Introduction and objectives: To report acute and late toxicity and first clinical results of external beam radiotherapy (EBRT) followed by a single dose of high-dose-rate (HDR) brachytherapy in a prospective cohort of intermediate and high-risk prostate cancer (pCa) patients.
Materials and methods: 394 patients with a median age of 66 (46-80) were treated between December 2014 and February 2019. Median IPSS was 4 (IPSS ≥15 3.9%). 55.3% of patients had high-risk pCa. 45.5% had a multiparametric-MRI available (79% since 2018). Tumor characteristics were as follows: Stage ≤T2a 36.3%, T2b-T2c 30.5%, ≥T3a 33.2%. Gleason score 6 18.5%, 7 58.4%, ≥8 23.1%. 48% had ≥50% affected cores. Perineural invasion 44.6%. 97% of patients received androgen-deprivation therapy. EBRT was administered in 13 fractions (36.4 Gy) to the prostate and seminal vesicles and 23 fractions (46 Gy) to the whole pelvis for intermediate-risk and high-risk patients, respectively. 98% of patients were treated by volumetric arc radiotherapy and image guidance was performed by cone-beam CT in 88.6%. HDR brachytherapy was administered in a single dose of 15 Gy as a boost following EBRT. Under general anesthesia, HDR was performed real-time and intraoperatively, guided by trans-rectal ultrasound imaging for needle insertion and dosimetry. Toxicity was prospectively evaluated by CTCAE v4.0.
Results: With a median follow-up of 31 months (5-95), 10 patients presented biochemical failure. Of these, 8 had a provable clinical relapse (7 presented it in the form of distant disease and 1 as local recurrence). Local control (LC) was 99.7%. Biochemical progression-free survival (bPFS) was 97.7%. Distant PFS was 98.2%. Overall survival (OS) was 97.9%. Cancer-specific survival remains at 100%. Actuarial 3-year estimates were LC 95.5%, bPFS 97.8%, distant PFS 98.7%, OS 97.3%. Acute genitourinary (GU) G2 toxicity was observed in 20.6% of patients, whereas acute gastrointestinal (GI) G2 toxicity was found in 5.8%. No G≥3 acute toxicity was observed. Late GU G3 toxicity was 0.8%, with 64.8% having no toxicity at all. 1.6% (6 patients) presented urethral stenosis. 83.7% had G0 GI toxicity, with no G≥3 toxicity reported.
Conclusions: Single dose HDR as a boost to EBRT is a safe and effective approach for intermediate-risk and high-risk pCa, with an excellent toxicity profile and promising results in terms of LC, PFS and OS.
