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Can cashews keep colon cancer patients alive?

Wednesday, May 17, 2017

Surprising new research scheduled to be unveiled at a major cancer meeting next month suggests that cashews and other tree nuts might be as effective as some of oncology’s most effective treatments at keeping colon cancer from recurring after surgery — and even keeping patients from dying.

The researchers did not find an association with eating peanuts. Only tree nuts seemed to matter, to an eye-popping degree. Of 826 patients, those who reported having two or more servings per week (as 19 percent did) had a 46 percent lower risk of their cancer returning and a 53 percent lower risk of dying than those who said they did not eat tree nuts.

Photo of Manish Shah, M.D. If the benefit is real, a daily handful or two of cashews (cost: less than $1) could work as well as standard chemotherapy (cost: thousands of dollars). But the reported benefit comes with a big “if.”

Although the study is from a respected clinical trial, this finding was not from the original research but, instead, an add-on. The original trial randomly assigned colon cancer patients to either of two drug treatments. Later, researchers looked at cancer survivors who simply went about their lives, doing as they pleased, and tried to evaluate whether eating nuts was associated with better outcomes.

In that kind of observational study, it’s not possible to say whether a given behavior — in this case, eating nuts — caused an outcome, or was instead simply associated with the true cause.

In a story that ran in STAT News, Manish Shah, M.D., warned about healthy patient bias - in other words, people who eat tree nuts, such as pecans, almonds, and walnuts, might be different from people who do not. They “might be more health-conscious,” said Shah. They might be wealthier, or better connected to the health care system, or have healthier habits in general. Any of those attributes might help patients survive colon cancer.

“The fear I have is that patients will say, ‘I’ll eat nuts instead of having chemo’” after surgery.

Heather Yeo, M.D., offered this perspective to HemOnc Today:

Photo of Dr. Heather YeoDr. Heather Yeo "This is an interesting study because of the level of detail the researchers were able to get on nut consumption. As with all observational studies, one must be careful about conclusions drawn. The data can only demonstrate a correlation, not causation, and it is difficult to know exactly what the strength of the effect is, as there are many unmeasurable influencing factors.

Those who consume more nuts may be more likely to be vegetarian and may use nuts as an alternative source of protein compared with red meat, which we know is a risk factor for colon cancer. Because higher nut consumption is linked to lower rates of diabetes, the effect we are seeing may be because of that.

It’s important to counsel patients on the importance of a healthy lifestyle, and it is nice to see that things we think of as healthy are associated with improved survival in these patients with colorectal cancer. However, there is no clear causation yet, and further studies need to be done. These healthy behaviors are not a substitute for good clinical treatment options, such as chemotherapy."

Dr. Yeo also commented on another study about the effects of exercise and healthy diet on colon cancer survival. Read the full story here.