Indium-111 octreotide and
thallium-201 scintigraphic studies were compared in 21 patients (16 with palpable and five with non-palpable lesions) suspected of having breast
malignancies on the basis of mammography. Early (15 min) and late (3 h) 201Tl (111 MBq) and 4-h and 24-h
111In-octreotide (111-148 MBq) static planar anterior images (matrix 256 x 256) were obtained on separate days. Images were evaluated both visually and quantitatively. Biopsy was performed following the imaging studies. Histopathology revealed 17
breast carcinomas (15 cases of invasive
ductal carcinoma, one
mucinous adenocarcinoma and one
intraductal carcinoma) and four benign breast lesions (two
fibroadenomas, one
abscess and one case of
fat necrosis). The means histopathological tumour size (mean largest diameter) was 3.38 +/- 1.9 cm.
111In-octreotide detected 16 of the 17 breast
cancers (94%) while 201Tl detected 13 of them (76%). Both
111In-octreotide and 201Tl missed one non-palpable
carcinoma showing only an isolated cluster of
microcalcifications on mammography. The smallest tumour size detected by both agents 1.5 x 1.5 cm. Of the four benign lesions, only the breast
abscess revealed both 201Tl and
111In-octreotide uptake.
111In-octreotide scan also showed tracer uptake in five of the six patients with histologically proven axillary
metastases, while four of these six patients showed 201Tl uptake. The tumour/background (T/B) ratios of late
111In-octreotide and 201Tl images were 1.71 +/- 0.38 and 1.46 +/- 0.30 respectively (P = 0.039). In this preliminary study,
111In-octreotide yielded more favourable results than 201Tl in the detection of
breast carcinomas. However, the diagnostic efficacy of
111In-octreotide imaging needs to be investigated in larger patient series.