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Incidence of internal mammary node in locally advanced breast cancer and it's correlation with metastatic disease: a retrospective observational study.

OBJECTIVE
To determine incidence of internal mammary nodes(IMN) at baseline computed tomography(CT) of locally advanced breast cancer(LABC) and ascertain prognostic implication.


METHODS AND MATERIALS
Retrospective review of all LABC patients from January 1,2012 through December 31, 2014 was done after approval from institutional review board. CT of 182 patients enrolled were reviewed by two radiologists independently and IMN were documented based on size, location and relation with breast primary. 3 year follow-up was analysed and incidence of metastases calculated as overall incidence, incidence in patients with and without discernible IMN at baseline imaging. Results are presented as numbers and percentages. Differences in metastases of two groups were compared using χ2 test. 95% confidence interval were calculated and p < 0.05 was considered significant.


RESULTS
77/182 had identifiable IMN (42.3% incidence). Majority of identifiable nodes were on ipsilateral side-of primary (incidence 90.90%) with higher incidence in patients with upper outer quadrant tumors (55.9%). Majority were seen in second intercostal space (44.4%). 36 (19.7%) developed distant metastases within 3 years of therapy. Of these, 21 (27.3%) had IMN as compared to 15 (14.3 %) without IMN on baseline imaging. Patients with identifiable IMN on baseline CT had significantly higher incidence of distant metastases (p = 0.0321).


CONCLUSION
Significant number LABC patients have identifiable IMN on baseline imaging with patients showing IMN on baseline CT showing significantly higher rate of metastatic disease following therapy.


ADVANCES IN KNOWLEDGE
Many LABC patients have identifiable IMNs on baseline imaging which show higher incidence of subsequent metastatic disease.