An open-label, multicenter, phase 1b/2 study of RP1, a first-in-class, enhanced potency oncolytic virus in solid organ transplant recipients with advanced cutaneous malignancies (ARTACUS)

TPS9597

Background: RP1 is an oncolytic virus (HSV-1) that expresses a fusogenic glycoprotein (GALV-GP R-) and granulocyte macrophage colony stimulating factor (GM-CSF). In preclinical studies, RP1 induced immunogenic tumor cell death and provided potent systemic anti-tumor activity. Clinical data in combination with nivolumab has demonstrated a high rate of deep and durable response in patients with advanced skin cancer. Solid organ transplantation (SOT) is an important lifesaving procedure for patients with a wide range of end-organ diseases, but requires patients (pts) to undergo lifelong immunosuppression to prevent allograft rejection, and skin cancers (SCs) – including cutaneous squamous cell carcinoma (CSCC) – are common post-transplant malignancies. SC in SOT pts is generally managed with surgical resection, radiation therapy, and chemotherapy or targeted therapy. The use of immune checkpoint inhibitors in SOT recipients has improved outcomes but is associated with a high risk of allograft rejection. Thus, there is a high unmet need for a safe and effective treatment that also protects pts from allograft rejection. The objective of this study is to assess the safety and efficacy of single-agent RP1 in SOT patients with SCs, with a focus on CSCC. Methods: This study will enroll up to 65 evaluable SOT pts with locally advanced or metastatic SCs. The study has two parts. In Part A, pts will receive an initial dose of 1 x 106 plaque-forming units (PFU) of RP1. Two weeks later they will receive 1 x 107 PFU of RP1 and continue every two weeks until pre-specified study endpoints are met. In Part B, after determining the safety and tolerability in the initial cohort with kidney and liver transplants, the study may also enroll heart and lung transplant recipients. RP1 will be administered by intra-tumoral injection, utilizing image guidance as clinically appropriate. Key inclusion criteria are pts with confirmed recurrent, locally advanced or metastatic CSCC and up to 10 pts with non-CSCC SC, stable allograft function and ECOG performance status of ≤1. Pts with prior systemic anti-cancer treatment are allowed. Key exclusion criteria are prior treatment with an oncolytic therapy, active herpetic infections or prior complications of HSV-1 infection and a history of organ graft rejection within 12 months. The primary objective of the trial is to assess efficacy determined by objective response rate and safety of single agent RP1. Additional secondary endpoints include duration of response, complete response rate, disease control rate, progression-free survival and overall survival. Clinical trial information: NCT04349436.

Multicenter phase I/II trial of encorafenib with and without binimetinib in combination with nivolumab and low-dose ipilimumab in metastatic BRAF-mutant melanoma

TPS9596

Background: Targeted therapy (BRAF + MEK inhibitors) and immunotherapy (anti-PD1 + anti-CTLA4) have improved overall survival for metastatic or unresectable BRAFV600E/Kmutant melanoma. Whereas targeted therapy has a high response rate, immunotherapy may deliver longer term disease control for a larger number of patients. Despite these treatments, patients with high risk metastatic melanoma such as those with brain or liver metastases, elevated lactate dehydrogenase (LDH) and bulky disease have inferior treatment outcomes with current therapies. A BRAF+MEK+PDL1 regimen has recently emerged however the role for this treatment remains unclear. Several recent trials combining MEK inhibition and immunotherapy have failed possibly because MEK inhibition can compromise T cell activation. Meanwhile the addition of CTLA4 blockade to PD1 inhibition appears to disproportionately benefit patients with non-T cell-inflamed tumors and potentially high-risk disease. For patients with high risk BRAF-mutant metastatic melanoma, further investigation of BRAF/MEK targeted and PD-1/CTLA-4 directed immunotherapy combination strategies remains a priority. Methods: This is an open label, multi-site, Phase 1/2 study of encorafenib (Enco) +/- binimetinib (Bini) + nivolumab (Nivo) + ipilimumab (Ipi) for the treatment of patients with unresectable or metastatic BRAF-mutated melanoma in high-risk cohorts (NCT04655157). An initial regimen confirming Phase I approach will be pursued on two schedules concurrently, with patients accruing equally to each group. Group 1 will receive 3mg/kg Nivo, and 1 mg/kg Ipi and 300mg Enco (12 participants, triple therapy) and Group 2 will receive 3mg/kg Nivo and 1mg/kg Ipi and 450mg Enco and 45mg Bini, (12 participants, quadruple therapy). Dose limiting toxicity (DLT) will be evaluated weeks 1-6. A recommended Phase II regimen (RP2R) [either triple or quadruple therapy] will be carried forward into two high risk metastatic disease cohort expansions of 30 participants each. Cohort 1 will include patients with symptomatic brain metastases, while cohort 2 will include patients with elevated LDH as well as either liver metastases OR bulky visceral disease (sum of longest diameters > 44mm). Patients meeting criteria for cohorts 1 and 2 will be placed in cohort 1. Patients with symptomatic brain metastases will be included with an ECOG up to 2 and on ≤ 4mg of dexamethasone or equivalent. Continuous Bayesian toxicity monitoring will be used throughout to monitor DLT. Pre and on-treatment tumor biopsies will assess changes in the tumor microenvironment while peripheral blood ctDNA and T cell Ki67% changes will assess early response and immune activation during triplet and quadruplet therapy. Clinical trial information: NCT04655157.

A phase 1 study of neoadjuvant chemotherapy followed by concurrent chemoradiation with gemcitabine, sorafenib, and vorinostat in pancreatic cancer

e16268

Background: The multi-kinase inhibitor sorafenib (S) and HDAC inhibitor vorinostat (V) demonstrated synergism against preclinincal pancreatic cancer (PaCa) models. The combination of S & V also potently radiosensitized pancreatic cancer cells and enhanced the activity of gemcitabine (G). This led to a phase 1 trial to determine the doses and schedule appropriate for phase 2 study of S & V with weekly G and intensity modulated radiotherapy (IMRT) as neoadjuvant treatment of PaCa following chemotherapy. Methods: Using a 3+3 dose-escalation design, adult patients with resectable, borderline resectable, unresectable, and lymph node positive PaCa were enrolled to 6 dose levels. Enrolled patients had completed at least 8w of neoadjuvant chemotherapy prior to IMRT. The schedule of administration was weekly 200mg/m2 G weekly during IMRT, S & V were dosed either 3x or 5x weekly during IMRT. Primary endpoint was to identify the dose and schedule for S & V with G based chemoradiation. Key secondary endpoints included antitumor activity, R0 resection rate, OS. Correlative studies to evaluate a variety of biomarkers and Nanostring expression analysis on pre- and post-therapy tumor specimens were also performed. Results: 22 patients were enrolled and 21 treated at 6 dose levels. Due to thrombocytopenia limiting drug exposure, the trial was modified to reduce G to 200mg/m2/wk and S & V to 3 d/wk instead of 5 d/wk. 13 patients were eligible for surgery, and 9 had R0 resections. Conclusions: Our findings indicate that the study regimen was well tolerated, typical toxicities of S (hand foot syndrome) were not observed with intermittent dosing. Uncomplicated cytopenias limited drug exposure, which was improved with intermittent S&V dosing. The RP2D of the combination is S (400mg po BID 3d/wk), V (200mg po qd 3d/wk), G 200mg/m2 IV weekly, with IMRT (50.4 Gy over 28 fractions, 5d/wk). Antitumor activity was observed across dose levels, with an encouraging R0 resection rate. These results warrant further investigation of combining S and V with G and IMRT as neoadjuvant treatment of PaCa following chemotherapy. Analyses of correlative studies and OS are underway. Clinical trial information: NCT02349867. [Table: see text]

Significant antitumor activity for low-dose ipilimumab (IPI) with pembrolizumab (PEMBRO) immediately following progression on PD1 Ab in melanoma (MEL) in a phase II trial

10004

Background: Combination PD1 + CTLA4 antibodies (Abs) shows greater response rate (RR) versus PD1 Ab alone in MEL, but RR after initial PD1 Ab progression awaits robust investigation. CTLA4 Ab alone after PD1 Ab progression has a historical RR of 13%. We report final results of the first prospective clinical trial evaluating IPI 1mg/kg + PEMBRO immediately following progression on PD1 Ab (NCT02743819). Methods: Patients (pts) with advanced MEL, no prior CTLA4 Ab for metastatic disease, and who had progressed on PD1 Ab as immediately prior therapy (or non-CTLA4 Ab combination) were eligible. Pts received PEMBRO 200 mg + IPI 1 mg/kg Q3W for 4 doses, then PEMBRO alone for up to two years. The primary endpoint was RR by irRECIST. After 35 pts, the study met its primary endpoint with 10/22 evaluable pts achieving a response. The trial was expanded to enroll a total of 70 pts in open-label accrual to further describe the RR for this regimen in an exploratory fashion. The data analysis cutoff was January 30, 2020. Results: 67/70 accrued patients were evaluable for treatment response. Prior treatments included 60 on PD1 Ab alone and 10 on PD1 Ab-based combinations. Of these, 10 pts had progressed in the adjuvant setting. Median length of treatment on prior PD1 Ab was 4.8 months. Response assessments included 4 CR, 17 PR and 16 SD for a RR of 31% (21/67) in evaluable pts, and 30% (21/70) in all enrolled pts. 4 pts with a PR and 6 with SD had unconfirmed responses making the irRECIST response rate 25% (17/67) and 24% (17/70) among evaluable and enrolled pts, respectively. Median progression free survival (PFS) was 4.7 mo (95% CI: 2.8-8.3) and PFS at six months was 45% (95% CI: 33%-57%). 15/70 (21%) pts experienced ≥ grade 3-4 drug-related AEs, the most common being diarrhea, rash and transaminase elevation. PD-L1 positive vs negative status from historical tumor specimens did not associate with RR. Conclusions: This is the largest prospective study of IPI 1mg/kg + PEMBRO, demonstrating significant antitumor activity and tolerability in MEL post-PD1 Ab. Clinical trial information: NCT02743819.

Long-term outcome analysis of Y90 radioembolization in hepatocellular carcinoma

e16633

Background: Yttrium-90 (Y90) radioembolization is a catheter-based therapy utilized in the treatment of hepatic tumors such as hepatocellular carcinoma (HCC). Multiple trials have evaluated the efficacy of Y90 in HCC; few have assessed long term hepatic function. These studies reported PFS ranging from 7.9 to 18 months (m), and median OS of 17.2 to 18 m for Child-Pugh (CP) Class A and 6.0 to 7.7 m for CP Class B. This study aimed to evaluate a clinical real-world experience of Y90 therapeutic effectiveness and long-term impact on hepatic function. Methods: A single-center retrospective chart review was performed for patients with a CP score of A or B who received Y90 for primary HCC between 2008 and 2016. Model for end stage liver disease (MELD) and CP scores were calculated for the day of treatment and at 1, 3, 6, 12, and 24 m post procedure. OS and PFS were characterized using a Kaplan-Meier survival analysis and a multivariate model. Results: 134 patients were included. Mean age was 60 years old, ranging from 44-90. Underlying liver disease included HCV – 66%, ETOH cirrhosis – 23%, NAFLD – 19%, HBV – 5%. CP Class A patients (79%) had a median OS of 16.59 m (95% CI: 8.90 to 23.10m) from date of Y90 treatment compared to a median of 7.90 m (95% CI: 4.60 to 15.64 m) for CP Class B. CP Class A patients had a median PFS of 3.45 m (95% CI: 2.99 to 5.55 m) from date of Y90 treatment compared to a median of 3.71 m (95% CI: 2.07 to 8.28 m) for CP Class B patients. These differences were not statistically significant. Median OS from date of diagnosis for the entire study population was 29.37 m (95% CI: 23.00 to 38.77 m). MELD scores were statistically significantly higher at 1, 3, 6 and 12 m post-treatment than on Day 0, with significant recovery at 24 vs 3 m. Older age, higher T stage, higher MELD and CP scores, and patients with a history of portal vein thrombosis (PVT) had significantly lower OS. PFS was significantly shorter in those with advanced stage at diagnosis and higher CP score. Conclusions: While our study supports the literature for OS in Y90 patients, we found a shorter PFS in this population. This may reflect the utilization of RECIST in clinical trials vs clinical radiology practice in determining progression. Over time, the most significant factors associated with OS were age, MELD and CP scores and PVT. For PFS, CP score and stage at diagnosis were significant. The increasing MELD and CP scores over time reflect a possible mix of radio embolization‐induced liver disease and progression of HCC. The downtrend at 24 m is likely due to durable survivors with significant benefit from therapy and no long-term complications from Y90.

Phase I study of regorafenib and sildenafil in advanced solid tumors

3593

Background: Regorafenib (R) is an oral multikinase inhibitor with anti-angiogenic properties approved for use in several solid tumors. Sildenafil (S) is an oral phosphodiesterase-5 (PDE5) inhibitor that interacts synergistically with R in both short-term and colony formation assays to kill multiple cancer cell types. Mechanistic studies identified that PDE5 knockdown enhances R lethality, suggesting a direct target effect for S. Methods: A single-center, open-label, dose-escalation study was conducted in adults with advanced solid tumors. Patients (pts) took R (120 or 160 mg) and S (50 or 100 mg) once daily days 1 through 21 of each 28-day cycle. Pts remained on study treatment until progression or excessive toxicity, with response assessments every 8 wks. The maximum tolerated dose (MTD) was defined as the maximum tested dose with ≤1/6 pts experiencing dose-limiting toxicity (DLT), with Cycle 1 as the DLT observation period. Results: 32 pts were enrolled and 29 treated at 3 dose levels (DLs). Median duration of treatment was 8 (range 2 – 101) wks. One of 6 evaluable pts treated at DL2 (160 mg R + 50 mg S) experienced DLT (grade 4 lipase increase). One of 12 evaluable pts treated at DL3A (160 mg R + 100 mg S, the MTD) experienced DLT (grade 3 rash and grade 3 muscle pain). The toxicity profile was generally consistent with that seen in R monotherapy at FDA-approved doses. 10 pts had a best response of progressive disease (PD). 14 pts had a best response of stable disease (SD), 5 of whom had stable disease duration > 24 wks. 5 treated pts were not evaluable for response. Notably, 2 pts with ovarian cancer and 1 with cervical cancer had stable disease > 24 wks. Analyses of correlative studies to examine pharmacokinetics and drug combination pharmacodynamic effects are underway. Conclusions: The combination was well-tolerated. The recommended phase 2 dose is 160 mg R + 100 mg S. Objective responses were not observed, but prolonged stable disease was seen in a subset of pts. Encouraging disease control was seen in gynecologic cancers. Dosing up to 100 mg S is safe concurrently with standard doses of R, and may be considered as an adjunct to R in future trials. Evaluation of R+S in gynecologic cancers warrants further consideration. Clinical trial information: NCT02466802 . [Table: see text]

Pembrolizumab versus placebo as adjuvant therapy in resected high-risk stage II melanoma: Phase 3 KEYNOTE-716 study

TPS9596

Background: Adjuvant pembrolizumab showed significantly longer recurrence-free survival than placebo in patients with resected stage III melanoma in the KEYNOTE-054 study. KEYNOTE-716 (NCT03553836) is a randomized, placebo-controlled, double-blind, multicenter phase 3 study of adjuvant pembrolizumab in patients with surgically resected high-risk stage II melanoma. Methods: Key eligibility criteria are age ≥12 y with newly diagnosed, completely resected stage IIB/IIC cutaneous melanoma, defined by the AJCC Cancer Staging Manual, 8th edition (wide excision and negative sentinel lymph node biopsy with no evidence of distant metastasis). Patients with mucosal or uveal melanoma or prior treatment (including radiation) for melanoma beyond resection of primary disease within 12 wk of the start of study treatment were excluded. In this 2-part study, in the double-blind phase (part 1), patients will be randomly assigned 1:1 to receive pembrolizumab 200 mg for patients ≥18 y or 2 mg/kg for patients ≥12 y to < 18 y (maximum dose, 200 mg) or placebo every 3 wk for 17 cycles. Study treatment will begin within 12 wk of complete resection. Tumor imaging will be performed every 24 wk while treatment is ongoing, at the end of treatment, every 6 mo for the first 3 y off treatment, and then yearly for up to 2 y or until recurrence (up to 5 y of total imaging). Adverse events will be recorded until 30 d after treatment end (90 d for serious AEs) and graded per National Cancer Institute Common Terminology Criteria for Adverse Events, version 4.0. In the unblinded phase (part 2), patients with confirmed recurrence may be rechallenged (patients received pembrolizumab in part 1) or crossed over to pembrolizumab (patients received placebo in part 1). Resected local or distant recurrence or unresectable disease will be treated for an additional 17 or 35 cycles, respectively. Tumor imaging in part 2 will occur every 12 wk during treatment. The primary end point is recurrence-free survival; secondary end points are distant metastasis-free survival, overall survival, and safety. Approximately 954 patients will be enrolled. Clinical trial information: NCT03553836.

Final analysis of phase II trial of regorafenib (REG) in refractory advanced biliary cancers (BC)

4083

Background: While gemcitabine plus cisplatin has demonstrated significant antitumor activity as 1st line therapy of BC, there is no effective treatment after failure of gemcitabine-based therapy. REG is an oral multi-kinase inhibitor that targets angiogenesis, oncogenesis and cancer proliferation/metastasis. We evaluated the efficacy of REG in BC. Methods: Patients (pts) with histologically proven BC who progressed on at least one line of systemic therapy received REG 160 mg daily 21 days on 7 days off, in 28 day cycles. The primary endpoint was 6-month (mo) overall survival (OS) and the secondary endpoints were median OS, progression free survival (PFS) and response rates (RR). Pre and post-treatment plasma were collected for cytokine evaluation. Results: A total of 39 pts received at least 1 dose of REG; 32 pts were evaluable for efficacy. Median age was 62 (range: 27-88) years and the primary sites of tumor were intrahepatic cholangiocarcinoma (68.8%), extrahepatic (18.8%), and gallbladder (12.5%). Pts were considered evaluable for efficacy if patients received more than 1 cycle of REG. For 32 evaluable pts, 6 mo OS was 52% with median PFS of 2.8 mo (95% CI: 1.1-4.5) and median OS of 7.9 mo (95% CI: 0-18.7). Median PFS and OS of the pts (n=20) failed 1 line of therapy were 3.7 mo (95% CI: 3.2-4.1) and 13.8 mo (95% CI: 1.8-25.8), respectively. Median PFS and OS of the pts (n=12) failed 2 lines were 1.8 mo (95% CI: 1.63-1.97) and 4.5 mo (95% CI: 2.6-6.3), respectively. RR was 9.4% (2 PR and 1 unconfirmed PR) and DCR was 62.5%. Total 71.8% of grade 3/4 adverse events (AE) were observed, and the most common AE were fatigue (56.4%) and hypertension (53.8%). Dose modification was required in 49% of the pts. Among the 23 cytokines analyzed, elevated baseline VEGF-A was associated with good prognosis (HR 0.62, p=0.01). Elevated baseline TIMP-1 (HR 1.79, p=0.04) and IL-6 (HR 1.33, p=0.05) were associated with poor prognosis. REG treatment decreased BMP-9, GP130, VEGF-R2 and VEGF-R3 and increased IL-6, PIGF, TIMP-1, VCAM-1 and VEGF-A significantly. Conclusions: The primary endpoint was met in this study. VEGF-A may be further evaluated as a predictive biomarker for REG in BC. Further randomized trials are warranted to confirm the efficacy and the correlative data. Clinical trial information: NCT02115542.

Phase III KEYNOTE-716 study: Adjuvant therapy with pembrolizumab versus placebo in resected high-risk stage II melanoma

TPS145

Background: Adjuvant pembrolizumab showed significantly longer recurrence-free survival compared with placebo in resected stage III melanoma in the KEYNOTE-054 study [1]. KEYNOTE-716 is a randomized, placebo-controlled, multicenter phase 3 study of adjuvant pembrolizumab in patients with surgically resected high-risk stage II melanoma. Methods: Patients must be ≥12 years of age and have newly diagnosed, completely resected stage IIB/IIC cutaneous melanoma, defined by the AJCC Cancer Staging Manual, 8th edition [2] (wide excision and negative sentinel lymph node biopsy, with no evidence of distant metastasis). Patients cannot have mucosal or uveal melanoma or have received prior treatment for melanoma, including radiation, beyond resection of primary disease within 12 weeks of the start of study therapy. The study has a 2-part design. In the double-blind phase (part 1), patients will be randomly assigned 1:1 to receive pembrolizumab 200 mg for patients ≥18 years or 2 mg/kg for patients 12-17 years (maximum dose, 200 mg) or placebo every 3 weeks for 17 cycles. Stratification: 1 stratum for pediatric patients (12-17 years); 3 strata for adult patients per T stage (T3b/T4a/T4b). Study treatment will begin within 12 weeks of complete resection. Tumor imaging will be performed every 24 weeks while treatment is ongoing, at the end of treatment, every 6 months for the first 3 years off treatment, and then yearly for up to 2 years or until recurrence (up to 5 years of total imaging). Adverse events will be graded per NCI Common Terminology Criteria for Adverse Events, version 4.0. In the unblinded phase (part 2), patients with confirmed recurrence may be rechallenged (patients received pembrolizumab in part 1) or crossed over to pembrolizumab (patients received placebo in part 1). Resected local or distant recurrence or unresectable disease will be treated for an additional 17 or 35 cycles, respectively. Tumor imaging in part 2 will occur every 12 weeks while treatment is ongoing. The primary end point is recurrence-free survival; secondary end points are distant metastasis-free survival, overall survival, and safety. Approximately 954 patients will be enrolled. Clinical trial information: NCT03553836.

Multi-institutional phase II trial of single agent regorafenib in refractory advanced biliary cancers

TPS468

Background: Currently, there is no standard second line treatment for patients with advanced biliary tract cancer (BC) who have failed prior systemic therapy. Aberrant activation of the Ras/Raf/MEK/ERK pathway occurs in more than 60% of BC indicating the importance of this pathway in biliary carcinogenesis. Furthermore anti-angiogenic agents such as the VEGF-antagonist bevacizumab, and the multikinase inhibitor sorafenib have been tested in BC in the first line setting with modest activity. Regorafenib is an oral multi-kinase inhibitor that targets multiple membrane-bound and intracellular kinases including VEGF, the Ras/Raf/MEK/ERK and PDGFR- ß pathways. Given the pivotal role of these pathways in biliary cancer biology, the clinical evaluation of regorafenib represents a novel and rational approach to treat this disease. Methods: This is a multi-institutional phase II single arm single-stage design trial using regorafenib as single agent. Patients with histologically or cytologically-proven locally advanced or metastatic biliary tract carcinomas that failed no more than 2 prior line of systemic chemotherapy are eligible for this study. Patients must have measurable disease per RECIST 1.1 criteria and never been treated with VEGF inhibitors. Patients will receive regorafenib 160 mg daily (21 days on and 7 days off) and will be evaluated for response every 2 cycles (1cycle = 28 days). The study’s primary endpoint is 6 month overall survival. Secondary endpoints are to define disease control, progression-free survival and toxicity related to treatment. Correlative biomarker studies using plasma samples will be performed to investigate levels of 40 relevant proteins associated with the above-mentioned pathways in the attempt to identify predictive markers of drug benefit. As per September 2015, twelve of the 39 planned patients have been accrued for the study. In addition to Moffitt Cancer Center, this trial will enroll patients at the UNC Lineberger Comprehensive Cancer Center and VCU Massey Cancer Center. Clinical trial information: NCT02115542.

Evaluation of dickkopf-1 (Dkk-1) expression in non-small cell lung, esophageal, and gastric cancer

e22203

Background: Dkk-1 is an inhibitor of the canonical Wnt/β-catenin signaling pathway. Inhibition of Wnt pathway results in the stabilization of β-catenin, leading to target gene expression such as cyclin D1, c-myc, VEGF and other factors associated with cell growth. Elevated levels of serum Dkk-1 in a variety of tumor types are well established, and are hypothesized to have a negative prognostic value. Tumor tissue expression of Dkk-1 has not been systematically examined. We evaluated Dkk-1 expression in various tumors. Methods: Utilizing an anonymous banked tumor repository, we identified 119 patient samples (NSCLC (squamous, n=19; adenocarcinoma, n=47), esophageal (squamous, n=15; adenocarcinoma, n=17) and gastric (n=20)). Immunohistochemical (IHC) staining was performed using commercially available antibodies. One pathologist evaluated all slides using IHC staining quantification on a 4-point scale (0, 1+, 2+, 3+). Results: Dkk-1 expression is more pronounced in tumor tissues than peritumoral normal tissues of lung and esophagus. Unexpectedly, Dkk-1 expression is seen in two staining patterns, perinuclear and cytoplasmic that varied by primary location and histology. Conclusions: Elevated Dkk-1 expression is demonstrated in lung, esophageal and gastric cancer regardless of histology. All except squamous cell lung express perinuclear Dkk-1 more frequently than cytoplasmic pattern. Additional studies are needed to understand significance of these patterns and potentially define Dkk-1 as a novel therapeutic target in these malignancies. [Table: see text]

ApoStream, an antibody-independent platform, compared to CellSearch for enumeration of circulating tumor cells (CTCs) in patients with metastatic prostate cancer

e21058

Background: Development of CTC detection platforms is a rapidly advancing field. The CellSearch technique relies on cell surface expression of EpCAM to select for rare tumor cells in whole blood specimens. Consequently, the use of EpCAM-based enrichment platforms to recover CTCs is limited to EpCAM expressing cells and is poorly suited for recovery of EpCAM negative cells like those having undergone epithelial mesenchymal transition (EMT). ApoStream is an antibody independent enrichment platform which utilizes the principle of continuous flow dielectrophoresis field-flow fractionation (DEP-FFF) to isolate and enrich for CTCs. A head to head comparison of CellSearch to ApoStream for recovery of CTCs in patients with metastatic prostate cancer was performed. Methods: Two 7.5 mL bloodsamples were collected at a single time point for each patient with stage IV prostate cancer. One sample was analyzed by CellSearch CTC enumeration kit, and one sample was analyzed by ApoStream. CTCs recovered by both devices were immunophenotyped using antibodies against cytokeratin (CK), CD45 and DAPI. CTCs were defined as CK+/CD45-/DAPI+ intact cells. CTCs recovered by ApoStream were further analyzed by quantitative laser scanning cytometry (LSC). A paired t-test was used to compare the cell counts in the two devices. Results: The ApoStream CTC enrichment platform isolated a greater number of CTCs from blood of eight patients compared to CellSearch (p= 0.0027). All cell counts obtained by the ApoStream technique were higher than CellSearch, and all patients had detectable CTCs by ApoStream, while only 75% of patients had detectable CTCs with CellSearch. Conclusions: The ApoStream platform is differentiated from EpCAM dependent platforms and is well suited for detection and recovery of CTCs in advanced stage disease where tumor cell heterogeneity is common and expression of EpCAM may be low or lost. [Table: see text]