Do hormone and HER2 status influence if lymph nodes need to be removed in breast cancer?

This study explored the risk of lymph node involvement in the different subtypes of breast cancer.

Different subtypes of breast cancer respond best to different treatments, therefore it is essential to determine the subtype for each patient. Hormone receptor positive breast cancers depend on the hormones estrogen and progesterone for growth, and cancers can be positive for just one or both of these growth factors. Human epidermal growth factor receptor 2 (HER2) breast cancers depend on the HER2 protein for growth. Triple negative breast cancers do not depend on either hormones or the HER2 protein for growth, meaning they cannot be targeted for therapy, and therefore these cancers tend to have worse prognoses (outlook) and higher recurrence rates.

Because this subtype is more aggressive, there is some concern over new guidelines suggesting that axillary (near to the breast) lymph node dissection is not necessary in triple negative breast cancers. The current study examined the frequency of affected lymph nodes in patients with different subtypes of breast cancer to determine the risk of lymph node involvement in triple negative breast cancer.

11,449 patients were included in this study. 74% were hormone receptor positive and HER2 negative; 8% were hormone receptor positive and HER2 positive; 5% were hormone receptor negative and HER2 positive; and 13% were triple negative. The rates of lymph node involvement for each subtype were measured.

Patients who were hormone receptor positive and HER2 positive were 2.5 times more likely than triple negative patients to have lymph node involvement. Patients who were hormone receptor positive and HER2 negative were 80% more likely to have lymph node involvement compared to triple negative patients and patients who were HER2 positive and hormone receptor negative were 70% more likely.

Compared to triple negative cancer, those with cancer that was hormone receptor positive and HER2 negative were 30% more likely to have more than 4 lymph nodes testing positive for cancer. Those with cancer that was hormone receptor positive and HER2 positive were 40% more likely, while those with cancer that was hormone receptor negative and HER2 positive were more than twice as likely to have more than 4 lymph nodes involved compared to triple negative patients.

The odds of having any nodal involvement were lowest overall for triple negative tumors.

This study concluded that triple negative breast cancers have a lower risk of lymph node involvement compared to other breast cancer subtypes, potentially indicating that there is no need for axillary lymph node dissection in patients with early triple negative breast cancer.