Prostate
A fractionation and dose-constraint day: UHF non-inferiority, 10-yr moderate-hypo durability, rectal D5% targets, and a Decipher-integrated risk system (C-index 0.77 vs 0.68 in training).
NRG/RTOG 0415 late toxicity tolerance doses
ForLow-risk prostate cancer, HRT arm of NRG/RTOG 0415
TL;DRRectal D5% (EQD2) ≤62 Gy predicted halving late ≥G2 GI toxicity from 20% to 10% after 70 Gy at 2.5 Gy/fx in low-risk prostate cancer.
The constraint that matters is a small-volume hotspot, not the high-dose V74Gy rule, which 16% of plans missed anyway. Pts with acute GI toxicity have a lower modeled tolerance (D5% ≤55 Gy for a 10% late GI rate), so planning targets may need to differ by acute course. Bladder dose explained nothing for GU, pointing elsewhere for mitigation.
In low-risk prostate cancer planned for moderate HRT at 2.5 Gy/fx, this supports adding a rectal D5% (EQD2) ceiling near 62 Gy as a GI-toxicity planning goal; it does not inform GU toxicity, where no bladder dose-response emerged. The longer read
The constraint that matters is a small-volume rectal hotspot (D5%), not the V74Gy rule that 16% of plans missed anyway. Pts with acute GI toxicity carry lower modeled tolerance (D5% ≤55 Gy for a 10% late GI rate), and bladder dose explained nothing for GU, pointing mitigation toward substructures.
11 details 1 trial watching
Secondary dose-volume analysis of the HRT arm of the multicenter NRG/RTOG 0415 trial, N=521. Cohort split 70%/30% into training and validation with preserved toxicity rates; univariate and multivariate logistic regression on bootstrapping.
Low-risk prostate cancer treated on the HRT arm. Median follow-up 5.9 yr.
70 Gy at 2.5 Gy/fraction, 3DCRT/IMRT N=108/413. Doses converted to EQD2 with rectum α/β 3 Gy and bladder 6 Gy; trial rectal constraint EQD2 74 Gy ≤15%.
Late ≥G2 GI and GU toxicity, plus proctitis and pollakiuria (the symptoms with rates ≥10%). Generalizability required validation AUC within training AUC ± SD, p≤0.05, and pHL >0.05.
Rectal D5% was the dominant GI predictor; with or without acute GI toxicity it generalized (AUCvalidation 0.64, 0.65). Modeled late GI falls from 20% to 10% at D5% ≤62 Gy. No GU dose-response was found, including at α/β 0.8 Gy.
| Late GI rate | D5% (Model IV) | D5% if acute GI tox (Model II) |
|---|---|---|
| 20% (observed) | 65 Gy | ≤59 Gy |
| 15% | ≤64 Gy | ≤58 Gy |
| 10% | ≤62 Gy | ≤55 Gy |
PROFIT, CHHiP, HYPRO and RTOG 0415 established moderate HRT with similar biochemical control to CFRT but a tendency to more late toxicity. The late GI rate here was 19% vs 2% in a cited high-dose CFRT IMRT series planned with a strict high-dose rectal constraint.
Validation is an internal random split of the same cohort, not an external dataset. The IMRT-heavy mix (79% vs 21%) left a technique interaction untestable, and constraint adherence was incomplete, so part of the signal may reflect plan quality rather than tolerance.
Results point to small rectal hotspots as the modifiable driver of excess late GI toxicity after moderate HRT, with authors also advocating rectal spacers. GU toxicity likely needs a substructure (not whole-bladder) approach.
Post-hoc NTCP modeling within one arm of a phase III; modest AUC 0.64-0.65, internal split validation only, no prospective test of the proposed D5% constraint.
- Does a prospective D5% ≤62 Gy rectal objective lower late GI toxicity?
- Which urinary substructure drives late GU toxicity after HRT?
- Does rectal spacer use make the D5% threshold redundant? n=500 · primary completion 2027-12 · SpaceOAR Vue effect on late GI toxicity, prostate SBRT
📚 Sources · 📄 1 paper
Moderate hypofractionation 70 Gy/28 fx, 10-year outcomes
ForLocalized prostate cancer, all NCCN risk groups, definitive RT ± ADT
TL;DR10-yr bRFS 71%, cRFS 86%, PCSM 6.8% after 70 Gy/28 fx IMRT for localized prostate cancer; late G≥3 GU 2%, GI 1%.
Failure after 70 Gy/28 fx was almost entirely distant: 117 of 125 clinical failures were metastatic, 8 local-only. The HR 10-yr bRFS of 42% came with only 5/244 HR pts receiving elective nodal RT, which the authors attribute to short ADT and rare nodal coverage rather than inadequate prostate dose.
In localized low and intermediate-risk prostate cancer, this supports 70 Gy/28 fx IMRT with daily IGRT as a durable schedule past 10 yr; it does not settle HR disease treated with short ADT and no pelvic nodal RT. The longer read
Failure after 70 Gy/28 fx was almost entirely distant (117 of 125 clinical failures; 8 local-only), so prostate dose is not the HR weak point. Low late toxicity was achieved with rectal/bladder V70 held to 5%, far tighter than NRG-GU005 allows, which gates whether the 2%/1% rates transfer.
12 details 3 trials watching
Single-institution consecutive series from a prospectively maintained registry, 854 pts treated 1998-2012. Median follow-up 11.3 yr (max 19). Not randomized; no comparator arm.
Biopsy-proven, clinically localized prostate adenocarcinoma across all NCCN risk groups: 266 LR, 238 FIR, 106 UIR, 244 HR. Median age 68, median PSA 8.6 ng/mL. ADT in 61%, mostly 1-6 mo.
70 Gy/28 fx at 2.5 Gy/fx, IMRT with daily IGRT (BAT ultrasound 94.8%). CTV prostate alone for LR, plus proximal SV for IR/HR; PTV margin 4-10 mm. Elective pelvic nodes in only 5 of 244 HR pts.
Whole-cohort 10-yr bRFS 71%, cRFS 86%, OS 69%, PCSM 6.8%. Of 125 clinical failures, 117 were distant and 8 local-only.
| Endpoint | LR | FIR | UIR | HR | p |
|---|---|---|---|---|---|
| bRFS | 88% | 78% | 71% | 42% | <.0001 |
| cRFS | 95% | 91% | 85% | 72% | <.0001 |
| PCSM | 2% | 5% | 5% | 15% | n/a |
10-yr late G≥3 GU 2% (mostly urethral stricture) and G≥3 GI 1% (mostly rectal bleeding). One grade 5 event each in GU and GI. 119 pts (14%) developed a new cancer, lung most common.
Authors place this alongside RTOG 0415, CHHiP, PROFIT, HYPRO and the MDACC series, none with 10-yr outcomes at publication. RTOG 0415 used the same 70 Gy/28 fx with G3 toxicity 3% to 4% at 5 yr, under looser dose-volume constraints and without mandatory IMRT.
Toxicity was physician-reported from retrospective chart review, likely underreporting events. Institutional constraints (rectal/bladder V70 5%, up to 10%) are far tighter than NRG-GU005 allows, so the toxicity rates may not hold under trial or community constraints.
The schedule controls the prostate well over 10+ yr; the risk-group gradient is driven by distant failure. What is left open is whether HR outcomes improve with longer ADT and nodal coverage at this fractionation.
Single-institution nonrandomized cohort without a comparator arm; long follow-up adds durability to randomized hypofractionation data but cannot establish equivalence on its own.
- HR outcomes with 70 Gy/28 fx plus ≥2 yr ADT and pelvic nodal RT recruiting Efficacy and Safety of Simultaneous Integrated Boost Radiotherapy in HR/VHR Prostate Cancer With EPLNI Phase 2n=30 · primary completion 2026-09 · hypofx SIB-VMAT + EPLNI in HR/VHR, bPFS endpointrecruiting Hypofractionated Radiotherapy With a Focal Microboost for High-Risk and Locally Advanced Prostate Cancer Phase 2n=46 · primary completion 2029-01 · hypofx + microboost, HR/VHR/N+ intact prostate
- Toxicity reproducibility under looser multi-institutional dose constraints n=400 · primary completion 2029-02 · 70 Gy/28 fx vs 60 Gy/20 fx, intact T1-3N0M0
- Whether tighter modern IGRT margins preserve low local failure
📚 Sources · 📄 1 paper
Integrated clinical-genomic risk groups (Decipher + NCCN)
ForLocalized prostate cancer, NCCN low to high risk, with Decipher available
TL;DR10y DM 3.5%/29.4%/54.6% for clinical-genomic low/int/high vs NCCN 7.3%/9.2%/38.0%/39.5% in localized prostate cancer; 30% reclassified.
The pre-RT setting is the biopsy validation cohort (n=235), where 10y DM ran 0%/25.9%/55.2% across clinical-genomic tiers. The reclassification hits the NCCN favorable/unfavorable intermediate boundary hardest (56.8% and 36.0% moved in prospective cohort I), which is the line that gates adding ADT to RT.
In NCCN intermediate-risk localized prostate cancer, a biopsy Decipher score can move the pt across the favorable/unfavorable line that frames the RT plus ADT discussion; it does not establish that treating to the new tier changes metastasis or survival. The longer read
Biopsy-based validation (n=235) is the pre-RT setting: 10y DM 0%/25.9%/55.2% by tier. Reclassification concentrates at the favorable/unfavorable intermediate split (56.8% and 36.0% moved), the boundary that gates ADT with RT, though adjusted HRs shrink to 3.5 and 6.1 once ADT and RT are modeled.
Training was on RP specimens, 476 (63%) treated with prostatectomy alone, 8-yr median f/u. NCCN low vs fav-int did not differ for DM (HR 1.2), while clinical-genomic high reached 54.6% 10y DM; in the prospective RP cohort 27.2% of NCCN high-risk were reclassified.
13 details 3 trials watching
Retrospective development (training n=756, RP genomic data) and validation (n=235, biopsy genomic data) with competing-risks DM estimates; training median follow-up 8 years. Two prospective cohorts (n=4,960 RP; n=977 biopsy) used for reclassification only.
Localized prostate cancer across NCCN low to high/very-high risk. Training cohort second-line therapy included adjuvant RT 7%, salvage RT 13%, salvage ADT 18%.
Outcome: distant metastasis at 10 years; PCSM secondary. Discrimination by time-dependent c-index; reclassification vs NCCN three-, four- and six-tier systems.
Clinical-genomic tiers separated DM where NCCN fav-int and unfav-int did not split from their neighbors; c-index 0.77 vs 0.68 for NCCN four-tier in training.
| Risk group | 10y DM, training | 10y DM, validation | HR DM, training (95% CI) |
|---|---|---|---|
| NCCN low | 7.3% | n/a | Ref |
| NCCN fav-int | 9.2% | n/a | 1.2 (0.5-3.0) |
| NCCN unfav-int | 38.0% | n/a | 5.4 (2.8-12.0) |
| NCCN high | 39.5% | n/a | 6.0 (3.2-13.0) |
| CG low | 3.5% | 0% | Ref |
| CG int | 29.4% | 25.9% | 9.3 (4.8-21.5) |
| CG high | 54.6% | 55.2% | 21.9 (11.1-50.4) |
| System | Cohort | C-index (95% CI) |
|---|---|---|
| CG 6-tier | Training | 0.77 (0.72-0.81) |
| NCCN 4-tier | Training | 0.68 (0.64-0.72) |
| NCCN 3-tier | Training | 0.65 (0.60-0.69) |
| CAPRA score | Training | 0.68 (0.62-0.74) |
| CG 6-tier | Validation | 0.84 (0.61-0.93) |
Benchmarked against NCCN risk groups and CAPRA (continuous score 0.68, groups 0.64 in training), both outperformed on DM discrimination. The authors frame NCCN as built to predict biochemical recurrence, which ICECaP found is not a surrogate for survival.
Adjusting for ADT and RT cuts clinical-genomic HRs from 9.3 and 21.9 to 3.5 and 6.1, so part of the gradient tracks treatment received. Training specimens date from 1997-2004, and many authors are GenomeDx employees.
The system turns a continuous classifier score into categories that fit existing NCCN-based decision rules, which is its practical value. It does not answer whether treatment intensification or de-intensification by the new tier changes outcomes.
Retrospective development with a 235-pt biopsy validation set and sparse low-risk events; prognostic only, no evidence that reclassification-driven treatment changes outcomes.
- Does genomic reclassification predict ADT benefit with RT? n=2050 · primary completion 2026-11 · phase 3 Decipher-guided RT ± ADT/darolutamide by riskn=222 · primary completion 2027-12 · UIR SBRT without ADT, Decipher-guided selection
- Independent validation in larger biopsy-based cohorts n=240 · primary completion 2023-07 · Decipher accuracy in AAM vs non-AAM, 1st-line pts
📚 Sources · 📄 1 paper
Abstract
HYPO-RT-PC
ForIntermediate/high-risk N0M0 prostate, PSA ≤20, no ADT, age ≤75
5yr FFS 84% vs 84%
adjusted HR 1.002 (95% CI 0.758-1.325), non-inferior vs HR limit 1.338
TL;DR5yr FFS 84% vs 84%, adjusted HR 1.002 (95% CI 0.758-1.325): 42.7 Gy/7 fx non-inferior to 78 Gy/39 fx in intermediate-to-high-risk prostate, no ADT.
The schedule tested is 42.7 Gy/7 fx every other weekday to a prostate-only CTV (no seminal vesicles) with a 7 mm fiducial margin, 80% 3DCRT, no ADT. That supports UHF for prostate-only volumes without ADT, not SV-inclusive or ADT-paired high-risk plans. Counsel on the 1yr G2+ GU bump (6% vs 2%).
In a man up to 75 with intermediate-risk, N0M0 prostate cancer, PSA ≤20 and no ADT planned, this supports 7-fraction UHF as disease-control equivalent to 39 fractions; it does not extend to pts needing ADT, PSA >20, or seminal vesicle coverage. The longer read
The schedule tested is 42.7 Gy/7 fx every other weekday to a prostate-only CTV (no seminal vesicles) with a 7 mm fiducial margin, 80% 3DCRT, no ADT. That supports UHF for prostate-only volumes without ADT, not SV-inclusive or ADT-paired high-risk plans. Counsel on the 1yr G2+ GU bump (6% vs 2%).
10 details 5 trials watching
Open-label randomised phase 3 non-inferiority trial, 1:1, 12 centres in Sweden and Denmark, N=1200 randomised 2005-2015. Median follow-up 5.0 yr (IQR 3.1-7.0).
Men up to 75 with intermediate-to-high-risk, T1c-T3a N0M0 prostate cancer, PSA ≤20, WHO PS 0-2. No ADT allowed. 89% intermediate risk, 11% high risk.
42.7 Gy/7 fx (3 d/wk, 2.5 wk) vs 78.0 Gy/39 fx (5 d/wk, 8 wk), prescribed as mean PTV dose and designed equi-effective for late effects at α/β = 3 Gy. CTV prostate only, no seminal vesicles; 7 mm isotropic margin with fiducials; 80% 3DCRT.
Primary: failure-free survival (Phoenix nadir+2 biochemical or clinical failure), per-protocol, NI margin 4% at 5yr (critical HR 1.338). Secondary: OS, PCSS, RTOG toxicity, erectile function.
Efficacy and toxicity by arm are tabulated above; the primary met NI with a point estimate of essentially no difference.
| Endpoint | UHF 42.7 Gy/7 fx | CF 78.0 Gy/39 fx | Comparison |
|---|---|---|---|
| 5yr FFS | 84% (80-87) | 84% (80-87) | adj HR 1.002 (0.758-1.325) |
| 5yr OS | 94% (92-96) | 96% (95-98) | HR 1.11 (0.73-1.69) |
| Acute G2+ GU, end RT | 28% (158/569) | 23% (132/578) | p=0.057 |
| G2+ GU at 1yr | 6% (32/528) | 2% (13/529) | p=0.0037 |
| G2+ GU at 5yr | 5% (11/243) | 5% (12/249) | p=1.00 |
| G2+ bowel at 5yr | 1% (3/244) | 4% (9/249) | p=0.14 |
| Endpoint | UHF | CF | Log-rank p |
|---|---|---|---|
| GU at 2yr | 13% (11-16) | 9% (7-12) | 0.63 |
| GU at 5yr | 18% (15-22) | 17% (14-20) | 0.63 |
| Bowel at 2yr | 6% (5-9) | 5% (4-8) | 1.00 |
| Bowel at 5yr | 10% (7-13) | 10% (7-13) | 1.00 |
UHF carries a higher acute and 1yr GU burden (G2+ at 1yr 6% vs 2%, p=0.0037) that converges by 5yr (5% vs 5%). Late bowel toxicity no different; patient-reported acute urinary and bowel symptoms higher with UHF.
CHHiP, RTOG 0415, PROFIT and HYPRO established moderate hypofractionation against conventional fractionation. HYPO-RT-PC is the first randomised test of ultra-hypofractionation, the evidence the 2018 ASTRO/ASCO/AUA guideline said it was waiting for.
The upper CI bound (1.325) clears the 1.338 limit narrowly. 80% 3DCRT and a 7 mm margin predate modern SBRT delivery, and 7 fx every other weekday is not the 5 fx schedule most programs use. Five-year median follow-up is short for late intermediate-risk failures.
The trial settles disease-control equivalence of UHF for prostate-only, ADT-free treatment. It leaves open UHF with ADT, with SV or nodal coverage, and against moderate hypofractionation.
CONSORT flow
Randomised phase 3, NI primary met at 5yr median f/u; open-label, per-protocol primary, redesigned from superiority mid-trial. Backs guideline-conditional UHF rather than redefining SOC alone.
- UHF with concurrent ADT or seminal vesicle coverage in high-risk disease n=120 · primary completion 2027-12 · randomized SBRT vs 76 Gy/38 fx IMRT, high-risk N0n=700 · primary completion 2033-10 · phase 3 2x2: SBRT dose escalation ± darolutamide, high-risk
- UHF versus moderate hypofractionation head-to-head active Radiation Hypofractionation Via Extended Versus Accelerated Therapy (HEAT) For Prostate Cancer Phase NAn=161 · primary completion 2027-02 · 36.25 Gy/5 fx vs 70.2 Gy/26 fx, 4-yr BF non-inferiorityn=503 · primary completion 2028-08 · moderate hypo vs SBRT vs EBRT+SBRT boost; BF, toxicityactive Standard Moderately Hypofractionated RT vs. Ultra-hypofractionated Focal Lesion Ablative Microboost in Prostate Cancer Phase NAn=484 · primary completion 2032-01 · UHF focal microboost vs 20-fx moderate hypo, int/high risk
- Late biochemical failure beyond 5-year median follow-up