Offering Surgical Oncology

Mission Hope Surgical Oncology| Santa Maria | 805-346-3456

Your Oncology Team

Diagnosing and treating cancer is complex. We use a multidisciplinary approach, which consists of different medical professionals to give you the best possible outcome. Your healthcare team meets twice weekly at Mission Hope Cancer Center for Tumor Board to discuss all cancer cases and share knowledge to determine the best possible treatment for our patients. Every patient receives an individualized treatment plan.

A Surgeon…

is a doctor who can perform biopsies to diagnose cancer and treat cancer using surgeries that remove the tumor and nearby tissue.A Plastic or Reconstructive Surgeon treats structures of the body affected aesthetically or functionally by cancer and its surgeries.

Colleen O’Kelly Priddy, MD, FACS


Dr. O’Kelly is board certified in General Surgery and subspecializes in Breast Surgical Oncology. With years of training and education focused on breast disease, she has an in-depth knowledge of cancer biology, genetics and the most advanced surgical options to help patients achieve the best possible results and can provide novel and innovative treatments for breast cancer patients.

Dr. O’Kelly is a Stanford University Alum and earned her medical degree from University of Nevada School of Medicine. She completed her residency in General Surgery at University of Washington and went on to do a subspecialty fellowship in Surgical Breast Oncology at the University of Southern California. Dr. O’Kelly received the Muzzy Family Endowed Fellowship in Oncoplastic Surgery Award in 2016 for excellence in oncoplastic surgery, which is a surgical approach to treat breast cancer effectively while leaving the breast appearing as normal as possible afterward.

After working in upstate New York, she, her husband and two sons returned to California to be closer to family. Dr. O’Kelly is pleased to collaborate with Cancer Care team at Mission Hope Cancer Center.

Jonathan Tammela, MD


Dr. Jonathan Tammela is a triple board-certified surgeon in Gynecologic Oncology, Hospice and Palliative care, and Obstetrics and Gynecology. He provides highly specialized care in the diagnosis, treatment, and management of cancers affecting the female reproductive tract.

He received his medical degree from Indiana University School of Medicine and completed his residency in OB/GYN at the University of Florida. He was selected to complete subspecialty training in Gynecologic Oncology at Roswell Park Cancer Institute in Buffalo, New York.

Dr. Tammela is a trailblazer in his field, having established the first robotic gynecologic oncology program in NE Wisconsin, when robotic surgery was just beginning to show clinical promise in surgical cancer care. He became a proctor and instructor for colleagues desiring to train in robotic surgery, and has himself performed over 1000 robotic surgeries.

He looks forward to bringing expert care to Mission Hope Cancer Center.



Dr. Thomas Bosshardt is board certified in General Surgery and is a Fellow of the American College of Surgeons who specializes in General, Thoracic, Gastrointestinal and Laparoscopic Surgery. He has practiced surgery on the Central Coast since 2004, and as an associate of the group Surgical Specialists, Inc., he serves as a member of Marian Regional Medical Center’s specialized surgical staff.

Dr. Bosshardt received his medical degree from UCLA School of Medicine where he graduated with honors as “Top Medical
Graduate.” He completed his internship at Naval Hospital Portsmouth and his residency at UC Davis East Bay. He later served as a clinical assistant professor of surgery for the University of California, San Francisco-East Bay Surgery Residency Program.

Dr. Bosshardt provides innovative, quality care in the surgical treatment of cancers of the lung, gastrointestinal tract, thyroid gland and soft tissue.