Marisa Siebel, MD

Marisa Siebel, MD, is director of gastrointestinal (GI) malignancies for the Eastern Region at Northwell Health Cancer Institute. Prior to her current appointment, she was the director of medical oncology at Imbert Cancer Center. She is assistant professor at Donald and Barbara Zucker School of Medicine at Hofstra/Northwell.

“For over 20 years, I’ve been doing this work because I love the connection with people,” she says. “I see people at the worst time of their lives, when they need sympathy and a compass, and I treat them like they are my own family.”

Dr. Siebel completed her hematology-oncology fellowship at Fletcher Allen Heath Care at the University of Vermont. She completed her residency at Maimonides Medical Center and is a graduate of St. George’s University School of Medicine and Brandeis University. She joined Northwell in 2016 to open the Imbert Cancer Center in Bay Shore. In 2021, Dr. Siebel was instrumental in developing a GI oncology program for the Eastern region at the Cancer Center in Greenlawn.

Dr. Siebel launched a weekly multidisciplinary GI oncology conference that serves as a concierge program, for patient’s cases to be reviewed by the entire medical team prior to the patient’s visit. This allows the patient to leave with a same-day inclusive treatment plan. “This is a major advantage for patients, as it enables them to see the entire team of specialists on the same day and under one roof, avoiding protracted appointments and back-and-forth travel,” she says, adding that consensus among the team often means treatment is initiated sooner.

Dr. Siebel enjoys teaching and mentoring young physicians during their training, as a way to deliver insight and expertise to the next generation of doctors.

Dr. Siebel anticipates more clinical trials that enroll patients and explore potential new treatments, as a way to advance research and beneficial outcomes. But she says the foundation of her practice will always be her personal connection to her patients.

“When I was an undergraduate, I was fortunate to shadow a radiation oncologist who taught me that care isn’t just about medicine, it’s also about listening,” she says. “That’s stayed with me, and it’s the approach I take as well. Everything is about patient relationships.”