ASSESSMENT OF TUMOR NECROSIS AND DETECTION OF MEDIASTINAL LYMPH-NODE METASTASIS IN BRONCHIAL-CARCINOMA WITH TC-99M SESTAMIBI IMAGING - COMPARISON WITH CT SCAN

Thirty-eight patients with four major types of bronchial carcinoma wer e studied to evaluate technetium-99m sestamibi imaging in the assessme nt of tumour necrosis and the detection of hilar and mediastinal lymph node metastasis. Quantitative analysis was also performed to ascertai n whether tumour uptake values correlate with histological types of br onchial carcinoma. Of the patients, 34 showed tumour uptake on planar imaging (n = 38) and 27 on single-photon emission tomography (SPET) (n = 29), the overall sensitivity in the localisation of primary tumour being 89% with planar imaging and 93% with SPET. Four types of tumour uptake pattern were identified: (1) focal uptake, (2) focal uptake wit h a central hypoactive focus, (3) ring-like uptake and (4) no uptake ( negative uptake). Tumour necrosis was diagnosed in 12 patients based u pon histopathology (n = 2) and density measurements and type of contra st enhancement on computed tomography (CT) scan (n = 12). Defective tu mour uptake was seen in 11 of these patients on planar images (focal u ptake with a central hypoactive focus, n = 7; ring-like uptake, n = 2; and no tumour uptake, n = 2) and in 12 patients on SPET (focal uptake with a central hypoactive focus, n = 7, ring-like uptake, n = 3, and no uptake, n = 2). Hilar and mediastinal lymph node involvement was de tected in ten patients on CT scan, nine on planar images and 11 on SPE T. A total of 26 metastatic lymph nodes were detected on CT scan; 24 o f these were seen on planar, and all 26 on SPET images. SPET disclosed five further lymph nodes with metastasis, all of which were confirmed by histopathological examination of the surgical material (n = 3). Th e sensitivity in establishing the hilar and mediastinal disease was 90 % on planar images, and 100% on SPET slices, but when the number of ly mph nodes was taken into account, these values were 62% and 100%, resp ectively. Also, brain metastases were detected with SPET in three pati ents. The results of quantitative analysis of tumour uptake did not di fferentiate between squamous cell carcinoma and adenocarcinoma. We con clude that Tc-99m-sestamibi, particularly with SPET imaging, is potent ially useful in the follow-up of patients with bronchial carcinoma by differentiating residual or recurrent disease from post-radiotherapy n ecrosis, and is as sensitive as CT scan in the detection of hilar and mediastinal lymph node metastasis.