Does obesity REDUCE the effectiveness of drugs in breast cancer?

Excess weight caused by the accumulation of excessive amounts of fat in the body, a condition that definitely requires professional help, namely obesity, is among the most important health problems of the modern age. Obesity, cardiovascular conditions, causes many diseases that pose life-threatening risks, such as hypertension and stroke, and also has a substantial effect on the development and progression of breast cancer. Journal of Clinical Oncology, in a study published in July 2020, showed that obesity also has a profound effect on the treatment of breast cancer. The study suggests that having a high body mass index (BMI) at the time of a breast cancer diagnosis may reduce the effectiveness of taxane-based adjuvant (postoperative protective) chemotherapy and lead to lower survival rates.

Previous studies show that a high body mass index in postmenopausal women is associated with a higher risk of breast cancer and a poorer disease course. Another recent study shows that an increased proportion of body fat in individuals with a BMI within the normal range may increase the risk of breast cancer in postmenopausal women.

Dr. Christine Desmedt, who took part in the research at the Translational Breast Cancer Research Laboratory, Department of Oncology, Catholic University of Leuven in Belgium, said: "In the study, we used a lipophilic drug called docetaxel (Taxotere). The results of the study show that the drugs used are absorbed by the surrounding body fat before reaching the tumor site. This result made us wonder whether paclitaxel, another taxane used as a chemotherapy agent, would also be affected in the same way."

Lower treatment responses were observed in people with a high body mass index

In the study, 2887 breast cancer patients were divided into obese and lean groups according to the specified criteria, and docetaxel was used as the chemotherapy agent.

The study results showed a significant reduction in disease-free survival and overall survival in obese patients compared with lean patients. Conversely, no difference was observed between the obese and lean patient groups receiving an adjuvant chemotherapy treatment without docetaxel in their rates of disease-free survival, overall survival or distant metastasis.

Commenting on the results of the study, the researchers stated that using docetaxel in breast cancer treatment requires a risk-benefit assessment based on body composition before a decision is made. Emphasizing that the results were multifactorial, the researchers pointed out that other health problems, such as hypertension and diabetes, which may cause lower treatment responses in people with a high BMI, also have an effect. This study also calls into question the results of randomized clinical trials of cancer drugs tested regardless of patients' body fat proportions. However, Christine Desmedt emphasizes that more research is needed before changes are made to current treatments.

The study also evaluated the association of estrogen receptor (ER) positive and negative breast cancers with BMI and treatment response. Although the study indicated that docetaxel-based chemotherapy may cause adverse effects in obese patients with ER-negative breast cancer, it stated that these results must be interpreted very carefully and that new studies are definitely needed.

Although the findings are extremely important, they show that new studies may lead to new adjustments in chemotherapy and that many patient-related factors need to be considered when deciding on a treatment approach. More importantly, this study once again emphasizes the importance of avoiding obesity and treating it. 

- The figure below shows "cancers directly associated with obesity":

- Related Topic: Exercise and the 14 types of cancer whose risk it reduces