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Updated: Apr 1, 2026
A Bioluminescent and Fluorescent Orthotopic Syngeneic Murine Model of Androgen-dependent and Castration-resistant Prostate Cancer
Published on: March 6, 2018
Impact of Intraprostatic Simultaneous Integrated Boost on Long-Term Outcomes in Unfavorable Intermediate-Risk
Cem Onal1,2, Aysenur Elmali2, Birhan Demirhan3
1Department of Radiation Oncology, Baskent University Faculty of Medicine, Adana Dr. Turgut Noyan Research and Treatment Center, Adana, Turkiye.
Background:
Unfavorable intermediate-risk prostate cancer (UIR-PCa) represents a biologically heterogeneous subgroup with a higher risk of recurrence compared with favorable intermediate-risk disease. Contemporary management frequently includes dose-escalated radiotherapy (RT) combined with short-term androgen deprivation therapy (ADT). Whether additional intraprostatic dose escalation using a simultaneous integrated boost (SIB) provides incremental oncologic benefit in this setting remains uncertain.
Methods:
We retrospectively analyzed 194 patients with UIR-PCa treated at three institutions between 2010 and 2023. All patients received image-guided intensity-modulated or volumetric modulated arc RT to 78 Gy with short-term ADT. An MRI-guided intraprostatic SIB (up to 86 Gy) was delivered in 77 patients (39.7%) at clinician discretion. Primary endpoints were biochemical recurrence-free survival (bRFS), distant metastasis-free survival (DMFS), and prostate cancer-specific mortality (PCSM). Multivariable Cox and competing-risk regression models were used to assess predictors of outcome.
Results:
After a median follow-up of 105 months, 8-year bRFS and DMFS rates for the entire cohort were 93.7% and 95.7%, respectively. Addition of SIB was not associated with improved bRFS (93.5% vs 93.6%, p = 0.36), DMFS (94.6% vs 96.7%, p = 0.15), or PCSM. Percent positive biopsy cores ≥ 50% was the only independent predictor of inferior bRFS on multivariable analysis. Treatment-related toxicity was low in both groups, with no significant differences in late grade ≥ 2 gastrointestinal or genitourinary toxicity.
Conclusions:
In patients with UIR-PCa uniformly treated with dose-escalated, image-guided RT and short-term ADT, long-term oncologic outcomes were excellent. The addition of an intraprostatic SIB was safe but did not confer measurable improvement in biochemical or distant disease control. These findings support a selective rather than routine use of focal intraprostatic dose escalation in contemporary UIR-PCa management.
