COMPARISON OF IN-111 OCTREOTIDE AND TL-201 SCINTIGRAPHY IN PATIENTS MAMMOGRAPHICALLY SUSPECTED OF HAVING BREAST-CANCER - PRELIMINARY-RESULTS

Indium-111 octreotide and thallium-201 scintigraphic studies were comp ared in 21 patients (16 with palpable and five with non-palpable lesio ns) suspected of having breast malignancies on the basis of mammograph y. Early (15 min) and late (3 h) Tl-201(111 MRq) and 4-h and 24-h In-1 11-octreotide (111-148 MBq) static planar anterior images (matrix 256x 256) were obtained on separate days. Images were evaluated both visual ly and quantitatively. Biopsy was performed following the im aging stu dies. Histopathology revealed 17 breast carci nomas (15 cases of invas ive ductal carcinoma, one mucinous adenocarcinoma and one intraductal carcinoma) and four benign breast lesions (two fibroadenomas, one absc ess and one case of fat necrosis. The means histopathological tumour s ize (mean largest diameter) was 3.38+/-1.9cm. In-111-octreotide detect ed 16 of the 17 breast cancers (94%) while Tl-201 detected 13 of them (76%). Both In-111-octreotide and Tl-201 missed one nonpalpable carcin oma showing only an isolated cluster of microcalcifications on mammogr aphy. The smallest tumour size detected by both agents 1.5x1.5 cm. Of the four benign lesions, only the breast abscess revealed both Tl-201 and In-111-octreotide uptake. In-111-octreotide scan also showed trace r uptake in five of the six patients with histologically proven axilla ry metastases, while four of these six patients showed Tl-201 uptake. The tumour/background (T/B) ratios of late In-111-octreotide and Tl-20 1 images were 1.71+/-0.38 and 1.46+/-0.30 respectively (P=0.039). In t his preliminary study, In-111-octreotide yielded more favourable resul ts than Tl-201 in the detection of breast carcinomas. However, the dia gnostic efficacy of In-111-octreotide imaging needs to be investigated in larger patient series.