Does lumpectomy followed by radiation improve survival outcomes in HER2 positive and triple-negative breast cancer with high tumor-infiltrating lymphocytes?

This study evaluated the survival outcomes after lumpectomy followed by radiation versus mastectomy alone in patients with early-stage HER2-positive (HER2+) breast cancer (BC) and triple-negative breast cancer (TNBC) with low or high tumor-infiltrating lymphocytes (TILs). The data showed that lumpectomy followed by radiation improves survival in patients with high TILs.

BC is classified into different subtypes depending on the presence or absence of certain receptors (proteins found on the surface of the cancer cells). HER2+ is a subtype of BC that tests positive for the HER2 protein. TNBC is a subtype of breast cancer (BC) that tests negative for female hormone receptors (estrogen and/or progesterone) and the HER2 protein. Treatments for HER2+ BC and TNBC usually involve a combination of surgery, chemotherapy, and radiotherapy (RT).

BC surgery can involve either the total removal of the breast (mastectomy) or a portion of the breast where the tumor is located (lumpectomy). RT is also commonly used following surgery to destroy any remaining cancer cells and reduce the risk of recurrence.

Tumor-infiltrating lymphocytes (TILs) are immune cells found in tumors. TILs are involved in killing cancer cells, and higher levels of TILs have been associated with increased survival in breast cancer. HER2+ BC and TNBC have around 20% of TILs. Whether lumpectomy followed by radiation improves survival outcomes compared to mastectomy alone in patients with early-stage HER2+ BC and TNBC with low or high TILs is still not known.

This study analyzed records of 190 women with early-stage HER2+ BC/TNBC. Patients were divided into 2 groups based on the number of TILs. Group 1 included 140 patients with low TILs (less than 50%). Group 2 included 50 patients with high TILs group (more than 50%). In group 1, 64 patients received mastectomy alone (M group) and 76 patients received lumpectomy followed by RT (L+R group). In group 2, 26 patients received mastectomy alone (M group) and 24 patients received lumpectomy followed by RT (L+R group).

In patients with high TILs, 100% of the patients in the L+R group were alive after 5 years without cancer coming back (DFS: disease-free survival) compared to 76% of the patients in the M group. Overall, 100% of the patients were alive in the L+R group after 5 years compared to 86% in the M group. 

In patients with low TILs, 87% of the patients in the L+R group were alive without cancer relapse 5 years later compared to 86% of the patients in the M group. Overall, 81% of the patients were alive in the L+R group after 5 years compared to 86% in the M group. These differences were not significant.

In patients with high TILs, none of the patients experienced recurrence in the L+R group versus 23% of the patients in the M group. In patients with low TILs, 10% of the patients experienced recurrence in the L+R group versus 14% of the patients in the M group.

This study concluded that lumpectomy followed by radiation improves survival outcomes only in HER2+BC/TNBC with high TILs compared to mastectomy alone.

The sample size was very small and the study looked back in time at medical records. Further studies with more patients are needed before drawing any conclusions.