High-risk breast cancer patients who most closely followed cancer-prevention guidelines published by the American Institute for Cancer Research (AICR) and American Cancer Society (ACS) before, during and after chemotherapy experienced a 37% reduced risk of disease recurrence and a 58% reduced risk of death, according to a study led by Roswell Park Comprehensive Cancer Center.

Researchers hope the information can be used to educate patients about ways they might improve their own outcomes even after diagnosis.

Rikki Cannioto, PhD, EdD, MS, of the Department of Cancer Prevention and Control at Roswell Park, was the first author of “Adherence to cancer prevention lifestyle recommendations before, during, and 2 years after treatment for high-risk breast cancer: Associations with disease recurrence and mortality,” published today in JAMA Network Open. Researchers from 11 institutions contributed to the study.

Dr. Cannioto says both the AICR and ACS publish and regularly update cancer-prevention guidelines based on modifiable lifestyle factors including:

• Don’t smoke.
• Eat a colourful variety of fruits and vegetables, as well as whole grains.
• Maintain a healthy body weight.
• Be physically active.
• Limit or avoid alcohol consumption.
• Limit or avoid consumption of sugar-sweetened beverages.
• Limit or avoid consumption of red and processed meats.

“The literature suggests that all these factors are associated with cancer risk, but until now we did not know whether they were also associated with improved survival outcomes in people who already have cancer,” Dr. Cannioto explains.

She and her colleagues believe their investigation is the first to make that connection for women with high-risk breast cancer.

Tracking lifestyle behaviours over time

Their research grew from an earlier prospective study — the Diet, Exercise, Lifestyles and Cancer Prognosis (DELCap) study, that examined how dietary supplements affect outcomes in high-risk breast cancer patients undergoing chemotherapy. Christine Ambrosone, PhD, Distinguished Professor and Senior Vice President for Population Sciences and Chair, Department of Cancer Prevention and Control, served as principal investigator for that cooperative group clinical trial, which questioned patients about their modifiable lifestyle factors at four different time points: before and during treatment, and at one and two years after treatment ended.

For purposes of the clinical trial, early-stage, high-risk breast cancer was defined as breast cancer with a high risk of recurrence: between stages 1 and 3 at the time of diagnosis, with cancer cells detected in the lymph nodes; and either a primary tumour 2 cm. or larger, or any tumour 1 cm. or larger that was hormone-receptor-negative, or any tumour 1 cm. or larger that was hormone-receptor-positive with a 21-gene recurrence score of 26 or greater.

The 21-gene recurrence score is based on the expression of 21 cancer-related genes detected in pre-treatment tumour specimens.

Dr. Cannioto leveraged data from that study to find out whether adherence to cancer-prevention lifestyles might also affect recurrence and survival.

Using a Lifestyle Index Score (LIS) derived in accordance with standardisation recommendations developed by a task force of scientists from the National Cancer Institute, she and her colleagues assigned points for patients’ responses regarding each of the seven modifiable lifestyle factors — 1 point for strong adherence, a half-point for partial adherence and zero for non-adherence.

Adding the points for all seven factors resulted in overall LIS scores ranging from a perfect 7 to a low of zero.

The first questionnaire, administered before treatment began, was completed by 1,340 participants, who were asked how well they adhered to the seven lifestyle factors prior to their diagnosis.

At the time of enrolment, the average participant was 51 years old.

Most were non-Hispanic White (83.7%) and had been diagnosed with hormone-receptor-positive breast cancer (65.3%).

No patients had previously undergone chemotherapy. 

Benefits seen even in more-aggressive breast cancers 

Researchers noted that reduced risk of recurrence and mortality was seen consistently among participants with a higher LIS, even among those with more-aggressive subtypes of breast cancer.

Says Dr. Cannioto, “The fact that these modifiable lifestyle factors were associated with reduced risk of disease recurrence in high-risk breast cancer patients has important clinical implications.” 

To zero in on the contribution of each of the seven lifestyle behaviours, the research group’s biostatistician removed the score for one behaviour at a time from the overall LIS to determine its relationship to disease recurrence and mortality, Dr. Cannioto explains. 

“The two factors that contributed most to the relationship between the LIS and improved outcomes were the strongest adherence to the smoking and physical activity recommendation."

“Strongest adherence to the fruit and vegetable and sugar-sweetened beverage recommendation also contributed to decreased risk  of both recurrence and mortality. For strongest adherence to the red and processed meats recommendation, we saw a significant decreased risk association only for mortality."

Asking patients about their lifestyle behaviours at four different time points is one unique aspect of the study.

“Most studies that look at the factors influencing treatment outcomes query patients just at the time of diagnosis,” says Dr. Ambrosone.

“Very few collect data through all stages of survivorship.”

“This study provides excellent data showing that even if patients don’t have these positive behaviours during treatment, what they do before and after treatment still makes an important difference in their outcomes,” concludes Dr. Ambrosone.

“Our findings support efforts to work with patients to encourage healthy lifestyle behaviours to improve cancer outcomes.”

Source: Roswell Park Comprehensive Cancer Center