PROJECT SUMMARY/ABSTRACT The Training in Oncology Population Sciences (TOPS) T32 program trains postdoctoral fellows to conduct research at the T3 and T4 interface to translate knowledge from the laboratory and clinical trials into practice and population health to reduce the burden of cancer. The need for translational research at the T3 and T4 interface stems from persistent disparities in cancer outcomes and implementation gaps between what is possible in the context of clinical trials and what happens in routine practice. The TOPS program trains 3 postdoctoral fellows each year in collaboration with 31 faculty from across the 7 institutions of the Dana- Farber/Harvard Cancer Center. Training provides fellows with the skills necessary to address the challenges and opportunities brought about by the tremendous growth in the complexity of cancer care, precision medicine, electronic health records, mobile health, machine learning and data sharing. The TOPS program has 3 strategies to achieve this overarching objective: 1) training in core methods and skills necessary for investigation through coursework and participation in regular seminars, workshops and reading; 2) intensive focus on a research project with close mentorship; and 3) training in professional and career development skills that are a prerequisite for investigation including project development, grant writing, presentation, building and working with diverse teams, running a dry laboratory, and the responsible conduct of research. The TOPS T32 is a continuation of the successful R25CA092203 Program in Cancer Outcomes Research Training (PCORT), which trained 52 pre- and post-doctoral fellows between 2002 and 2017. Funded as a T32 since 2017, TOPS is co-led by Dr. Nancy Keating, a primary care physician, and Dr. Jennifer Mack, a pediatric oncologist. TOPS trains postdoctoral students with degrees in the fields of medicine, nursing, behavioral science, pharmacy, economics, clinical epidemiology, health policy, informatics, and engineering for careers dedicated to cancer-focused population science. The core of the program is a group of 31 faculty mentors (inclusive of the co-PIs) and 14 emerging mentors with expertise in 1) qualitative research, survey research, and patient-reported outcomes; 2) observational studies and comparative effectiveness; 3) intervention studies; 4) clinical informatics, mHealth/eHealth, machine learning, and AI; 5) health policy, economics and decision science; 6) implementation science; 7) health equity; and 8) computational biology. At the end of the two-year training, TOPS program participants are well-equipped with the skills necessary to launch independent research careers in cancer-focused population science and have access to the core resources of the DF/HCC and the Harvard Catalyst program for translational research training. The TOPS co-directors and are supported by a 6-member Steering Committee that includes leaders from each of the 7 institutional m...