Finding out that you have breast cancer that has already spread to an organ outside the breast and axillary lymph nodes, otherwise known has “de novo stage IV breast cancer” or metastatic breast cancer, can be disheartening. Unfortunately, this is the stage when up to 6% of all new breast cancer diagnoses in the United States are made.
For patients diagnosed at this stage, removal of the tumor from the breast, whether by partial or total mastectomy, was originally thought to be unproductive considering the continued presence of tumors in distant organs such as the bones, liver or brain. As such, standard therapy consists of chemotherapy and/or a hormone blocking pill, such as Tamoxifen, Arimidex or Exemestane. These standard therapies fight cancer throughout the body.
Over the past 10-15 years, however, evidence has emerged that surgical removal of the primary tumor in the breast might extend the lives of some patients with metastatic breast cancer. A few retrospective studies (studies that review past outcomes) have shown that some women with de novo stage IV breast cancer who had the breast tumor removed lived longer than those who did not.
However, these retrospective studies are often considered flawed because of a concept called “selection bias”. We do not know if the improved survival seen in one group of women is due to the removal of the tumor itself rather than, say, the participating surgeons preferentially selecting patients most likely to live longer, due to other factors like younger age, less aggressive tumor growth, or metastases in organs less critical to life (e.g. bones vs. brain). Several research groups have tried to account and control for selection bias using scientific methods that strive to offset other possible factors when comparing patients who underwent surgery to those who did not.
One such study recently discovered that patient age, the tumor’s grade as well as its estrogen and progesterone receptor levels, and how successfully the tumor and patient respond to initial chemotherapy were much more predictive of the patient’s ultimate outcome than whether or not she underwent surgery. This finding led the study doctors to conclude that it would be better to identify specific subgroups of patients who might benefit from surgery as opposed to surgeons making their judgments solely based on average surgery outcomes.
Prospective clinical trials (i.e., large-scale studies conducted over multiple years wherein surgeons cannot choose which patients undergo surgery) designed to definitively answer the question as to whether surgical removal of the tumor will help women with metastatic breast cancer live longer are underway around the world. Early results from India and Turkey showed no improved survival after surgery, although it is thought that women present with much more advanced disease in those countries due to more limited access to healthcare. Longer follow-up in the Turkish trial, however, revealed 5 year overall survival of 42% with surgery vs. 25% with systemic therapy alone. A similar study (clinical trial) in the United States completed patient enrollment and the medical community eagerly awaits its long term outcomes in the hope they will help guide their treatment of patients with this complex diagnosis. Early analyses of this U.S. based clinical trial study found that surgery did not extend overall patient survival.