• Michael E Ray, Larry B Levy, Eric M Horwitz, Patrick A Kupelian, Alvaro A Martinez, Jeff M Michalski, Thomas M Pisansky, Michael J Zelefsky, Anthony L Zietman, and Deborah A Kuban.
• Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan 48109-0010, USA. mray@umich.edu
• Urology. 2006 Dec 1; 68 (6): 1257-62.

ObjectivesTo determine whether nadir prostate-specific antigen (PSA) levels within 12 months (nadir PSA12) after completion of radiotherapy (RT) can be used as an early marker of recurrence risk.MethodsA total of 4839 patients were treated with RT and without hormonal therapy from 1986 to 1995 for Stage T1-T2 prostate cancer at nine institutions. Of these 4839 patients, 4833, with a median follow-up of 6.3 years, met the criteria for analysis. The study endpoints included freedom from PSA failure, initiation of androgen deprivation, or documented local or distant failure (PSA-DFS); freedom from clinically apparent distant metastasis (DMFS); and overall survival (OS).ResultsPatients with a nadir PSA12 of 2.0 ng/mL or less had an 8-year PSA-DFS, DMFS, and OS rate of 55%, 95%, and 73%, respectively, compared with 40%, 88%, and 69%, respectively, for patients with a nadir PSA12 of more than 2.0 ng/mL. Multivariate analysis confirmed that a nadir PSA12 of greater than 2 ng/mL was an independent predictor of PSA-DFS, DMFS, and OS. Classification and regression tree analysis identified the nadir PSA12 levels after RT associated with PSA-DFS, DMFS, and OS. Nadir PSA12, combined with the pretreatment PSA level, identified patients at particularly high risk of distant metastasis.ConclusionsThe results of this large, multi-institutional study have demonstrated that nadir PSA12 is predictive of clinical outcomes for patients with localized prostate cancer after RT. A high pretreatment PSA level and high nadir PSA12 will identify patients at particularly high risk who might benefit from early adjuvant therapy.

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