The Margie Petersen Breast Center, a Center of Excellence

The Margie Petersen Breast Center at Providence Saint John’s Health Center offers the most compassionate and innovative care in Southern California. We care for and treat the whole person: mind, body, and spirit, providing an array of services to support your emotional and physical wellbeing. Our unique partnership with the Saint John’s Cancer Institute offers an environment that combines clinical excellence with novel research so that the care you receive is outcomes-based and optimized specifically to you. Get answers to your questions today.

“We are a comprehensive, multidisciplinary Breast Clinic and Oncology provider that is ready to support you.”

Clinical Excellence and Improved Quality of Life

Our care team understands that each case is unique, while we treat every patient with dignity and compassion. We understand the challenges of coping with cancer and other life-changing decisions, and we are ready to guide you every step of the way. With an outcomes-based approach and our multi-disciplinary team, we work to develop the most optimal treatment plan for you based on your needs and the input of many of our oncologists, pathologists, and scientists. clinical excellence is our commitment to you.

Dr. Grumley greets a patient prior to their examination.

“I got an assessment the same day and didn’t even need a referral. I am so relieved and thankful you are here. Truly an amazing team.” -L.R.

“Thank you Dr. Grumley for your extraordinary care. My husband and I are extremely grateful for both the technical side and very personal, human side of our relationship.” -Kristy

“Dr. Parvin Peddi, MD has a glowing personality and is the true definition of the best of the best…” -Ching

We treat the whole person, and we treat them like family.

– Dr. Janie Grumley

Breast Care Team - Margie Petersen Breast Center
The Breast Care Team of the Margie Petersen Breast Center is ready to guide and support you.

Our History and Approach Patient Care

For almost 30 years, Saint John’s Cancer Institute has maintained a center dedicated to the treatment and research of breast cancer. Extraordinary supporters, such as Joyce Eisenberg Keefer and Margie Petersen, have enabled the center to become what it is today—a premiere provider that is fundamentally changing breast health.

With a highly advanced diagnostic center on site, we immediately identify and treat breast issues, often seeing patients the same day, and without requiring a referral. Our integrated approach to your care, which involves many specialists, including experts in surgery, medical oncology, and radiotherapy, we surrounded each patient with a dedicated team of healthcare and wellness professionals whose mission is to focus on the whole person.

Your Multi-disciplinary Team at Margie Peterson Breast Center

We are making a difference and we prove it every day.

Under the leadership of Dr. Janie Grumley, Director of the Comprehensive Breast Program at Margie Petersen Breast Center, our clinical team, including medical oncologist, Dr. Parvin Peddi and radiation oncologist, Dr. Robert Wollman, welcomes all your questions and concerns. As a multi-disciplinary team, we have successfully treated thousands of patients and look forward to providing you and your family additional information and support.

Breast Treatment & Services

Women come to the Margie Petersen Breast Center because we can fully evaluate any breast condition in one day. Thankfully, most lumps found in the breast are not cancer, but it is important to have it checked sooner than later. If a biopsy is needed, we perform the biopsy the same day, or as soon as possible. Our team of breast specialists can quickly determine next steps and guide your care. With an annual exam, we can conduct regular screenings, which is essential for early cancer detection.

Breast Health

Breast Health involves assessment of symptoms, conditions, and genetics, as well as prevention. (See Breast Health)

  • Genetic testing and family history are considered to determine risk and recurrence.
  • Common conditions may involve breast pain, masses (or lumps), skin conditions, and lesions.
  • Prevention involves wellness recommendations and steps you can take to be well.

Breast Evaluation

Breast Evaluation involves how we assess the extent of conditions. (See Breast Evaluation)

  • Breast exams help to establish regular assessment and early cancer detection.
  • Technologies, including ultrasound, mammograms, CT scans, and Magnetic Resonance Imaging (MRI), provide visual references and measurements for the care team.
  • Biopsies aim to validate if a cancerous condition is present.

Breast Cancer Treatment

Treating breast cancer may require one or more types of treatment, which are prescribed as appropriate to maximize curative effect and improve quality of life. For example, surgery may be followed by radiotherapy and chemotherapy, whereas a small, solid tumor may be treated with just radiotherapy depending on its location and the presence of metastasis. Additional treatment may include endocrine therapy (hormone therapy) and immunotherapy (helps your immune system fight cancer). Our goal is to determine the best possible care path for you based on the type of breast cancer you have, its stage, your overall health status, and your treatment preferences. We are here to support you every step of the way.


Removal of the cancerous gland, organ, or affected tissues (See Surgery for Breast Cancer)

  • May be performed with the aid of robotics
  • Used to repair tissues affected by cancer and surgery, including breast reconstruction
  • Can be utilized with other types of treatment


Focused beams of energy that disrupt tumor growth (See Radiotherapy for Breast Cancer)

  • Used primarily for solid tumors and in difficult to reach areas
  • May require specialized imaging to determine the exact location of the tumor
  • Can be externally via beam or internally using specialized instruments
  • Can be utilized with other types of treatment


Medical treatment that addresses cancers that have or can spread to other areas (See Chemotherapy for Breast Cancer)

  • Reduces the speed of fast-growing cancer cells throughout the body
  • Encompasses systemic therapies, such as biologic, endocrine, and immunotherapy treatment
  • Can be utilized with other types of treatment

Breast Reconstruction

Redeveloping the appearance of the breast after partial or complete breast removal (mastectomy) (See Breast Reconstruction)

  • Common for women who undergo breast tissue removal
  • May take place immediately after the surgical removal of cancerous tissue
  • Encompasses different kinds of on reconstruction, including Direct-to-Implant, Autologous Tissue, and Nipple-Areola Reconstruction After Mastectomy


Supportive services we offer that can improve your wellbeing aside from your primary cancer treatment (See Wellness for Breast Cancer)

  • Complementary nutritional consultation
  • Yoga classes for men or women
  • Meditation (Mindfulness and Stress reduction)
  • HeartMath®
  • Cancer Rehabilitation Services
  • Counseling and Psychiatric Services
  • Cancer Related Financial Resource Information
  • Neurocognitive Services
  • Spiritual Care Services
  • Appearance and Cancer Program
  • Other Support Services including care-giver support
  • Palliative Care

The Breast Oncology team at the Margie Petersen Breast Center is ready to support you and your family. We welcome your questions and recommend coming in for an exam as soon as possible. We will discuss common conditions, treatment options, and offer additional details for each of our services based on your health, as well as other cancer support services.

Contact us today.

Let’s start by answering your questions

Speak to someone today and get answers to your specific questions.

Call 310-582-7100.

Our care team is available to answer your questions and can relay your question to one of our specialists and get back to you. Know that you are always well-supported and treated with compassion at the Saint John’s Cancer Institute and our health center.

Dr. Trevan Fischer discusses treatment options with a breast cancer patient
Dr. Trevan Fischer discusses treatment options with a breast cancer patient.

Request an Appointment

Please provide your contact information and your question below and we will respond to you as soon as possible. We can also provide appointment availability.

Saint John’s Cancer Institute is leading with innovation

An Outcomes-based Approach

Saint Johns Cancer Institute Epigenetics Breast Research
Research at the Saint John’s Cancer Institute is improving patient outcomes.

The doctors at the Margie Petersen Breast Center have the advantage of working alongside other researchers, including geneticists, biologists, immunologists, drug discovery scientists, and clinical trials experts at the Saint John’s Cancer Institute, who collaborate with dozens of academic and industry organizations worldwide.

Together, they apply decades of research, genetic insights, and data from thousands of cancer cases, to improve clinical practice and quality of life for our patients. For example, we can identify biomarkers and genetic profiles that indicate who is more likely to have a recurrence of cancer, which can guide early treatment strategies and other preventive measures. As a patient, you can be assured that highly recognized doctors and peer-reviewed, published physicians and scientists are all working together to develop the best care approach and medical solutions.

Advancements in Radiotherapy

Intraoperative Radiation Therapy (IORT) - Saint John's Cancer Institute
IORT delivers a targeted dose of radiation to the cancerous area at the time of surgery.

Intraoperative Radiation Therapy (IORT)

Highly targeted radiation therapy delivery that limits the radiation to just the treatment area (See Radiation Therapy Treatments).

  • Used during breast conserving surgery
  • Used in early-stage breast cancer
  • Treats the area that the tumor previously occupied
  • Delivered as a single treatment of radiation
  • Patients receiving IORT after surgery may not need future radiation
  • Reduces the need for additional care visits compared to external beam treatment
  • Lowers the risk of cancer recurrence

Accelerated Partial Breast Irradiation (APBI)

Balloon Catheters - APBI Treatment
APBI is delivered via a catheter and balloon device after the tumor is removed.

Provides the radiation oncologist greater options by focusing radiation to just a portion of the breast (See Radiation Therapy Treatments).

  • Applied using a catheter and lumens, or balloon, device
  • A portion of the catheter remains outside of the breast and is connected to a computer-controlled machine that delivers the radiation
  • Treats the surrounding tissue close to the tumor site
  • Equivalent to a 5-week course of whole-breast radiotherapy
  • Treatment is performed twice a day for a total of 5 days
  • Reduced treatment time comparted to external beam radiation
  • An outpatient procedure

Programs Expansion

Saint John’s Cancer Institute Translational Immunology Program

Cancer Cell and T-cell - Immunology and Breast Research
Immunotherapies are designed to support the immune system, reducing the spread of cancer cells.

Launched in 2021, our Immunology program works to define and isolate the mechanisms by which cancer cells evade the immune system (See Translational Cancer Immunology).

The goals of the Immunology program include:

  • Identify the inhibitors of immune response that prevent the body from healing itself
  • Promote novel immuno-therapeutic agents for improving immune response
  • Develop targeted immunotherapies specific to the genetic profile of a patient
  • Predict with greater accuracy relapse-free survival

If you have questions regarding breast examination or treatment, please call today.

Recent Publications & Research

Dr. Janie Grumley and team of oncologists have published and co-authored dozens of peer-reviewed, breast research articles. View additional articles for Dr. Grumley at

NIH Article - Breast Research