Since joining the staff in 1997, Dr. Horwitz's contributions include spearheading the clinical program as it grew exponentially in size and patient volumes. He developed advanced treatment programs using intensity-modulated radiation therapy (IMRT), image-guided radiation therapy and brachytherapy, including high-dose-rate (HDR) brachytherapy for prostate cancer and CT based adaptive radiation therapy.  As a result, Fox Chase was the first in the eastern United States to offer HDR implants to men with prostate cancer.

In addition, Dr. Horwitz integrated the use of an MRI treatment simulator into prostate cancer treatment planning for both permanent, low-dose prostate implants and external radiation therapy. Fox Chase was the first in the world to use MRI in radiation treatment planning.

Dr. Horwitz has published extensively in peer-reviewed journals and is a co-author of multiple chapters in various oncology texts. He has been invited to give numerous lectures and presentations at professional meetings in the United States and abroad. Dr. Horwitz has been named a top doctor by Castle Connolly's "American's Top Doctors" and is annually listed as one of Philadelphia magazine's "Top Docs."

He serves on the editorial board of the journal Brachytherapy and is the past-President and Chairman of the Board of the American Brachytherapy Society. He is also active in the American Society of Radiation Oncology and the American Board of Radiology.

Dr. Horwitz received his MD from Albany Medical College in New York after earning his undergraduate degree at the University of Pennsylvania in Philadelphia. He completed both his internship and residency at William Beaumont Hospital in Royal Oak, Mich., where he was chief resident in radiation oncology. Dr. Horwitz joined Fox Chase in 1997.  Since 2008, he has been the Chair of the Department of Radiation Oncology at Fox Chase.  In 2009, he was promoted from Associate Professor to Professor and holder of the Gerald E. Hanks Chair in Radiation Oncology with tenure in Fox Chase's division of medical science.  In 2022, he led the integration of the Department of Radiation Oncology across the Temple University Health System and now leads the single radiation oncology department at Fox Chase and the Lewis Katz School of Medicine at Temple University.