Inflammation increases breast cancer risk and reduces survival. Breast cancer growth, invasion and metastasis all are promoted by inflammation. Plasma C-reactive protein (CRP) is a measure of inflammation that can be obtained with a routine blood test. Elevated CRP levels have been shown to be associated with reduced survival.

Inflammation involves chronic activation of the immune system

Acute inflammation, which occurs after an injury, infection or exposure to certain irritants, results in temporary symptoms such as redness, pain, swelling and heat.
Systemic inflammation, which is the "inflammation" discussed in the remainder of this article, is a persistent state of inflammation that involves the chronic activation of the immune system. This immune system activation results in the release of pro-inflammatory cytokines (small signaling molecules used in intercellular communication) from immune system-related cells. CRP is produced in the liver in response to infection or injury.

Inflammation increases breast cancer risk

Laboratory studies have demonstrated that pro-inflammatory cytokines can facilitate tumor growth and metastasis by altering tumor cell biology and activating cells in the tumor microenvironment. This is especially true among women with HER2 overexpressing (HER2+ prognosis) disease. In addition, inflammation has been shown to be important to the growth and activity of cancer stem cells.
Studies of human populations have also found a link between inflammation and breast cancer:
  • A 2024 Danish study reported that elevated pre-treatment CRP in women with early-stage breast cancer was an independent marker of increased risk of recurrence.
  • A major 2023 French study found that pro-inflammatory diets were significantly associated with increased breast cancer risk.
  • A 2022 meta-analysis of data from 35 previous studies reported that high CRP was associated with poor prognosis in women with metastatic breast cancer.
  • A 2021 meta-analysis of data from 21 previous studies found that a pro-inflammatory diet was a risk factor for breast cancer, especially for postmenopausal and/or obese women.
  • A 2021 study found that a pro-inflammatory diet was significantly associated with greater risk of breast cancer than an anti-inflammatory diet, especially among those with BMI > 25 kg/m2 and ever smokers.
  • A prospective UK study of 223,393 initially cancer-free people who had a blood sample taken between 2000 and 2008 compared the inflammation status of the 22,715 who subsequently developed cancer with that of those who did not. Cancer patients, including those with breast cancer, were found to have had higher CRP levels and other markers of inflammation at baseline.
Periodontal disease, which qualifies as a chronic inflammatory disorder, has also been shown to be associated with increased risk of postmenopausal breast cancer.

Inflammation promotes breast cancer recurrence

Growing evidence links inflammation to breast cancer progression. One Danish prospective study was designed to investigate whether circulating CRP levels are associated with breast cancer prognosis. The study included 2,910 women whose CRP levels were measured at the time of diagnosis. A total of 383 women died during up to seven years of follow-up, of whom 225 died from breast cancer, and another 118 women had a recurrence (without dying during the study period). Elevated CRP levels at the time of diagnosis were found to be associated with reduced overall survival and with increased risk of breast cancer-specific death. Five-year breast cancer-free survival was 87% among women with low CRP levels compared to 74% for those with high CRP. Among women with HER2+ tumors, those with the highest compared to the lowest third of CRP levels were 8.6 times more likely to die from any cause.
Another study evaluated the relationship between circulating markers of inflammation and breast cancer survival in 734 disease-free breast cancer survivors in the Health, Eating, Activity, and Lifestyle (HEAL) Study. Circulating CRP protein and serum amyloid A (SAA, another marker of inflammation) were determined approximately 31 months after breast cancer diagnosis. Elevated CRP and SAA were both found to be associated with reduced survival.

Anti-inflammation lifestyle and diet

Inflammation is influenced by both lifestyle and nutrition. Regular exercise can reduce inflammation whereas obesity increases it, as does metabolic syndrome (which is characterized by abdominal obesity, high blood sugar levels, impaired glucose tolerance, dyslipidemia, and hypertension). Cigarette smoking also increases inflammation.
High consumption of dietary fiber has been shown to be associated with low levels of inflammation in breast cancer survivors. Numerous studies have also documented the influence of individual foods and food groups on inflammation. Most deeply colored fruits and vegetables have anti-inflammatory properties. Below are anti-inflammatory foods that have also been associated with reduced risk of breast cancer:

Foods that increase inflammation

Inflammation has been found to increase as a result of consuming the following foods:
Please see our article on how to optimize your breast cancer diet for information on what to eat during all stages of treatment and recovery. Below are links to 20 recent studies concerning inflammation and breast cancer. For a more complete list of studies, please click on the tag inflammation.