Is it possible to compare PSA recurrence-free survival after surgery and radiotherapy using revised ASTRO criterion--"nadir + 2"?

OBJECTIVES

The new American Society for Therapeutic Radiology and Oncology/Radiation Therapy Oncology Group consensus definition of biochemical failure after radiotherapy for prostate cancer is defined as a prostate-specific antigen level at or greater than the absolute nadir PSA level plus 2 ng/mL. Because this definition inevitably will be used to compare cancer control rates after radiotherapy to those after surgery, this study examined the effect of this comparison.

METHODS

We reviewed the data from 2570 men who had undergone radical prostatectomy from 1985 to 2004. Biochemical failure was defined as any measurable PSA level of 0.2 ng/mL or greater. We evaluated how the nadir+2 definition affected the failure rate when applied to this series.

RESULTS

The actuarial 5, 10, and 15-year biochemical recurrence-free survival probability with failure defined as a PSA level of 0.2 ng/mL or more and a PSA level of 2 ng/mL or more was 88.6%, 81.2%, and 78.1% and 94.6%, 89.4%, and 84.3%, respectively (P <0.0001). The median time to biochemical progression was 2.8 years for the greater than 0.2 ng/mL definition and 7.9 years for the 2 ng/mL or more definition. The nadir+2 definition systematically overestimated the biochemical recurrence-free survival, even after stratifying patients into standard prognostic risk groups, especially in men who developed local recurrence.

CONCLUSIONS

When applied to a mature series of surgically treated patients with localized prostate cancer, the American Society for Therapeutic Radiology and Oncology "nadir+2" definition resulted in a systematic delay in the determination of biochemical failure. Because patients in this series who experienced a detectable PSA level took more than 5 years to progress to a PSA level of 2 ng/mL or greater, the 5-year biochemical control rates with the definition of 0.2 ng/mL or more should be compared with the 10-year biochemical control rates using the nadir+2 definition.