Increasing external beam dose for T1-T2 prostate cancer: effect on risk groups

Area of Science:

• Oncology
• Radiation Oncology
• Prostate Cancer Research

Background:

• External beam radiotherapy is a standard treatment for T1-T2 prostate cancer.
• Accurate risk stratification is crucial for tailoring treatment and predicting clinical failure (CF).
• Conventional risk groups were established when lower radiation doses were common.

Purpose of the Study:

• To investigate how increasing radiation doses affect risk groups for clinical failure in T1-T2 prostate cancer.
• To determine if conventional risk classifications remain valid at higher radiation doses.

Main Methods:

• Utilized recursive partitioning analysis (RPA) on 4,537 patients treated with external beam radiotherapy.
• Dose ranges were analyzed to ensure dose was not a predictor of CF within each range.
• Specifically examined the 70-76 Gy dose range (1,136 patients) to compare risk groups with conventional classifications.

Main Results:

• Risk group cutpoints shifted to higher PSA levels and Gleason scores as radiation dose increased.
• Risk groups for clinical failure within the 70-76 Gy dose range differed significantly from conventional risk groups.
• This indicates a dose-dependent effect on patient risk stratification.

Conclusions:

• Conventional risk group classification, developed in the early PSA era (<70 Gy), is inconsistent with current higher dose (>70 Gy) external beam radiotherapy for prostate cancer.
• Risk-group classifications require ongoing re-evaluation as radiation therapy trends evolve towards higher total doses.
• This highlights the need for updated risk stratification models in radiation oncology.