Internal mammary lymph node metastasis in breast cancer: predictive models to assist with prognostic influence

Background

Metastatic breast cancer in the internal mammary nodes (IMN) indicates a poor prognosis. Several recent epidemiological surveys have determined a reduction in survival for patients with medial compared to lateral sector tumors attributing this to a higher rate of unrecognized IMN metastasis and hence these patients are undertreated with adjuvant therapy. ^{1], 2], 3], 4], 5] and 6]}

Aim

Through mathematical modeling based on large datasets we aim to quantify the impact on survival of IMN metastases at different tumor and axillary stages.

Methods

Mathematical models were created to estimate the survival of patients with and without IMN metastasis. It was assumed that the different rate of survival between medial and lateral sector breast cancers was a result of the differential rate of unrecognized IMN metastases with resultant under-staging and under treatment. We applied these models on a retrospective database analysis from the Surveillance, Epidemiology and End-Results (SEER) registries from 1994 to 2003.

Results

The 10-year odds of death (OOD) from breast cancer for patients with medial compared with lateral sector tumors ranged from 1.2 to 1.5 depending on stage. The predicted odds of breast cancer death for patients with unrecognized IMN metastases ranged from 2.4 to 20, with the highest OOD in the groups with small tumors and no axillary node metastasis.

Conclusions

Through modeling we have been able to predict and quantify the significantly worse survival outcomes for patients with undiagnosed IMN metastasis.