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Published on: February 6, 2019
Prognostic Impact and Metastasis Propensity of Grade Group 5 Prostate Cancer Following Permanent Seed Implantation
Tomomasa Matsuo1, Yu Ozawa1, Atsunori Yorozu2
1Department of Urology, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.
Objectives:
To evaluate the prognostic impact of Grade Group (GG) 5 following permanent seed implantation brachytherapy-based trimodality therapy.
Methods:
We retrospectively analyzed 352 men with National Comprehensive Cancer Network high-risk prostate cancer treated with trimodality therapy (low-dose-rate brachytherapy, external beam radiation therapy, and androgen deprivation therapy [ADT]) between 2003 and 2019. Staging included computed tomography, magnetic resonance imaging, and bone scintigraphy. Endpoints were biochemical recurrence (BCR; Phoenix definition), overall survival (OS), and cancer-specific survival (CSS). Survival outcomes were assessed using the Kaplan-Meier and log-rank tests. Multivariable Cox proportional hazards models, adjusting for prostate-specific antigen, clinical stage, duration of ADT, and biologically effective dose (BED), evaluated the association between GG5 and BCR. Clinical recurrence patterns post-BCR were assessed.
Results:
Median follow-up was 8.2 years (interquartile range [IQR] 5.4-10.0); median BED was 214 Gy (IQR 207-222). Among three study groups (GG1-3, GG4, and GG5), GG5 (n = 106) exhibited significantly lower BCR-free survival (p = 0.002) and CSS (p = 0.045), while OS was comparable (p = 0.3). GG5 remained an independent risk factor for BCR after the adjustment (vs. GG1-4, hazard ratio 2.78, 95% confidence interval 1.60-4.82, p < 0.001). GG5 recurrences predominantly involved the pelvic nodes or bone, whereas local and visceral metastases were infrequent.
Conclusions:
This study demonstrated that GG5 is an independent predictor of BCR and cancer-specific mortality after trimodality therapy. Despite high BED, the propensity for nodal and bone metastases suggests the need for intensified staging and systemic therapy to optimize outcomes for GG5 disease.