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Isaac A. Klein, MD, PhD

Medical Oncology

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  • Physician
  • Instructor in Medicine, Harvard Medical School


Clinical Interests

  • Breast cancer
  • Novel therapies

Diseases Treated

Contact Information

  • Appointments617-632-2175 (new)
    617-632-3800 (established)
  • Office Phone Number617-632-3800
  • Fax617-632-1930


Dr. Klein received an undergraduate degree from Cornell University in 2004, a PhD in biology from the Rockefeller University in 2011, and an MD from the Weill Cornell Medical College in 2013. He then completed a residency in internal medicine at the Brigham and Women's Hospital and Harvard Medical School in 2016 and a fellowship in Medical Oncology at Dana-Farber Cancer Institute with a clinical focus on breast cancer in 2019. Dr. Klein is a physician-scientist and practicing medical oncologist in the DFCI Breast Oncology Center and performs biomedical research at the Whitehead Institute of the Massachusetts Institute of Technology. In the laboratory, Dr. Klein studies the mechanisms of dysregulated gene expression in breast cancer, the function of the estrogen receptor, and biomolecular condensates in malignancy. He aims to use this understanding to develop more effective therapies for breast cancer. In the clinic, Dr. Klein cares for patients with both early and metastatic breast cancer, with an interest in novel therapies and personalized treatment.

Board Certification:

  • Internal Medicine, 2016


  • Dana-Farber Cancer Institute, Medical Oncology


  • Brigham and Women's Hospital, Internal Medicine

Medical School:

  • Weill Cornell Medical College


Dana-Farber Cancer Institute
450 Brookline Avenue
Boston, MA 02215
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