Abstract
BackgroundAdvances in imaging, biomaterials and precision radiotherapy provide new opportunities to salvage locally recurrent prostate cancer (PC). This study evaluates the efficacy and safety of re-irradiation using stereotactic body radiation therapy (SBRT). We hypothesized that patients with castrate-resistant PC (CRPC) would benefit less from local salvage.MethodsA prospective clinical database was reviewed to extract 30 consecutive patients treated with prostate re-irradiation. Gallium prostate specific membrane antigen (PSMA) ligand positron emission tomography was performed following prostate-specific antigen failure in all patients and biopsy was obtained in 18 patients (60%). Re-irradiation was either focal (n = 13) or whole-gland (n = 17). Endo-rectal balloons were used in twenty-two patients and hydrogel spacers in eight patients. The median prescription dose was 5 fractions of 6.5 (range: 6–8) Gray (Gy).ResultsMedian follow-up was 28 months. Failure occurred in 10 (out of 11) CRPC patients versus 6 (out of 19) castrate-sensitive patients (91% vs. 32%, p = 0.008) after a median of 13 and 23 months, respectively. Metastases occurred in 64% (n = 7) of CRPC patients versus 16% (n = 3) of castrate-sensitive patients (p = 0.007). Two patients experienced local in-field recurrence, thus local control was 93%. The 2 and 3-year recurrence-free survival were 84% and 79% for castrate-sensitive patients versus 18% and 9% for CRPC patients (p < 0.001), and 3-year metastasis-free survival was 90% versus 27% (p < 0.01) for castrate-sensitive and CRPC patients, respectively. Acute grade II and III genitourinary (GU) toxicity occurred in 27% and 3%, and late GU toxicity in 30% and 3%, respectively. No ≥ grade II acute gastrointestinal (GI) toxicity occurred, and only one patient (3%) developed late grade II toxicity.ConclusionsEarly delivery of salvage SBRT for local recurrence is associated with excellent 3-year disease control and acceptable toxicity in the castrate-sensitive phenotype. PSMA imaging for detection of local recurrence and the use of precision radiotherapy with rectal protective devices should be further investigated as a novel salvage strategy for radio-recurrent PC.
Highlights
Advances in imaging, biomaterials and precision radiotherapy provide new opportunities to salvage locally recurrent prostate cancer (PC)
castrate-resistant PC (CRPC) patients had all received androgen ablation following failure of primary radiation and were not initially referred for consideration of local salvage by their treating physicians. They subsequently developed a biochemical failure on androgen deprivation therapy (ADT), were find to harbor local disease on imaging and referred for salvage radiation. Ga68 prostate specific membrane antigen (PSMA) Positron emission tomography (PET) imaging was performed in all patients prior to salvage stereotactic body radiation therapy (SBRT), demonstrating at least a local pathological PSMA uptake
One third of patients (n = 11) received ADT-only as first salvage treatment upon failure for a median duration of 53 months (7–191 months) leading to the emergence of CRPC prior to their referral for local salvage treatment. Ga68 PSMA PET scans were performed in all patients prior to salvage SBRT
Summary
Biomaterials and precision radiotherapy provide new opportunities to salvage locally recurrent prostate cancer (PC). Recurrence of PC after local definitive radiation therapy (RT) is a common clinical scenario. Acceptable treatment options includes local salvage with radical prostatectomy, cryotherapy, and focal therapies such as high-intensity focused ultrasound (HIFU) [5]. As these options are often associated with urinary and sexual morbidity, many patients are managed with lifelong androgen deprivation therapy (ADT) [6, 7], which has a major impact on quality of life [8], is not curative by itself, and eventually induces a more aggressive CRPC phenotype [9]. Re-irradiation using brachytherapy [10,11,12,13,14] has been included in guideline options and SBRT is under investigation [15,16,17]
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