DR RUGO: I think that the majority of data that we have is actually on the risk of developing breast cancer, but there’s also data on the risk of recurrence after and having even a new cancer after your initial diagnosis. And I think, if you take this data into the context of risk of recurrence and data that’s been reported from cooperative group studies where you look at weight, body mass index and look at risk of recurrence and death, that what you get out of that is that gaining weight, which is often associated with a higher-fat diet and eating a higher-fat diet, seems to be associated with a worse outcome.

Does that mean that a patient who has terrible triple-negative breast cancer that’s growing on chemo can affect their outcome by changing their diet? No. So I think you have to take it into perspective. It’s the patients who have hormone receptor-positive disease. And what I do is talk about weight gain and diet in every single patient in the adjuvant setting. And we talk about it over time. If they exercise, of course, they’ll help to control their weight. Controlling their diet, but they don’t need to go on a vegan diet. There’s a lot of balancing that needs to take place.

DR LOVE: Any hypotheses on what the mechanisms might be involved here?

DR RUGO: I think that we believe that if you eat a higher-fat diet, certainly you gain more weight, and that truncal obesity in particular that occurs in women who’ve gone through menopause — and, of course, it’s increased in women on adjuvant hormone therapy — is associated with the weight gain in postmenopausal women. We now make more premenopausal women postmenopausal, particularly those with high-risk disease. So I think that part of it is certainly storing estrogen.

But I don’t think that that’s all of the story. There’s really fascinating data on fatty acid metabolism, oxidation — that’s work, actually, by someone at my institution, Andrei Goga, and also some data from Memorial Sloan Kettering — all of which suggests that there may be some ability of these fat cells and fat collections to actually stimulate cancer growth.

Genomic assays and (neo)adjuvant treatment decision-making

Early-stage breast cancer in the adjuvant and neoadjuvant settings

Management of metastatic breast cancer (mBC)

CDK4/6 inhibitors for the treatment of breast cancer

Checkpoint inhibitors and other novel immunotherapeutic approaches to breast cancer

Triple-negative and BRCA mutation-positive breast cancers