Background
Phase III RCT from MD Anderson Cancer Center. 301 patients with T1b–T3 prostate cancer (excluding T1ab Gleason ≤5 and T3 with any Gleason ≤5 in the low-risk group) randomized 1:1 between 1993 and 1998 to dose-escalated (78 Gy) versus standard-dose (70 Gy) 3D conformal radiotherapy (3D-CRT). This was among the first randomized trials to demonstrate a benefit of dose escalation in prostate cancer, establishing 78 Gy as superior to 70 Gy.
Interventions and follow up
Arm A: 78 Gy in 39 fractions (2 Gy/fx) with 3D-CRT
Arm B: 70 Gy in 35 fractions (2 Gy/fx) with 3D-CRT
Primary endpoint: Freedom from biochemical and clinical failure (bNED)
mFollow up: Median 8 years (Kuban IJROBP 2008 report)
Arm B: 70 Gy in 35 fractions (2 Gy/fx) with 3D-CRT
Primary endpoint: Freedom from biochemical and clinical failure (bNED)
mFollow up: Median 8 years (Kuban IJROBP 2008 report)
Results
8-year bNED (all patients): 78% (78 Gy) vs 59% (70 Gy), P=.004
8-year bNED (high-risk, PSA >10 ng/mL): 78% (78 Gy) vs 39% (70 Gy), P=.001
8-year bNED (low-risk): 85% vs 76% (not statistically significant)
Distant metastases: No significant difference (both <5%)
8-year bNED (high-risk, PSA >10 ng/mL): 78% (78 Gy) vs 39% (70 Gy), P=.001
8-year bNED (low-risk): 85% vs 76% (not statistically significant)
Distant metastases: No significant difference (both <5%)
Adverse events
Main adverse events: Late grade ≥2 GI toxicity: 26% (78 Gy) vs 13% (70 Gy), P=.013. Late grade ≥2 GU toxicity: similar between arms (~15% each). No significant increase in grade 3+ toxicity. Higher GI toxicity with 78 Gy reflects the limitations of 3D-CRT (before IMRT-era normal tissue sparing).
Conclusions
Dose escalation from 70 Gy to 78 Gy significantly improves 8-year biochemical failure-free survival in prostate cancer, with the greatest benefit in high-risk patients (PSA >10). Higher GI toxicity with 78 Gy using 3D-CRT was acceptable, and with modern IMRT, comparable doses can be delivered with substantially lower rectal toxicity. This trial helped establish dose escalation as the standard approach.
Key Limitations
Key Limitations: 3D-CRT technique (not IMRT) — modern IMRT achieves equivalent dose escalation with significantly lower late GI toxicity. Predates PSA definitions and modern risk stratification. Higher GI toxicity (26%) with 78 Gy/3D-CRT would be considered unacceptable by modern IMRT standards (where grade ≥2 GI toxicity should be <10–15%). Does not incorporate ADT, which is now standard for intermediate- and high-risk patients.
Clinical Context
The MD Anderson dose escalation trial (Kuban 2008) is one of three key dose-escalation RCTs (with Dutch CKVO 96-10 and MRC RT01) establishing 78 Gy as the optimal dose for prostate radiotherapy. With modern IMRT and hypofractionation, 78 Gy equivalents are delivered more safely. The CHHiP trial subsequently showed that 60 Gy/20 fx (biologically equivalent to ~74 Gy conventional) is non-inferior to 74 Gy/37 fx. Current standard-of-care uses 78 Gy (39 fx), 76 Gy (38 fx), or hypofractionated equivalents, all with IMRT.
References