Baseline Circulating Tumor Cell Count as a Prognostic Marker of PSA Response and Disease Progression in Metastatic Castrate-Sensitive Prostate Cancer (SWOG S1216).

PURPOSE: In metastatic castrate-sensitive prostate cancer (mCSPC), combined androgen axis inhibition is a standard of care. Noninvasive biomarkers that guide initial therapy decisions are needed. We hypothesized that CellSearch circulating tumor cell (CTC) count, an FDA-cleared assay in metastatic castrate-resistant prostate cancer (mCRPC), is a relevant biomarker in mCSPC. EXPERIMENTAL DESIGN: SWOG S1216 is a phase III prospective randomized trial of androgen deprivation therapy (ADT) combined with orteronel or bicalutamide for mCSPC. CellSearch CTC count was measured at registration (baseline). Prespecified CTC cut-off points of 0, 1-4, and ≥5 were correlated with baseline patient characteristics and, in a stratified subsample, were also correlated with two prespecified trial secondary endpoints: 7-month PSA ≤0.2 ng/mL versus 0.2-4.0 versus >4.0 (intermediate endpoint for overall survival); and progression-free survival (PFS) ≤ versus >2 years. RESULTS: A total of 523 patients submitted baseline samples, and CTCs were detected (median 3) in 33%. Adjusting for two trial stratification factors (disease burden and timing of ADT initiation), men with undetectable CTCs had nearly nine times the odds of attaining 7-month PSA ≤ 0.2 versus > 4.0 [OR 8.8, 95% confidence interval (CI), 2.7-28.6, P < 0.001, N = 264] and four times the odds of achieving > 2 years PFS (OR 4.0, 95% CI, 1.9-8.5, P < 0.001, N = 336) compared with men with baseline CTCs ≥5. CONCLUSIONS: Baseline CTC count in mCSPC is highly prognostic of 7-month PSA and 2-year PFS after adjusting for disease burden and discriminates men who are likely to experience poor survival outcomes.

Everolimus Exposure as a Predictor of Toxicity in Renal Cell Cancer Patients in the Adjuvant Setting: Results of a Pharmacokinetic Analysis for SWOG S0931 (EVEREST), a Phase III Study (NCT01120249).

BACKGROUND: S0931 is assessing recurrence-free survival in renal cell carcinoma (RCC) patients randomized to receive everolimus (EVE) versus placebo for one year following nephrectomy. Due to a higher than expected dropout rate, we assessed EVE trough levels in the adjuvant setting to evaluate the relationship between EVE exposure and probability of toxicity. METHODS: Patients received 10 mg daily EVE for nine 6-week cycles. Pre-dose whole blood samples were collected pre-cycle 2 and pre-cycle 3 and analyzed for EVE. Patients with pre-cycle 2 and/or pre-cycle 3 EVE results were used in the analysis. Patients were segregated into quartiles (Q) based on EVE levels and logistic regression was used to model the most common adverse event outcomes using EVE trough as a predictor. Hazard and odds ratios were adjusted for age, BMI and performance status. RESULTS: A total of 467 patients were included in this analysis. Quartiles normalized to an EVE dose of 10 mg/day were < 9.0, 9.0-12.9, 12.9-22.8, and > 22.8 ng/mL, respectively. EVE trough levels increased with increasing age (p < 0.001). Furthermore, EVE trough levels were higher in men than women (19.4 versus 15.4 ng/mL, p = 0.01). Risk of grade 2 + triglycerides was increased in Q2 and Q3 vs Q1 (OR = 2.08; p = 0.02 and OR = 2.63; p = 0.002). Risk of grade 2 + rash was increased in Q2 and Q4 vs Q1 (OR = 2.99; p = 0.01 and OR = 2.90; p = 0.02). There was also an increased risk of any grade 3 + tox in Q2 vs Q1 (OR = 1.71; p = 0.05). CONCLUSIONS: We identified significant gender and age-related differences in EVE trough levels in patients receiving adjuvant treatment for RCC. Furthermore, our analysis identified significant associations between EVE exposure and probability of toxicity.

Circulating tumor cell counts are prognostic of overall survival in SWOG S0421: a phase III trial of docetaxel with or without atrasentan for metastatic castration-resistant prostate cancer.

PURPOSE: Circulating tumor cell (CTC) enumeration has not been prospectively validated in standard first-line docetaxel treatment for metastatic castration-resistant prostate cancer. We assessed the prognostic value of CTCs for overall survival (OS) and disease response in S0421, a phase III trial of docetaxel plus prednisone with or without atrasentan. PATIENTS AND METHODS: CTCs were enumerated at baseline (day 0) and before cycle two (day 21) using CellSearch. Baseline counts and changes in counts from day 0 to 21 were evaluated for association with OS, prostate-specific antigen (PSA), and RECIST response using Cox regression as well as receiver operator characteristic (ROC) curves, integrated discrimination improvement (IDI) analysis, and regression trees. RESULTS: Median day-0 CTC count was five cells per 7.5 mL, and CTCs < versus ≥ five per 7.5 mL were significantly associated with baseline PSA, bone pain, liver disease, hemoglobin, alkaline phosphatase, and subsequent PSA and RECIST response. Median OS was 26 months for < five versus 13 months for ≥ five CTCs per 7.5 mL at day 0 (hazard ratio [HR], 2.74 [adjusting for covariates]). ROC curves had higher areas under the curve for day-0 CTCs than for PSA, and IDI analysis showed that adding day-0 CTCs to baseline PSA and other covariates increased predictive accuracy for survival by 8% to 10%. Regression trees yielded new prognostic subgroups, and rising CTC count from day 0 to 21 was associated with shorter OS (HR, 2.55). CONCLUSION: These data validate the prognostic utility of CTC enumeration in a large docetaxel-based prospective cohort. Baseline CTC counts were prognostic, and rising CTCs at 3 weeks heralded significantly worse OS, potentially serving as an early metric to help redirect and optimize therapy in this clinical setting.