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    Daniel O'Neil, MD, MPH

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    Assistant Professor
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    Additional Titles

    Affiliated Faculty, Yale Institute for Global Health

    Clinical Member, Yale Cancer Center

    About

    Titles

    Assistant Professor

    Affiliated Faculty, Yale Institute for Global Health; Clinical Member, Yale Cancer Center

    Biography

    Daniel O’Neil, MD, MPH, is an Assistant Clinical Professor of Medicine (Medical Oncology) and cares for patients with breast cancer as part of the Smilow Cancer Hospital Care Center in Waterbury. 

    Dr. O’Neil received his medical degree from Albert Einstein College of Medicine and completed his residency at Brigham and Women's Hospital in both Internal Medicine and Global Health Equity, and fellowship at NewYork-Presbyterian/Columbia University Medical Center. He received his MPH with a focus on epidemiology at Harvard T.H. Chan School of Public Health. 

    Dr. O’Neil is also a global oncology breast cancer researcher. He is particularly interested in understanding the quality of breast cancer care delivered in low- and middle-income countries.

    Dr. O’Neil treats women with breast cancer of all stages and subtypes, as well as women with high-risk benign breast lesions. He strongly believes in the value of multidisciplinary patient care and collaboration. He aims to incorporate the latest evidence-based practices, alongside a holistic understanding of each of his patients, to offer truly personalized care.

    He studies the impact of comorbid HIV on breast cancer outcomes. Women living with both HIV and breast cancer consistently demonstrate higher overall mortality than women living with only breast cancer. Dr. O'Neil's comparisons of breast cancer treatment quality in South African women with and without comorbid HIV have shown that this disparity in mortality is not primarily driven by differences in cancer care. He is currently working with collaborators in Johannesburg and New Haven, looking for differences in tumor behavior or anti-tumor immune response in women living with HIV.

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    Education & Training

    Internal Medicine Intern/Resident
    Brigham and Women's Hospital (2023)
    Global Health Equity Resident
    Brigham and Women's Hospital (2023)
    Hematology/Oncology Fellow
    Columbia University Irving Medical Center (2019)
    MPH
    Harvard T.H. Chan School of Public Health (2016)
    MD
    Albert Einstein College of Medicine

    Research

    Overview

    Dr. O’Neil is a global oncology breast cancer researcher. He is particularly interested in understanding the quality of breast cancer care delivered in low- and middle-income countries. To demonstrate the feasibility of quality monitoring in resource-constrained settings, he has adapted quality metrics from the United States and Europe to describe care in Rwanda and South Africa. That work has addressed receipt of standard of care cancer treatments, treatment delays, and patient adherence to chronic anti-cancer medicines. He is currently studying techniques for improving early detection of breast cancer in South Africa, where access to mammography is limited.

    He also studies the impact of comorbid HIV on breast cancer outcomes. Women living with both HIV and breast cancer consistently demonstrate higher overall mortality than women living with only breast cancer. Dr. O'Neil's comparisons of breast cancer treatment quality in South African women with and without comorbid HIV have shown that this disparity in mortality is not primarily driven by differences in cancer care. He is currently working with collaborators in Johannesburg and New Haven, looking for differences in tumor behavior or anti-tumor immune response in women living with HIV.

    Medical Research Interests

    Global Health; Quality of Health Care

    Public Health Interests

    Cancer; Global Health

    Research at a Glance

    Publications Timeline

    A big-picture view of Daniel O'Neil's research output by year.
    12Publications

    Publications

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    Clinical Care

    Overview

    Daniel O’Neil, MD, MPH, is a medical oncologist who specializes in breast cancer.

    “It’s incredibly rewarding to work with breast cancer patients,” Dr. O’Neil says. “I meet people during one of the most stressful moments in their lives, usually shortly after they've been diagnosed, and I have the opportunity to give them the information they need to make the best decisions about how to take care of their disease. I try to reassure them that they are making a good choice for themselves and for their families.”

    Dr. O’Neil says he enjoys getting to know his patients and their families. “In many cases, breast cancer patients are cured completely. I get to see my patients for years afterwards as they've continued to live their lives and everything has returned to normal,” he says. “And even in cases where there is more aggressive or advanced disease, there is still an opportunity to help patients choose the right treatment to maintain their quality of life, to help them live with their disease for as long as possible, and to help them make good choices about what's important to them.”

    At Smilow Cancer Hospital, a team approach is beneficial to patients, Dr. O’Neil says. “When you're being treated for breast cancer, there are the physicians you interact with directly, such as your surgeon, medical oncologist, and radiation oncologist. And then there are the doctors who are behind the scenes, like pathologists and radiologists, who interpret many of the tests that you're undergoing and are hugely important to your care,” he says.

    Dr. O’Neil’s research is focused on understanding the quality of breast cancer care delivered in low- and middle-income countries. He is also interested in how HIV affects breast cancer mortality in women.

    Clinical Specialties

    Medical Oncology

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