Molecular Targets and Therapies for Ampullary Cancer

Ampullary carcinomas are rare but increasing in incidence. Ampullary cancers have molecular alterations that guide choice of therapy, particularly in nonresectable cases. These alterations can be more common by subtype (intestinal, pancreaticobiliary, or mixed), and next-generation sequencing is recommended for all patients who cannot undergo surgery. In this article, we review the approach to tissue acquisition and consideration for molecular testing. Common molecular targets of interest in ampullary cancer are also discussed in this review, including HER2/ERBB2, HER3, tumor mutational burden, microsatellite instability, KRAS, and germline BRCA and ATM mutations, along with emerging and rarer alterations.

Treatment of Oligometastatic GI Cancers

Oligometastatic state is believed to potentially represent a transitional stage between early, locoregional state disease and widely metastatic disease. Historically, locoregional approaches, particularly in advanced colorectal cancers, have demonstrated efficacy in select patients with limited burden of metastatic disease. Recent strides in systemic therapies, including biomarker-based treatments and immunotherapy, alongside innovations in surgical techniques and novel locoregional approaches such as stereotactic radiotherapy and ablation, have ushered in a new era of therapeutic possibilities across all oligometastatic GI cancers. Despite these advancements, there remains a significant gap in high-quality prospective evidence guiding patient selection and treatment decisions across various disease types. Ongoing clinical trials are anticipated to provide crucial insights into oligometastatic states, fostering the refinement of disease-specific oligometastatic state definitions and treatment algorithms. This article reviews existing data on the management of oligometastatic GI cancer, summarizes current state of knowledge for each disease state, and provides updates on ongoing studies in this space.

Neoadjuvant Stereotactic MR-Guided Ablative Radiation Therapy (SMART) and Surgical Outcomes in Patients with Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

The benefit of neoadjuvant radiation therapy for patients undergoing surgery for pancreatic ductal adenocarcinoma (PDAC) remains unclear. Stereotactic MR-guided adaptive radiation therapy (SMART) treatment to ablative doses is a newer technique that is well tolerated and has increased local control in unresectable pancreatic cancer. For resectable pancreatic cancer, neoadjuvant SMART has the potential to decrease local recurrence risk and positive margin rates. However, there is concern for perioperative risks associated with ablative dose treatments. We report the efficacy and safety of surgical resection in patients who have received neoadjuvant SMART at our institution.

MATERIALS/METHODS

We conducted a retrospective analysis of all consecutive patients diagnosed with PDAC who had noted vascular involvement of the celiac axis, superior mesenteric, and/or portal vessels between January 2016 and December 2022 at a single, high-volume, academic institution. Perioperative events were defined according to the Clavien-Dindo classification. The Kaplan Meier method was applied to estimate disease free survival (DFS) and overall survival (OS).

RESULTS

Seventeen patients with PDAC and vessel involvement at time of diagnosis who received SMART were included. Median follow-up time was 14.3 months; all patients underwent surgery, at a median time after radiation of 28 days (range: 15 - 90). Median length of postoperative stay was 7 days (range: 3 - 15). Five patients (29%) underwent vascular resection. Fifteen patients (88%) achieved R0 resection, with two R1 resections noted at the SMA and pancreatic neck respectively. Seven patients (41%) had adverse events attributable to surgery, with the majority being defined as abscess or infection (n = 5; 29%). One (6%) Clavien-Dindo grade III or higher toxicity was observed - a cortical cerebrovascular event following surgery. No major bleeding events requiring surgical intervention were noted. At time of event censorship, there were no observable locoregional failures. The median DFS and OS were not reached; however, 1-year DFS and OS were 62% and 87%, respectively.

CONCLUSION

Neoadjuvant SMART appears to be safe, with low rates of surgical complications and promising outcomes. Further identification of patients for this approach requires additional investigation.

Abstract 5327: Automated organoid alignment for clonal response characterization in pancreatic ductal adenocarcinoma

Background: Therapeutic screening Pancreatic Ductal Adenocarcinoma (PDAC) relies on well-level assessment for high throughput response evaluation. Patient-derived cancer organoids (PCOs) model subclonal populations, however the significance of resistant populations is uncertain when characterized with well-level response. Using a high-throughput screening assay, we present an automated alignment algorithm to characterize populations of organoid growth as compared to validated well-level therapeutic response assays.

Methods: High content imaging was performed in low volume (10uL), 96-well angiogenesis plating format (Ibidi, Inc) at 4x objective with 5-frame Z-stack (600um) with brightfield imaging captured at 0h and 72h. Images underwent processing using Gen5 suite (Biotek, Inc) including Z-projection to render organoids into single two-dimensional planes. Baseline objects were defined between 50µm and 750µm, and filtration based on circularity defined as >0.4. Object alignment was performed based on root-mean-square-deviation (RMSD) between all combinations of objects to optimize match determination. This analysis was performed in drug screen of 80 independent agents in early clinical trials in combination with CDK7 inhibitor, SY-5609. Well level viability was performed using standardized 3D CellTiterGlo (CTG, Promega Inc.) (33% v/v). Response was assessed using descriptive statistics, effect size (Glass’s Δ), and Therapeutic Sensitivity Index (TSI) defined as the weighted average between elements with growth from media control versus treated population.

Results: Z projection of 600um in Low-volume plating (10µL) of matrix suspension yielded 1.68 organoids per µL relative to the traditional hanging drop design (50µL) 0.75 organoids per µL (p<0.005). Organoid alignment across the continuum of RMSD yielded maximum successful matches at 75µm with 66.1% of objects versus 6.7% based on randomly assigned objects across validation experimental sets (n=1380). An optimal circularity value was determined at 0.4; an increase of circularity by 0.1 yielded a >5% reduction in of matched objects, while a decrease in circularity by 0.1 yielded a <5% reduction in unmatched objects. A poor correlation was seen for the percent of growing organoids within a population and well level normalized viability via CTG (R = 0.37). The normalized CTG value had improved in correlation when compared to effect size relative to control (R = 0.54) and TSI (R = 0.56).

Conclusion: We provide a method for high fidelity alignment of PCOs in low-volume format for matrix-based screening applications. These techniques can be adapted to existing staining protocols to characterize subclonal response in the context of both molecular heterogeneity and clinical outcomes.

Citation Format: Ethan Samuel Lin, Md Shahadat Hossan, Austin Stram, Eleanor E. Riedl, Luke J. Koeppel, Jaimie M. Warner, Jeremy D. Kratz. Automated organoid alignment for clonal response characterization in pancreatic ductal adenocarcinoma. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5327.

Spatial Alignment of Organoids Tracking Subclonal Chemotherapy Resistance in Pancreatic and Ampullary Cancer

Pancreatic and ampullary cancers remain highly morbid diseases for which accurate clinical predictions are needed for precise therapeutic predictions. Patient-derived cancer organoids have been widely adopted; however, prior work has focused on well-level therapeutic sensitivity. To characterize individual oligoclonal units of therapeutic response, we introduce a low-volume screening assay, including an automated alignment algorithm. The oligoclonal growth response was compared against validated markers of response, including well-level viability and markers of single-cell viability. Line-specific sensitivities were compared with clinical outcomes. Automated alignment algorithms were generated to match organoids across time using coordinates across a single projection of Z-stacked images. After screening for baseline size (50 μm) and circularity (>0.4), the match efficiency was found to be optimized by accepting the diffusion thresholded with the root mean standard deviation of 75 μm. Validated well-level viability showed a limited correlation with the mean organoid size (R = 0.408), and a normalized growth assayed by normalized changes in area (R = 0.474) and area (R = 0.486). Subclonal populations were defined by both residual growth and the failure to induce apoptosis and necrosis. For a culture with clinical resistance to gemcitabine and nab-paclitaxel, while a therapeutic challenge induced a robust effect in inhibiting cell growth (GΔ = 1.53), residual oligoclonal populations were able to limit the effect on the ability to induce apoptosis (GΔ = 0.52) and cell necrosis (GΔ = 1.07). Bioengineered approaches are feasible to capture oligoclonal heterogeneity in organotypic cultures, integrating ongoing efforts for utilizing organoids across cancer types as integral biomarkers and in novel therapeutic development.

Abstract A073: Multiplexed therapeutic sensitivity of patient derived pancreatic cancer organoids after neoadjuvant chemotherapy by high content imaging

Background: Therapeutic development in pancreatic ductal adenocarcinoma (PDAC) requires accurate models for assessing response. Patient-derived cancer organoids (PCOs) have been shown to faithfully recapitulate genomic features of advanced PDAC. Mechanisms of subclonal resistance or intratumoral heterogeneity cannot be characterized using well-level viability assays. Methods: A high-content imaging platform was adapted in low volume, 96-well format for using Cytation 5 (Biotek). PDAC PCOs were plated from organoid suspension in 1:1 reduced growth factor Cultrex plating 10uL per well. After 24h, physiologic chemotherapy was applied to match pharmacologic exposure of FOLFIRINOX (FFX) and gemcitabine/nab-paclitaxel (g/n-pac). Initial response was assessed by normalized change in PCO area at 72h. Subsequent viability staining was performed for single organoid level response for apoptosis (caspase-3/7-FITC) and necrosis (TO-PRO-3). Analyses were automated in Gen5.12 (Biotek) with selection for elements using circularity (>0.4) and alignment by location within <88 mm. Response was assessed using descriptive statistics and effect size (Glass’s Delta) normalized to media control. Results: PCOs were generated from patient-derived pancreatic tumor without prior treatment. Low volume plating facilitated imaging with reduced Z stack (300 mm) with an average of 14 PCOs evaluable per well. Increasing markers of apoptosis by caspase-3/7 staining stratified serial decrease in mean organoid growth by quartile [+285, +175, +42%, +28]. Increasing markers of necrosis using TO-PRO-3 staining stratified serial decrease in mean organoid growth by quartile [+259, +191, +54%, +26]. Normalized change in area was reduced with g/npac +11.9% (GD=1.43) and FFX +20.4% (GD=1.38) versus control +281%. Subclonal populations existed with normalized change in area >50% which represented 17.8% of g/npac and 18.5% of FFX treated PCOs. Individual organoids with mean area staining positive for apoptosis was increased in g/npac +67.3% (GD=2.96) and FFX +65.1 (GD=2.84) versus background control +12.8%. Individual organoids with mean with area staining positive for necrosis was increased in g/npac +47.3% (GD=1.88) as compared to both FFX +34.9 (GD=1.20, p<0.002) and background control staining of +11.1% (p<0.001). Conclusions: High content imaging in PDAC PCOs provide scalable model for response assessment. This method can track subclonal populations with residual growth after treatment with chemotherapy. Here, we provide proof of concept in patient-derived tissue for clinically relevant response assessment with increased induced necrosis with g/npac in comparison to FFX. Ongoing investigations are generating sensitivity thresholds to define subclonal populations with residual growth and viability for application in clinical prediction.

Citation Format: Md Shahadat Hossan, Ethan S. Lin, Ellie E. Riedl, Austin Stram, Jamie M. Warner, Jeremy D. Kratz. Multiplexed therapeutic sensitivity of patient derived pancreatic cancer organoids after neoadjuvant chemotherapy by high content imaging [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A073.

Esophagogastric Cancers: Integrating Immunotherapy Therapy Into Current Practice

Immunotherapy (IO) agents have led to significant improvements in patient outcomes across many tumor types. There have been great efforts to introduce immune checkpoint inhibitors into the treatment paradigm of esophagogastric cancers as well. A number of randomized phase III trials, which will be reviewed here, established the role of these agents in both early-stage and advanced-stage disease. Adjuvant nivolumab is US Food and Drug Administration-approved after neoadjuvant chemoradiation and resection of esophageal and gastroesophageal junction cancers on the basis of the phase III CheckMate 577 trial. In the advanced setting, patients with programmed death receptor ligand-1-positive tumors should be recommended IO in combination with chemotherapy in the first-line setting on the basis of the results from KEYNOTE 590, CheckMate 649, and CheckMate 648. Across trials, chemotherapy continues to play a critical role in the first-line setting and should be offered to all patients who are eligible for systemic therapy, including those with biomarker select tumors. In the later lines of treatment, IO has modest activity, and prior studies have grown largely irrelevant because of the enrollment of IO-naive patients. Similar to other disease types, patients with microsatellite unstable (microsatellite instability high) tumors represent a unique cohort that is more sensitive to IO. However, there are no randomized studies evaluating how best to apply IO in early or advanced stages specifically for the treatment of patients with microsatellite instability high upper GI tumors. Questions remain how to best select patients who benefit from IO treatments, how to augment IO activity in programmed death receptor ligand-1-negative tumors, and how to incorporate IO in late-line settings or for recurrent disease that has been treated with IO-containing regimens during early stages.

Technologies to Assess Drug Response and Heterogeneity in Patient-Derived Cancer Organoids

Patient-derived cancer organoids (PDCOs) are organotypic 3D cultures grown from patient tumor samples. PDCOs provide an exciting opportunity to study drug response and heterogeneity within and between patients. This research can guide new drug development and inform clinical treatment planning. We review technologies to assess PDCO drug response and heterogeneity, discuss best practices for clinically relevant drug screens, and assert the importance of quantifying single-cell and organoid heterogeneity to characterize response. Autofluorescence imaging of PDCO growth and metabolic activity is highlighted as a compelling method to monitor single-cell and single-organoid response robustly and reproducibly. We also speculate on the future of PDCOs in clinical practice and drug discovery.Future development will require standardization of assessment methods for both morphology and function in PDCOs, increased throughput for new drug development, prospective validation with patient outcomes, and robust classification algorithms.

Phase I/II trial of perioperative avelumab in combination with chemoradiation (CRT) in the treatment of stage II/III resectable esophageal and gastroesophageal junction (E/GEJ) cancer

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Background: Neoadjuvant CRT followed by surgery is the standard of care for patients (pts) with stage II/III E/GEJ cancer, yet recurrence rates remain high. Immunotherapy has demonstrated activity in advanced E/GEJ cancer and was recently approved for adjuvant treatment of early stage disease. This trial evaluated the safety and efficacy of avelumab with perioperative CRT in resectable E/GEJ cancer. Methods: This is a two part phase I/II trial. Phase I was a safety run-in of 6 pts. Phase II planned to enroll an additional 18 pts in an expansion cohort. Pts with E/GEJ adenocarcinoma or squamous cell cancer received CRT (41.4 Gy in 23 fractions) with weekly carboplatin and paclitaxel. Three doses of avelumab (10 mg/kg IV, q14 days) were administered starting on day 29 of treatment, to coincide with the last chemotherapy dose. Surgery was performed 8-10 weeks after CRT completion. Pts received 6 doses of avelumab after resection (10 mg/kg IV, q14 days). The primary endpoint of the Phase 1 was safety and tolerability. The primary endpoint of the Phase II was pathologic complete response (pathCR) rate, assessing patients from the safety run in and expansion cohorts. Results: Between 6/2018 and 10/2021, 22 pts (20 males, median age 64) enrolled in the study. Enrollment was stopped after 16 patients in the expansion cohort due to accrual delays and changes in standard treatment. 19/22 patients (86%) had adenocarcinoma; 15/22 (68%) had lymph node positive disease at diagnosis. 19 pts underwent successful resection while on study. 3 pts went off study before resection due to grade 3 avelumab-related infusion reaction (1), patient preference (1), and non-adherence (1). There were no unexpected surgical complications. 4 pts (21%) had R1 resection with 3/4 having positive radial margin and 1/4 positive proximal margin. At resection, 5 pts (26%) had pathCR (3/16 adenocarcinomas, 2/3 squamous cell), 4 ypT1N0 disease, and 14/19 were ypN0. 42% had tumor regression score of 0 or 1. The combination of CRT and avelumab had an acceptable toxicity profile. No grade ≥3 immune-related AEs were observed. Immune-related hypothyroiditis was seen in 2 patients (grade 2). Three patients had grade 2 infusion-related reaction, but were able to continue with treatment. 21/22 pts had reversible grade ≥3 lymphopenia; 13/22 grade ≥ 3 wbc decrease; 6/22 grade 3 neutropenia. As of data cutoff on 2/1/2022, 1 patient remains on study treatment, 15 in follow up, 5 expired, 1 off study. Additional efficacy data is being collected. Correlative studies are ongoing. Conclusions: Perioperative CRT with avelumab is well tolerated with no unexpected toxicities. Neoadjuvant chemoradiation with immunotherapy is a promising approach for patients with E/GEJ tumors. Additional safety, efficacy and correlative analysis from this study will be presented at the meeting. Clinical trial information: NCT03490292.

Impact of baseline culture conditions of cancer organoids when determining therapeutic response and tumor heterogeneity

Representative models are needed to screen new therapies for patients with cancer. Cancer organoids are a leap forward as a culture model that faithfully represents the disease. Mouse-derived cancer organoids (MDCOs) are becoming increasingly popular, however there has yet to be a standardized method to assess therapeutic response and identify subpopulation heterogeneity. There are multiple factors unique to organoid culture that could affect how therapeutic response and MDCO heterogeneity are assessed. Here we describe an analysis of nearly 3500 individual MDCOs where individual organoid morphologic tracking was performed. Change in MDCO diameter was assessed in the presence of control media or targeted therapies. Individual organoid tracking was identified to be more sensitive to treatment response than well-level assessment. The impact of different generations of mice of the same genotype, different regions of the colon, and organoid specific characteristics including baseline size, passage number, plating density, and location within the matrix were examined. Only the starting size of the MDCO altered the subsequent growth. These results were corroborated using ~ 1700 patient-derived cancer organoids (PDCOs) isolated from 19 patients. Here we establish organoid culture parameters for individual organoid morphologic tracking to determine therapeutic response and growth/response heterogeneity for translational studies.

Prognostic impact of common pathologic alterations in pancreatic ductal adenocarcinoma from the veterans health administration

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Background: The Veteran Health Administration’s (VHA) National Precision Oncology Program was established to provide comprehensive molecular profiling for US military veterans with advanced cancers. There is an urgent need for precision strategies in pancreatic ductal adenocarcinoma (PDAC), as it is a leading cause of cancer-related mortality. We hypothesized that contributions of molecular alterations in PDAC would fail to stratify overall survival (OS), as current strategies are largely dependent on the activity of cytotoxic chemotherapy. Methods: A retrospective, multicenter cohort of 342 veterans with PDAC were identified from January 2016 to March 2021 who underwent comprehensive next-generation sequencing of tumor using FoundationOne CDx (UW IRB#2020-0696). Subjects were stratified by localized (L) or metastatic (M) disease at the time of diagnosis. Molecular alterations were compared by disease presentation using chi-squared analysis, and the clinical outcomes of overall survival (OS) were evaluated using Student’s t-test. Results: Baseline characteristics were representative of the VA population across 80 independent sites. The cohort was male-dominant (97%) with a median age of 69 years at diagnosis. Of this sample, 55% had M disease (n=189) compared to 45% with L disease (n=153). Median OS for M PDAC was 8.9±10.2 months (mo) v. L PDAC with median OS 22.5±18.0 mo (p<0.00005). Primary driver alterations were representative of PDAC and comparable between L and M on presentation, respectively; these included KRAS (92% v. 91%), TP53 (73% v. 80%), CDKN2A (29% v. 32%), SMAD4 (18% v. 23%), ARID1A (15% v. 16%) and BRCA2 (9% v. 12%). Primary driver alterations did not confer differences in OS across the population when comparing mutant (mt) to wildtype (wt) for KRAS (10.7 v. 11.8 mo, n=312), TP53 (10.3 v. 11.8 mo, n=263), CDKN2A (10.2 v. 10.9 mo, n=105), ARID1A (10.8 v. 10.9 mo, n=53), SMAD4 (11.3 vs 10.7 mo, n=72), and BRCA2 (13.8 v. 10.7 mo, n=37). Conclusions: Using the largest report of molecular profiles in veterans with PDAC to date, current therapeutic strategies fail to differentiate clinical outcomes by common molecular alterations with cytotoxic chemotherapy. The molecular profiles of veterans are representative of PDAC and do not vary significantly between localized and metastatic disease. There remains a persistent unmet need for therapeutic strategies including ongoing investigations of novel metabolic and immune-based therapies.

Metastatic bulk to predict subclonal heterogeneity by ctDNA in RAS/RAF-wildtype colorectal cancer

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Background: Distinct molecular subgroups of colorectal cancer (CRC) have been afforded with use of next-generation sequencing (NGS) as standard in clinical practice for advanced disease. We have previously demonstrated that disease bulk predicts clinical resistance to EGFR inhibition in RAS/RAF-wildtype (WT) CRC. We hypothesized bulky disease would predict advanced subclonal heterogeneity by circulating tumor DNA (ctDNA) in RAS/RAFWT CRC. Methods: Following IRB-approval, a retrospective review of molecular profiles in advanced CRC (n = 965) were compiled from the Veteran Administration’s (VA) National Precision Oncology Program (NPOP) and University of Wisconsin Precision Medicine Molecular Tumor Board (MTB). Disease bulk was defined as the longest diameter of metastatic disease or short axis for advanced lymphadenopathy. Molecular profiling was performed using commercially available platforms including Strata Oncology (MTB) and FoundationOne (NPOP). Bulky was compared as categorical (> 35 cm) and continuous variable against the count of pathologic variants. Results: The population was largely representative of advanced CRC with alterations in TP53 (80.5%), KRAS (44.8%), PIK3CA (22.0%) and BRAF (12.8%). Veterans had increased frequency of alterations in PIK3CA (22.7% v. 13.0%, p < 0.02) and BRAF (13.3% v. 6.9%, p < 0.05). There was no difference in metastatic bulk at the time of NGS for tissue biopsy between MTB and NPOP populations (t = 0.80). Disease bulk did not predict the number of pathologic variants from tissue sampling in RAS/RAFWT CRC (n = 96, t = 0.24). RAS/RAFMT cancers had increased frequency of subclonal alterations by ctDNA (9.1±4.0) v. RAS/RAFWT (4.5±3.4, p < 0.0001). Using ctDNA, bulky disease in RAS/RAFMT CRC was not predictive of increased pathologic variants (8.8±3.5 v. 9.5±4.8, t = 0.62). Bulky disease (> 35mm) in RAS/RAFWT CRC predicted increased subclonal variants (6.2±3.6 v. 3.5±2.9, p < 0.02). As a continuous variable, disease bulk predicted the number of pathologic variants in RAS/RAFWT CRC (R = 0.51). Conclusions: These data indicate that metastatic bulk is a predictor of subclonal heterogeneity by ctDNA in RAS/RAFWT CRC. Molecular profiling of tissue alone did not predict differences in subclonal heterogeneity when stratified by disease bulk in RAS/RAFWT CRC. Limited subclonal heterogeneity in non-bulky cancers support ongoing prospective investigations to select non-bulky cancers for early incorporation of anti-EGFR inhibition (NCT04587128).

Sensitivity of HER2-amplified colorectal organotypic cancer spheroids at ex vivo resistance to panitumumab and trastuzumab

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Background: HER2 amplification is an emerging biomarker in colorectal cancer (CRC) with increased copy number associated with improved clinical outcomes to HER2 targeting. RAS/RAF wildtype CRC also benefit from use of epidermal growth factor receptor inhibition (EGFRi). The sequencing of EGFRi versus HER2 inhibition in low copy number HER2 amplified CRC remains uncertain. Patient-derived cancer organoids (PDCOs) allow an ex vivo method to assess treatment sensitivity. We examined treatment sensitivity of a HER2 amplified PDCO at baseline and following resistance to panitumumab and trastuzumab. Methods: Following IRB-approval, fresh CRC tissue was cultured to maturation. After expansion, subcultures were treated with stepwise (20%) increase to physiologic Cmax of panitumumab (230ug/mL) and trastuzumab (180ug/mL). Threshold for escalation was median relative growth of +20% at 96h. Sensitivity was assessed on primary culture (RC1), panitumumab resistance (RC1-P) and trastuzumab resistance (RC1-T) using 96h of physiologic Cmax panitumumab, trastuzumab, and combination trastuzumab/pertuzumab. Individual sphere response was assessed for change in mean NADH autofluorescence intensity and ratio of NADH/FAD signal. Response was assessed at 96h in comparison to control using effect size of Glass’s Delta (GΔ). Results: Molecular profiling revealed HER2 copy number of 14 with no concurrent alterations in RAS, RAF, or PIK3CA. Time to resistance was similar between panitumumab (55 days) and trastuzumab (51 days). RC1 had baseline growth (+116%) which was reduced with single agent panitumumab (+17%, GΔ=1.40) with intermediate sensitivity to trastuzumab (+48%, GΔ=0.95) and trastuzumab/pertuzumab (46%, GΔ=0.99). Normalized NADH/FAD ratio revealed significant metabolic response to panitumumab (-20%, GΔ=0.66) and trastuzumab/pertuzumab (-35%, GΔ=1.16) with insignificant effect of single agent trastuzumab (-14%, GΔ=0.46). Following resistance to panitumumab, RC1-P had persistent growth with trastuzumab (+68%) which improved in combination trastuzumab/pertuzumab (+34%, GΔ=1.16). Following resistance to trastuzumab, RC1-T was insensitive to EGFRi with panitumumab including persistent growth (+58%, GΔ=0.70) and unchanged metabolism (+2%, GΔ=-0.10). Conclusions: Therapeutic dose escalation in a single PDCO of HER2 amplified CRC suggests improved sensitivity to EGFRi and dual HER2 targeting with trastuzumab/pertuzumab. Resistance to EGFRi resulted in persistent sensitivity to dual HER2 inhibition using trastuzumab/pertuzumab, however resistance to single agent trastuzumab. Resistance to trastuzumab resulted in future insensitivity to EGFRi. Molecular profiling at resistance revealed no pathologic alterations in EGFR or ERBB2 signaling, with ongoing analysis of transcriptional changes by RNAseq.

Diagnostic challenges in an aggressive case of peripheralizing marginal zone lymphoma

B-cell lymphomas with atypical presentation or immunophenotype pose diagnostic challenges. Conventional ancillary tests (cytogenetics, FISH) can help, but have technical limitations. New technologies such as mate-pair sequencing (MPSeq) offer a route around these technical limitations.

Abstract B27: MTORC1/2 inhibition as a treatment strategy for PIK3CA mutant colorectal cancer

Colorectal cancer (CRC) is a leading cause of cancer-related death. PIK3CA mutations are common, leading to a constitutively active phosphoinositide-3 kinase (PI3K). An effective means to target this pathway has yet to be identified. We investigated the use of a panel of inhibitors targeting the PI3K pathway including copanlisib (dual PI3K/mTOR), BYL-719 (alpha isomer specific PI3K), GDC-0941 (pan PI3K), and TAK-228 (MTORC1/2). To test the efficacy of these inhibitors in CRC, murine organotypic cancer spheroids (MDOCS) were generated from the invasive adenocarcinomas of Apc and Pik3ca transgenic mice. These inhibitors were investigated at clinically relevant doses (100-400nM). Copanlisib and TAK-228 were the only inhibitors to result in a significant reduction in the size of the MDOCS (200nM; 27% p-value&lt;0.001, 18% p-value&lt;0.001, respectively). This result correlated with a decrease in the phosphorylation of AKT (ser473), RPS6, and 4EBP1. Minimal induction of apoptosis was observed using these inhibitors alone as measured by cleaved PARP and cleaved caspase 3. These results were confirmed in vivo using transgenic mice with TAK-228 (1mg/kg/day) and copanlisib (10mg/kg q2d x5) resulting in a reduction in lumen occlusion of the colon tumors. Persistent BCL-2 and BCL-xL signaling was hypothesized to be preventing the induction of apoptosis. To determine if inhibition of these BCL-2 family members would further sensitize these MDOCS to copanlisib and TAK-228, these inhibitors were tested in combination with navitoclax (ABT-263; BCL-2 family inhibitor). A dramatic enhanced sensitivity was observed in MDOCS (30% p-value&lt;0.001, 23% p-value&lt;0.001, respectively). This correlated with an induction of apoptosis as measured by cleaved caspase 3. Next a panel of eight CRC patient-derived organotypic cancer spheroids (PDOCS) were treated with the combination of TAK-228 and navitoclax. Differential sensitivity was observed across the panel (25% resistant, 37.5% intermediate, and 37.5% highly sensitive) owing to the importance of mutational profile with targeted therapies. These studies indicate the benefit of MTORC1/2 for the treatment of PIK3CA mutant CRC and with enhanced activity of the combination of MTORC1/2 inhibition in combination with BCL-2 family inhibition. These therapies deserve further investigation for the treatment of patients with PIK3CA mutant CRC.

Citation Format: Rebecca A. DeStefanis, Susan N. Payne, Devon Miller, Cheri A. Pasch, Christopher Babiarz, Alyssa DeZeeuw, Stephanie L. Fricke, Carley Sprackling, Alexander E. Yueh, Demetra P. Korkos, Dana R. Van De Hey, Gioia Sha, Aurora Greane, Jeremy D. Kratz, Linda Clipson, Kristina A. Matkowskyj, Michael A. Newton, Dustin A. Deming. MTORC1/2 inhibition as a treatment strategy for PIK3CA mutant colorectal cancer [abstract]. In: Proceedings of the AACR Special Conference on Targeting PI3K/mTOR Signaling; 2018 Nov 30-Dec 8; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Res 2020;18(10_Suppl):Abstract nr B27.

Abstract 2701: Patient-derived colorectal cancer organoid therapeutic escalation: Tracking resistance to EGFR inhibition for predicting therapeutic sensitivity

Background: Precision oncology requires translational tools predictive of clinical benefit. Epidermal growth factor receptor inhibition (EGFRi) yields a survival advantage in RAS/RAF wildtype (wt) colorectal cancer (CRC), however clinical tools do not predict individual patient response or resistance mechanisms. Patient-derived cancer organoids (PDCOs) allow for an ex vivo method to track subclonal response. Here, we examine the development of PDCO EGFRi resistance as a novel biomarker to differentiate treatment sensitivities.

Methods: Fresh CRC tissue was obtained following consent to an IRB-approved protocol. Molecular profiling was performed on expanded PDCOs and in parallel to clinical hotspot sequencing. Cultures were treated with stepwise (20%) increases in panitumumab (46ug/mL per escalation) up to the physiologic Cmax (230ug/mL). A HER2 amplified culture was also assessed by escalation of trastuzumab with 20% stepwise increase to physiologic Cmax (180ug/mL). Threshold for escalation to the next dose level was a median relative growth of 20% at 96h. Time to resistance (TTR) was defined from start to persistent PDCO growth at 100% Cmax. Treatment studies assessed the longest diameter of individual spheres, assessed at 48h and compared to control using effect size (Glass's (G) Δ). TTR was compared to molecular profiles of primary resistance and clinical outcomes.

Results: CRC PDCOs were derived from 10 patients (5 localized and 5 metastatic samples). PDCOs had diverse molecular profiles: 3 KRAS mutant (mt), 1 PTEN mt, 7 TP53 mt, and 7 RAS/RAF wt. TTR ranged from 26-226 days, with 90% of PDCOs lines achieving resistance. RAS mt PDCOs had a homogeneous TTR of 27.0±1.4 days. RAS wt PDCOs displayed marked variation in therapeutic response with TTR of 51.5±61.7 days (p=0.06, compared to RAS mt). A HER2-amplified PDCO (copy number 14) showed intermediate sensitivity to EGFRi (TTR 55 days), similar to dose escalation of HER2-targeting trastuzumab (TTR of 51 days). This HER2-amplified PDCO showed intermediate sensitivity to single agent trastuzumab (GΔ = 0.56), yet no sensitivity to trastuzumab following EGFRi resistance (GΔ = 0.09). Prospective clinical correlation was possible for 1 PDCO line, a RAS wt PDCO derived prior to EGFRi which showed marked sensitivity with growth and metabolic arrest achieved at 40% CMax consistent with clinical response.

Conclusions: We present therapeutic dose escalation using PDCOs as a translational tool to track the clonal dynamics of resistance to EGFRi in CRC. This technique provides an objective measure of TTR to differentiate culture specific sensitivity in a clinically relevant timeframe. Molecular profiling of resistant cultures is ongoing which may provide an ex vivo tool for predicting individual resistance as cancers evade therapeutic pressure of targeted selection.

Citation Format: Jeremy D. Kratz, Aishwarya Sunil, Meghan Conroy, Cheri A. Pasch, Nicole Lassen, Hannah Houtler, Kayla K. Lemmon, Linda Clipson, Daniel E. Abbott, Evie H. Carchman, Elise H. Lawson, Noelle K. Loconte, Sam J. Lubner, Kristina A. Matkowskyj, Daniel L. Mulkerin, Nataliya Uboha, Dustin A. Deming. Patient-derived colorectal cancer organoid therapeutic escalation: Tracking resistance to EGFR inhibition for predicting therapeutic sensitivity [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2701.

Abstract 1494: Etiologies of patient-derived colorectal cancer organoid growth heterogeneity across multiple patient samples and culture conditions

Background: Patient-derived cancer organoids (PDCOs) are emerging as an in vitro model to recapitulate the molecular and phenotypic features of colorectal cancer (CRC). Heterogeneity in established CRC PDCOs has been observed in the underlying molecular profiles and growth characteristics at the individual organoid level. Here, we present a dedicated assessment of individual organoid growth as a function of experimental culture parameters.

Methods: CRC PDCO cultures were established from patient biopsy/resection specimens following patient consent to an IRB-approved protocol. Growth was assessed by relative change in diameter at 48h. Baseline size was compared to relative growth at 48h using coefficient of determination (R). Interquartile sets were compared by effect size of Glass's Delta (GΔ) to compare change difference in average growth normalized to standard deviation and defined with significance 1.0. Impact of density was assessed by manual count of spheroids and lines plated across varied densities and compared to 48h relative growth. Growth rates were compared as both absolute and relative passage number.

Results: 22 unique cultures were established from fresh tissue and representative of CRC including pathologic alterations in APC, KRAS, NRAS, BRAF, PIK3CA TP53, MTOR and PTEN. Pairwise spheres were assessed at baseline and 48h for analysis (n=1714) with mean relative growth rate of 27.1% (range -40.0, 156.2%). Baseline size did not predict relative growth at 48h (R=0.023) with insignificant interquartile effect size [0.10, 0.07, 0.32]. Replicates (n=63) across a range of passages [1, 36] including line-specific relative passage number [0-14] did not predict change in relative growth (R&lt;0.001) with insignificant interquartile effect size [-0.02, 0.15, 0.19]. Fields of view (n=135) were assessed for absolute sphere number [1, 72]. Increased sphere density across cultures also did not predict change in relative growth (R=0.002) with insignificant interquartile effect size [-0.29, -0.32, -0.29]. Two individual cultures were assessed for the impact of density on respective growth without significance at relative plating ratios of 1:5 (GΔ=-0.52, 0.42), 1:10 (GΔ=-0.63, 0.07), and 1:50 (GΔ=-0.40, 0.12).

Conclusions: Following culture maturation, CRC PDCOs have heterogeneous growth rates at the organoid level. These studies demonstrate that the growth rate is independent of baseline organoid size, passage number, or culture plating density. Understanding the effect of culture variation helps to define meaningful population effects in response and resistance to therapy and supports the translation of this technology as a future predictive biomarker.

Citation Format: Aishwarya Sunil, Jeremy D. Kratz, Sarbjeet K. Makkar, Suhjah Rehman, Amani A. Gillette, Katherine A. Johnson, Cheri A. Pasch, Linda Clipson, Kristina A. Matkowskyj, Melissa C. Skala, Dustin A. Deming. Etiologies of patient-derived colorectal cancer organoid growth heterogeneity across multiple patient samples and culture conditions [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1494.

Efficacy of single-agent epidermal growth factor receptor inhibition in the second-line setting for metastatic colorectal cancer with a goal towards retreatment strategies

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Background: Advances in the understanding of colorectal cancer (CRC) biology, including clonal evolution are leading to novel treatment strategies. Epidermal growth factor receptor inhibition (EGFRi) with cetuximab or panitumumab has shown significant clinical utility in KRAS/NRAS/BRAF wildtype (wt) CRC. These inhibitors are most commonly used in the third-line treatment setting in the United States. Upon the development of resistance to EGFRi, withdrawal of the EGFR inhibitor can lead to decay of resistant clones allowing for EGFR inhibitor retreatment in additional lines of treatment. Earlier-line use of single agent EGFRi could allow more patients to utilize a retreatment strategy, however no large prospective clinical trials have assessed the clinical activity of second line EGFRi in the setting of molecular selection. Here, we assess the clinical outcomes of EGFRi monotherapy for advanced KRAS wt CRC after initial progression on a single line 5FU based chemotherapy. Methods: A retrospective chart review examined patients who received single agent EGFRi in KRAS wt CRC in the second line setting. Line of therapy was defined at time of metastatic disease or recurrence within 6 months of adjuvant therapy. Clinical outcomes of overall response rate (ORR) and progression free survival (PFS) were assessed per RECIST v1.1. Results: 20 cases were identified who received single agent EGFRi (panitumumab or cetuximab) as monotherapy in the second line setting. All pts received prior 5FU based chemotherapy. Reasons for using EGFR inhibitor monotherapy in this setting included to avoid toxicities from prior chemotherapy (largely immunosuppression and GI toxicities), bridge from recent operative management, or maintain functional performance status. Patients had median age of 62 [45, 89] and majority with ECOG PS 0-1 (78.5% of those reported). Best responses included complete response 7%, partial response 21%, stable disease 64% and progressive disease 7%, and a disease control rate of 93%. The 6 and 8 month PFS were 70% and 50%, respectively. PFS ranged from 1.5 to 17.3 months with median PFS 8.2 ± 3.6 months. Conclusions: This work demonstrates preliminary efficacy data to use single agent EGFRi in the second-line setting for KRASwt patients with CRC. Future investigations will aim to prospectively validate the benefit of this treatment strategy to facilitate EGFRi retreatment and improve patient survival.

Effect size as a tool to identify subpopulations with improved clinical outcomes in metastatic colorectal cancer

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Background: ASCO defined meaningful trial endpoints in colorectal cancer (CRC) to include OS HR ≤0.67 (Ellis, JCO 2014). This measure is limited in identifying treatment benefit for subgroups from heterogeneous populations. Effect size (Glass’s Δ) calculates the absolute difference in median clinical outcomes normalized to the control group standard deviation. We hypothesized that durable effect sizes ≥2 would be useful in predicting which trials possess subgroup populations of clinical significance despite a HR > 0.67. Methods: Prospective phase II-III trials in metastatic CRC from the ASCO Meeting Library (2016-2019) were cataloged by clinical outcomes of PFS and OS. Effect size was calculated from trials reporting confidence intervals and compared with absolute difference in clinical outcome, hazard ratio and therapeutic intervention. Trials with an indeterminant HR, yet effect size > 2 were reviewed in subgroup analyses. Results: 385 abstracts were reviewed with 99 clinical analyses available for effect size calculation. Absolute difference in PFS correlated with effect size (R = 0.64) and was inversely proportional to HR (R = -0.63). The absolute difference in OS correlated with effect size (R = 0.69) and was inversely proportional to HR (R = -0.57). When stratified by clinically significant HR (defined ≤0.67), median effect size for PFS was 13.7±13.3 (SD) which was significantly different from HR > 0.67 with median effect size 1.0±3.8 (p < 0.001). Median effect size for OS when stratified by HR ≤0.67 was 3.7±2.5 which was significantly different when compared to endpoints with HR > 0.67 with median effect size 0.9±1.4 (p < 0.003). Subgroup populations with survival benefit included combination checkpoint blockade durvalumab/tremelimumab vs supportive care with effect size 3.1 (HR 0.72; NCT02870920). First-line PFS benefit was predicted in KRAS wildtype liver-limited CRC treated with FOLFOX+cetuximab vs FOLFOX+bevacizumab by effect size of 3.2 (HR 0.80; NCT01836653). Conclusions: Effect size holds potential as a measure to delineate improved clinical outcomes from heterogeneous populations and could identify those trials for which further subgroup analysis should be explored.

Defining population response of patient-derived colorectal cancer organoids against prospective clinical outcomes

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Background: No current clinical tool can predict the efficacy of cancer therapeutics for patients with colorectal cancer (CRC). We recently demonstrated the feasibility of using patient-derived cancer organoids (PDCOs) to examine therapeutic response and tumor heterogeneity for individual patients with CRC via optical metabolic imaging (OMI). Here we expand these analyses in a cohort of patients with clinical outcomes. Methods: CRC tissue was collected from patients on IRB-approved protocols. PDCOs were matured and treated with chemotherapy regimens concurrent with patient treatment. Previously established effect size response thresholds were used for diameter ( > 1.5) and OMI ( > 0.5) following 48 hours of treatment. OMI measures the intrinsic autofluorescence of NAD(P)H and FAD using 2-photon microscopy without specific reagents or dyes. Clinical outcomes were prospectively collected by manual chart review. Results: 12 CRC PDCOs were established from patients with CRC. PDCOs were collected from initial diagnosis and advanced setting of both primary and metastatic sites by core needle biopsy and surgical resection. Differential growth rates were observed across lines. PDCOs with RAS/RAF alterations had more uniform growth, while PDCOs without these alterations demonstrated more heterogeneous growth and metabolism. Clinical correlation of PDCOs response with recurrence of disease in the adjuvant setting will be presented. Cases with prior 5-FU-based chemotherapy at the time of PDCO collection had intermediate sensitivity. For PDCOs collected pre-treatment, PDCO response predicted clinical response for 5 of 6 cases using predefined sensitivity thresholds. In the case that overall PDCO response did not predict clinical response, a heterogenous response was observed with distinct sensitive and resistant populations. Across PDCOs, greater post-treatment heterogeneity was observed in resistant lines compared to those with treatment sensitivity. Conclusions: Tumor heterogeneity in treatment response can be assessed using PDCOs growth and metabolism. The utility of PDCOs to predict clinical outcomes for patients with CRC deserves further prospective validation.

Metastatic Bulk Independently Predicts Outcomes for EGFR Precision Targeting in Colorectal Cancer

Background: Molecular profiles guide the clinical management of metastatic colorectal cancer (mCRC), particularly related to the use of anti-epidermal growth factor receptor (EGFR) antibodies. Tumor sidedness has also been implicated in resistance to these therapies, but has largely been studied in the first-line setting. We examined the role of tumor sidedness and disease bulk in predicting clinical outcomes to anti-EGFR therapy in the treatment-refractory setting. Methods: We identified a retrospective cohort of 62 patients with KRAS wild-type mCRC who received anti-EGFR therapy in the late-line setting. Response was assessed per RECIST 1.1, with bulky disease defined as any single lesion >35 mm in longest cross-sectional diameter or nodal short axis. Primary sidedness was defined in relation to the splenic flexure. Results: Patients with right-sided primary tumors at time of late-line EGFR therapy presented with increased tumor bulk and worsened overall survival (OS) relative to left-sided primary tumors. Tumor bulk, defined as either a categorical or continuous variable, predicted worsened progression-free survival (PFS) and OS, which persisted when controlling for differences in the primary tumor location. Within the right-sided cohort, no objective responses were observed for bulky disease or during treatment with anti-EGFR monotherapy. The nonbulky cohort experienced clinical benefit with anti-EGFR monotherapy, showing similar PFS and an improved response rate compared with sequential chemotherapy. Conclusions: In an effort to expand understanding of the role of primary sidedness in clinical response to anti-EGFR therapy, we identified sidedness and tumor bulk as potential predictive biomarkers of clinical response in late-line mCRC. Future prospective studies of EGFR targeting should consider tumor bulk in addition to molecular profiling in the identification of populations most likely to achieve meaningful clinical benefit.

Utility of effect size to define populations with durable clinical outcomes across trials of metastatic colorectal cancer

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Background: ASCO defined clinically meaningful trial endpoints in colorectal cancer (CRC) as absolute overall survival (OS) of 3-5 months and OS hazard ratio (HR) ≤0.67. Few tools predict clinically distinct subgroups from heterogeneous populations. Effect size (Glass’s delta) calculates the absolute difference in clinical outcomes relative to the standard deviation of control group. We hypothesized that effect sizes ≥1 would be useful in predicting subgroup populations of clinical significance for trials with an indeterminate HR. Methods: Prospective phase II-III trials in metastatic CRC were queried from clinicaltrials.gov and cataloged by clinical outcomes of PFS and OS. Effect size was back-calculated from trials reporting 95% confidence intervals and compared with absolute difference in clinical outcome and hazard ratio. Results: 46 prospective trials were evaluable including 49% with biomarker selection, 57% in the first-line setting, and more commonly studied with targeted therapy over chemotherapy (70 v. 30%; p < 0.001). EGFR inhibitors were studied in 34% and VEGF inhibitors in 23%. Both effect size and HR correlated similarly with PFS (correlation coefficients, R = 0.65 vs. 0.76) and OS (R = 0.83 vs. 0.84) across these studies. Of studies with an indeterminate HR (0.69-0.86; n = 24), 10 studies had a significant effect size (Glass’s delta > 1), indicating the potential for sub-populations with improved clinical benefit within the experimental treatment group. These included 4 trials with planned biomarker analyses. Remaining trials were enriched for studies investigating anti-angiogenic therapies (83% vs. 23%, p = 0.001), including bevacizumab, aflibercept, regorafenib, and ramucirumab. Conclusions: Effect size holds potential as a measure to indicate the presence of subpopulations of patients benefiting in clinical trials. Those trials with a significant effect size despite an indeterminate HR should be examined closely for such populations. In CRC, effect size indicates the potential of a subgroup of patients who benefit significantly from anti-angiogenic agents. Further investigations are needed to validate effect size as a tool to delineate improved clinical outcomes from heterogeneous populations.

Targeted Therapy in Metastatic Colorectal Cancer: Current Standards and Novel Agents in Review

PURPOSE OF REVIEW

Treatment options for patients with metastatic colorectal cancer continue to advance as the therapeutic implications of the molecular subtypes of this disease are becoming better understood. DNA sequencing and mismatch repair assessment are now standard of care analyses for patients with metastatic colorectal cancer Thi review describes important aspects of the biology of the clinically relevant molecular subtypes of colorectal cancer based on the current standard of care testing. In addition, the clinical treatment strategies available now and potentially in the future for these colorectal cancer subtypes are discussed.

RECENT FINDINGS

Currently for metastatic colorectal cancer, standard of care molecular testing is done for mutations in exons 2, 3, and 4 of KRAS and NRAS, and BRAF V600E. Testing for mismatch repair (MMR) deficiency/microsatellite instability (MSI) status is also done. These aberrations are well known to change the clinical prognosis and guide patients' treatment strategies. Additionally, three new subtypes have emerged: PIK3CAmut, HER2 amplified, and NTRK fusions. With the addition of these emerging subtypes, tumor heterogeneity further validates the need to examine mCRC as a heterogeneous disease. Here we present recent exciting data from translational research and clinical trials exhibiting possible distinct treatment strategies for these different subtypes.

SUMMARY

Altogether these data show promising treatment strategies for many of these well-known and emerging subtypes of mCRC. In addition, these also give better clinical prognostic and predictive information. We believe that as molecular testing expands PIK3CA mutation, HER2 amplification, and NTRK fusion molecular testing will be included in standard of care analyses. This incorporation of testing in clinical practice will generate further information regarding prognostic and therapeutic options for these and other CRC subtypes in the future.

Patient-derived colorectal cancer spheroids for single cell characterization of intratumor heterogenity in response to EGFR inhibition

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Background: Epidermal growth factor receptor inhibitors (EGFRi) have improved clinical outcomes in patients (pts) with metastatic colorectal cancer (mCRC). Molecular profiling and primary tumor sidedness are used to predict population benefit. Our group has recently demonstrated that patient-derived organotypic cancer spheroids (PDOCS) and optical metabolic imaging (OMI) can predict in vivo chemotherapy response. Translational tools are needed to characterize targeted therapeutic response to predict clinical outcomes. Methods: PDOCS were generated from patients with mCRC at time of molecular profiling. Following culture maturation, PDOCS were treated with physiologic doses of EGFRi panitumumab. Response was evaluated by change in sphere diameter and OMI to exploit intrinsic autofluorescence of NAD(P)H and FAD at spheroid and single-cell level. Effect size was calculated using Glass’s delta (GΔ) defined as differences in means between treatment groups normalized to control standard deviation with comparison to predetermined sensitivity thresholds. Results: PDOCS from pts with mCRC were generated from tissue biopsies, surgical specimens, and malignant effusions (n = 38). Mutational profiles were stratified by RAS status from next-generation sequencing. Six PDOCS were evaluable for experimental and clinical response. KRAS mutation predicted primary resistance to EGFRi with no difference in diameter (GΔ = -0.01) or single cell response by OMI (GΔ = 0.02). RAS wild-type PDOCS had significant response with decreased diameter with EGFRi (P < 0.001). Gaussian fit of single-cell analyses revealed heterogeneity in EGFRi sensitivity. Differential sensitivity to EGFRi in RAS wild-type population correlated with clinical response. Conclusions: PDOCS predict response to panitumumab in these preliminary investigations. Diameter and OMI analyses provide complementary information of line-specific sensitivity. Further studies are warranted to characterize the molecular profiles underlying intratumor heterogenity. Prospective investigations are needed to understand the predictive role of this technique in targeted therapeutic response.

MTORC1/2 Inhibition as a Therapeutic Strategy for PIK3CA Mutant Cancers

PIK3CA mutations are common in clinical molecular profiling, yet an effective means to target these cancers has yet to be developed. MTORC1 inhibitors are often used off-label for patients with PIK3CA mutant cancers with only limited data to support this approach. Here we describe a cohort of patients treated with cancers possessing mutations activating the PI3K signaling cascade with minimal benefit to treatment with the MTORC1 inhibitor everolimus. Previously, we demonstrated that dual PI3K/mTOR inhibition could decrease proliferation, induce differentiation, and result in a treatment response in APC and PIK3CA mutant colorectal cancer. However, reactivation of AKT was identified, indicating that the majority of the benefit may be secondary to MTORC1/2 inhibition. TAK-228, an MTORC1/2 inhibitor, was compared with dual PI3K/mTOR inhibition using BEZ235 in murine colorectal cancer spheroids. A reduction in spheroid size was observed with TAK-228 and BEZ235 (-13% and -14%, respectively) compared with an increase of >200% in control (P < 0.001). These spheroids were resistant to MTORC1 inhibition. In transgenic mice possessing Pik3ca and Apc mutations, BEZ235 and TAK-228 resulted in a median reduction in colon tumor size of 19% and 20%, respectively, with control tumors having a median increase of 18% (P = 0.02 and 0.004, respectively). This response correlated with a decrease in the phosphorylation of 4EBP1 and RPS6. MTORC1/2 inhibition is sufficient to overcome resistance to everolimus and induce a treatment response in PIK3CA mutant colorectal cancers and deserves investigation in clinical trials and in future combination regimens.

Tumor bulk to predict clinical outcomes of anti-EGFR therapy in treatment refractory metastatic colorectal cancer independent of sidedness

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Background: Epidermal growth factor receptor (EGFR) antibodies, cetuximab (C) and panitumumab (P) have shown improvement in clinical outcomes for distinct molecular profiles in metastatic colorectal cancer (mCRC). In the first line setting, EGFR targeting of left-sided tumors has shown favorable clinical outcomes when compared to right-sided tumors. Here we examined the efficacy of EGFR therapy in the treatment refractory setting as well as the impact of tumor bulk on clinical outcomes. Methods: A retrospective cohort of 72 patients (pts) with KRAS wild-type mCRC were identified who received either C or P in the late-line setting. Tumor measurements were performed per RECIST v1.1. Disease bulk was defined as single lesion with longest diameter or lymph node with short axis > 3.5 cm. Right colon primary was defined proximal to splenic flexure. Results: In pts with treatment refractory right-sided disease the response rate (RR) was 16.7%, progression free survival (PFS) was 3.7 months (mo), and overall survival (OS) was 14.0 mo. This was compared to left sided disease with RR of 26.0%, PFS 6.2 mo (p < 0.05), and OS 15.0 mo. In the non-bulky cohort the RR was 32.4%, PFS 7.9 mo, and OS 18.4 mo. In the bulky cohort the RR was 5.3% (p < 0.01), PFS 4.0 mo (p < 0.02), and OS 6.6 mo. In the right-sided non-bulky cohort there was a RR of 33% v. 0% in the right-sided bulky cohort. In the left-sided non-bulky cohort there was a RR of 32.3% v. 7.7% in the bulky cohort (p < 0.05). Conclusions: These data indicate that tumor bulk can predict clinical outcomes for anti-EGFR targeting. In the late line setting, pts with left-sided cancers overall trended towards improvements in clinical outcomes, consistent with prior understanding in first line setting. Despite a limited cohort size, response was observed in pts with non-bulky right-sided disease. There was limited-to-no benefit of anti-EGFR targeting with right-sided bulky disease. Left-sided non-bulky patient received the greatest benefit from anti-EGFR targeting. Future prospective studies of targeted therapeutics should incorporate tumor bulk and sidedness when assessing clinical outcomes and tumor biology.

Gynaecomastia in two men on stable antiretroviral therapy who commenced treatment for tuberculosis

Gynaecomastia is a common clinical presentation that varies from benign presentations in stages of human development to hormonal pathology, mainly due to hepatic dysfunction, malignancy, and adverse pharmacologic effects. We describe the development of significant bilateral gynaecomastia after starting treatment for pulmonary tuberculosis (TB) in two males with WHO stage III Human Immunodeficiency Virus (HIV) infection on stable antiretroviral regimens. Emerging reports suggest that distinct hepatic impairment in efavirenz metabolism modulates oestrogenic activity, which may be potentiated by anti-tuberculosis therapy. Clinical application includes early recognition of efavirenz-induced gynaecomastia, especially after commencing tuberculosis treatment. To avoid decreased adherence resulting from the distressing side effect of gynecomastia, transition to an alternative ART regimen over the course of tuberculosis treatment should be considered.

Tumor bulk as an independent marker of anti-EGFR therapeutic benefit in metastatic colorectal cancer

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Background: Molecular testing and location of the primary tumor (right-sided (R) versus (vs) left-sided (L)) are useful in predicting the clinical benefit of the anti-epidermal growth factor receptor (EGFR) antibodies, cetuximab (cet) and panitumumab (pan), in metastatic colorectal cancer (mCRC). We hypothesized that tumor bulk might also be predictive of treatment benefit given the potential for increased intra-tumor heterogeneity and reduced penetration of antibodies into bulkier lesions. Methods: A single institution retrospective cohort of 69 patients (pts) with KRAS wild-type mCRC were identified who received either cet or pan in the late-line setting +/- chemotherapy. Metastatic sites were cataloged including independent review of CT imaging prior to initiation of anti-EGFR therapy. Disease bulk was defined categorically as single metastatic lesion with diameter measuring > 3.0 cm. Results: This cohort represents a diverse group having received varying prior lines of therapy and having assorted disease sites including mediastinal, pulmonary, hepatic, omental, and osseous lesions. When treated with anti-EGFR therapies, pts with pre-treatment metastases ≤3.0 cm in diameter had significant improvement in median progression free survival (mPFS) (6.2 months (mos)) vs pts with metastases > 3.0 cm (3.9 mos, p < 0.01). A trend towards improvement in overall survival was observed for pts with non-bulky (15.8 mos) vs bulky disease (8.6 mos, p = 0.08). A trend towards increased mPFS existed in L (5.1 mos) vs R cancers (2.5 mos, p = 0.11). In R cancers, no significant difference in mPFS was noted between bulky (2.5 mos) and non-bulky disease (2.9 mos, p = 0.53). Non-bulky L cancers had a significantly improved mPFS of 7.5 mos compared to 3.9 mos with L bulky disease (p < 0.01). Non-bulky L cancers trended towards improved overall survival of 17.0 mos compared to 9.6 mos with L bulky disease (p = 0.08). Conclusions: Despite limited small sample size, these data indicate that tumor bulk is a potential predictor of the therapeutic benefit of anti-EGFR agents in left-sided mCRCs across a heterogeneous pt population. Disease bulk deserves further evaluation in larger datasets of mCRC across targeted therapeutics.

Atherosclerosis and Nanotechnology: Diagnostic and Therapeutic Applications

Over the past several decades, tremendous advances have been made in the understanding, diagnosis, and treatment of coronary artery disease (CAD). However, with shifting demographics and evolving risk factors we now face new challenges that must be met in order to further advance are management of patients with CAD. In parallel with advances in our mechanistic appreciation of CAD and atherosclerosis, nanotechnology approaches have greatly expanded, offering the potential for significant improvements in our diagnostic and therapeutic management of CAD. To realize this potential we must go beyond to recognize new frontiers including knowledge gaps between understanding atherosclerosis to the translation of targeted molecular tools. This review highlights nanotechnology applications for imaging and therapeutic advancements in CAD.

The Multidisciplinary Management of Colorectal Cancer: Present and Future Paradigms

As treatment strategies for patients with colorectal cancer advance, there has now become an ever-increasing need for multidisciplinary teams to care for these patients. Recent investigations into the timing and duration of perioperative therapy, as well as, the rise of molecular profiling have led to more systemic chemotherapeutic options. The most efficacious use, in terms of timing and patient selection, of these therapies in the setting of modern operative and radiotherapy techniques requires the generation of care teams discussing cases at multidisciplinary conferences. This review highlights the role of multidisciplinary team conferences, advances in perioperative chemotherapy, current clinical biomarkers, and emerging therapeutic agents for molecular subtypes of metastatic colon cancer. As our understanding of relevant molecular subtypes increases and as data becomes available on treatment response, the treatment of colorectal cancer will become more precise and effective.

Molecular Profiles Guide Colorectal Cancer Treatment

An improved understanding of colorectal cancer as a collection of multiple cancer subtypes is paving the way to precision medicine-based treatments.

Discovery of selective bioactive small molecules by targeting an RNA dynamic ensemble

Current approaches used to identify protein-binding small molecules are not suited for identifying small molecules that can bind emerging RNA drug targets. By docking small molecules onto an RNA dynamic ensemble constructed by combining NMR spectroscopy and computational molecular dynamics, we virtually screened small molecules that target the entire structure landscape of the transactivation response element (TAR) from HIV type 1 (HIV-1). We quantitatively predict binding energies for small molecules that bind different RNA conformations and report the de novo discovery of six compounds that bind TAR with high affinity and inhibit its interaction with a Tat peptide in vitro (K(i) values of 710 nM-169 μM). One compound binds HIV-1 TAR with marked selectivity and inhibits Tat-mediated activation of the HIV-1 long terminal repeat by 81% in T-cell lines and HIV replication in an HIV-1 indicator cell line (IC(50) ∼23.1 μM).