Standard and hypofractionated dose escalation to intraprostatic tumour nodules in localised prostate cancer: 5 year efficacy and toxicity in the DELINEATE trial.

To report 5 year efficacy and toxicity of intra-prostatic lesion boosting using standard and hypofractionated radiotherapy.

XXXXXXXXX (ISRCTNxxxxxxx) is a single centre phase II multi-cohort study including standardly fractionated (Cohort A: 74Gy/37F to prostate and seminal vesicles (psv); Cohort C 74 Gy/37F to psv plus 60 Gy/37F to pelvic lymph nodes) and moderately hypofractionated (Cohort B: 60Gy/20F to psv) prostate IMRT in patients with NCCN intermediate/high-risk disease. Patients received an integrated boost of 82Gy (Cohorts A/C) and 67Gy (Cohort B) to multiparametric MRI-identified lesion(s).

late RTOG gastrointestinal (GI) toxicity at 1 year. Secondary endpoints: acute and late toxicity (clinician and patient reported) and freedom from biochemical/clinical failure (FFBCF) at 5 years.

265 men were recruited (55 Cohort A, 153 Cohort B and 48 Cohort C). Median follow up for each cohort was > 5 years. Cumulative late RTOG grade 2+ GI toxicity at one year was 3.6% (95% CI 0.9% - 13.8%) (Cohort A), 7.2% (95% CI 4%-12.6%) (Cohort B) and 8.4% (95% CI 3.2% -20.8%) (Cohort C). Cumulative late RTOG grade 2+ GI toxicity to 5 years was 12.8% (95% CI 6.3%-25.1%) Cohort A, 14.6% (95% CI 9.9%-21.4%) Cohort B and 20.7% (95% CI 11.2%-36.2%) Cohort C. Cumulative RTOG grade 2+ genitourinary (GU) toxicity to 5 years was 12.9% (95% CI 6.4%-25.2%) Cohort A, 18.2% (95% CI 12.8%- 25.4%) Cohort B and 18.2% (95% CI 9.5%-33.2%) Cohort C. Five-year FFBCF was 98.2% (95% CI 87.8-99.7%) Cohort A, 96.7% (95% CI 91.3- 98.8%) Cohort B and 95.1% (95% CI 81.6-98.7%) Cohort C.

The XXXXXXXXX trial has shown safety, tolerability and feasibility of focal boosting in 20 or 37 fractions. Efficacy results indicate a low chance of prostate cancer recurrence five years after radiotherapy. Evidence from ongoing phase III randomised trials is awaited.

International journal of radiation oncology, biology, physics. 2022 Sep 20 [Epub ahead of print]

Alison C Tree, Laura Satchwell, Emma Alexander, Irena Blasiak-Wal, Nandita deSouza, Annie Gao, Emily Greenlay, Helen McNair, Chris Parker, James Talbot, David Dearnaley, Julia Murray

The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, SM2 5PT; Division of Radiotherapy and Imaging, Institute of Cancer Research, Cotswold Road, Sutton, SM2 5NG. Electronic address: ., The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, SM2 5PT. Electronic address: ., The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, SM2 5PT., The Royal Marsden NHS Foundation Trust, Downs Road, Sutton, SM2 5PT; Division of Radiotherapy and Imaging, Institute of Cancer Research, Cotswold Road, Sutton, SM2 5NG., Division of Radiotherapy and Imaging, Institute of Cancer Research, Cotswold Road, Sutton, SM2 5NG.

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