Objective: The stereotactic body radiotherapy (SBRT) is considered an option for treatment of low or intermediate risk clinically localised prostate cancer (PCa). However, the outcome of SBRT for high risk localised PCa is not well elucidated. We observed oncologic outcomes of SBRT in high risk PCa and compared them to those of low and intermediate risk PCa with median follow up of 69 months.
Materials and method: Between May 2003 and December 2015, 93 patients with localised PCa received SBRT in our hospital. Among them 86 patients were followed for more than 12 months and enrolled in this study. Patients were stratified to low (n=17), intermediate (n=24), and high (n=45)-risk groups by their initial PSA, Gleason score, and clinical tumour stage according to the NCCN risk criteria. Sixty two percent (28/45) of high-risk and 22% (9/41) of low/intermediate risk patients received adjuvant hormone therapy (AHT). Biochemical recurrence (BCR) was defined by 2005 Phoenix criteria.
Results: High risk patients were older (70.4y vs 67.2y, p=0.03) and had higher mean initial PSA (41.4ng/ml vs 7.2ng/ml, p=0.006) than low/intermediate risk group. Mean radiation dose was identical between 2 groups (34.3 Gy vs 34.1Gy, p=0.30). High risk group showed higher nadir PSA (0.82ng/ml vs 0.28ng/ml) and shorter time to nadir PSA (26.8mo vs 33.0mo) without statistical significance. BCR (24.4% vs 9.8%, p=0.073) and local recurrence (24.4% vs 4.9%, p=0.026) were more common in high risk group. 5-year BCR free survival rate (BCRFS) and 5-year recurrence free survival rate (RFS) of low/intermediate risk versus high risk patients were 93.1% vs 73.7%, p=0.136 and 96.6% vs 78.6%, p=0.052, respectively. BCRFS and RFS was not affected by AHT in low/intermediate group. However, patients who underwent SBRT without AHT for high risk PCa showed significantly low 5-year BCRFS and RFS compared to SBRT with AHT (48.8% vs 91.3%, log rank p=0.003; 60.3% vs 90%, log rank p=0.006, respectively). There was no distant metastasis or cancer specific mortality.
Conclusion: In high risk patients, when SBRT was done combined with AHT, acceptable cancer control was achieved. Well controlled, randomised, prospective study was needed to confirm the efficacy of SBRT for high risk PCa.
