Obesity is linked to a worse prognosis for women diagnosed with breast cancer. One reason for this link could be that factors related to obesity make breast cancer treatments less effective. A small study found that Herceptin (chemical name: trastuzumab) worked equally well in obese and non-obese women diagnosed with HER2-positive, metastatic breast cancer. These results were presented at the 2010 annual meeting of the European Society for Medical Oncology (ESMO).
Herceptin is a targeted therapy medicine approved by the U.S. Food and Drug Administration to treat advanced-stage, HER2-positive breast cancers and to lower the risk of recurrence of early-stage, HER2-positive breast cancer with a high risk of recurrence. HER2-positive cancers make too much of the HER2 protein. The HER2 protein sits on the surface of cancer cells and receives signals that tell the cancer to grow and spread. About one out of every four breast cancers is HER2-positive. Herceptin works by attaching to the HER2 protein and blocking it from receiving growth signals.
The researchers looked at the medical records of 54 women diagnosed with HER2-positive, metastatic breast cancer and treated with Herceptin. Some of the women got only Herceptin (monotherapy) and others got Herceptin combined with chemotherapy medicines. Thirty of the women were obese, which means they had a body mass index (BMI) of 30 or higher. The other 24 women weren't obese.
The average amount of time before the cancer grew (called time to disease progression) was about the same for obese (14.8 months) and non-obese (19.6 months) women treated with Herceptin.
The difference in average time to disease progression wasn't statistically significant, which means that the difference could have been due to chance and not because of the difference in the women's weights.
The likelihood of responding to Herceptin was different for the obese and non-obese women, but this difference also wasn't statistically significant.
This study is reassuring for doctors who were concerned that Herceptin might be less effective in obese women diagnosed with HER2-positive, metastatic breast cancer. Still, more research is needed to fully understand any influence obesity may have on breast cancer treatments, including Herceptin.
You can learn more about Herceptin in the Breastcancer.org Targeted Therapies section.