Omission of Axillary Surgery in Patients with Negative Axillary Evaluation Integrated with LymphPET: A Prospective Clinical Study.

[BACKGROUND] Sentinel lymph node biopsy (SLNB) is the standard surgical approach for axillary node staging in patients with early-stage breast cancer (EBC). However, there is an increasing trend in investigating the omission of SLNB, as molecular tumor biology has become a primary determinant of systemic therapy, overshadowing the importance of nodal status.

[PATIENTS AND METHODS] The SOAPET trial constitutes a prospective phase II study structured into two phases. In the first stage, we demonstrated that LymphPET could be utilized to screen patients to potentially forego SLNB, achieving a negative predictive value of 91%. In the second stage, SLNB was omitted for patients with a negative preoperative axillary evaluation (PAE) integrated with LymphPET. Primary endpoints were the 3-year distant disease-free survival (DDFS) and locoregional recurrence-free survival (LRRFS).

[RESULTS] A total of 304 patients were enrolled with a median age of 52.5 years (IQR 44-62 years). Of these patients, 240 (78.9%) presented with clinical T1 tumors. Among all the cases, 218 (71.7%) were classified as luminal-like breast cancer. The median follow-up was 43.5 months. The 3-year DDFS and LRRFS rates were 100% and 99.7% (95% CI 99.0-100.0), respectively. In the entire cohort, two cases (0.7%) of ipsilateral axillary node relapse, one (0.3%) ipsilateral in-breast recurrence, and one (0.3%) distant metastasis were reported.

[CONCLUSIONS] The second phase of the study corroborates the oncologic safety of omitting SLNB on the basis of PAE incorporating LymphPET. For patients with clinically node-negative EBC with high-risk characteristics, SLNB might be safely spared with the added diagnostic benefit provided by LymphPET.

[TRIAL REGISTRATION] ClinicalTrials.Gov ID NCT04072653.