Underestimation of regional myocardial perfusion with Tc-99m sestamibi single-day rest-stress SPECT: a "drug washout" pitfall?

Myocardial perfusion scintigraphy with a Tc-99m sestamibi single-day SPECT protocol is a widely used technique to examine patients with possible or known coronary artery disease. A 76-year-old man with a clinical history suggestive of ischemic heart disease underwent Tc-99m sestamibi myocardial SPECT imaging with a same-day rest and stress protocol after temporary discontinuation of his current therapy, which included calcium channel and beta blockers and nitrates. The scintigraphic pattern was consistent with an asymptomatic infarction of the posterolateral myocardial wall and periinfarct ischemia. One week later, the patient had a Tc-99m sestamibi myocardial SPECT study at rest without discontinuing therapy, and scintigraphic images showed normalization of the posterolateral wall perfusion defect. The angiographic study showed a 90% stenosis of the circumflex artery. This case suggests that, during a 1-day cardiac SPECT protocol, washout of therapeutic pharmaceuticals may be responsible for underestimation of myocardial rest perfusion in territory supplied by a coronary artery with a critical stenosis.

A multicentre observational study of radionuclide therapy in patients with painful bone metastases of prostate cancer.

A multicentre observational study was conducted by the Italian Association of Nuclear Medicine between 1996 and 1998. Twenty-nine Nuclear Medicine Departments participated. The aims of the study were to systematically evaluate the efficacy, toxicity and repeatability of radionuclide therapy of painful bone metastases (RTBM) in a large number of patients and to assess its incidence in patients with prostate cancer. Out of 818 treatments performed with a single i.v. dose of 148 MBq of strontium-89 chloride or 1,295 MBq of rhenium-186 hydroxyethylidene diphosphonate (HEDP), 610 could be evaluated (527 with 89Sr and 83 with 186Re-HEDP). Eighty-one patients received multiple (up to five) RTBM. The total number of retreatments was 100. Patients were followed up for a period of 3-24 months. Results, assessed according to pain relief and consumption of analgesic drugs, were expressed at four levels: 1, no response; 2, mild response; 3, good response; 4, excellent response. Responses were: level 1 in 19%, level 2 in 21.3%, level 3 in 33.3% and level 4 in 26.4% of cases. Retreatments showed significantly (P<0.01) worse responses (48% levels 3+4), in comparison to first RTBM. Duration of palliation was 5.0+/-3.5 months, and was longer in cases of excellent response, in first RTBM, in patients with limited metastases and when 89Sr was used. Better responses were found in cases of limited skeletal disease, under good clinical conditions, when life expectancy exceeded 3 months, and in radiologically osteoblastic or mixed bone lesions. The only statistically significant predictive factor was life expectancy (P<0.001). Flare phenomenon (14.1% of cases) did not correlate with the response. Haematological toxicity (mild to moderate in most cases) mainly affected platelets, and was observed in 25.5% of cases overall and in 38.9% of retreatments. RTBM did not seem to prolong life, though in some cases scintigraphic regression of bone metastases was observed. The two radiopharmaceuticals did not show any statistically significant differences in palliative efficacy and toxicity, either in first RTBM or in retreatments.

Radionuclide therapy for painful bone metastases. An Italian multicentre observational study. Writing Committee of an Ad Hoc Study Group.

BACKGROUND: It has been affirmed that observational studies give analogous results to randomised controlled ones. METHODS: A multicentre observational trial was conducted between 1996-1998 in order to evaluate the efficacy of palliative radionuclide therapy for bone metastases in a large number of patients. An evaluation was made on 510 patients with prostate cancer and painful bone metastases, treated with a single iv. dose of 89Sr-chloride (527 treatments) or 186Re-HEDP (83 treatments), in 29 Italian Nuclear Medicine Departments. Eighty-one patients received up to five injections, totalling 100 retreatments. Patients were followed up for a period of 3 months-2 years. Results were expressed at four levels of response: excellent, good, mild, and nil. RESULTS: Responses were excellent in 26.4%, good in 33.3%, mild in 21.3% and nil in 19% of all treatments, while good and excellent responses were obtained in 48% of retreatments. No statistically significant correlations were found between response and age of patients, skeletal extension of tumour, pretherapeutic PSA levels, evidence of non-bony metastases, previous chemotherapy and/or external-beam radiotherapy; osteolytic lesions responded worse than osteoblastic or mixed ones. Hematological toxicity (mild to moderate), mainly affecting platelets, was observed in 25.5% of all treatments and in 38.9% of retreatments. No clear differences were found between the two radiopharmaceuticals employed. CONCLUSIONS: Bearing in mind that observational studies can provide just as accurate results as randomised controlled trials, this study confirms the main findings of various limited monocentre trials.