Lobular histology is not a strong independent predictor of sentinel lymph node biopsy (SLNB) positivity in early-stage clinically node-negative breast cancer, a study published January 6 in Clinical Breast Cancer found.
A team led by Francesca Accomasso, MD, from the University of Turin in Italy, reported that tumor size and vascular invasion remain the strongest predictors and that axillary ultrasound and MRI are reliable tools to guide treatment decisions.
“SLNB omission in well-selected clinically node-negative patients, including those with invasive lobular cancers [ILCs], may be considered in tailored and selected patients,” Accomasso and colleagues wrote.
SLNB is the standard procedure for axillary staging in clinically node-negative patients. While it provides important prognostic information, recent research suggests it has no direct therapeutic benefit and can lead to complications such as lymphedema, infection, and restricted arm mobility.
However, invasive lobular breast cancers show different biological behavior compared with nonspecial-type tumors, which could compromise staging accuracy and impact treatment decisions if SLNB is omitted.
Accomasso and colleagues investigated whether lobular histology independently predicts SLNB positivity in early-stage clinically node-negative breast cancer. They also identified other predictive factors of SLNB positivity and evaluated the diagnostic performance of preoperative axillary imaging. Finally, the researchers evaluated the cumulative incidence of local and distant recurrences.
The retrospective analysis included 661 women, with the researchers assessing clinical, pathological, and radiological data. They calculated the cumulative incidence of axillary and distant recurrences, including only women with at least two years of follow-up (n = 495). Invasive lobular cancers were present in 16.9% of cases.
The team reported the following findings:
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SLNB positivity occurred in 16.1% of invasive lobular cancers and 20% of nonspecial-type tumors (p = 0.3).
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No significant differences emerged among axillary lymph node dissection rates or nodal upstaging between histologies.
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Axillary ultrasound and MRI showed high specificity (95% and 79%, respectively) and negative predictive value (80% and 98%, respectively) in identifying node-negative patients.
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No axillary recurrences occurred after a median follow-up of 49.3 months.
Finally, tumor size greater than 20 mm and vascular invasion were independent predictors of SLNB positivity on both univariate and multivariate analysis. This included odds ratios (ORs) of 2.57 and 2.15 for tumor size, and ORs of 5.57 and 5.87 for vascular invasion, respectively. These findings achieved statistical significance.
Lobular histology achieved ORs of 0.73 and 0.82, respectively, with neither finding having statistical significance.
The results support selective omission of SLNB in well-defined, low-risk patients, the study authors highlighted. They also highlighted axillary ultrasound as a potentially valuable tool in refined decision-making in this area.
“As the field moves toward more personalized, less invasive treatment strategies, future prospective studies — particularly those including a higher representation of ILCs — will be essential in defining new standards of care that optimize both oncologic safety and quality of life,” the authors wrote.
Read the full study here.