If the cancer is found only in the breast and has not spread to other parts of the body, 99 percent of the people who receive such a diagnosis go on to live cancer-free lives for a minimum of 5 years.
And, if the cancer has spread to the surrounding lymph nodes, 85 percent of patients with breast cancer have the same 5-year survival rate. However, this rate drops to 27 percent if the cancer has traveled to distant parts of the body.
But what are some of the factors that influence the survivors' outlook? Some studies have revealed that being obese, for example, raises the risk of breast cancer recurrence, even death, by 35–40 percent.
Does this mean that following a low-fat diet will impact a patient's chance of cancer recurrence and overall survival? Scientists led by Dr. Rowan T. Chlebowski, Ph.D. — of the City of Hope National Medical Center in Duarte, CA — set out to investigate.
Their findings were published in the journal JAMA Oncology.
'Significantly greater overall survival'
Dr. Chlebowski and colleagues set out to re-examine the results from the Women's Health Initiative (WHI) randomized clinical trial, which showed a preliminary association between better overall survival and low-fat diet following a breast cancer diagnosis.
The WHI trial then investigated 48,835 postmenopausal women who enrolled in the study between 1993 and 1998. At the time, however, the trial did not offer insights as to whether the improved outlook was due to the eating habits that the women had before developing breast cancer.
Also, there was the possibility that a low-fat diet improved other health outcomes that are unrelated to breast cancer. Therefore, the longer lifespans could have been due to these other outcomes.
So, to clarify these uncertainties, Dr. Chlebowski and colleagues conducted the present study — which is also a randomized trial.
Specifically, the researchers examined 19,541 women diagnosed with breast cancer who reduced their dietary fat intake by 20 percent and upped the amount of fruits and vegetables that they consumed.
The researchers also examined a control group of 29,294 breast cancer patients who continued their usual diets. The dietary interventions lasted for 8.5 years, on average, while the analysis carried out by the researchers took place 11.5 years after their diagnosis, on average.
The study revealed that "breast cancer overall survival was significantly greater for women in the dietary intervention group than in the usual-diet comparison group."
In fact, the 10-year survival rate for the women who consumed less fat was 82 percent, compared with 78 percent in the control group.
Additionally, far fewer deaths were registered in the group that consumed less fat, compared with the usual-diet group. Specifically, 120 women died in the control group, compared with only 68 in the intervention group.
"A dietary change may be able to influence breast cancer outcome," explain the researchers, who conclude that "sustained dietary intervention is needed" to maintain this positive effect.