Image-guided dose-escalated intensity-modulated radiation therapy for prostate cancer: treating to doses beyond 78 Gy

Study Type - Therapy (case series) Level of Evidence 4 What's known on the subject? and What does the study add? High doses of radiotherapy correspond to higher cure rates. Most radiation centers in the UK and Australia limit prescription doses to 74-78 Gy and do not use IGRT and IMRT for all patients. The combination of IGRT and IMRT can limit the rectum and bladder to low doses allowing doses above 78 Gy to be delivered, including pelvic lymph node treatment, with low side effects. This paper provides a detailed guide of planning technique and expected toxicity to enable implementation of similar dose escalated prostate programmes in other radiotherapy centres.

Objective: To determine the short-term side-effects of dose-escalated image-guided intensity-modulated radiation therapy (IG-IMRT) for the definitive treatment of prostate cancer.

Patients and methods: Eligible patients were treated at doses >78 Gy and with definitive intent. Patients from a prospective database with International Prostate Symptom Score (IPSS) and Common Terminology Criteria for Adverse Events, version 3.0 (CTCAE) toxicity were recorded weekly during treatment and at follow-up.

Results: In all, 101 patients were included, with doses ranging from 78.3 to 84 Gy (median = 79.3). The median (range) age was 71 (46-83) years; 60% received concurrent androgen deprivation and 35% had pelvic lymph node treatment. The median (range) IPSS at baseline, on treatment and at first follow-up were 7 (0-35), 15 (1-34) and 6 (0-30), respectively. The percentages of patients with grade 2 or higher toxicity during treatment, at 3 months and at 2 years were, respectively, 6.9%, 1% and 2% for gastrointestinal symptoms and 39%, 6.9% and 3% for genitourinary symptoms. There was no significant difference in gastrointestinal toxicity during treatment (P= 0.860) or at 3 months (P= 0.334) between patients with and without lymph node treatment.

Conclusion: Doses >78 Gy delivered using daily image guidance and IMRT are well tolerated, and by 3 months short-term side-effects have normalized for the majority of patients.