Women who undergo surgery for breast cancer will often consider an adjuvant therapy, usually a precautionary regimen of chemotherapy to ensure the cancer is completely gone.
It was widely believed to ensure better long-term outcomes for the most common types of breast cancers, Invasive Lobular Carcinoma (ILC) and Invasive Ductal Carcinoma (IDC).
But, new research from the journal Cancer, shows that adjuvant chemotherapy may not be as cut and dry, particularly if these cancers are estrogen receptor (ER)-positive and human epidermal growth factor receptor 2 (HER2)-positive.
“Our initial thought was that histologic subtype, meaning the two common sub categories of breast cancer, would not be a factor for determining the use of adjuvant chemotherapy” said Schelomo Marmor, PhD., MPH, assistant professor in the Department of Surgery at the University of Minnesota Medical School who led the research. “But because no studies looked at treatment on this granular level, we felt it was worth exploring so that we could know for certain how best to treat our patients.”
Marmor and colleagues within the Masonic Cancer Center, University of Minnesota analyzed data from the California Cancer Registry spanning 2004 to 2013. They identified 32,149 patients with early stage ER -positive and HER2-negative IDC and 4,095 patients with early stage ER-positive and HER2-negative ILC.
The data demonstrate that the ILC patients did not benefit from adjuvant chemotherapy, while the IDC patients who received adjuvant chemotherapy had an improved 10-year overall survival.
“Most patients assume that breast cancers, no matter their subtype, can be treated in similar ways,” said Todd Tuttle, MD, MS, professor in the Department of Surgery and collaborator on the study. “This is not always the case and it might be beneficial for some patients to avoid ineffective chemotherapy because it also comes with risks.”
While more research is needed before considering changes in counseling patients, the findings have prompted investigators to rethink assumptions about chemotherapy for ILC.
Marmor added, “Because most ILC patients have stage I or II disease, avoiding chemotherapy when it’s not necessary could markedly reduce potential for side effects as well as the economic and emotional burden that comes with breast cancer treatment.”