A Comparative Validation of Primary Surgical Versus Post-neo-adjuvant Chemotherapy Sentinel Lymph Node Biopsy for...

Sentinel lymph node biopsy (SLNB) is the standard of care for staging N0 primary early breast cancers (EBC). Patients in developing countries mostly present with large (LOBC) or locally advanced cancers (LABC) and are treated with neo-adjuvant chemotherapy (NACT). Accuracy of SLNB in staging stage III N0 and post-NACT N0 patients is uncertain. This prospective validation study on LOBC/LABC patients compared the accuracy of SLNB between primary versus post-NACT surgery.

Fifty T3/T4, N0 patients undergoing primary surgery (Group I) and 70 LOBC/LABC (index stage) treated with NACT and N0 at the time of surgery (Group II) were inducted. Validation SLNB was performed using low-cost methylene-blue and (99m)Tc-Antimony colloid. SLN identification (IR) and false-negative (FNR) rates were compared between the groups. Sub-group analysis was done in Group II per index tumor and nodal stage to identify factors predicting SLN IR and FNR in post-NACT patients. SLN IR and FNR in both groups were compared with those in previously published SLN validation study and meta-analysis in EBC.

Using combination of blue-dye and radio-colloid, post-NACT SLN IR and FNR (82.9, 13.5 %) were far inferior to T3/T4 primary surgery group (94, 7.7 %; p values 0.034, 0.041) and in EBC. SLN IR using blue-dye alone was dismally low in post-NACT LABCs. Factors predicting unidentified post-NACT SLN and false-negative SLNB included young age, LVI, skin infiltration, extra-nodal spread or N2a stage, and UOQ tumors.

Accuracy of SLNB in T3, N0 tumors undergoing primary surgery is comparable to that of SLNB for N0 EBC. In post-NACT patients, SLNB IR are lower and FNR are higher. Factors predictive of non-identification and false-negative SLNB include pre-NACT skin involvement (T4b), N2a stage or extra-nodal invasion and LVI, and to a lesser extent, young age and UOQ location of the tumor.