1219 - Stereotactic Prostate Cancer Ablative RE-Irradiation: A Systematic Review and Meta-Analysis (SPARE)
Presenter(s)
A. G. Gouveia1, G. Pond2, J. Tao3, K. Dong3, V. F. Bratti4, G. A. Viani5, A. Y. Ye6, A. A. Rosa7, D. M. Palhares8, F. L. Cury9, C. J. Villafuerte10, A. Dal Pra11, F. Y. Y. Moraes12, R. A. Olson6, and T. Tsakiridis13; 1McMaster University, Juravinski Cancer Center, Hamilton, ON, Canada, 2Escarpment Cancer Research Institute McMaster University, Hamilton, ON, Canada, 3The University of British Columbia, Vancouver, BC, Canada, 4Queen's Cancer Research Institute, Kingston, ON, Canada, 5Hospital das Clínicas of the São Paulo State University (UNESP), Medical School, Botucatu., Botucatu, SP, Brazil, 6University of British Columbia, Vancouver, BC, Canada, 7Hospital Santa Izabel, Salvador, Brazil, 8McMaster University, Hamilton, ON, Canada, 9McGill University, Montreal, Canada, 10Ateneo School of Medicine and Public Health, Manilla, Philippines, 11Department of Radiation Oncology, University of Miami/Sylvester Comprehensive Cancer Center, Miami, FL, 12Department of Radiation Oncology, University of Toronto, Toronto, ON, Canada, 13Juravinski Cancer Centre, McMaster University, Hamilton, ON, Canada
Purpose/Objective(s): Stereotactic ablative radiotherapy (SABR) is emerging as an alternative treatment for patients with locally recurrent prostate cancer after previous radiation. This approach allows for precise targeting while minimizing toxicity risks. However, reported outcomes following re-irradiation of the prostate with SABR have shown significant variability. This systematic review and meta-analysis aimed to evaluate and quantify the efficacy and toxicity associated with prostate re-irradiation with SABR.
Materials/Methods: A systematic review and meta-analysis compliant with PRISMA guidelines was conducted to evaluate studies of SABR for local re-irradiation of prostate cancer. Random-effects models were employed to aggregate the following outcomes: biochemical recurrence-free survival (BRFS), local relapse-free survival (LRFS), metastasis-free survival (MFS), and the gastrointestinal (GI) and genitourinary (GU) toxicities after with SABR re-irradiation. All outcomes were pooled as proportions using the Freeman–Tukey double arcsine transformation, heterogeneity was assessed with I². Statistical analyses were performed using Stata version 19.5, with p-values less than 0.05 considered statistically significant.
Results: A total of 30 studies with 1,099 patients were analyzed. The pooled rates for 2 years biochemical recurrence-free survival (BRFS), local recurrence-free survival (LRFS), and metastasis-free survival (MFS) were 62.5% (95% CI, 54.1–70.6%; I² = 81.9%), 89.9% (95% CI, 80.6–96.5%; I² = 85.5%), and 84.6% (95% CI, 77.3–90.7%; I² = 77.8%), respectively. Acute severe side effects were rare, with pooled rates of combined grade 3-4 GI toxicities of 0.7% (95% CI, 0.3–1.4%; I² = 0%) and grade 3-4 GU toxicities of 1.1% (95% CI, 0.6%–1.9%; I² = 0%). Similarly, late grade 3-4 toxicity remained low, with pooled rates of 1.0% (95% CI, 0.5–1.7%; I² = 0%) for GI and 3.3% (95% CI, 2.0–5.0%; I² = 46.1%) for GU.
Conclusion: Prostate cancer reirradiation with SABR is associated with favorable short- and intermediate-term oncologic outcomes, including high local control and metastasis-free survival, with acceptable toxicity profiles. The heterogeneity observed across studies underscores the need for prospective trials to better define patient selection, dose–fractionation strategies, and long-term outcomes.
| Outcomes | Studies (n) | Patients (n) | Pooled rate % (95% CI; I2) |
| 1 year BRFS | 24 | 835 | 83.7% (95% CI, 79.1%–87.8%; I² = 63.7%). |
| 2 years BRFS | 19 | 801 | 62.5% (95% CI, 54.1%–70.6%; I² = 81.9%). |
| 3 years BRFS | 9 | 382 | 56.1% (95% CI, 44.0%–67.8%; I² = 81.4%) |
| 2 years LRFS | 12 | 384 | 89.9% (95% CI, 80.6%–96.5%; I² = 85.5%) |
| 2 years MFS | 12 | 554 | 84.6% (95% CI, 77.3%–90.7%; I² = 77.8%) |
| Acute GU G3–4 | 27 | 1027 | 1.1% (95% CI, 0.6%–1.9%; I² = 0%) |
| Acute GI G3-4 | 28 | 1052 | 0.7% (95% CI, 0.3%–1.4%; I² = 0%) |
| Late GU G2 | 25 | 871 | 11.7% (95% CI, 7.3%–17.0%; I² = 79.5%) |
| Late GU G3-4 | 30 | 1099 | 3.3% (95% CI, 2.0%–5.0%; I² = 46%) |
| Late GI G2 | 26 | 896 | 2.2% (95% CI, 1.3%–3.2%; I² = 0%) |
| Late GI G3-4 | 30 | 1099 | 1.0% (95% CI, 0.5%–1.7%; I² = 0%) |