spacer placement, defined as the ability to successfully deploy the spacer without complications. Secondary endpoints included acute and late toxicity (graded per CTCAE v5.0), quality of life using EPIC and IPSS as well as biochemical disease-free survival-based on PSA kinetics.

Results:

Between 2022-2024, 10 patients were enrolled. Median age and PSA at recurrence were 68.1 years (IQR: 66.1-72.7) and 3.45 (IQR: 3.2-4.8), respectively. Six and 4 patients had ISUP Grade group 2 and 3 disease. Rectal spacer placement was successfully performed in 9 of the 10 patients (90%). Spacer placement was unsuccessful in 1 patient due to inability to hydrodissect. No acute or late complications were reported with spacer placement. Radiation related acute Grade 2 or higher gastrointestinal (GI) and genitourinary (GU) toxicities were observed in 10% and 30% of patients, respectively. No acute Grade ≥3 toxicities were reported (Table 1). At a median follow-up of 19.6 months, PSA kinetics was available for 8 patients, and all were alive without evidence of local or distant failure. The PSA nadir achieved a median value of 0.07 ng/mL at a median time of 12.6 months.

Conclusions:

Rectal spacer placement in conjunction with SBRT for radio-recurrent prostate cancer was feasible in most patients, with no acute or late complications. This treatment option provides acceptable toxicity and encouraging early oncologic outcomes. Longer follow-up is necessary to assess long-term efficacy and safety.