Abstract 369: Identification of pathways that enhance cell death in NOTCH1-mutant HNSCC

Head and neck squamous carcinoma (HNSCC) is dominantly driven by mutations in tumor suppressor genes making it challenging to devise biomarker-based targeted therapy. In order to meet this pressing clinical need, our group recently demonstrated that HNSCCs with loss of function NOTCH1 mutations were more sensitive to phosphoinositide-3 kinase (PI3K) pathway inhibition than their wild-type counterparts.Modest clinical responses and acquired resistance are leading causes of failure for molecular targeted therapies that are otherwise well tolerated. In order to address this challenge and identify drugs that could work in combination with PI3K inhibitors against NOTCH1-mutant HNSCC, we performed a high throughput screen of 5669 drugs (0-1µM) with diverse targets. We used a laser-based confocal imaging platform to determine actual cell numbers using DAPI staining before and after drug treatment of NOTCH1-mutant HNSCC cells (HN31, UMSCC22A). We used 2 metrics of efficacy to identify potential candidates to combine with PI3K inhibition: an arbitrary cut off value of ≤ 0.9 for the area under the curve, growth rate index and area over the curve lethal dose (AOC_LD). We calculate both metrics using the normalized growth rate inhibition curve in order to avoid the confounding effect of the rate of cell division. The AOC_LD is > 0 only when there are fewer cells after treatment than before (i.e., there was cell death). Of the resulting 340 candidates, we excluded chemotherapy, PI3K inhibitors, and non-specific drugs. When several candidates targeted the same pathway, we chose 2-3 of the most specific drugs to use in the combination screen. We combined the resulting 74 drugs with PI3K inhibitors, bimiralisib (0-1µM) or copanlisib (FDA approved, 0-100nM), for 72 h. Synergistic effects from these combinations were assessed using Bliss, HAS, Zip, and Loewe models. Trametinib (MEK inhibitor) and copanlisib were synergistic with the combination leading to 0.90 fraction of cells affected at concentrations of 30nM and 100nM respectively. These concentrations are target-specific and clinically achievable. Likewise, low concentrations of inhibitors of EGFR (10nM afatinib, 50nM AZ5104), HER2 (25nM sapitinib, 10nM poziotinib), and PLK1 (50nM BI2536, 50nM volasertib) were both effective and additive to synergistic with PI3K inhibitors. These combinations will further be validated in vitro using an independent approach to test for apoptosis (cleaved PARP and caspase-3 induction and TUNEL assay) and cell counts in multiple NOTCH1 mutant HNSCC cell lines. We will test the most promising combination in vivo. We have identified four drug classes that not only maximize the killing of NOTCH1-mutant HNSCC, but may also prevent resistance at clinically relevant concentrations. The identified pathways may give us insight into mechanisms of resistance. If validated, these combinations may lead to the first biomarker-specific, targeted therapy for HNSCC.

Citation Format: Pooja A. Shah, Tuhina Mazumdar, Reid T. Powell, Li Shen, Jing Wang, Clifford C. Stephen, Mitchell J. Frederick, Faye M. Johnson. Identification of pathways that enhance cell death in NOTCH1-mutant HNSCC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 369.

Comparative assessment of the eighth and seventh AJCC staging edition prognostic performance of patients with p16 positive oropharynx cancer

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Background: The American Joint Committee on Cancer (AJCC) TNM staging system defines the anatomical extent of disease and serves as a guide for treatment and prognosis. The favorable prognosis of p16+ oropharyngeal squamous cell carcinoma (OPSCC) compared to p16 negative counterpart led to major updates in the AJCC 8th edition. Its prognostic performance, however, warrants further validation. Methods: We included patients diagnosed with p16+ OPSCC enrolled in a prospective registry ( Stiefel) at The University of Texas MD Anderson Cancer Center between March 2015 and December 2018. Patients’ stage at diagnosis was classified according to the AJCC 7th (AJCC-7) and 8th (AJCC-8) editions. Overall survival (OS) and progression-free survival (PFS) was defined as time from diagnosis to death or to progression or death, respectively. The Kaplan-Meier method was used to calculate 1- and 3-year survival probabilities. Differences between groups were compared using the log-rank test. Prognostic discriminative performance of each staging system was evaluated using Harrel’s C-statistic. Survival differences between heavy (> 10 pack-years [PY]) vs. light/never smokers (≤ 10 PY) by AJCC-8 staging groups was assessed with the log-rank test. Results: Of 463 patients, the median follow-up was 34.7 months (2.3-169.74). Nearly 90% (N=413) of patients were down-staged from AJCC-7 to AJCC-8 with 69% of patients with IVA disease based on AJCC-7 (N=319) re-staged as stage I (N=196 [42%]), II (N=79 [17%]) or III (44 [10%]) according to AJCC-8. Over 60% (N=279) of patients were staged as I with AJCC-8. Compared to AJCC-7, AJCC-8 had improved prognostic ability (C-statistic, 0.58 for AJCC-7 vs. 0.63 for AJCC-8) and provided better discriminative survival probabilities at 1 and 3-year follow-up (Table). Similar results were observed for PFS. Smoking status did not impact OS when stratified by AJCC-8 staging groups: I, p=0.347; II, p=0.310; and III, p=0.532 for > 10 vs. ≤ 10 PY. Conclusions: Our cohort validates that the AJCC-8 provides better prognostic discriminative performance when compared to AJCC-7, however, a disproportionate number of patients were classified as stage I. Smoking was not associated with survival within each staging group.[Table: see text]

Outcomes of patients with oropharyngeal squamous cell carcinoma treated with induction chemotherapy followed by concurrent chemoradiation compared with those treated with concurrent chemoradiation

BACKGROUND

Induction chemotherapy (IC) has been associated with a decreased risk of distant metastasis in locally advanced head and neck squamous cell carcinoma. However, its role in the treatment of oropharyngeal squamous cell carcinoma (OPSCC) is not well established.

METHODS

The outcomes of patients with OPSCC treated with IC followed by concurrent chemoradiation (CRT) were compared with the outcomes of those treated with CRT alone. The primary outcome was overall survival (OS), and the secondary end points were the times to locoregional and distant recurrence.

RESULTS

In an existing database, 585 patients met the inclusion criteria: 137 received IC plus CRT, and 448 received CRT. Most patients were positive for human papillomavirus (HPV; 90.9%). Patients receiving IC were more likely to present with a higher T stage, a higher N stage, and low neck disease. The 3-year OS rate was significantly lower in patients receiving IC (75.7%) versus CRT alone (92.9%). In a multicovariate analysis, receipt of IC (adjusted hazard ratio [aHR], 3.4; P < .001), HPV tumor status (aHR, 0.36; P = .002), and receipt of concurrent cetuximab (aHR, 2.7; P = .002) were independently associated with OS. The risk of distant metastasis was also significantly higher in IC patients (aHR, 2.8; P = .001), whereas an HPV-positive tumor status (aHR, 0.44; P = .032) and completion of therapy (aHR, 0.51; P = .034) were associated with a lower risk of distant metastasis. In HPV-positive patients, IC remained associated with distant metastatic progression (aHR, 2.6; P = .004) but not OS.

CONCLUSIONS

In contrast to prior studies, IC was independently associated with worse OS and a higher risk of distant metastasis in patients with OPSCC. Future studies are needed to validate these findings.

Cytotoxic and targeted systemic therapy in patients with advanced cutaneous squamous cell carcinoma in the head and neck

BACKGROUND

The outcomes of patients treated with cytotoxic or targeted systemic therapy is not well defined for cutaneous squamous cell carcinoma of the head and neck (cSCCHN).

METHODS

Patients with cSCCHN treated with cytotoxic or targeted systemic therapy were included. Patients were divided into two groups based on the presence of distant metastasis (M1 vs. M0) at presentation. A proportional hazards model was used to assess for independent predictors of overall survival.

RESULTS

Of 129 patients with cSCCHN, 20 (16%) were M1 and 109 (84%) were M0. Independent predictors of improved survival were M0 status, treatment of locally advanced disease with radiotherapy, and lower Eastern Cooperative Oncology Group (ECOG) score.

CONCLUSIONS

Survival was worse in M1 patients treated with cytotoxic or targeted systemic therapy and poor baseline performance status but improved in those receiving radiotherapy. These data can serve as historical controls for future systemic therapy trials, including immunotherapy.

Lung cancer models reveal SARS-CoV-2-induced EMT contributes to COVID-19 pathophysiology

COVID-19 is an infectious disease caused by SARS-CoV-2, which enters host cells via the cell surface proteins ACE2 and TMPRSS2. Using a variety of normal and malignant models and tissues from the aerodigestive and respiratory tracts, we investigated the expression and regulation of ACE2 and TMPRSS2. We find that ACE2 expression is restricted to a select population of highly epithelial cells. Notably, infection with SARS-CoV-2 in cancer cell lines, bronchial organoids, and patient nasal epithelium, induces metabolic and transcriptional changes consistent with epithelial to mesenchymal transition (EMT), including upregulation of ZEB1 and AXL, resulting in an increased EMT score. Additionally, a transcriptional loss of genes associated with tight junction function occurs with SARS-CoV-2 infection. The SARS-CoV-2 receptor, ACE2, is repressed by EMT via TGFbeta, ZEB1 overexpression and onset of EGFR TKI inhibitor resistance. This suggests a novel model of SARS-CoV-2 pathogenesis in which infected cells shift toward an increasingly mesenchymal state, associated with a loss of tight junction components with acute respiratory distress syndrome-protective effects. AXL-inhibition and ZEB1-reduction, as with bemcentinib, offers a potential strategy to reverse this effect. These observations highlight the utility of aerodigestive and, especially, lung cancer model systems in exploring the pathogenesis of SARS-CoV-2 and other respiratory viruses, and offer important insights into the potential mechanisms underlying the morbidity and mortality of COVID-19 in healthy patients and cancer patients alike.

NOTCH1 Signaling in Head and Neck Squamous Cell Carcinoma

Biomarker-driven targeted therapies are lacking for head and neck squamous cell carcinoma (HNSCC), which is common and lethal. Efforts to develop such therapies are hindered by a genomic landscape dominated by the loss of tumor suppressor function, including NOTCH1 that is frequently mutated in HNSCC. Clearer understanding of NOTCH1 signaling in HNSCCs is crucial to clinically targeting this pathway. Structural characterization of NOTCH1 mutations in HNSCC demonstrates that most are predicted to cause loss of function, in agreement with NOTCH1's role as a tumor suppressor in this cancer. Experimental manipulation of NOTCH1 signaling in HNSCC cell lines harboring either mutant or wild-type NOTCH1 further supports a tumor suppressor function. Additionally, the loss of NOTCH1 signaling can drive HNSCC tumorigenesis and clinical aggressiveness. Our recent data suggest that NOTCH1 controls genes involved in early differentiation that could have different phenotypic consequences depending on the cancer's genetic background, including acquisition of pseudo-stem cell-like properties. The presence of NOTCH1 mutations may predict response to treatment with an immune checkpoint or phosphatidylinositol 3-kinase inhibitors. The latter is being tested in a clinical trial, and if validated, it may lead to the development of the first biomarker-driven targeted therapy for HNSCC.

Conditional survival among patients with oropharyngeal cancer treated with radiation therapy and alive without recurrence 5 years after diagnosis

BACKGROUND

Risk of recurrence among patients with oropharyngeal cancer (OPC) who survive 5 years is low. The goal of this study was to assess long-term survival of patients with OPC alive without recurrence 5 years after diagnosis.

METHODS

This study included newly diagnosed patients with OPC, who had been treated with radiation and were alive without recurrence 5 years after diagnosis. Overall survival (OS) probabilities beyond 5 years were estimated using the Kaplan-Meier method. Factors associated with OS were determined using Bayesian piecewise exponential survival regression. Standardized mortality ratios for all-cause death were estimated controlling for study year, age, and sex in the US general population.

RESULTS

Among 1699 patients, the additional 2-year, 5-year, and 10-year OS probabilities were 94%, 83%, and 63%, respectively, and were lower than those in the general population. Patients who were older, were current or former smokers, had other than tonsil or base of tongue tumors, or had T4 tumors had a higher risk of death. Patients who had base of tongue tumors and had received intensity-modulated radiation therapy (IMRT) or lower-radiation doses had a lower risk of death. Standardized mortality ratios were higher among current and heavy smokers and lower among recipients of IMRT and lower radiation doses.

CONCLUSIONS

In this large cohort, long-term survival among patients with OPC was good but lower than predicted for the general population. Patients treated with IMRT and those with less tobacco exposure had better outcomes.

Prognostic significance of pre-treatment neutrophil-to-lymphocyte ratio (NLR) in patients with oropharyngeal cancer treated with radiotherapy

Background

This study aimed to evaluate the prognostic value of pre-treatment NLR in patients with oropharyngeal cancer.

Methods

Patients who completed definitive radiotherapy (RT) for oropharyngeal cancer and had blood counts taken pre-RT from 2002 to 2013 were included. NLR was calculated as total neutrophil/lymphocytes. Survival rates were estimated using the Kaplan–Meier method. Univariable and multivariable analyses were conducted with linear and Cox regression methods. NLR was analysed posteriori and dichotomised on the discovered median.

Results

Eight hundred and forty-eight patients were analysed. The median pre-RT NLR was 3. Patients with NLR of <3 had improved overall survival (OS) than those with NLR ≥ 3 (5-year OS 85 vs 74%, p < 0.0001). OS differences remained significant when stratified according to HPV status (HPV-positive p = 0.011; HPV-negative p = 0.003). Freedom from any recurrence (FFR), locoregional control (LRC) and freedom of distant recurrence (FDR) were better in those with NLR < 3. The negative impact of elevated pre-RT NLR on OS (HR = 1.64, p = 0.001), FFR (HR = 1.6, p = 0.006) and LRC (HR = 1.8, p = 0.005) remained significant on multivariable analysis.

Conclusions

Pre-RT NLR is an independent prognostic factor in patients with oropharyngeal cancer regardless of HPV status. Patients with lower NLR had more favourable OS and disease control.

Abstract 1662: In vivo drug response evaluation in anaplastic thyroid cancer patient-derived tumor xenografts following high-throughput screening

Background Anaplastic thyroid cancer (ATC) is a rare, aggressive, and deadly disease. Robust pre-clinical models are needed to adequately develop and study novel therapeutic agents. Patient-derived xenograft (PDX) models are thought to closely resemble patient tumors by preserving the tumor microenvironment, making them excellent pre-clinical models for drug response evaluation. We used two distinct ATC PDX models and evaluated drug response following a high-throughput screening (HTS).

Methods A HTS, using NCI's Approved Oncology Set V (n=112) and a custom collection of agents (n=145), was conducted on patient-derived thyroid cancer cell lines. To identify the most effective drugs, we selected individual agents with maximal growth inhibition at each dose level relative to wells examined on the day of treatment (top 25th percentile) and subsequently used non-parametric statistics to compare effect size with other drugs and controls. This allowed us to identify classes of systemic agents which demonstrated preferential effectiveness against ATC cell lines and certain mutations. Following our prior successful work on orthotopic xenograft models, we used two established ATC PDX models, HOSC68 and HOSC199, harboring distinct genetic profiles and expanded each of them into 50 athymic mice. HOSC68 has a BRAFV600E and a TP53 mutation, while HOSC199 is wild-type for both genes, but has an HRAS mutation. Equal pieces of 4 × 4mm of tumor were transplanted subcutaneously at the level of the right flank. Following tumor growth, the mice were separated into four treatment arms. All mice received their treatment intraperitoneally following standard drug administration schedules. Tumor volume was measured on the first day of treatment and every two to three days thereafter until trial completion (14 days). Drug response was analyzed by evaluating percent tumor growth inhibition (TGI). Mouse weight was recorded over time to evaluate treatment toxicity. Following treatment completion, tumors were surgically retrieved and evaluated morphologically and histologically.

Results Microtubule inhibitors, antimetabolites, and HDAC inhibitors were some of the most effective drug classes identified against ATC cell lines. Specifically, in this study, mice were treated with control (CTR), Docetaxel (DOC)-microtubule inhibitor, Pralatrexate (PRA)-antimetabolite, and LBH-589 (LBH)-HDAC inhibitor. Forty-four HOSC68 and 43 HOSC199 mice successfully grew tumor and were included in the trial. Compared to CTR, HOSC68 mice treated with DOC showed a 37% TGI (p=0.04), 88% with PRA (p&lt0.001), and 83% with LBH (p&lt0.001), while HOSC199 mice had a 2% TGI with DOC (p=0.56), 76% with PRA (p=0.005), and 83% with LBH (p=0.002). PRA and LBH were significantly more toxic than DOC and CTR (p&lt0.001) in HOSC68 mice, while all three drugs were significantly more toxic than CTR in the HOSC199 mice (p&lt0.001).

Conclusion We report the first large-scale evaluation of drugs identified through a HTS analysis on ATC PDX models. This trial demonstrates the feasibility of using this platform for in vivo drug testing, while providing an avenue for future drug testing and resistance evaluation, as well as personalized therapeutics development.

Citation Format: Anastasios Maniakas, Abdallah S. Mohamed, Ying C. Henderson, Hu Hei, Shaohua Peng, Diana Bell, Michelle D. Williams, Steve Scherer, David A. Wheeler, Gary L. Clayman, Mark Zafereo, Jennifer R. Wang, Maria E. Cabanillas, Clifford Stephan, Faye M. Johnson, Stephen Y. Lai. In vivo drug response evaluation in anaplastic thyroid cancer patient-derived tumor xenografts following high-throughput screening [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 1662.

Abstract B14: Variations in the proteasome activity are associated with human papilloma virus (HPV) gene expression and patient survival in HPV+ oropharyngeal tumors

Variations in the molecular function of human papillomavirus (HPV) have been associated with outcome in HPV-positive oropharyngeal squamous cell carcinomas (HPV+OPSCC). HPV-mediated carcinogenesis is initiated by the E6 and E7 proteins, which promotes the inhibition of the p53 and pRb proteins by targeting them for degradation by the proteasome system. Considering that the proteasome system is an important mediator of HPV molecular activity, we hypothesize that its activity may be an important modifier of HPV+OPSCC phenotypes. To test this hypothesis, we analyzed the in silico expression of proteasome genes among HPV+ oropharyngeal squamous cell carcinoma cases from The Cancer Genome Atlas (TCGA) and explored the proteasome activity of HPV+ squamous cell carcinoma cell lines in vitro. Higher expression of proteasome genes was significantly associated with worse 5-year overall survival (p=0.0003), lower expression levels of E1^E4 gene (p = 0.032), and more HPV integration (p = 0.028). In vitro analysis indicated that proteasome activity was distinct between E1^E4 negative and E1^E4 positive HPV+ cell lines. Interestingly, E1^E4 negative cell lines, which exhibited higher levels of some proteasome genes, were more sensitive to proteasome inhibition than E1^E4 positive cells. These results indicate that proteasome activity may vary significantly among HPV+ OPSCC cases and may represent an important modulator of tumor phenotypes. Expression of proteasome genes and also proteasome activity was highly correlated with expression of HPV genes and may function as a potential predictive biomarker. Finally, proteasome targeting may represent a potential therapeutic alternative for a subgroup of HPV+ OPSCC patients.

Citation Format: Frederico O. Gleber-Netto, Meng Gao, Li Shen, Jing Wang, Jeffrey N. Myers, Faye M. Johnson, Curtis R. Pickering. Variations in the proteasome activity are associated with human papilloma virus (HPV) gene expression and patient survival in HPV+ oropharyngeal tumors [abstract]. In: Proceedings of the AACR-AHNS Head and Neck Cancer Conference: Optimizing Survival and Quality of Life through Basic, Clinical, and Translational Research; 2019 Apr 29-30; Austin, TX. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_2):Abstract nr B14.

Prospective, longitudinal digital activity monitoring before and after treatment of low-risk oropharyngeal squamous cell carcinoma: A feasibility study

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Background: Given the expected excellent prognosis of low-risk oropharyngeal squamous cell carcinoma (OPSCC), consideration of long-term toxicity and functional outcomes has become increasingly important. Activity monitors (e.g. FITBIT) are imperfect but have been shown to have reasonable validity in healthy adults. Here we aimed to test the feasibility of using medical grade longitudinal digital activity monitoring to better define objective functional outcomes after treatment of low-risk OPSCC. Methods: This prospective, observational parallel cohort study included patients with previously untreated stage I-III (AJCC 7) OPSCC eligible for standard of care single-modality treatment with either Intensity-Modulated Proton Therapy (IMPT) or TransOral Robotic Surgery (TORS). Objective Actigraph accelerometer data (Actigraph, Pensacola, FL) were collected continuously for 1 week at baseline, 3, 6 and 12 months after treatment along with subjective patient-reported outcome (PRO) measures. Results: Forty-four patients (34M, 10F) enrolled with median age 59 years (range: 42-78). Baseline, 3 and 6 month activity data were available for 40 patients (91%): 16 IMPT and 24 TORS. There was a significant decrease in mean percent of day performing moderate to vigorous physical activity (MVPA) (-0.78, 0.021) mean number of steps/minute (-1.1, p = 0.035), and mean kcals/day (-115.9, p < 0.001) from baseline to 3 months after treatment for the overall cohort. A significant decrease in mean kcals/day (-82.2, p = 0.004) persisted for the overall cohort at 6 months with no significant difference between groups. Conclusions: Longitudinal digital activity monitoring is feasible before and after treatment of low-risk OPSCC. This approach may offer objective functional endpoints for future de-escalation trials. Similar short-term decreases in objective activity measurements were observed after IMPT and TORS. Long-term (12 month) activity data and correlations to subjective PRO measures will be available at the time of presentation. Clinical trial information: 02663583 .

Single-arm study of bimiralisib in head and neck squamous cell carcinoma (HNSCC) patients (pts) harboring NOTCH1 loss of function (LOF) mutations

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Background: Effective targeted therapies are needed for HNSCC that is lethal despite recent advances with immunotherapy. A major challenge to personalize treatment is that most genomic alterations are in tumor suppressors, including NOTCH1 that is mutated in ~20% of HNSCC. We recently published that HNSCC cell lines harboring NOTCH1 LOF mutations undergo cell death in vivo and in vitro following PI3K inhibition, in contrast to PIK3CA mutant cell lines that merely undergo cell cycle arrest when exposed to the same drugs. Based on these results we initiated a novel genomic biomarker-driven phase II clinical trial treating NOTCH1 mutant HNSCC pts with the dual PI3K/mTOR inhibitor bimiralisib (PQR309). Methods: The primary objective is to determine the objective response rate (ORR) of recurrent/metastatic HNSCC harboring NOTCH1 LOF mutations to bimiralisib. Pts who have already received standard platinum chemotherapy and immunotherapy will receive bimiralisib orally twice per wk unless progression or intolerable toxicity occurs. Tumors will be evaluated using RECIST q 6 wks. A Simon’s optimal two-stage design is used. To have 80% power to detect an ORR of 30%, (one-sided α = 0.05, β = 0.20) 10 pts will be enrolled in the first stage. If ≤1 pts respond, the trial will be closed for futility. If ≥2 pts have an OR, the study will enroll an additional 19 pts in the second stage. The null hypothesis (ORR ≤ 10%) will be rejected if ≥ 6 in 29 pts have an OR. Seven pts have enrolled. The algorithm for determining NOTCH1 mutation function is based on the patterns of mutations in HNSCC vs. leukemia where mutations are activating. It may be difficult to determine whether NOTCH1 mutations are homo- or heterozygous due to normal cell contamination. Therefore, levels of activated NOTCH1 in pretreatment tumors may be assessed by IHC with an antibody against activated NOTCH1 (NICD). In parallel with the trial, to further confirm NOTCH1 LOF, we can use site-directed mutagenesis to re-create NOTCH1 mutations from trial pts that will then be introduced into NOTCH1-null cell lines to assay for NICD and growth inhibition with culture on NOTCH1 ligand. All pts will have serial collection of blood for pharmacokinetics and for ctDNA to examine clonal evolution associated with acquired resistance. Samples with high NOTCH1 mutation ctDNA VAF will be analyzed by WES and compared with pretreatment tissue. In the second stage, IHC and WES may be performed on pre- and post- treatment (day 15 and progression) tissue to examine pharmacodynamics and mechanisms of resistance. Clinical trial information: NCT03740100 .

Patterns of Failure After Intensity Modulated Radiation Therapy in Head and Neck Squamous Cell Carcinoma of Unknown Primary: Implication of Elective Nodal and Mucosal Dose Coverage

Purpose

We evaluated the geometric and dosimetric-based distribution of mucosal and nodal recurrences in patients with metastatic head and neck squamous cell carcinoma to cervical lymph nodes of unknown primary after intensity modulated radiation therapy using validated typology-indicative taxonomy.

Methods and Materials

We reviewed the data of 260 patients who were irradiated between 2000 and 2015 and had a median follow-up time for surviving patients of 61 months. The mucosal and nodal recurrences were manually delineated on computed tomography images demonstrating the recurrences. The images were overlaid on the treatment plan using deformable image registration. The locations of the recurrences were determined relative to the original planning target volumes and doses using centroid-based approaches. Subsequently, the pattern of failures were classified into 5 types based on combined spatial and dosimetric criteria: A (central high dose), B (peripheral high dose), C (central elective dose), D (peripheral elective dose), and E (extraneous dose). For patients with type A failure with simultaneous nontype A lesions, the overall pattern of failures was defined as type A.

Results

Thirty-two patients had mucosal or nodal recurrences. The most common clinical nodal stage was N2b (66%). Preradiation therapy neck dissections were performed in 6 patients. The median dose delivered to clinical tumor volume 1 was 66 Gy. The majority (84%) had total/partial pharyngeal mucosa elective irradiation. Twenty-three patients had nodal recurrences, 8 had mucosal recurrences, and 1 had both nodal and mucosal recurrences. Twenty-one patients (91%) had type A nodal failure, and 7 of the mucosal failures (89%) were type C.

Conclusions

The majority of nodal recurrences occurred within the high-dose area, demanding the need for identification of radioresistant areas within malignant nodes. Future studies should focus on either dose escalation of high-risk volumes or novel radiosensitizers.

Impact of Neoadjuvant Durvalumab with or without Tremelimumab on CD8+ Tumor Lymphocyte Density, Safety, and Efficacy in Patients with Oropharynx Cancer: CIAO Trial Results

PURPOSE

In oropharyngeal squamous cell carcinoma (OPC), high CD8⁺ tumor-infiltrating lymphocyte (CD8⁺TIL) density confers improved prognosis. We compared neoadjuvant durvalumab (PD-L1 inhibitor) with durvalumab + tremelimumab (CTLA-4 inhibitor) in terms of impact on CD8⁺TIL density, safety, and efficacy in patients with OPC.

PATIENTS AND METHODS

Patients with newly diagnosed stage II-IVA OPC or locoregionally recurrent OPC amenable to resection were included. Patients were randomized to two cycles of durvalumab or durvalumab + tremelimumab before surgery. The primary endpoint was change between baseline and resection specimen in CD8⁺TIL density between arms. Secondary endpoints included safety, response rate per RECIST, major pathologic response (MPR; ≤10% viable tumor cells) rate, and patient-reported outcomes.

RESULTS

Of 28 eligible patients (14/arm), 20 (71%) had newly diagnosed OPC, and 24 (86%) were p16-positive. The posttreatment to pretreatment median CD8⁺TIL density ratio was 1.31 for durvalumab and 1.15 for combination treatment (P = 0.97; 95% CI: -1.07-2.28). In each group, 6 patients (43%, 95% CI: 17.66-71.14) had a response. Eight patients (29%) had a MPR at the primary tumor and/or nodal metastases. Neither baseline CD8⁺TIL density nor PD-L1 expression level correlated with overall response, but a trend toward greater CD8⁺TIL change in patients with a MPR was seen (P = 0.059; 95% CI: -0.33-3.46). Four patients (14%) had grade ≥3 adverse events. At median follow-up time of 15.79 months, all patients were alive, and one had an additional recurrence.

CONCLUSIONS

Durvalumab + tremelimumab did not increase CD8⁺TIL density more than durvalumab alone did. The observed safety and activity support further investigation of neoadjuvant checkpoint inhibitor for OPC.

Weekly paclitaxel, carboplatin, cetuximab, and cetuximab, docetaxel, cisplatin, and fluorouracil, followed by local therapy in previously untreated, locally advanced head and neck squamous cell carcinoma

BACKGROUND

The survival advantage of induction chemotherapy (IC) followed by locoregional treatment is controversial in locally advanced head and neck squamous cell carcinoma (LAHNSCC). We previously showed feasibility and safety of cetuximab-based IC (paclitaxel/carboplatin/cetuximab-PCC, and docetaxel/cisplatin/5-fluorouracil/cetuximab-C-TPF) followed by local therapy in LAHNSCC. The primary end point of this phase II clinical trial with randomization to PCC and C-TPF followed by combined local therapy in patients with LAHNSCC stratified by human papillomavirus (HPV) status and T-stage was 2-year progression-free survival (PFS) compared with historical control.

PATIENTS AND METHODS

Eligible patients were ≥18 years with squamous cell carcinoma of the oropharynx, oral cavity, nasopharynx, hypopharynx, or larynx with measurable stage IV (T0-4N2b-2c/3M0) and known HPV by p16 status. Stratification was by HPV and T-stage into one of the two risk groups: (i) low-risk: HPV-positive and T0-3 or HPV-negative and T0-2; (ii) intermediate/high-risk: HPV-positive and T4 or HPV-negative and T3-4. Patient reported outcomes were carried out.

RESULTS

A total of 136 patients were randomized in the study, 68 to each arm. With a median follow up of 3.2 years, the 2-year PFS in the PCC arm was 89% in the overall, 96% in the low-risk and 67% in the intermediate/high-risk groups; in the C-TPF arm 2-year PFS was 88% in the overall, 88% in the low-risk and 89% in the intermediate/high-risk groups.

CONCLUSION

The observed 2-year PFS of PCC in the low-risk group and of C-TPF in the intermediate/high-risk group showed a 20% improvement compared with the historical control derived from RTOG-0129, therefore reaching the primary end point of the trial.

Lymphopenia during radiotherapy in patients with oropharyngeal cancer

PURPOSE/OBJECTIVE

Radiation-induced lymphopenia has been associated with poor survival outcomes in certain solid tumors such as esophageal, lung, cervical and pancreatic cancers. We aim to determine the effect of treatment-related lymphopenia during radiotherapy on outcomes of patients with oropharyngeal cancer.

MATERIALS/METHODS

A retrospective analysis of all patients who completed definitive radiotherapy for oropharyngeal cancer at The University of Texas MD Anderson Cancer Center and had blood counts taken during radiotherapy from 2002 to 2013 were included. Patient, tumor and treatment characteristics, clinical outcomes and lymphocyte counts during radiotherapy were recorded. Lymphopenia was graded according to the CTCAE v4.0. Survival rates were estimated using the Kaplan-Meier method and compared with log-rank tests.

RESULTS

850 patients were evaluated. The median age was 57 years. The majority of the cohort had p16/HPV-positive disease (71%), 8% had HPV-negative disease and 21% were unknown. The median radiation total dose was 70 Gy. 45% of patients had induction chemotherapy, and 87% had concurrent chemotherapy. 703 (83%) patients developed ≥grade 3 (G3) lymphopenia and 209 (25%) had grade 4 (G4) lymphopenia during radiotherapy. The median follow-up was 59 months; the 5-year overall survival rate was 81%. There were no significant differences in overall survival rates nor in disease control rates, in those who developed G3/G4 lymphopenia compared with those who did not. No significant effect of lymphopenia on survival was observed when analyzed according to p16/HPV status.

CONCLUSION

In this large cohort of patients with oropharyngeal cancer, the development of lymphopenia during radiotherapy did not impact outcomes.

Abstract 4942: Variations in HPV function are associated with patient outcome and identify new candidate therapeutic approaches

Human papilloma virus (HPV) is an oncogenic driver for a subset of head and neck squamous cell carcinomas (HNSCC), primarily from the oropharyngeal tissue subsite (OPSCC). These tumors are increasing in incidence and have recently surpassed cervical cancer as the most common HPV-driven malignancy in the United States. Fortunately, these tumors generally respond well to radiation-based therapy (XRT), and long-term (5 yr) survival is around 85%. However, the XRT treatment can generate significant morbidity, including problems with speech and swallowing. There is a clinical effort to reduce the treatment-related morbidity without compromising survival outcomes, through de-escalation treatment protocols. However, there is a subset of HPV+ OPSCC patients who do not respond to the current therapies and should not be given less intense treatment. This has generated the need to stratify patients based on their risk of recurrence or death, but currently no molecular biomarkers are available for risk assessment in OPSCC. By analyzing genomic data from The Cancer Genome Atlas (TCGA) we have identified a gene expression signature associated with expression of HPV genes. This signature identified 2 groups within the HPV+ tumors that demonstrate different levels of HPV function. One group seems to have reduced HPV function and present with intermediate phenotypes between HPV+ and HPV- tumors. Importantly, this signature is also highly prognostic in HPV+ OPSCC (p&lt;0.0001) and significant on multivariate analysis (p&lt;0.01). With the tumors showing reduced HPV function having worse outcomes. This prognostic signature was validated in independent OPSCC (p&lt;0.0001) and cervical cancer cohorts (p&lt;0.0026). The signature is most strongly associated with differential expression in the HPV gene E1^E4 but not with expression of the oncogenic driver genes of E6 and E7 genes. In vitro, we have associated the signature with sensitivity to XRT, suggesting a mechanism for the differences in patient outcome. An in vitro high throughput drug screen has identified candidate druggable targets in both the high and low risk groups, with 2 key pathways being cellular metabolism and proteasome function. Single agent and combination treatments targeting these pathways are currently being evaluated. In conclusion, we have identified a novel prognostic signature for HPV+ tumors that is associated with variations in HPV function among patients. This has the potential to translate into a biomarker assay for risk stratification, for use with de-escalation treatment protocols. Additionally, it has identified key functions of HPV that appear to be targetable and could lead to new therapeutic approaches for the subset of HPV+ patients who do not respond to XRT treatment.

Citation Format: Frederico O. Gleber-Netto, Meng Gao, Xiayu Rao, Christopher P. Vellano, Joseph R. Marszalek, Jing Wang, Faye M. Johnson, Curtis R. Pickering. Variations in HPV function are associated with patient outcome and identify new candidate therapeutic approaches [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4942.

Checkpoint inhibitors assessment in oropharynx cancer (CIAO): Safety and interim results

6008

Background: Anti-PD-1/PD-L1 are active in metastatic oropharynx squamous cell carcinoma (OPC). Durvalumab (durva) and tremelimumab (tremi) target respectively PD-L1 and CTLA-4, which in combination may be synergistic. Here we report the safety and interim results of durva vs. durva+tremi prior to surgery in a window of opportunity trial in OPC. Methods: Pts were randomized 1:1 to durva 1500 mg or durva 1500 mg + tremi 75 mg IV Q4W x 2 cycles. The primary objective was to quantify pre- and post-treatment differences in CD8+ tumor infiltrating lymphocytes for the two arms. Secondary objectives included safety, toxicity, ORR by RECIST, fraction of patients undergoing surgery at 8 wks, and percentage viable tumor cells in the surgical specimen. Serial pre- and post-treatment blood and tumor specimens were collected for ongoing correlative analyses. Results: 28 pts enrolled: median age 64y, 27 (96%) male, 19 (68%) newly diagnosed, most (63%) at stage IVA (AJCC 7th Ed), 9 (32%) had locoregional recurrence, 24 (86%) p16 positive, and 22 (79%) had ≤ 10 PPY smoking history. Median follow-up was 7.6 months. The most common AEs were fatigue (36%), leukopenia/lymphopenia (25%), transaminitis (25%), and rash (21%). Grade 3 AEs occurred in 4 (14%) pts: 2 elevated lipase, 1 diarrhea, and 1 hepatitis, all were manageable. There were no grade >3 AEs. ORR was 43%: 50% had SD (including 29% tumor shrinkage in 1 pt). Treatment effect in the surgical specimen was observed in 19 (79%) of 24 evaluable pts; 2 pts had major pathologic response (≤ 10% viable tumor) at the primary site. Efficacy was equivalent in both arms. The 2 pts with PD and 1 pt with SD were switched to chemotherapy after durva +/- tremi before resection; interestingly, each achieved a pCR in the primary. Most pts (57%) didn’t receive radiotherapy after surgery. There was a statistically significant association between ORR and treatment effect (p=0.014). The median percentage of viable tumor in the primary was 37.5% in pts with PR, and 82.5% in SD (p=0.003). Conclusions: Durva +/- tremi prior to surgery was well tolerated in OPC pts. Activity is encouraging with treatment effect seen in 79% of pts. The primary endpoint and complete efficacy data will be presented. Clinical trial information: NCT03144778.

Induction chemotherapy with and without erlotinib in patients with oral cavity squamous cell carcinomas (OCSCCs) amenable for surgical resection

6067

Background: We have previously demonstrated activity of erlotinib in head and neck SCCs as monotherapy prior to surgical resection, or in combination with chemotherapy for recurrent/metastatic disease (William et al. ASCO 2011, 2017). The aim of this study was to evaluate the efficacy of induction chemotherapy with a platinum-taxane regimen and explore the potential benefit of erlotinib as part of induction therapy in patients with resectable OCSCCs. Methods: This was a randomized, placebo-controlled, phase II trial of induction chemotherapy (cisplatin 75 mg/m2 or carboplatin AUC 6 with docetaxel 75 mg/m2 every 3 weeks for 3 cycles) with erlotinib (150mg oral daily) or placebo in patients with OCSCCs stage III-IVB amenable for surgical resection. The primary endpoint was major pathological response (MPR, defined as < 10% viable tumor cells in the surgical specimen). Secondary endpoints included safety and long-term efficacy outcomes. Results: From April 1, 2014, to June 7, 2017, 52 patients were enrolled, of whom 47 underwent planned surgery. MPR was achieved in 7/23 (30%) in the erlotinib group and 10/24 (41%) in the placebo group. With a median follow up of 26.5 months, the 2-year long-term progression-fee survival (PFS) were estimated at 75% (95% CI: 59.5-94.5) in the erlotinib arm, and 58.6% (95% CI: 40.9-84.1) in the placebo arm, and 2-year overall survival at 73.5% (95% CI: 57.2-94.5) for the erlotinib group and 73.1% (95% CI: 55.9-95.6) for the placebo group. In patients who achieved MPR (n = 17), the 2-year PFS was 77.4% (95% CI: 57.3-100), compared to 64.5% (95% CI: 49.0-84.8) in patients who did not achieve MPR (n = 29, p = .16). All 7 patients in the erlotinib group who achieved MPR remained disease-free. The majority of patients (87%) completed all 3 cycles of induction chemotherapy. The common side effects were expected and distributed similarly between erlotinib and placebo groups. As expected, rash, diarrhea and dehydration were more common in the erlotinib group. Conclusions: Platinum and docetaxel-based induction chemotherapy induced major pathological response in 17/47 (36%) of resectable OCSSC patients. Two-year overall survival was 73%. Responders had improved long-term outcome. Addition of erlotinib did not improve the rate of MPR, but might have contributed to improved PFS. Clinical trial information: NCT01927744.

Non-canonical cMet regulation by vimentin mediates Plk1 inhibitor-induced apoptosis

To address the need for improved systemic therapy for non-small-cell lung cancer (NSCLC), we previously demonstrated that mesenchymal NSCLC was sensitive to polo-like kinase (Plk1) inhibitors, but the mechanisms of resistance in epithelial NSCLC remain unknown. Here, we show that cMet was differentially regulated in isogenic pairs of epithelial and mesenchymal cell lines. Plk1 inhibition inhibits cMet phosphorylation only in mesenchymal cells. Constitutively active cMet abrogates Plk1 inhibitor-induced apoptosis. Likewise, cMet silencing or inhibition enhances Plk1 inhibitor-induced apoptosis. Cells with acquired resistance to Plk1 inhibitors are more epithelial than their parental cells and maintain cMet activation after Plk1 inhibition. In four animal NSCLC models, mesenchymal tumors were more sensitive to Plk1 inhibition alone than were epithelial tumors. The combination of cMet and Plk1 inhibition led to regression of tumors that did not regrow when drug treatment was stopped. Plk1 inhibition did not affect HGF levels but did decrease vimentin phosphorylation, which regulates cMet phosphorylation via β1-integrin. This research defines a heretofore unknown mechanism of ligand-independent activation of cMet downstream of Plk1 and an effective combination therapy.

Rescue of Immunotherapy-Refractory Metastatic Merkel Cell Carcinoma With Conventionally Fractionated Radiotherapy and Concurrent Pembrolizumab

Merkel cell carcinoma has historically had dismal prognosis with limited cytotoxic chemotherapy options that provide durable control of metastatic disease. The advent of anti-programmed death protein (anti-PD1)/anti-programmed death-ligand 1 (anti-PD-L1) directed immunotherapy has shown initial promise in Merkel cell carcinoma and radiation might augment immune responses. We present a case report of a 70-year-old male who underwent resection of Merkel cell carcinoma of the right thigh with a close margin and positive right inguinal involvement. Due to high-risk features, the patient was treated with adjuvant radiation to the right groin and with systemic carboplatin/etoposide, but developed local failure requiring salvage surgical resection. The patient then developed metastatic disease with biopsy proven retroperitoneal involvement refractory to doxorubicin/cyclophosphamide chemotherapy. The patient was then transitioned to single-agent pembrolizumab with a partial response for 10 months until developing progressive disease involving the left inguinal and left external iliac nodal regions. The progressive left inguinal/pelvic disease was treated with conventionally fractionated intensity modulated radiation therapy to a dose of 45 Gy delivered in 25 fractions. Following radiation therapy, the patient had complete response of all sites of disease throughout the body on imaging by RECIST criteria including retroperitoneal and mediastinal disease outside the radiation field. At 20 months post-radiation, the patient remains on pembrolizumab without evidence of disease on imaging. Herein, we present a case of durable response of metastatic Merkel cell carcinoma treated with concurrent radiation and pembrolizumab, providing evidence that radiation might improve systemic responses to anti-PD1/PD-L1 directed immune therapy. Ongoing prospective trials evaluating the utility of radiation in conjunction with immunotherapy for Merkel cell carcinoma are anticipated to provide clarity on the frequency and durability of abscopal responses when radiation is combined with immune checkpoint inhibitors.

PDK1 Mediates NOTCH1-Mutated Head and Neck Squamous Carcinoma Vulnerability to Therapeutic PI3K/mTOR Inhibition

PURPOSE

Head and neck squamous cell carcinoma (HNSCC) is driven largely by the loss of tumor suppressor genes, including NOTCH1, but lacks a biomarker-driven targeted therapy. Although the PI3K/mTOR pathway is frequently altered in HNSCC, the disease has modest clinical response rates to PI3K/mTOR inhibitors and lacks validated biomarkers of response. We tested the hypothesis that an unbiased pharmacogenomics approach to PI3K/mTOR pathway inhibitors would identify novel, clinically relevant molecular vulnerabilities in HNSCC with loss of tumor suppressor function.Experimental Design: We assessed the degree to which responses to PI3K/mTOR inhibitors are associated with gene mutations in 59 HNSCC cell lines. Apoptosis in drug-sensitive cell lines was confirmed in vitro and in vivo. NOTCH1 pathway components and PDK1 were manipulated with drugs, gene editing, knockdown, and overexpression.

RESULTS

PI3K/mTOR inhibition caused apoptosis and decreased colony numbers in HNSCC cell lines harboring NOTCH1 loss-of-function mutations (NOTCH1 ^MUT) and reduced tumor size in subcutaneous and orthotopic xenograft models. In all cell lines, NOTCH1 ^MUT was strongly associated with sensitivity to six PI3K/mTOR inhibitors. NOTCH1 inhibition or knockout increased NOTCH1 ^WT HNSCC sensitivity to PI3K/mTOR inhibition. PDK1 levels dropped following PI3K/mTOR inhibition in NOTCH1 ^MUT but not NOTCH1 ^WT HNSCC, and PDK1 overexpression rescued apoptosis in NOTCH1 ^MUT cells. PDK1 and AKT inhibitors together caused apoptosis in NOTCH1 ^WT HNSCC but had little effect as single agents.

CONCLUSIONS

Our findings suggest that NOTCH1 ^MUT predicts response to PI3K/mTOR inhibitors, which may lead to the first biomarker-driven targeted therapy for HNSCC, and that targeting PDK1 sensitizes NOTCH1 ^WT HNSCC to PI3K/mTOR pathway inhibitors.

Variations in HPV function are associated with survival in squamous cell carcinoma

Incidence of HPV+ oropharyngeal squamous cell carcinoma (OPSCC) has been increasing dramatically. Although long-term survival rates for these patients are high, they often suffer from permanent radiotherapy-related morbidity. This has prompted the development of de-escalation clinical protocols to reduce morbidity. However, a subset of patients do not respond even to standard therapy and have poor outcomes. It is unclear how to properly identify and treat the high- and low-risk HPV+ OPSCC patients. Since HPV positivity drives radiotherapy sensitivity, we hypothesized that variations in HPV biology may cause differences in treatment response and outcome. By analyzing gene expression data, we identified variations in HPV-related molecules among HPV+ OPSCC. A subset of tumors presented a molecular profile distinct from that of typical HPV+ tumors and exhibited poor treatment response, indicating molecular and clinical similarities with HPV- tumors. These molecular changes were also observed in vitro and correlated with radiation sensitivity. Finally, we developed a prognostic biomarker signature for identification of this subgroup of HPV+ OPSCC and validated it in independent cohorts of oropharyngeal and cervical carcinomas. These findings could translate to improved patient stratification for treatment deintensification and new therapeutic approaches for treatment-resistant HPV-related cancer.

Differential Sensitivity Analysis for Resistant Malignancies (DISARM) Identifies Common Candidate Therapies across Platinum-Resistant Cancers

PURPOSE

Despite a growing arsenal of approved drugs, therapeutic resistance remains a formidable and, often, insurmountable challenge in cancer treatment. The mechanisms underlying therapeutic resistance remain largely unresolved and, thus, examples of effective combinatorial or sequential strategies to combat resistance are rare. Here, we present Differential Sensitivity Analysis for Resistant Malignancies (DISARM), a novel, integrated drug screen analysis tool designed to address this dilemma.

EXPERIMENTAL DESIGN

DISARM, a software package and web-based application, analyzes drug response data to prioritize candidate therapies for models with resistance to a reference drug and to assess whether response to a reference drug can be utilized to predict future response to other agents. Using cisplatin as our reference drug, we applied DISARM to models from nine cancers commonly treated with first-line platinum chemotherapy including recalcitrant malignancies such as small cell lung cancer (SCLC) and pancreatic adenocarcinoma (PAAD).

RESULTS

In cisplatin-resistant models, DISARM identified novel candidates including multiple inhibitors of PI3K, MEK, and BCL-2, among other classes, across unrelated malignancies. Additionally, DISARM facilitated the selection of predictive biomarkers of response and identification of unique molecular subtypes, such as contrasting ASCL1-low/cMYC-high SCLC targetable by AURKA inhibitors and ASCL1-high/cMYC-low SCLC targetable by BCL-2 inhibitors. Utilizing these predictions, we assessed several of DISARM's top candidates, including inhibitors of AURKA, BCL-2, and HSP90, to confirm their activity in cisplatin-resistant SCLC models.

CONCLUSIONS

DISARM represents the first validated tool to analyze large-scale in vitro drug response data to statistically optimize candidate drug and biomarker selection aimed at overcoming candidate drug resistance.

A Novel Method for Quantifying Total Thoracic Tumor Burden in Mice

Mouse models are powerful tools to study lung cancer initiation and progression in vivo and have contributed significantly to recent advances in therapy. Using micro-computed tomography to monitor and study parenchymal and extra-parenchymal metastases in existing murine models of lung cancer is challenging owing to a lack of radiographic contrast and difficulty in achieving respiratory gating. To facilitate the analysis of these in vivo imaging studies and study of tumor progression in murine models we developed a novel, rapid, semi-automated method of calculating thoracic tumor burden from computed tomography images. This method, in which commercially available software is used to calculate the mass of the thoracic cavity (MTC), takes into account the aggregate tumor burden in the thoracic cavity. The present study showed that in tumor-free mice, the MTC does not change over time and is not affected by breathing, whereas in tumor-bearing mice, the increase in the MTC is a measure of tumor mass that correlates well with tumor burden measured by lung weight. Tumor burden calculated with our MTC method correlated with that measured by lung weight as well as or better than that calculated using four established methods. To test this method, we assessed metastatic tumor development and response to a pharmacologic PLK1 inhibitor in an orthotopic xenograft mouse model. PLK1 inhibition significantly inhibited tumor growth. Our results demonstrate that the MTC method can be used to study dynamic changes in tumor growth and response to therapeutics in genetically engineered mouse models and orthotopic xenograft mouse models of lung cancer.