Past:
Invasive lobular carcinoma (ILC) is recognized to be biologically distinct from the more common invasive ductal carcinoma (IDC). ILC demonstrates an infiltrative growth pattern, with a tendency for discohesive growth and proclivity for nodal involvement. It is inherently insidious, and may pose diagnostic and clinical challenges.1 These traits have raised skepticism regarding the applicability of the practice-changing ACOSOG Z0011 trial to these cancers, which comprised a small minority of the study population. Widespread adoption of the Z0011 results has revolutionized the treatment of early-stage breast cancers by demonstrating the safety of omitting axillary dissection (ALND) in T1-T2, clinically node-negative patients with 1 or 2 positive sentinel nodes (SLNs) undergoing breast-conservation therapy (BCT).2 However, lobular histology remains independently predictive of ALND even among patients otherwise meeting criteria for omission.3 In an era of precision medicine aimed at optimizing outcomes while reducing the burden of cancer treatment, it is of utmost importance to avoid unnecessary overtreatment in this understudied population.
Present:
In this population of 813 consecutive clinical T1-T2 N0 patients with positive SLNs prospectively treated per the Z0011 approach, we found that those with ILC were no more likely than patients with IDC to require ALND, despite a higher proportion of sentinel node macrometastases and association with additional positive nodes at ALND.4 These findings, along with the absence of any isolated axillary recurrences to date, support the application of this treatment strategy. With their overwhelmingly estrogen receptor-positive (ER+) and low-grade phenotype, ILCs derive great benefit from adjuvant endocrine therapy, which is known to further improve locoregional outcomes,5 and which was received by the vast majority of patients. Despite the differing growth pattern and behavior of these cancers, results demonstrated in this contemporary population support the validity of the application of Z0011 results to patients with lobular carcinoma.
Future:
Ever-improving multidisciplinary strategies have ushered in an era of individualized treatment aimed at maximizing efficacy while minimizing morbidity. The ACOSOG Z0011 trial is a pivotal example of this progress, and has allowed for avoidance of unnecessary ALND without any compromise in outcomes. As molecular characterization of tumors continues to improve, it is possible that axillary staging of clinically node-negative patients, such as those included in this study, will no longer be necessary in the future.
Footnotes
Disclosures: Dr. Morrow has received honoraria from Genomic Health and Roche.
References
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