Radiation Oncologists in California
Data updated monthly · Last refresh October 2026
734 Radiation Oncology providers practice in California, including 310 (42%) offering telehealth. The largest concentration is in Los Angeles. Profiles include federal Open Payments records of money received from drug and device companies in 2025. Listings are drawn from federal public records and are not endorsements.
734providers
310telehealth
Los Angelestop city
Radiation Oncology by city in California
Choose a city to see providers there.
Radiation Oncology providers in California
Listed by city, largest first. Payment figures come from the federal Open Payments program, which requires drug and device companies to report what they pay physicians for consulting, speaking, meals, travel and royalties. A disclosed payment is a financial relationship, not evidence of wrongdoing, and many totals reflect a single meal. Figures cover calendar year 2025.
Dr. Michael Chen, M.D.Santa Rosa, CA · No drug or device payments recorded (2025) ·
(707) 537-8068 Dr. April Vassantachart, MDSherman Oaks, CA · $74 in drug and device payments (2025) · Telehealth ·
(818) 997-1522 Dr. Leslie Botnick, M.D.Sherman Oaks, CA · $2,025 in drug and device payments (2025) ·
(818) 997-1522 Dr. Mary Ozohan, MDSherman Oaks, CA · No drug or device payments recorded (2025) ·
(818) 997-1522 Dr. Ronny KalashSherman Oaks, CA · $22 in drug and device payments (2025) · Telehealth ·
(818) 997-1522 Dr. Ari Kassardjian, MDSimi Valley, CA · No drug or device payments recorded (2025) ·
(805) 955-6000 Dr. Eugene Ahn, MDSimi Valley, CA · $198 in drug and device payments (2025) ·
(805) 584-6611 Dr. Pericles Ioannides, M.D.Sonora, CA · $16 in drug and device payments (2025) · Telehealth ·
(209) 536-6915 Dr. Benjamin Cahan, M.D.South Pasadena, CA · No drug or device payments recorded (2025) · Telehealth ·
(626) 396-2900 Dr. Helen Chen, MDSouth Pasadena, CA · No drug or device payments recorded (2025) · Telehealth ·
(626) 396-2900 Dr. Jason Liu, MDSouth Pasadena, CA · $81 in drug and device payments (2025) · Telehealth ·
(626) 396-2900 Dr. Dasarahally Mohan, MDSouth San Francisco, CA · No drug or device payments recorded (2025) ·
(650) 827-6500 Dr. Deep Patel, MDSouth San Francisco, CA · No drug or device payments recorded (2025) ·
(850) 742-2000 Dr. Joseph Song, MDSouth San Francisco, CA · $244 in drug and device payments (2025) ·
(650) 827-6500 Dr. Laura Millender, M.D.South San Francisco, CA · No drug or device payments recorded (2025) ·
(850) 742-2000 Dr. Milan Patel, M.D.South San Francisco, CA · $80 in drug and device payments (2025) ·
(650) 827-6500 Dr. Adam Bartret, M.D.Stanford, CA · No drug or device payments recorded (2025) ·
(650) 723-4000 Dr. Andrew Martella, M.D.Stanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Anusha Kalbasi, MDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Beth Beadle, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-4000 Dr. Beth Neilsen, MD, PHDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Billy Loo, MD, PHDStanford, CA · $144 in drug and device payments (2025) · Telehealth ·
(650) 736-7143 Dr. Carol Marquez, MDStanford, CA · $147 in drug and device payments (2025) · Telehealth ·
(650) 723-4000 Dr. Catherine Salem, M.D.Stanford, CA · No drug or device payments recorded (2025) ·
(650) 723-4000 Dr. Clement Ho, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-4000 Dr. Daniel Kapp, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-6171 Dr. Daniella Klebaner, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-4000 Dr. Elham Rahimy, M.D.Stanford, CA · $27 in drug and device payments (2025) · Telehealth ·
(650) 723-4000 Dr. Elizabeth Kidd, M.D.Stanford, CA · $184 in drug and device payments (2025) · Telehealth ·
(650) 723-6171 Dr. Everett Moding, MDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(336) 832-7272 Dr. Faisal Ahmed, MDStanford, CA · $47 in drug and device payments (2025) ·
(650) 723-6171 Dr. Farhan Amanullah, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-8463 Dr. Hilary Bagshaw, MDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 736-2457 Dr. Jason Ross, MDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Jennifer Jones, M.D.Stanford, CA · No drug or device payments recorded (2025) ·
(650) 723-6171 Dr. Kathleen Horst, M.D.Stanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 736-7715 Dr. Kevin Day, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-4527 Dr. Lynn Million, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 723-5055 Dr. Mallika Marar, MDStanford, CA · $135 in drug and device payments (2025) · Telehealth ·
(650) 723-4000 Dr. Mark Buyyounouski, M.D.Stanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Maximilian Diehn, M.D./PH.D.Stanford, CA · $6,465 in drug and device payments (2025) · Telehealth ·
(650) 723-6171 Dr. Melanie Smitt, MDStanford, CA · No drug or device payments recorded (2025) ·
(650) 498-5710 Dr. Michael Binkley, M.D.Stanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Michael Clarke, M.D.Stanford, CA · No drug or device payments recorded (2025) ·
(650) 498-5710 Dr. Nam Cho, M.D., PH.D.Stanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-6661 Dr. Nicholas Trakul, MD, PHDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Noah Kastelowitz-lieberman, MDStanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-4000 Dr. Quynh-thu Le, M.D.Stanford, CA · $9,669 in drug and device payments (2025) · Telehealth ·
(650) 723-4000 Dr. Richard Hoppe, M.D.Stanford, CA · No drug or device payments recorded (2025) · Telehealth ·
(650) 723-5510 Dr. Rishabh Chaudhari, MDStanford, CA · $46 in drug and device payments (2025) · Telehealth ·
(650) 723-4000 Common questions
How many Radiation Oncology providers are in California?There are 734 Radiation Oncology providers with active NPI records practicing in California, according to federal NPPES data refreshed monthly.
Do Radiation Oncology providers in California offer telehealth?Yes. 310 of the 734 Radiation Oncology providers in California (about 42%) report offering telehealth services in CMS data.
Which cities in California have the most Radiation Oncology providers?Los Angeles (97), San Francisco (46), Stanford (43) have the highest concentration of Radiation Oncology providers in California.
How many Radiation Oncology providers in California received drug or device company payments?359 of 734 Radiation Oncology providers in California (49%) received at least one payment from a drug or device company in 2025, according to the federal Open Payments program.
Where does this data come from?Provider counts and profiles come from the federal NPPES registry and CMS Doctors and Clinicians files. Payment figures come from the CMS Open Payments program for calendar year 2025. The directory refreshes monthly.
Do most Radiation Oncologists in California work in independent practices or large health systems?Among 516 Radiation Oncologists in California enrolled in Medicare, 16% bill through a solo or small practice with fewer than 10 clinicians, 17% through a mid-size group of 10 to 99, and 67% through a large group or health system with 100 or more clinicians, according to CMS enrollment records.
Which hospitals do Radiation Oncologists in California work at?According to CMS facility affiliation records, the California hospitals where the most Radiation Oncologists hold privileges are UCSF Medical Center in San Francisco; Stanford Health Care in Stanford; UC San Diego Health Hillcrest - Hillcrest Med Ctr in San Diego.
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