Department of Research & Evaluation News

A new Kaiser Permanente study showed that fewer breast cancer survivors received recommended annual breast cancer imaging in the time after the COVID-19 pandemic period compared to before the pandemic.

The study was published in JAMA Oncology in July 2025. Little has been known previously about the impact of the COVID-19 pandemic on post-treatment surveillance for patients with breast cancer.

“The COVID-19 pandemic created a disruption in our health care system. Many health care services cannot be done virtually—and this is especially true for patients diagnosed with breast cancer,” said the study’s lead author Erin E. Hahn, PhD, MPH, an investigator with the Kaiser Permanente Southern California Department of Research & Evaluation. “Breast cancer surveillance, which starts after cancer treatment ends, includes annual imaging. COVID may have prevented patients in surveillance for breast cancer from accessing recommended care.”

Study compared women with early-stage breast cancer

This study compared breast cancer surveillance imaging before and after the COVID-19 pandemic began in the U.S. in 2020 among patients diagnosed with early-stage breast cancer within Kaiser Permanente Southern California. For this research, scientists identified 3,369 patients who received their breast cancer diagnosis between 2015 and 2016, and 3,925 who had similar demographic and cancer characteristics who received their diagnosis between mid-2018 and mid-2020, each with 2 years of surveillance This later group would have needed their annual surveillance imaging after the pandemic had begun.

The study found:

• A significantly smaller proportion of later post-COVID-19 group received surveillance imaging than the earlier pre-COVID-19 group.
• 2589 [85%] in the pre–COVID-19 group vs 2829 [78%] post–COVID-19 group.
• Those patients who received radiation treatment or endocrine therapy were significantly more likely to receive recommended imaging than other patients.
• Those diagnosed with Stage 1 disease were more likely to undergo surveillance than those with Stage 2.
• There was no significant difference by insurance type, race and ethnicity, or other illnesses.
• There was not a significant difference between pre– and post–COVID-19 periods on proportion of patients with breast cancer recurrence or progression within the surveillance period.

Kaiser Permanente known for quality of care

Dr. Hahn noted that breast cancer screening and outcomes at Kaiser Permanente Southern California have been outstanding. A recent study in The Permanente Journal showed this by comparing Kaiser Permanente cancer data with national statistics.

Within this study, researchers did not see an increased diagnosis of new cancers in the post–COVID-19 group compared to the pre–COVID-19 group. Dr. Hahn stressed that it will be important to do longer-term studies as the data become available.

Next steps will look at cancer recurrence over time

She said the next step in the work would include evaluating cancer recurrence over 5- and 10-year periods to assess the potential impact of less surveillance in the post–COVID-19 period.

“It is critically important to ensure that patients diagnosed with cancer receive high-quality cancer survivorship care after their treatment ends,” Dr. Hahn said. “Research studies such as these can help us find and address potential gaps in care, improving care and outcomes for our members.”

In addition to Dr. Hahn, other authors include Sarah Eng, MPH; Aiyu Chen, MPH; Eric C. Haupt, ScM; Corrine E. Munoz-Plaza, MPH; Huong Q. Nguyen, PhD, RN; Michael K. Gould, MD, MS; and senior author, Ernest Shen, PhD, of the Department of Research & Evaluation; Shannon Goodall, MD, of Tulane University School of Medicine, New Orleans; and Patricia A. Ganz, MD, of UCLA. Dr. Hahn, Dr. Eng, and Dr. Gould also are with the Kaiser Permanente Bernard J. Tyson School of Medicine in Pasadena, Calif. Dr. Eng is also with Truveta, Inc, Bellevue, Wash.