Abstract
ObjectivePrior studies have suggested that prostate-specific antigen (PSA) nadir of 0.5 ng/mL is an important surrogate endpoint for prostate cancer-specific and all-cause mortality. This study analyzed our well-followed patient cohort to assess whether this endpoint was associated with differences in prostate cancer-specific endpoints in patients receiving dose-escalated radiation.MethodsPatients with intermediate- or high-risk prostate cancer (≥T2b, or prostate-specific antigen >10 ng/mL, or Gleason score ≥7) who were treated with external beam radiation to a minimum dose of 7560 cGy +/- androgen deprivation between 2003 and 2011 were identified. Biochemical control, distant metastasis-free survival (DMFS), prostate cancer-specific survival (PCSS), and overall survival (OS) were compared between those who achieved a nadir PSA ≤0.5 ng/mL with those who did not via Kaplan-Meier analysis. Univariable and multivariable Cox regression was performed on all endpoints to assess their impact on OS.ResultsThere were 367 patients identified with a median follow-up of 99.5 months. Two hundred five patients (55.9%) received androgen deprivation for a median of 24 months (range 1-81 months). Most patients (n = 308, 83.9%) achieved a nadir PSA ≤0.5 ng/mL, which was associated with improvement across all endpoints at 10 years. This included biochemical control (68.0% versus 24.0%, p < 0.001), DMFS (89.6% versus 80.8%, p = 0.019), PCSS (91.1% versus 85.7%, p = 0.01), and OS (55.7% versus 45.8%, p = 0.048). On multivariable analysis, nadir PSA >0.5 ng/mL remained strongly associated with worse outcomes across all endpoints.ConclusionsAchievement of nadir PSA ≤0.5 ng/mL after completion of dose-escalated radiation therapy was associated with improvement of all prostate cancer endpoints.
Highlights
Prostate cancer is the most common genitourinary cancer with a lifetime risk estimated to be approximately one in six for men in the United States [1]
Most patients (n = 308, 83.9%) achieved a nadir prostate-specific antigen (PSA) ≤0.5 ng/mL, which was associated with improvement across all endpoints at 10 years
Nadir PSA >0.5 ng/mL remained strongly associated with worse outcomes across all endpoints
Summary
Prostate cancer is the most common genitourinary cancer with a lifetime risk estimated to be approximately one in six for men in the United States [1]. There are several definitive treatment options available for prostate cancer including external beam radiation therapy (EBRT), brachytherapy, or surgery. After completion of radiation therapy (RT), biochemical failure is generally defined as a 2.0 ng/mL or higher rise in prostate-specific antigen (PSA) above the PSA nadir [3]. This definition does not always translate to other important clinical endpoints, such as metastases and prostate cancer-specific death [4]. A patient may die of any one of multiple competing risks and not necessarily due to prostate cancer. Several studies have sought to identify other prognostic PSA
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