Stereotactic body radiotherapy with a focal boost to the intraprostatic tumor for intermediate and high risk prostate cancer: 5-year efficacy and toxicity in the hypo-FLAME trial.

Abstract

METHODS

Patients with intermediate- or high-risk PCa were enrolled in the phase II hypo-FLAME trial. All patients were treated with 35 Gy in 5 weekly fractions to the whole prostate gland with an iso-toxic integrated boost up to 50  Gy to the multiparametric MRI-defined tumor(s). If the dose constraints to the normal tissues would be exceeded, these were prioritised over the focal boost dose. The current analysis reports on the 5-year bDFS, late toxicity and health-related quality of life (HRQoL).

CONCLUSION

Ultra-hypofractionated focal boost SBRT is associated with encouraging biochemical control rates up to 5-year follow-up in patients with intermediate- and high-risk PCa. Furthermore, prostate SBRT with iso-toxic focal boosting is associated with acceptable late genitourinary and gastrointestinal toxicity rates.

BACKGROUND

The addition of an integrated focal boost to the intraprostatic lesion is associated with improved biochemical disease-free survival (bDFS) in patients with intermediate- and high-risk prostate cancer (PCa) in conventionally fractionated radiotherapy. Furthermore, whole gland stereotactic body radiotherapy (SBRT) demonstrated to be non-inferior to conventional radiotherapy for low- and intermediate-risk PCa. To investigate the combination of ultra-hypofractionated prostate SBRT with iso-toxic focal boosting for intermediate- and high-risk PCa, we performed the hypo-FLAME trial.

RESULTS

Between 2016 and 2018, 100 men were treated with a median follow-up of 61 months. The estimated 5-year bDFS (95 % CI) was 93 % (86 % to 97 %). At 5 years, the prevalence of grade 2 + genitourinary and gastrointestinal toxicity was 12 % and 4 %, respectively.