Purpose: To investigate the effect of dose escalation within prognostic risk groups in prostate cancer.
Patients and methods: Between 1997 and 2003, 664 patients with localized prostate cancer were randomly assigned to receive 68- or 78-Gy of radiotherapy. Two prognostic models were examined: a risk group model (low-, intermediate-, and high-risk) and PSA-level groupings. High-risk patients with hormonal therapy (HT) were analyzed separately. Outcome variable was freedom from failure (FFF) (clinical failure or PSA nadir+2 microg/L).
Results: In relation to the advantage of high-dose radiotherapy, intermediate-risk patients benefited most from dose escalation. However no significant heterogeneity could be demonstrated between the risk groups. For two types of PSA-level groupings: PSA<10 and > or = 10 microg/L, and <8, 8-18 and >8 microg/L, the test for heterogeneity was significant (p=0.03 and 0.05, respectively). Patients with PSA 8-18 microg/L (n=297, HR=0.59) derived the greatest benefit from dose escalation. No heterogeneity could be demonstrated for high-risk patients with and without HT.
Conclusion: Intermediate-risk group derived the greatest benefit for dose escalation. However, from this trial no indication was found to exclude low-risk or high-risk patients from high-dose radiotherapy. Patients could be selected for high-dose radiotherapy based on PSA-level groupings: for patients with a PSA<8 microg/L high-dose radiotherapy is probably not indicated, but should be confirmed in other randomized studies.
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