A comparison of the single and double factor high-risk models for risk assignment of prostate cancer treated with 3D conformal radiotherapy

Purpose: Two models for stratification of prostate cancer aggressiveness predominate for the purposes of daily treatment decision making. This study investigates the relationships between these two clinically popular models. Methods: Both risk stratification models use the same definition for low risk: Gleason score (GS) less than or equal to6, pretreatment initial prostate specific antigen (iPSA) less than or equal to10 ng/mL, and stage T1c-T2c. For the single factor high risk model (SF), intermediate risk (IR) is defined as the presence of GS 7 or PSA>10-20 ng/mL, without the presence of any high-risk feature; high risk (HR) was defined as the presence of GS 8-10, iPSA >20, or palpation stage T3. For the double factor high risk (DF) model, IR and HR were defined as one and more than one of the following: GS greater than or equal to7, iPSA >10, or stage T3. Between April 1989 and October 2001, 1,597 patients were treated definitively with 3D conformal radiation therapy (3D-CRT) alone for prostate cancer at our institution. The main clinical endpoint was freedom from biochemical failure (FFBF). Results: The 5-year actuarial FFBF rate for the low-risk group was 83%. The SF model resulted in FFBF rates of 76% and 47% for IR and HR patients respectively. The DF model resulted in FFBF rates of 70% and 52% for IR and HR patients, respectively. The FFBF rate for patients defined as IR and HR by both models was 76% and 40%, respectively. Those classified as IR by the DF model and then further subdivided into IR and HR by the SF model had a 76% and 52% 5-year FFBF rate (p=0.0004). Those classified as HR by the DF model and then further subdivided into IR and HR by the SF model had a 71% and 40% 5-year FFBF (P=0.0014). Conclusions: The SF model created prognostic groups with a greater internal consistency than the DF model. The SF was also better at identifying patients with high-risk prostate cancer who may benefit from a more aggressive approach. (C) 2004 Elsevier Inc.