LAS VEGAS – In women aged 70 years or older with hormone receptor–positive invasive breast cancer, their tumor size, grade, and histology – but not human epidermal growth factor receptor–2 status – predicted nodal positivity, according to a retrospective analysis.
Investigators at the Mayo Clinic, Rochester, Minn., reviewed 52,532 women in the National Cancer Database from 2010 to 2013 who were at least 70 years old with hormone receptor–positive invasive breast cancer and clinically node negative disease, who had axillary surgery performed. Two-thirds of the cohort was used to identify risk factors, and the remaining third to validate them. About 16% in both groups had cancer in their axillary lymph nodes.
On multivariate analysis, higher clinical T stage, higher grade, and invasive lobular and invasive mammary histology were all associated with positive nodes. Although significant on univariate analysis, age (P = .57) and HER2 status (P = .32) fell out on multivariate analysis.
Nodal positivity was more than five times as likely with clinical T2 tumors, compared with T1a tumors, and far less likely for patients with invasive mucinous carcinoma than for those with invasive ductal carcinoma.
The team expects to release a nomogram for general use in clinical practice to predict the risk of positive nodes for various combinations of tumor size, grade, and histology in older women. When the model predicted a less than 10% chance of node positive disease, the actual rate in the validation set was around 5.5%. When it predicted a 30%-39% chance, the actual rate was 32.6%. The area under the receiver operating characteristic curve was 0.7 in both the development and validation sets, indicating good discrimination.
The work grew out of an effort to implement the Society of Surgical Oncologists’ recommendation not to do routine sentinel node biopsies in clinically node negative, hormone receptor–positive invasive breast cancer in women over the age of 70 years, a recommendation the group made as part of its contribution to the Choosing Wisely campaign.
“After the guideline was released, we were sitting in the clinic thinking how to apply it to our patients,” lead investigator Jessemae Welsh, MD, a surgeon at the Mayo Clinic, said at the American Society of Breast Surgeons annual meeting.
The problem is that nodal positivity is important to know for other aspects of care, including regional nodal irradiation and duration of systemic hormone therapy, and axillary lymph node staging might still be indicated if older women are truly at high risk. “We [wanted] to develop a multivariate model that gives a precise estimate of nodal risk,” to help “patients and surgeons to decide together based on an individual risk” how best to proceed. Also, a prediction of low risk “can help reassure patients that they will do well without axillary surgery,” she said.
Mayo’s nomogram is unique in that it focuses specifically on women 70 years and older. Development of previous nomograms incorporated older women, but did not focus on them specifically, Dr. Welsh said.
Dr. Welsh said she had no relevant disclosures.