Rate of occult metastases in patients (pts) with biochemically-recurrent prostate cancer (BRPC) from a phase 2 trial of sipuleucel-T and androgen deprivation therapy (STAND)

e16516 Background: Identifying occult metastases in men with BRPC is critical, as treatment depends on disease state (biochemical recurrence vs oligometastatic disease). It is prudent to investigate pts for metastases, even men with low prostate-specific antigen (PSA) levels, to select appropriate salvage, local or systemic treatments. We evaluated baseline parameters of BRPC pts with occult metastases identified during screening for STAND (phase 2, NCT01431391). Methods: STAND eligibility criteria included prostate cancer primary therapy and PSA doubling time (PSADT) ≤12 months. Pts with metastases were excluded. We compared pts with and without metastases. Results: Of 99 screened pts, 68 entered STAND with non-metastatic BRPC, 11 (11%) failed screening due to metastases and 20 (20%) due to other reasons. In this small sample, no baseline parameters were identified that clearly distinguished between pts with or without metastases. For pts with metastases vs STAND pts, median age was similar (66 vs 65 y); all were Caucasian. Baseline median (range) PSA levels were numerically higher (4.3 [1.7–141.7] vs 2.4 [0.3–47.8] ng/mL) and PSADT values were numerically shorter (3.5 [1.1–7.6] vs 5.1 [1.0–16.4] months) for pts with metastases vs STAND pts, respectively. The proportion of pts with PSA > 10 ng/dL was 29% vs 19%, or PSADT < 6 months was 80% vs 59% for pts with metastases vs STAND pts, respectively. Baseline lactate dehydrogenase, alkaline phosphatase and hemoglobin levels were similar between groups. Conclusions: A substantial proportion (11%) of BRPC pts with presumed non-metastatic disease had undiagnosed occult metastases at low PSA levels. Such pts may benefit from closer monitoring with improved imaging technology, continuous androgen deprivation therapy or potentially docetaxel. While more rigorous screening (even at low PSA levels) may be advantageous, identifying such pts is challenging as their baseline parameters may not differ significantly vs BRPC pts with no metastases. In the future, detection of oligometastatic disease is likely to increase due to more sensitive imaging modalities, thus, the BRPC state will be reduced. Clinical trial information: NCT01431391.