A link has been found between breast cancer survival and high levels of two proteins in the blood that are indicators of inflammation.
The study results were reported in the Journal of Clinical Oncology.
Inflammation is an immune response. It is part of the body's natural defense against harmful elements, such as pathogens, damaged cells, or other irritants, and helps facilitate the healing process.
Inflammation can be classified as either acute or chronic. Acute inflammation is the short-term, beneficial response to harmful stimuli. Chronic inflammation is a disease in which the inflammatory state persists and may result in tissue damage.
Using data from the Health, Eating, Activity and Lifestyle (HEAL) study, researchers found that breast cancer patients with elevated levels of C-reactive protein (CRP) and serum amyloid A (SAA) were about two to three times more likely to die sooner or have their cancer return than those patients who had lower levels of these proteins. This is regardless of the patient's age, tumor stage, race, body mass index, or history of previous cardiovascular issues.
CRP and SAA accumulate in the blood in response to inflammation. CRP is produced by the liver, as well as by fat cells, and has several immune-related functions.
SAA, which is also secreted by the liver, is involved in both the transport of cholesterol from the liver to the bile and the recruitment of immune cells to sites of inflammation.
Both proteins are found in higher concentrations in the blood of people with low-grade chronic inflammation.
Chronic inflammation is believed to contribute to the development and spread of breast cancer, and breast cancer survivors with chronic inflammation may be at a higher risk of recurrence. Elevated CRP is also linked to increased risk of heart disease.
"This HEAL study of inflammation and breast cancer survival contributes uniquely to this emerging research in that it is the largest study to date to examine this association," says Dr. Rachel Ballard-Barbash, a co-author of the study and principal investigator of the HEAL study at the National Cancer Institute (NCI).
"Because of the detailed data on diet, physical activity, and weight in the HEAL study, we were able to examine the extent to which these health behaviors altered this association," she says.
This study joins an increasing body of research indentifying CRP and SAA as indicators of reduced survival from cancer.
Previous studies have shown an association between elevated levels of CRP and poor survival outcomes in metastatic prostate cancer, as well as gastroesophageal, colorectal, inoperable non-small-cell lung, and pancreatic cancers.
In other studies, a similar association was shown for SAA and gastric cancer and renal cell carcinoma. Although research has indicated that inflammation may play a role in the progression of cancer, the exact mechanism by which this happens has been unclear.
This is one of many papers to come out of NCI's HEAL study, an initiative designed to investigate the effects that physical activity, eating habits, weight patterns, diet, hormones, and other factors have on breast cancer prognosis.
For this study, 1,183 women with early-stage breast cancer were studied.
Participants completed a lifestyle questionnaire when they joined the study and the researchers collected blood samples (which were analyzed for CRP and SAA levels) and height and weight measurements at a subsequent visit two years later (approximately 2.5 years after their initial diagnosis).
The women will be followed for a total of 10 years.
This is the first large, population-based study to look at the relationship between breast cancer survivorship and biomarkers of inflammation that were measured after treatment.
Because the biomarkers were measured approximately 31 months after diagnosis, enough time had passed so that the researchers could accurately assess the effect of chronic inflammation, as opposed to acute inflammation that may have been a result of the breast cancer treatments each patient received.
The researchers examined the relationships between the inflammation biomarkers and both overall survival and disease-free survival. Overall survival was defined as the amount of time from the follow-up appointment until the patient died (from any cause) or the study period ended.
Disease-free survival was defined as the amount of time from the follow-up appointment until the patient's breast cancer returned, another, new cancer was diagnosed, the patient died, or the study period ended.
The researchers found that elevated levels of both SAA and CRP were associated (statistically significant) with reduced overall survival.
Women with high levels of SAA were three times as likely to die sooner, and women with high levels of CRP were two times as likely to die sooner.
They found similar, but weaker, associations with disease-free survival, in that women with high levels of SAA were two times as likely to die or have their cancer return, and women with high levels of CRP were more than 1.5 times as likely to die or have their cancer return.
This suggests that SAA and CRP may be more closely related to overall survival than disease-free survival. More research is needed to get a better understanding of these associations and other potential mediating factors, in order to create more precise risk estimates.
"Inflammation has been associated with several modifiable risk factors, such as obesity, low physical activity, and cardiovascular disease, all of which can affect a cancer survivor's prognosis," says Robert Croyle, director of NCI's Division of Cancer Control and Population Sciences.
"Investigating the effect that reductions in these markers, through medications or lifestyle changes, can have on breast cancer recurrence and survival will be an important next step," he says.
Always consult your physician for more information.
Breast cancer is the most frequently diagnosed cancer in women. American Cancer Society (ACS) estimates for 2009 include 192,370 new cases of invasive breast cancer being diagnosed in the US.
In addition, carcinoma in situ will be responsible for 62,280 new cases this year. Of these, 85 percent will be ductal carcinoma in situ.
In 2009, it is estimated that 1,910 men will be diagnosed with breast cancer.
Year 2009 estimates include 40,610 deaths occurring from breast cancer in the US alone - this includes approximately 40,170 women and 440 men.
Breast cancer ranks second among cancer deaths in women after lung cancer.
Regardless of age, African-American women have the highest breast cancer mortality rates.
Any woman may develop breast cancer. However, the following risk factors may increase the likelihood of developing the disease.
A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases, including cancers, have different risk factors.
Knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.
Risk factors that cannot be changed:
The most frequently cited lifestyle-related risk factors:
Environmental risk factors include exposure to pesticides, or other chemicals, and is currently being examined as a possible risk factor.
Always consult your physician for more information.