Moderately Hypofractionated Radiotherapy in Node-positive Prostate Cancer

Aims: Node-positive prostate cancer is a unique subgroup, with varied practice on locoregional treatment. Definitive treatment with hypofractionated radiotherapy has not been widely reported. We have routinely used standard regimens of hypofractionated radiotherapy for node-positive disease and report our results of toxicity, biochemical control and survival.

Materials and methods: Medical records of patients diagnosed with prostate cancer between February 2011 and April 2016 with radiologically involved pelvic nodes on magnetic resonance imaging/computed tomography without distant metastases were analysed. All patients were treated with long-term androgen deprivation therapy (ADT) and hypofractionated radiotherapy. Acute and late toxicities were assessed using Radiation Therapy Oncology Group acute and late morbidity scoring criteria. Biochemical control and survival were computed using Kaplan-Meier survival statistics.

Results: In total, 61 patients were identified with node-positive disease, with a median age of 68 years and a median initial prostate-specific antigen level of 40.1 ng/ml. Most, 50 (81.9%), had T3 disease; 47.6% had Gleason 8-10 disease. All were treated with hypofractionated intensity-modulated radiotherapy, predominantly 60 Gy/20 fractions/4 weeks, with a dose of 44 Gy/20 fractions to the pelvic nodes. Twenty-five patients (41%) who had residual radiologically enlarged nodes after 3-6 months of ADT received nodal boost to the involved nodes, to a dose of 54-60 Gy as simultaneous boost. Incidences of late grade 2 + gastrointestinal and genitourinary toxicities were 13.1 and 18%, respectively, with no grade 4 toxicities. With a median follow-up of 48 months, 15 (24.6%) patients developed biochemical failure, with only four locoregional failures. The 4-year biochemical control rate was 77.5% and overall survival was 91%. Patients who had residual enlarged nodes after initial ADT had worse biochemical control (53.9% versus 93.1% at 4 years, P < 0.001).

Conclusion: Moderately hypofractionated radiotherapy using an established fractionation schedule with long-term ADT for node-positive prostate cancer patients is feasible and results in excellent biochemical control rates at 4 years, with acceptable late toxicity rates. The response to initial ADT predicts outcomes.