Patients with very small, invasive breast tumors — called microinvasive breast carcinomas — may not benefit from lymph node biopsies, researchers from Allina Health suggest.
The study, “Clinicopathologic analysis of a large series of microinvasive breast cancers,” shows that only 1.5% of breast cancer patients whose tumors measure 1 millimeter or less had cancer in their lymph nodes, suggesting that patients may skip standard lymph node biopsies, a procedure that is often linked to side effects.
“These findings allow surgeons to select which patients with microinvasive tumors may actually benefit from lymph node sampling, while sparing other patients from this procedure,” Tamera Lillemoe, MD, pathologist and the study’s co-author, said in a press release.
The study was supported by the Engelsma Family Foundation and Abbott Northwestern Hospital Foundation and appeared in The Breast Journal, the official journal of the National Consortium of Breast Cancers.
Microinvasive breast carcinoma is a rare type of cancer that accounts for roughly 1 percent of all breast cancers. The American Joint Committee on Cancer Staging Manual defines microinvasion as the overgrowth of cancer cells into the adjacent tissue, with a size no greater than 1 millimeter.
Little is known about this type of tumor, their behavior, and outcomes, but treatment guidelines recommend they be monitored and treated as any other invasive cancer. Lymph node biopsies are routinely performed to assess breast cancer progression, but the procedure is linked to potential adverse effects. The most common is lymphedema, a collection of fluid that causes swelling in the arms, hands, underarms, and sometimes the trunk.
Researchers at the Virginia Piper Cancer Institute, which is part of Allina Health, aimed to determine the risk of microinvasive breast carcinoma spreading to the lymph nodes and to identify prognostic markers of cancer progression. They examined clinical records of 294 patients treated between 2001 and 2015 and followed for a mean time of 4.63 years.
Among the 260 patients who underwent axillary staging, only 1.5% were positive for lymph node metastases. While most (98.9%) patients with microinvasive breast carcinomas had associated non-invasive ductal carcinoma in situ (DCIS) lesions, those with positive lymph nodes had DCIS lesions larger than 5 centimeters, compared with a median DCIS tumor size of 2.5 centimeters.
During follow-up, no patients developed close or distant metastasis, and only two patients developed new breast cancers after undergoing surgery and radiation therapy — the new cancers were in different places than the initial microinvasive breast cancer site.
“Lymph node metastases are uncommon and were only seen with ductal type microinvasive carcinoma,” the researchers wrote, concluding that routine node sampling may not be beneficial for patients.