Most patients with invasive lobular carcinoma (ILC) breast cancer could be treated with hormones alone and not with chemotherapy, according to a study published in Clinical Breast Cancer (2015; doi:10.1016/j.clbc.2015.08.001). This study analyzed the use of the Oncotype DX gene expression test to predict recurrence of invasive lobular carcinoma.

Researchers reviewed all consecutive cases of ILC breast cancer diagnosed at the Allina Health Laboratory (affiliated with the Virginia Piper Cancer Institute at Abbott Northwestern Hospital in Minneapolis, Minnesota) in the past 8 years. This included 158 patients with ILC breast cancer who tumors were analyzed with the Oncotype DX gene expression test.

The researchers defined a model that included characteristics of a tumor most predictive of the recurrence risk identified on the Oncotype DX gene expression test: progesterone receptor expression, Ki-67 (proliferation index), estrogen receptor expression, patient age, and tumor size.

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“This model, if validated, may be useful in changing local practice patterns of ordering Oncotype DX testing for many ILC cases with low-risk features. This would enable earlier and more cost-effective treatment decision making for patients with this breast cancer subtype,” said Michaela Tsai, MD, oncologist with Minnesota Oncology and breast cancer researcher at Virginia Piper Cancer Institute.

The Oncotype DX test costs approximately $4000 and is performed by Genomic Health in Redwood City, California.

According to the American Cancer Society, invasive breast cancer is diagnosed in more than 180,000 women in the United States each year. Approximately 10% have ILC. Invasive lobular carcinoma tends to develop in women older than 60 years, feels like thickened tissue rather than a lump, and can spread throughout the breast before it is detected.

“Less is known about the optimal management of this less common subtype of breast cancer. It has been lumped together with ductal cancer and treated the same way. Our study helps prove that not all breast cancers are the same. This subtype requires a unique treatment approach,” Tsai said.