In Patients Experiencing Biochemical Failure After Radiotherapy, Pretreatment Risk Group and PSA Velocity Predict Differences in Overall Survival and Biochemical Failure-Free Interval
Received 12 January 2008; received in revised form 27 February 2008; accepted 29 February 2008. published online 09 May 2008.
Purpose
To characterize the demographics and survival outcomes of localized prostate cancer patients who developed biochemical failure (BF) according to a prostate-specific antigen (PSA) nadir plus 2 ng/mL.
Methods and Materials
We identified 375 prostate cancer patients who had undergone external beam radiotherapy without androgen deprivation therapy but with sufficient PSA data to study PSA kinetics. Of these patients, we identified 82 with BF. The pretreatment PSA velocity was calculated for each patient.
Results
For the BF cohort, 26% were low-risk and 74% were intermediate- or high-risk patients. Of the 82 BF patients, 16 (20%) were noted to have both low-risk disease and a pretreatment low PSA velocity of ≤2 ng/mL/y (termed “low-risk low-velocity” [LRLV]). The remaining BF patients had either intermediate- or high-risk features or a high PSA velocity >2 ng/mL/y (termed “higher risk” [HR]). For patients who had BF, the LRLV group had a delayed median time to BF of 55 months compared with 33 months for the HR patients (p = 0.04). With a median clinical follow-up of 112 months, the 5-year overall survival rate was 100% for the LRLV BF patients vs. 84% for the HR patients (p = 0.02).
Conclusions
We observed that LRLV BF patients represent a sizeable proportion of all patients with treatment failure. However, when comparing LRLV BF with HR BF patients, the former had significantly better overall survival and a longer interval to BF. This suggests that not all BF events are equivalent and emphasizes the challenges associated with using BF alone as a surrogate for a survival endpoint.
∗Department of Radiation Oncology, University of Michigan, Ann Arbor, MI
†Department of Biostatistics, University of Michigan, Ann Arbor, MI
‡Division of Radiation Oncology, Peter MacCallum Cancer Centre and University of Melbourne, Melbourne, VC, Australia
Reprint requests to: Daniel E. Soto, M.D., M.S., Department of Radiation Oncology, University of Michigan, 1500 E. Medical Center Dr., B2 C490, Box 0010, Ann Arbor, MI 48109-0010. Tel: (734) 936-4288; Fax (734) 763-7370
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ABSTRACT
In Patients Experiencing Biochemical Failure After Radiotherapy, Pretreatment Risk Group and PSA Velocity Predict Differences in Overall Survival and Biochemical Failure-Free Interval