Overall survival outcomes in occult primary breast cancer.

BACKGROUND

Counseling patients with occult primary breast cancer (OPBC) can be challenging due its infrequency and the paucity of oncologic outcomes data. We aimed to evaluate the management and overall survival (OS) of patients with OPBC compared to patients with primary breast tumors.

METHODS

We identified patients with node positive breast cancer from the National Cancer Database (2010-2021). OPBC was classified at cT0. OS was assessed using Kaplan-Meier method and multivariable Cox proportional hazards models.

RESULTS

Of 254,708 patients with cT0-4N1-3 disease, 2680 patients with OPBC were identified (cT0N1 63.4%, cT0N2 72.5%, cT0N3 80.7%). Five-year OS for cT0N1 (88.5%) was most similar to cT1N1 disease (88.2%) and better than cT2-4N1. On multivariable analysis, cT1-4N1 had significantly worse survival than cT0N1 (HR: 1.30-3.84, each p < 0.001). Patients with cT0N2 disease had similar 5-year OS to cT1N2, both 83.4%. Similarly, patients with cT0N2 had improved survival compared to patients with cT2-4N2 (HR: 1.62-3.02, each p < 0.001). In cN3 patients, OS of OPBC was 72.8% vs 73.9% for cT1, 73.3% for cT2, 67.2% cT3, and 52.6% cT4. Within OPBC, increasing age (HR 1.64, p < 0.001), triple negative biology (HR 1.27, p = 0.0499) and increasing nodal category were associated with worse survival.

CONCLUSIONS

Outcome for OPBC is favorable and is similar to cT1N + disease across all cN categories. Factors that impact OS included older age, increasing clinical N category, worse Charlson Deyo Comorbidity Score, non-white race and triple negative tumor biology.