Alpaugh, R. Katherine

3039 Background: Patients with multiple organ metastases have poorer prognoses than those with a single organ metastasis, are frequently associated with drug resistance, and have higher tumor burden. Engorged (≥50um) Cancer Associated Macrophage-Like Cells (CAMLs) are a circulating stromal cell subtype detected in the blood of patients with solid tumors at high risk for recurrence or progression. While numerous studies have shown that ≥50um CAMLs predict poor clinical outcomes, meta-analysis of these studies have also suggested that hyper engorged CAMLs ≥100um (heCAMLs) may be associated with multifocal metastatic disease and even worse outcomes. In this prospective study, we evaluated the presence of heCAMLs in patients with metastatic disease and demonstrated a strong relationship with multi organ spread, which also correlated with shorter Progression Free Survival (PFS) and Overall Survival (OS). Methods: We prospectively recruited 151 patients with metastatic (m) mbreast (n = 58), mlung (n = 34), mprostate (n = 39), and mrenal (n = 20) cancers. Peripheral blood was collected prior to the induction of new treatment for metastatic cancer. Cells were isolated following standard CellSieve techniques, then imaged and measured in ZenBlue. Multi organ metastasis was defined as spread to ≥2 distant organ sites, or any spread to the brain. Single factor ANOVA was conducted to compare heCAML presence in multi organ metastatic patients versus patients with single organ site metastasis. Univariate and multivariate analysis was run to evaluate for PFS and OS against heCAMLs, and all known clinical parameters. Results: 150 viable samples (excluding 1 failed sample) were obtained. Multi organ metastases were present in 55% (n = 83/150) of patients. heCAMLs were found in 59% (n = 49/83) of the multi organ metastatic population, but only in 16% (n = 11/67) of the single site metastatic cohort (p < 0.001). heCAML presence appeared to differentiate multi organ vs single organ metastases in mbreast (85% vs. 52%, p = 0.006), mlung (71% vs. 26%, p = 0.025), mprostate (75% vs. 37%, p = 0.029), and mRCC (88% vs. 36%, p = 0.025). Further, in all n = 150 patients, heCAML presence predicted a significantly shorter median PFS of 4.5 versus 7.2 months, 24 month PFS (HR = 1.67, 95%CI = 1.13-2.45, p = 0.013), and significantly shorter median OS of 13.1 versus 20.4 months, 24 month OS (HR = 2.05, 95%CI = 1.24-3.39, p = 0.008). Conclusions: We examined a non-invasive prognostic blood based assay to determine its relationship to multi organ metastatic spread as well as its prognostic value in several solid cancers. These results showed patients with heCAMLs had higher rates of multi organ metastases, and appear to predict for shorter PFS and OS. Studies of larger cohorts are needed for prospective validation of these initial findings.

3535 Background: Peripheral blood allows for a simple non-invasive method for isolating various cancer associated circulating stromal cells (CStCs) which may predict for cancer presence. Cancer Associated Macrophage-Like cells (CAMLs), a specific CStC, are phagocytic myeloid cells that derive from an immunological response to cancer and emanate from primary tumors. Using a filtration platform we screened the peripheral blood of untreated newly diagnosed cancer patients (n = 308) for CAMLs. In parallel, we screened patients with newly diagnosed non-malignant diseases, i.e. lupus, benign cysts, etc. (n = 39), and healthy control samples (n = 76). We found that CAMLs are highly prevalent (87%) in the blood of cancer patients, but uncommon in non-malignant conditions (20%) & absent in healthy individuals (0%). Methods: Anonymized peripheral blood were taken from 308 cancer patients after confirmation of invasive malignancy [stage I (n = 76), stage II (n = 73), stage III (n = 72), stage IV (n = 65) and unstaged non-metastatic (n = 22)] with pathologically confirmed lung (n = 65), pancreas (n = 53), breast (n = 52), prostate (n = 40), esophageal (n = 30), renal cell (n = 18), hepatocellular (n = 15), neuroblastoma (n = 10), melanoma (n = 8), and other (n = 17). Further, anonymized blood was taken from patients with untreated non-malignant conditions including benign breast masses (n = 19), lupus (n = 11), liver cirrhosis (n = 5), benign prostatic hyperplasia (BPH) (n = 3), and viral infection (n = 1); or from healthy control volunteers (n = 76). CAMLs were isolated from whole peripheral blood by the CellSieve™ microfiltration technique and defined as enlarged, multinuclear cells with cytokeratin and/or CD45/CD14 positive. Results: CAMLs were found in 87% of all cancer patients regardless of stage, ~5.4 CAMLs/7.5mL blood. Specifically, CAMLs were found in 80% of Stage I, 90% Stage II, 89% Stage III, and 97% Stage IV patients. No CAMLs were found in any healthy controls, but were found in 26% of benign breast masses, 18% of lupus, 0% of BPH and 0% of cirrhosis. In total, CAML sensitivity in cancer vs healthy was 87% (CI95% 82-90%), specificity = 100% (CI95% 95-100%), PPV = 100% (CI95% 100%), NPV = 67% (CI95% 58-71%). CAML sensitivity in cancer vs benign was 87% (CI95% 82-90%), specificity = 80% (CI95% 64-91%), PPV = 97% (CI95% 95-98%), NPV = 43% (CI95% 35-51%). Conclusions: CAMLs, a Circulating Stromal Cell subtype, is a sensitive blood based biomarker found in all stages of cancer that is rare in non-malignant conditions and absent in healthy individuals.

Abstract Background: Tumor-associated macrophages have been shown to play a critical role in metastasis, angiogenesis, and immune escape. Cancer associated macrophage-like cells (CAMLs) are circulating stromal cell with macrophage expression subtypes, detected in the peripheral blood of patients with solid tumors. We have previously shown that enlargement of CAML cells is an independent predictor of poorer overall survival and an indication of progression in patients with metastatic breast cancer (MBC). However changes in CAML sizes after induction of therapy has not been investigated. Here we evaluated the association between early changes in numbers and sizes of CAMLs as it relates to clinical response after induction of new therapy. Method: Peripheral blood samples from 29 patients with metastatic breast cancer who failed at least 2 prior lines of therapies were prospectively collected. Baseline (BL) blood samples were taken prior to initiation of a new therapy and the second samples (T1) were taken approximately 30 days after initiation of a new systemic therapy. Blood samples were filtered using CellSieveTM filtration. The quantity and size of CAMLs were measured then compared between the BL and T1 time points. Univariate analysis was used to determine the association of changes in CAML numbers and changes in CAML size, with objective response at the first follow up CT scan with progression free survival (PFS). Results: CAMLs were detected in 97% of BL samples (averaging 20.9 CAMLs/7.5ml blood) and 93% of T1 samples (averaging 18.5 CAMLs/7.5mL blood). At the time of the first follow up CT scan, 17 of 29 patients (58.6%) had progressive disease based on the RECIST criteria. Among those, 14 of 17 patients (82%) had an increase in CAML size (~85% overall enlargement) and 3/17 (18%) had a decrease CAML size (~60% overall shrinkage) in T1 samples compared to baseline. In contrast, 10 of 12 patients (83%) with clinical benefit, including stable disease and partial or complete response, had a 92% reduction in their CAML’s size and 2 of 12 patients (17%) had 61% enlargement in their CAML’s size after treatment. Overall, CAML size change after therapy induction was 83% accurate in predicting clinical benefit based on subsequent scans. Furthermore, patients with enlarging CAML size at T1 had significantly shorter PFS of 4 months compared to 10 months in patients with decreasing CAML size (HR 3.7; 95%CI1.5-10.1; p 0.020). Conclusion: CAMLs can be commonly found in most treatment-refractory metastatic breast cancer patients and their morphological size is clinically correlated to poorer survival. Our data suggests that monitoring the size changes of a patient’s CAMLs after 30 days of new treatment initiation may predict clinical benefit earlier than conventional scans and act as real time monitoring of MBCs response to new therapies. Additional studies are currently ongoing to validate these results. Citation Format: Saranya Chumsri, Markus D. Lacher, William V. Williams, R. K. Alpaugh, Stuart S. Martin, Rena Lapidus, Cha-Mei Tang, Massimo Cristofanilli, Daniel L Adams. Circulating cancer associated macrophage-like cells (CAMLs) are early predictors of response to new line therapies in metastatic breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-06-27.

605 Background: Pre-clinical and nonrandomized clinical data support synergy of the combination of bevacizumab and trastuzumab. We conducted a randomized double-blinded phase III trial of chemotherapy/trastuzumab ± bevacizumab to evaluate efficacy (PFS after treatment initiation) of the addition of bevacizumab in first-line treatment of HER2+ MBC. Methods: Days 1, 8 and 15 paclitaxel ± carboplatin were administered with trastuzumab and either placebo or bevacizumab 10 mg/kg every 2 weeks for a total of 6 months. Antibody therapy was then continued without chemo every 3 weeks, until disease progression or unacceptable toxicity. Disease assessments were performed every 3 months. Results: Ninety-six of the planned 489 analyzable patients (pts) were accrued between 2007 and 2009, at which time the study terminated due to poor accrual. Seventy % of pts were post-menopausal, 60% had ER+/HER2+ BC. Median age was 55 years (28-80). Outcomes and toxicities are summarized on the tables below. Median follow-up was 30 months. Conclusions: The combination of chemotherapy, trastuzumab, and bevacizumab did not significantly increased toxicity, and was overall safe and well tolerated. No significant differences in clinical benefit were observed between both treatment arms. Data on CTCs and Quality of Life will be presented at the meeting. This study was conducted by the Eastern Cooperative Oncology Group (Robert L. Comis, MD, Chair) and supported in part by Public Health Service Grants CA23318, CA66636, CA21115, CA32291, CA31946, CA49957, CA27525, CA14548, CA17145, CA32102, CA25224, CA49. [Table: see text] [Table: see text]

e14048 Background: Cancer associated macrophage like cells (CAMLs), a circulating stromal cell subtype, has been shown as an independent prognostic indicator of survival in late stage metastatic breast cancer when cells enlarge to ≥50µm. However, no study has evaluated the clinical relationship between changes in CAML size and their ability to predict treatment response. While CAMLs are prognostic for progression, we hypothesized that monitoring changes in CAMLs after initiation of therapy may be predictive for responsiveness of new treatment regimens. Methods: A prospective 12 months blind multi-institutional pilot study was undertaken to evaluate CAMLs before, and after, induction of a new line of investigational therapy based on CT scans. Patients with progressive metastatic breast cancer (n = 29) who had failed at least 2 prior therapies were recruited. A baseline (BL) blood sample was taken prior to induction of a new therapy and a 2nd sample (T1) taken after initiation (~30 days). Blood was filtered by CellSieve filtration.The quantities and sizes of CAMLs were analyzed based on PFS hazard ratios (HRs) by censored univariate analysis. Results: CAMLs were found in 97% of BL samples and 93% of T1 samples. At first CT scan, after the assigned dose of investigational treatment, 17 of 29 patients had clinical progression with 14/17 (82%) patients having an increased CAML size and 3/17 (18%) having a decreased CAML size. The remaining 12 of 29 patients saw clinically stable, or regression, of disease with 10/12 (83%) having decreased CAML size and 2/12 (17%) having increased CAML size. Overall CAML size change after therapy induction was 83% accurate at predicting response or progression based on CT scans. Further, patients with increasing CAML size at T1 had a 4 month mPFS vs 10 month mPFS for decreasing CAMLs, with a lower 12 month PFS HR = 3.7 (95%CI = 1.5-10.1, p = 0.020). Conclusions: Our data suggests that in metastatic breast cancer, monitoring CAMLs changes over the first 30 days of treatment accurately predicts responsiveness of disease to new treatments. Further, we suggests using blood sampling may increase the clinical value of blood based diagnostics by rapidly predicting the benefit of subsequent therapies.

11503 Background: Cancer Associated Macrophage-Like cells (CAMLs) are a recently described circulating stromal cell subtype commonly found in the peripheral blood of patients in all stages of solid malignancies and in a variety of cancer subtypes. However, while their biological association to cancer is being studied, their clinical utilization as it relates to cancer prognosis has not been evaluated. Methods: A two year prospective study was undertaken to evaluate the relationship of CAMLs and overall survival (OS) in 6 solid tumor types. The single blind multi-institutional study consisted of 269 stage I-IV patients; breast (n = 57), esophageal (n = 21), prostate (n = 43), pancreatic (n = 59), lung (n = 54), and renal cell (n = 35), in treatment (n = 134) and untreated baseline (n = 135). 7.5mL of whole blood was filtered by CellSieve microfiltration assay and CAMLs enumerated, as previously described. Patients were grouped by CAML number ( < 6 or ≥6) and by size ( < 49 or ≥50 µm) to evaluate hazard ratios (HR) by censored univariate & multivariate analysis. Results: CAMLs were identified in 93% of samples, averaging 8.2 CAMLs/7.5mL blood sample, and found in all 6 cancers at baseline and during treatment. Average CAML number was associated with disease stage and CAML positivity was 4.4 & 80% (Stage I), 4.7 & 93% (Stage II), 9.3 & 98% (Stage 3), 12.1 & 97% (Stage IV). Univariate analysis of patients (n = 269) stratified by ≥6 CAMLs had reduced OS (HR = 1.8, 95%CI 1.1-2.9, p = 0.03). Further, CAML size also had reduced OS in patients with ≥50 µm CAMLs (HR = 2.7, 95%CI 1.8-4.0, p < 0.0001). Conclusions: Our data suggests that in solid malignancies, CAML number and size appear to clinically correlate with OS in early and late stage disease. Given these results relating CAMLs with OS, further analysis is warranted to determine if CAMLs can serve as a clinically-relevant blood-based marker.