the usefulness of spect/ct in sentinel node mapping of early stage breast cancer patients showing negative or equivocal findings on planar scintigraphy

Objective(s): this study sought to determine the diagnostic yield of spect/ct in localizing axillary sentinel lymph nodes (slns) in early breast cancer patients where planar scintigraphy (ps) was equivocal or negative. methods: prospective analysis of early stage breast cancer patients with nonpalpable axillary nodes undergoing sln localization prior to nodal sampling for axillary staging. ps findings were categorized as: category a: non-visualization of sln; category b: unusual uptake location; category c: equivocal uptake / difficult interpretation. the k-coefficient of cohen was used to evaluate the correlation between ps and spect/ct results. ps and spect/ct images were interpreted separately, and sln identification on each of the modalities was correlated to bmi (body mass index) and peroperative radio guided results. results: between april 2015 and january 2017, 1028 early breast cancer cases underwent sentinel lymphoscintigraphy. of total, 134 (13%) patients underwent spect/ct in addition to ps. all were females with mean age of 48.15 years (range: 26-82 years). right sided in 68, left in 64 and 2 with bilateral carcinoma. by tnm classification: 49 (37%) t1, 78 (58%) t2 and 7 (5%) had dcis/paget’s disease. overall slns were detected on both ps and spect/ct in 60% cases. of category a (n=54); 35/54 (64%) sln localized on spect/ct; 32 were level-i; 2 level-ii; 1 level-iii nodes. in 19, sln was not localized. of category b (n=18), 5 had prior lumpectomy, spect/ct localized tracer uptake to 17 level-i sentinel nodes, 3 level-ii and level iii / imc in 9. of category c (n=62), 29 had prior lumpectomy. spect/ct confirmed sln in all the cases. radio-guided surgery confirmed spect/ct results. the correlation between the two techniques was low (k=0.34). where ps was negative; spect/ ct localized nodes in statistically significant number of cases (p=0.01). ps identified sln uptakes in 80/134 (60%) cases with a mean bmi of 21.6±4.8 kg/ m^2 while spect/ct detected ‘‘hot’’ nodes in 115/134 (86%) cases with a mean bmi of 29.6±5.6 kg/m^2. for overweight/obese patients (n=59) (bmi>25 kg/m^2), ps failed to identify slns in 49 and spect/ct failed to do so in 18 (p<0.001). conclusion: spect/ct has diagnostic yield and helps in precise sln localization where planar imaging is negative or shows unusual site of uptake.