Rena Desai Callahan MD

Dr. Rena Desai Callahan is a board-certified hematologist and medical oncologist who specializes exclusively in the diagnosis and treatment of breast cancer. Practicing in Santa Monica and Santa Clarita, she integrates the latest advances in precision medicine, molecular diagnostics, and targeted therapies to deliver highly personalized care. As an Associate Clinical Professor of Medicine at the David Geffen School of Medicine at UCLA, Dr. Callahan is deeply involved in breast cancer research and remains at the forefront of emerging treatment strategies.

Dr. Callahan is committed to using state-of-the-art tools to guide clinical decisions, including genomic profiling, advanced imaging, and biomarker-driven approaches. She believes in a collaborative, patient-centered model of care, where each treatment plan is tailored to the individual’s biology, goals, and lifestyle. Her open-minded and empathetic approach fosters trust and empowers patients to actively participate in their care journey.

A graduate of the University of Pennsylvania School of Medicine, Dr. Callahan earned high honors and was inducted into the Alpha Omega Alpha Honor Medical Society. She completed her residency in internal medicine and fellowship in hematology/oncology at UCLA, and holds a Bachelor of Science in Biology from Yale University. A frequent speaker at both local and national conferences, Dr. Callahan is passionate about advancing breast cancer care and is dedicated to improving outcomes through innovation, education, and compassionate expertise.