Obesity may affect response to breast cancer treatment: study

July 16, 2012

Women who are obese continue to have higher levels of oestrogen than women of normal weight even after treatment with hormone-suppressing drugs, raising the possibility that they might benefit from changes to their treatment.

The study, led by a team at The Institute of in London and The Royal Marsden Foundation Trust, found hormone-suppressing drugs did markedly reduce oestrogen levels in obese women – but that their levels of oestrogen remained more than double those of women of .

The research, which is published today in the Journal of Clinical Oncology, could lead to improvements in doctors' ability to select the most appropriate treatment for overweight and obese women. But scientists stressed the effect of obesity was modest and that women taking treatment should not be concerned by the findings.

Over three-quarters of breast cancers require oestrogen to grow, so one of the main ways of treating the disease is by blocking the hormone's production or action. have higher levels of oestrogen than women of normal weight, and the new findings show that although their oestrogen levels are markedly reduced with hormone-suppressing drugs called aromatase inhibitors, the levels are higher during treatment than those in similarly treated normal weight women.

Senior author Professor Mitch Dowsett, a team leader in the Breakthrough Breast Cancer Research Centre at The Institute of Cancer Research and head of the academic department of biochemistry at The Royal Marsden, said: "We found that women with higher BMIs had more oestrogen remaining in their blood after treatment than healthy-weight women, which is consistent with previous suggestions that aromatase inhibitors might be slightly less effective in these women.

"Our findings are based on laboratory studies, so we would need to carry out clinical trials to tell us whether women with a higher BMI would benefit from changes to their treatment. Women with higher BMIs should certainly not be alarmed by this finding or stop taking their treatment. Our study takes us a step closer to understanding which of the treatment options available might be the most suitable for individual women."

Professor Dowsett and colleagues set out to probe a recent study that indicated the aromatase inhibitor anastrozole was no more effective than older-style tamoxifen in women with higher BMI, unlike in the general population where it is clearly more effective.

One possible explanation is that tamoxifen is more effective in overweight women, but the team wanted to investigate the other possibility – that in these women aromatase inhibitors are less effective.

The scientists examined two aromatase inhibitors: anastrozole and a more potent called letrozole. The study included 54 postmenopausal women with oestrogen receptor positive breast cancer who were treated at the Edinburgh Breast Unit with either three months of adjuvant anastrozole followed by three months of letrozole, or the drugs in the opposite sequence. Data on body mass index (BMI) and oestrogen levels – before and after treatment with the first drug, as measured by levels of estradiol and oestrone sulphate in the blood - were available for 44 patients.

The study found that, prior to treatment, women with higher BMIs had higher oestrogen levels – those with BMIs from 30 to 35 had around three times more plasma oestrogen than those with BMIs of less than 25.

After treatment with letrozole, women with BMIs of 30 to 35 still had levels of plasma oestrogen nearly three times as high as for healthy-weight women. The same trend was found for anastrozole, but did not reach statistical significance.

Professor Alan Ashworth, Chief Executive of The Institute of Cancer Research, said: "Aromatase inhibitors have played an increasing role in breast over the past decade, so it is important to understand the factors that affect how well they work in individual in order to allow doctors to choose the best possible drug from the range available."

Explore further: New hope for advanced post-menopausal breast cancer patients resistant to hormonal therapy

More information: "Suppression of Plasma Estrogen Levels by Letrozole and Anastrozole Is Related to Body Mass Index in Patients With Breast Cancer" with corresponding author Mitch Dowsett publishes online first in the Journal of Clinical Oncology on Monday 16 July 2012

Related Stories

New hope for advanced post-menopausal breast cancer patients resistant to hormonal therapy

September 26, 2011
Results from a phase III clinical trial have shown that combining two existing cancer drugs to treat post-menopausal women with advanced breast cancer resistant to hormonal therapy significantly improves outcome. Researchers ...

Estrogen treatment with no side-effects in sight

April 11, 2011
Oestrogen treatment for osteoporosis has often been associated with serious side-effects. Researchers at the Sahlgrenska Academy, University of Gothenburg, Sweden, have now, in mice, found a way of utilising the positive ...

Scientists find new drug target in breast cancer

May 22, 2011
Researchers have identified a new protein involved in the development of drug resistance in breast cancer which could be a target for new treatments, they report today in the journal Nature Medicine.

Recommended for you

Breaking the genetic resistance of lung cancer and melanoma

July 25, 2017
Researchers from Monash University and the Memorial Sloan Kettering Cancer Center (MSKCC, New York) have discovered why some cancers – particularly lung cancer and melanoma – are able to quickly develop deadly resistance ...

Anti-cancer chemotherapeutic agent inhibits glioblastoma growth and radiation resistance

July 24, 2017
Glioblastoma is a primary brain tumor with dismal survival rates, even after treatment with surgery, chemotherapy and radiation. A small subpopulation of tumor cells—glioma stem cells—is responsible for glioblastoma's ...

New therapeutic approach for difficult-to-treat subtype of ovarian cancer identified

July 24, 2017
A potential new therapeutic strategy for a difficult-to-treat form of ovarian cancer has been discovered by Wistar scientists. The findings were published online in Nature Cell Biology.

Immune cells the missing ingredient in new bladder cancer treatment

July 24, 2017
New research offers a possible explanation for why a new type of cancer treatment hasn't been working as expected against bladder cancer.

No dye: Cancer patients' gray hair darkened on immune drugs

July 21, 2017
Cancer patients' gray hair unexpectedly turned youthfully dark while taking novel drugs, and it has doctors scratching their heads.

Shooting the achilles heel of nervous system cancers

July 20, 2017
Virtually all cancer treatments used today also damage normal cells, causing the toxic side effects associated with cancer treatment. A cooperative research team led by researchers at Dartmouth's Norris Cotton Cancer Center ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.