3T Multiparametric Magnetic Resonance Imaging-Guided High-Dose Salvage Radiotherapy in Prostate Cancer

To analyze the efficacy and toxicity of high-dose salvage intensity-modulated radiotherapy (IMRT) in patients with tumor pelvic recurrence detected by 3T multiparametric magnetic resonance imaging (mpMRI). Between 2009 and 2014, 55 consecutive patients with biochemical recurrence of prostate cancer after radical prostatectomy who were considered for salvage IMRT were included. mpMRI was carried out in all patients before treatment. Salvage IMRT doses were escalated on macroscopic recurrence detected by mpMRI. Biochemical failure after IMRT was defined using PSA nadir plus 0.2 ng/mL definition. Treatment-related complications were evaluated using Common Terminology Criteria for Adverse Events (CTCAE v4.03). mpMRI was positive in 19/55 (34.5%) patients. Local recurrence and pelvic lymph node and bone metastases were found in 13, 4 and 2 patients respectively. Median pre-IMRT PSA was 0.4 ng/mL (interquartile range 0.30–1.93 ng/mL). Patients with a positive mpMRI showed PSA level significantly higher compared to those with a negative mpMRI (0.4 [0.4] vs 2.2 [4.1] ng/mL, p=0.003). Median doses of IMRT in patients with negative and positive mpMRI were 70 (64-74) vs 76 (64-80) Gy, respectively. Seventeen patients (31.5%) received androgen-deprivation therapy as a component of their salvage treatment and eight of these had positive MRI. The mean follow-up was 41 months (range 6-81 months). The 3-year cancer specific survival was 98% (95%CI 94.1-100%) and overall survival was 92.5% (95%CI 85.3-99.6%). Global 3-year biochemical disease-free survival (bDFS) was 82.3% (95%CI 71.7-92.9%). In patients with a negative and positive mpMRI, the 3-year bDFS was similar (82.3% vs 82.5%). The 3-year incidence of grade ≥ 2 rectal and urinary late toxicity was 1.9 % and 14.8 %, respectively. The late grade ≥2 toxicity was resolved without sequelae in 8 of these 9 patients. High-dose salvage IMRT on macroscopic mpMRI recurrence was an effective and safe treatment. High doses salvage radiation could explain the good biochemical control observed in patients with high PSA levels and positive mpMRI.