The Han Lab
Our research focuses on understanding the genetic and environmental etiology of complex disease and developing and evaluating efficient screening strategies based on etiological understanding. The areas of our research interests include statistical genetics, molecular epidemiology, cancer screening, health policy modeling, and risk prediction modeling. We have developed various statistical methods to analyze high-dimensional data to identify genetic and environmental risk factors and their interactions for complex disease. These approaches include employing a unified framework that integrates a class of disease risk models for modeling the joint effects of genes and environmental exposures and using a set of constraints that are biologically plausible in order to increase the power of tests and to reduce false-positives.
Currently we are working on various projects that aim to:
- Evaluate the genetic, environment, and clinical risk factors for second primary lung cancer to establish efficient screening strategies for lung cancer survivors
- Identify gene-gene interactions for Alzheimer’s disease applying a graphical model based module search to incorporate biological network/pathway and functional information.
- Evaluate genetic, epigenetic, and metabolomic biomarker predictors of PTSD and Resilience following TBI
- Develop efficient risk-based screening strategies for lung cancer using an algorithm for simulating lifetime trajectories of risk factors for lung cancer
- Evaluate the interactions among traumatic brain injury, sex, and apolipoprotein E(APOE4) on the risk of developing Alzheimer’s disease using large case-control study data
Department of Neurosurgery
The Han Lab is part of the Department of Neurosurgery.
(July 29, 2021) SPLC-RAT is a web-based risk prediction tool for second primary lung cancer (SPLC) among lung cancer patients. By simply entering patients’ demographic data, tumor characteristics, and smoking history, the estimates for 5-year and 10-year risks of developing SPLC after initial diagnosis of lung cancer can be provided.
(July 25, 2021) We developed a prediction model for second primary lung cancer (SPLC) risk among ever-smoking lung cancer patients that integrates various risk factors for SPLC, utilizing large population-based cohort data. The proposed model was built using various competing risk modeling approaches and validated using two external populations that are heterogeneous with regards to smoking history and race/ethnicity. This study provides the first effort to incorporate comprehensive risk factors including smoking information, medical history, treatment, and tumor characteristics in predicting SPLC risk using large population-based data. We implemented the proposed model into a user-friendly web-based tool, SPLC-RAT that can help the decision-making of patients and clinicians for guiding surveillance and screening for IPLC cases. This work has been published in the Journal of National Cancer Institute.
Postdocs/Research Assistant for Bioinformatics
July 22, 2021: Applications are invited for postdoctoral fellow positions to join Dr. Summer Han’s research group in the Stanford Center for Biomedical Informatics Research at Stanford University. This position emphasizes developing and applying statistical and machine learning methods for analyzing genomic data (RNA-seq, DNA methylation, and single-cell RNA-seq data) and for building prediction models for various cancers using time-to-event outcomes.
July 6, 2021: We leveraged on the data from a large, population-based study – the National Lung Screening Trial (NLST) – to identify a cohort of lung cancer patients with information on metastasis after cancer diagnosis. We found that patients whose lung cancers were diagnosed by screening with Low-Dose CT imaging were at a significantly reduced risk for brain metastasis compared to those who were diagnosed by other methods (including X-ray screening or clinical symptoms). Our further analyses among those detected in early stages (Stage I-III) and those who underwent surgery for lung cancer treatment show that this reduction in risk may not be fully explained by early detection or curative surgery. To the best of our knowledge, our study is the first effort showing subsequent impact of lung cancer screening on metastasis to other organs. This work further affirms the importance of screening for lung cancer.
The work has been featured in the press on EurekaAlert! by the American Association for the Advancement of Science (AAAS), on Medical Xpress, as well as on Twitter by various major academic organizations including National Cancer Institute (NCI), The International Association for the Study of Lung Cancer (IASLC), Journal of Thoracic Oncology (JTO).
May 2, 2021: We developed a novel statistical method to evaluate gene-gene or gene-environment interaction using genome-wide association study (GWAS) data. This effort provides a robust test for additive interaction under the trend effect of genotype, applying an empirical Bayes-type shrinkage estimator of the relative excess risk due to interaction. The application of the proposed method to examine SNP by APOE*4 interaction for late onset Alzheimer’s disease demonstrated a substantial improvement in controlling false positives over the existing method when the assumption on gene-gene independence was violated. To the best of our knowledge, the proposed method is the first approach that evaluates additive gene-gene or gene-environment interaction under the trend effect of genotype by combining the traditional prospective likelihood-based and the retrospective likelihood-based estimators to relax the strict gene-environment independence assumption. This method is implemented in the CGEN bioconductor package.
Many individuals, especially Blacks, at high risk of lung cancer are not eligible for screening by U.S. Preventive Services Task Force (USPSTF) guidelines, according to a new study. "Current national screening guidelines for lung cancer can induce disparities related to race, socioeconomic status, and comorbidity, and hence a more comprehensive screening approach such as risk-based screening should be considered," Dr. Summer S. Han of Stanford University School of Medicine, in Stanford, California, told Reuters Health by email.
NCI R01 funded for the project, "Evaluation of genetic, clinical, and environmental risk factors to establish effective screening strategies for second primary lung cancer" (PI: Han, 1R01CA226081) (2018)
We developed a novel statistical method to identify genetic associations by integrating a class of disease risk models for the joint effects of genetic and environmental risk factors--appeared in Biometrics (2015)