Department of Research & Evaluation News

Kaiser Permanente research found that breast cancer survivors have a higher risk of developing other cancers if they have other preexisting health conditions, such as high blood pressure and diabetes.

“Preexisting health conditions are common in people diagnosed with cancer and what we’ve learned with this study is that comorbidities — experiencing multiple illnesses or disorders concurrently — may increase risk of developing a second cancer,” said the study’s senior author, Reina Haque, PhD, MPH, of the Kaiser Permanente Southern California Department of Research & Evaluation.

The study was published in June, 2025, in Cancer Epidemiology.

Research cohort was more than 37,000 patients

To conduct the study, researchers looked at medical health records of more than 37,000 breast cancer survivors aged 18 and over who had been diagnosed with in-situ, local, or regional first primary breast cancer between 2008 and 2020 at Kaiser Permanente Southern California. Patients were followed electronically until the end of 2021.

Of 37,222 female breast cancer survivors in the study, more than half had a comorbid condition.

The study also found that

• 6% of breast cancer survivors developed a new cancer of other organs during the follow-up, which averaged about 5 years.
• Breast cancer survivors with 1 or more comorbid conditions had a greater risk of developing cancers of other organs compared to those without any comorbidities.
• That risk increased with the comorbidity burden. For example, those with 3 or more comorbid conditions had a 24% increased risk of developing new cancers.

Research a first to examine association

Researchers believe this is the first epidemiologic study to evaluate the association of higher risk of second primary non-breast cancer with increasing comorbidity burden among breast cancer survivors.

“As breast cancer survivors are living longer, their risk of developing cancers of other organs is also increasing, while at the same time, comorbidities such as hypertension, diabetes, and high cholesterol, are on the rise,” said the study’s lead author, Amrita Mukherjee*, PhD.  “Although many of these comorbidities are modifiable, they are often overlooked and left unmanaged, especially in cancer survivors. Given that many of the common comorbidities share similar underlying risk factors as cancer, it was important to determine if comorbidity burden was correlated with risk of other new cancers in breast cancer survivors.”

What the research means for patients

What this research means for patients and health care providers is that paying attention to health conditions in addition to cancer and keeping on top of those health care appointments is important.

“Receiving a cancer diagnosis is difficult and it can be overwhelming to undergo cancer treatments,” said Dr. Haque, who is a senior cancer epidemiologist. “Many common comorbidities such as high blood pressure, high cholesterol, diabetes, and obesity can be managed with lifestyle modifications and/or with medications. Managing comorbidities may protect against developing new cancers.”

Living healthy may be key to prevention

She suggested that other health conditions might be managed by making lifestyle changes such as exercising more, eating better, and sometimes using medications.

“Maintaining a healthy diet and engaging in regular physical activity is crucial for all people,” Dr. Haque said. “But with this study, we see that closely monitoring breast cancer survivors and effectively managing health conditions may help in reducing the risk of secondary cancers.”

In addition to Dr. Mukherjee and Dr. Haque, other authors on the study included Zheng Gu, MPH, and Lie Hong Chen, DrPH, of the Department of Research & Evaluation; Rowan T. Chlebowski, MD, PhD, of The Lundquist Institute at Harbor-UCLA Medical Center in Torrance, Calif.; and Arnold L. Potosky, PhD, of the Georgetown University Medical Center, Washington D.C. and the Kaiser Permanente Bernard J. Tyson School of Medicine. Dr. Haque also is a professor at the School of Medicine.

*A former researcher at the Kaiser Permanente Department of Research & Evaluation, Dr. Mukherjee became an assistant professor of Public Health at the University of Arizona in June 2025.