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K. Boyd



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    MO05 - Prognostic and Predictive Biomarkers II (ID 95)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Medical Oncology
    • Presentations: 1
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      MO05.11 - The Effect of Two BRM Promoter Polymorphisms on the Risk of Advanced Non-Small Cell Lung Cancer (NSCLC) and Small Cell Lung Cancer (SCLC) in Smokers (ID 1987)

      17:15 - 17:20  |  Author(s): K. Boyd

      • Abstract
      • Presentation
      • Slides

      Background
      BRM, an ATPase subunit of the SWI/SNF chromatin remodeling complex, is a putative tumor susceptibility gene in lung cancer. Loss of BRM expression occurs in 15% of lung cancers. Two BRM promoter insertion polymorphisms (BRM-741 and BRM-1321) lead to epigenetic silencing of BRM and highly correlate with loss of BRM expression and function in lung tumors. Pharmacologic reversal of the epigenetic changes of BRM is feasible. We previously demonstrated a strong risk association between these two polymorphisms and susceptibility to early stage NSCLC. Here, we evaluate the association between the two BRM polymorphisms and risk of developing: 1) advanced NSCLC, and 2) SCLC among smokers.

      Methods
      Genotyping for BRM promoter polymorphisms was performed using TaqMan. The cohorts analyzed were: 1) 417 stage III-IV NSCLC cases and 2) 111 SCLC cases treated at the Princess Margaret Cancer Centre (PMCC), Toronto; and 3) 43 SCLC cases from the University of Florida (U of F), all with a smoking history of ≥1 pack-year. Cases were matched to healthy controls by frequency distribution (1:2 for PMCC cases; 1:1 for U of F cases) based on age, gender, pack-year smoking history, and either current smoking status (PMCC) or ethnicity (U of F). Adjusted odds ratios (aORs) with their 95% confidence intervals (CI) of the association between polymorphisms and lung cancer risk were estimated by multiple logistic regression models.

      Results
      Of the 417 NSCLC cases, 59% were male; 41%, current smokers; 63%, adenocarcinoma; 51%, stage IV; median age, 63 years. The frequency of homozygosity was BRM-741, 21%; BRM-1321, 20%; both, 11%. The homozygous variants of BRM-741 and BRM-1321 were associated with an increased risk of advanced NSCLC compared to the wild types, with aOR’s of 1.6 (95% CI: 1.1-2.2; p=0.008) and 1.4 (95% CI: 1.0-2.0; p=0.04), respectively. Being homozygous for both BRM promoter variants carried an even greater risk (aOR 2.4 [95% CI: 1.4-4.0; p=0.0009]), with the strongest effect observed among current smokers (aOR 3.4; p=0.0005), and those with a histological diagnosis other than adenocarcinoma (aOR 3.2; p=0.0005). Among the 111 PMCC SCLC cases, 62% were male; 56%, current smokers; median age 65 years; of the 43 U of F SCLC cases, 35% were male; median age, 63 years. The presence of double homozygous variants of BRM-741 and BRM-1321 had no effect on the risk of developing SCLC in either of the two cohorts analyzed, with aOR’s of 1.1 (95% CI: 0.3-3.5; p=0.94) and 0.3 [95% CI: 0.04-2.41; p=0.27), respectively.

      Conclusion
      The presence of double homozygous variants of the BRM promoter polymorphisms, BRM-741 and BRM-1321, significantly increases the risk of advanced NSCLC among individuals with a smoking history greater than one year, with the strongest effect observed among current smokers. In contrast, the same two polymorphisms had no effect on the risk of developing SCLC in either of the two cohorts analyzed. Thus, this study offers further insight into potential mechanisms underlying the genetic susceptibility to developing advanced NSCLC among smokers. Validation in larger populations is warranted.

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    O01 - Prognostic and Predictive Biomarkers I (ID 94)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Medical Oncology
    • Presentations: 1
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      O01.03 - BRM Promoter Variants and Survival Outcomes of Advanced Non-Small Cell Lung Cancer (NSCLC) Patients: A Validation Study in the NCIC Clinical Trials Group (NCIC-CTG) BR24 Clinical Trial (ID 1999)

      10:50 - 11:00  |  Author(s): K. Boyd

      • Abstract
      • Presentation
      • Slides

      Background
      BRM, an ATPase subunit of the SWI/SNF chromatin remodeling complex, is a putative tumor susceptibility gene in NSCLC. Loss of BRM expression occurs in 15% of NSCLC, and has been linked to adverse outcome. Two BRM promoter insertion variants (BRM-741 and BRM-1321) result in epigenetic silencing of BRM through recruitment of histone deacetylases. The presence of double homozygous BRM variants is linked to loss of BRM expression and function in lung tumors, and double the risk of lung cancer. Pharmacological reversal of the epigenetic changes of BRM is feasible. In this study we evaluated the association between the BRM promoter variants and survival outcomes of advanced NSCLC patients.

      Methods
      The training cohort consisted of 564 stage III-IV NSCLC patients treated at the Princess Margaret Cancer Centre, Toronto 2006-2010. The validation cohort comprised 219 stage IIIb-IV NSCLC patients from the NCIC-CTG BR24 clinical trial, a phase II/III double-blind randomized trial of cediranib versus placebo in patients receiving carboplatin/paclitaxel for the treatment of advanced or metastatic NSCLC. Genotyping for the BRM promoter variants was performed using Taqman. Associations of BRM promoter variants and overall (OS) and progression free survival (PFS) were assessed using Cox proportional hazard models adjusted for clinically relevant variables, and in the case of the BR24 population, stratified by treatment arm.

      Results
      Among the training cohort, 73% were Caucasian, 52% male, median age 63 yrs, 55% stage IV disease, and 67% adenocarcinoma. Median OS was 1.6yrs; median follow up, 3.6yrs. The frequency of homozygosity was BRM-741, 23%; BRM-1321, 21%; both 12%. Homozygous variants of BRM-741 were strongly associated with worse OS (adjusted HR [aHR] 2.5 [95% CI: 1.9-3.3; p=6x10E-10]) and PFS (aHR 2.0 [95% CI: 1.6-2.6; p=9x10E-8]) compared to the wild types. Similar findings were observed for the BRM-1321 homozygous variants (aHR for OS of 2.0 [95% CI: 1.5-2.6; p=2x10E-6]; aHR for PFS of 1.8 [95% CI: 1.4-2.4; p=3x10E-6]). The presence of double homozygous BRM-741 and BRM-1321 variants was strongly associated with worse OS (aHR 2.8 [95% CI: 1.9-4.0; p=7x10E-8]) and PFS (aHR 2.7 [95% CI: 1.9-3.8; p=1x10E-8]). Genotyping was possible for 219/296 BR24 participants. Of these, 59% were male, median age 59 yrs, 83% stage IV, 46% adenocarcinoma, with 50% receiving cediranib. Individuals carrying the homozygous variants of both BRM-741 and BRM-1321 (13% of cases) had a substantially worse OS (aHR 9.0 [95% CI: 4.3-18.5; p=1x10E-9]) and PFS (aHR 3.8 [95% CI: 1.9-7.3; p=3x10E-5]) compared to the wild types, irrespective of whether they were treated with cediranib (aHR for OS of 6.4; p=1x10E-4; aHR for PFS of 2.1; p=0.02) or placebo (aHR for OS of 16.8; p=2x10E-7; aHR for PFS of 8.3; p=1x10E-4).

      Conclusion
      The same two homozygous BRM promoter variants that are associated with increased risk of NSCLC are also strongly associated with adverse OS and PFS in this study of advanced NSCLC patients. We are completing additional studies focusing on the relationship between the BRM promoter variants and BRM protein expression; results will be presented at the meeting.

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    O24 - Cancer Control and Epidemiology III (ID 134)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Prevention & Epidemiology
    • Presentations: 1
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      O24.05 - The impact of body mass index on survival in stage 3 and 4 lung cancer (ID 663)

      16:55 - 17:05  |  Author(s): K. Boyd

      • Abstract
      • Presentation
      • Slides

      Background
      Obesity has been shown to be an adverse prognostic factor in several cancers, including breast, colorectal, endometrial, ovarian, pancreatic and prostate. However, studies of body mass index (BMI) and outcomes in lung cancer are lacking. Understanding the clinical impact of body weight on cancer outcomes is important given the high prevalence of obesity globally. We retrospectively evaluated the distribution of BMI at diagnosis and its effects on survival in stage 3 and 4 lung cancer patients.

      Methods
      1,121 patients with stage 3 or 4 lung cancer from a single institution were analyzed. Clinicopathologic data were collected retrospectively. Adjusted hazard ratios (aHR) for overall survival (OS) and progression-free survival (PFS) were generated by Cox regression for each BMI (kg/m[2]) category (underweight: <18.5, normal: 18.5-24.9, overweight: 25.0-29.9, obese: ≥30), after adjusting for age, gender, Charlson Comorbidity Index, performance status (PS), clinical stage and treatment regimen.

      Results
      In this cohort (n=1,121), the frequencies of stage 3A, 3B and 4 lung cancers were 35%, 32% and 33%, respectively. There were 633 (57%) adenocarcinomas, 238 (21%) squamous cell carcinomas, 38 (3%) small cell lung cancers, and 210 (19%) other histologies. Patients had variable BMI: 82 (7%) underweight, 550 (49%) normal weight, 333 (30%) overweight, 156 (14%) obese. Being overweight/obese was associated with older age (p=0.002) and stage 3A disease (p=0.001); underweight patients were more likely current smokers (p<0.001). OS was significantly decreased with age ≥65, males, PS 2-3, stage 4, and lack of systemic treatment (p<0.001). Median OS in underweight, normal weight, overweight and obese patients were 14, 23, 24 and 26 months, respectively. Compared with BMI ≥18.5, being underweight was associated with significantly poorer OS (aHR 1.33, 95% CI 1.01-1.77, p=0.045), but not PFS (aHR 1.12, 95% CI 0.86-1.46, p=0.414). The magnitude of this association was greatest among those aged less than 65 years (aHR 1.57, 95% CI 1.11-2.22, p=0.011).

      Conclusion
      In stage 3 and 4 lung cancer, being underweight at diagnosis is associated with significantly poorer OS, especially in patients younger than 65 years of age. Lower BMI is mostly observed in current smokers, while above normal BMI is seen in older patients and stage 3A disease. Unlike other malignancies, obesity does not increase mortality in this population. The BMI-survival relationship in lung cancer requires further study.

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    P1.05 - Poster Session 1 - Preclinical Models of Therapeutics/Imaging (ID 156)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Biology
    • Presentations: 1
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      P1.05-007 - Large scale establishment of genetically diverse patient-derived primary tumor xenografts from resected early stage non-small cell lung cancer (NSCLC) patients (ID 1539)

      09:30 - 09:30  |  Author(s): K. Boyd

      • Abstract

      Background
      The fidelity of established NSCLC cell line models to reflect patient tumors has been challenged. Patient-derived primary tumor xenografts (PTXGs) established directly from patient tumors in immunodeficient mice reproduce closely the histology of the primary tumors, thus are potentially better preclinical models to investigate novel therapies. We previously reported that early stage NSCLC patients whose tumors form PTXGs have significantly greater risk of relapse after surgery (Clin Cancer Res 2011; 17: 134-141). We report here a more extended analysis of clinical-molecular-pathological features of early stage NSCLC that are associated with engraftment and its impact on patient outcome.

      Methods
      Resected NSCLC tumors were harvested within 30 minutes after surgery and were implanted into severely immunodeficient mice to establish PTXGs. Tumors that grew were propagated for up to 3 passages. The mutational profiles of the primary tumors were assessed by the MassARRAY platform that included 133 mutations with ‘putative’ driver function, which have been reported in COSMIC database as recurrent in NSCLC. All identified mutations were verified by direct sequencing in both the primary and PTXG tumors. Engraftment rate among clinical factors were tested using the Fisher’s exact or Mann-Whitney tests. The Kaplan-Meier method was used to estimate 3-year overall (OS) and disease-free survival (DFS) probabilities. The effect of engraftment on OS and DFS adjusting for clinical variables was assessed using a Cox proportional hazards model.

      Results
      From April 2005 to December 2010, 261 rigorously verified resected primary non-carcinoid NSCLCs were engrafted; 38 xenografts that were lymphoma were excluded from further analysis. For the remaining 223 primaries, 101 (45.3%) successfully engrafted and formed PTXG lines. Engraftment rates were 33.8% (48/142) for adenocarcinoma (AdC), 67.7% (42/62) for squamous cell carcinoma (SqCC), 66.7% (4/6) for large cell neuroendocrine carcinoma, and 53.8% (7/13) for others. The tumors forming PTXGs were more likely to be poorly differentiated (p=0.00012) and of larger tumor size and higher pT stage (p<0.0001), but were not correlated with the pN stage. Among 95/101 (94.1%) PTXG cases profiled for mutations, 6 had mutations in the EGFR tyrosine kinase domain, 18 in KRAS/HRAS, 5 in PIK3CA, 2 in paxillin and 1 in STK11/LKB gene; 56 (62.2%) were negative for mutations. The median follow-up time was 2.7 years (range 0.04 – 7.5 years). Patients whose tumors engrafted had decreased DFS (HR 2.68, 95% CI 1.16-4.60, Wald p<0.0001) and OS (HR 3.14, 95% CI 1.56-6.33, Wald p=0.0014). Significantly poorer survival was maintained in AdC. Among 33 patients with EGFR mutation, only 6 (18.2%) engrafted. Engraftment was associated with significantly poorer DFS (HR 4.76; 1.43-15.86, log-rank p=0.005) and OS (HR 8.55, 95% CI 0.77-94.3, log-rank p=0.035) in this population.

      Conclusion
      The ability to form PTXGs of early stage NSCLC is confirmed as a very strong poor prognostic marker. Although EGFR mutant tumors usually do not engraft, engraftment of EGFR mutant tumors is associated with poor patient survival. PTXGs appear to represent biologically aggressive NSCLC.