Evaluation of suspected malignant pulmonary lesions with 201Tl single photon emission computed tomography

Comparative evaluation of 99mTc-depreotide and 201Tl chloride single photon emission tomography in the characterization of pulmonary lesions

PURPOSE

To compare (99m)Tc-depreotide and (201)Tl chloride SPET in the characterization of pulmonary lesions.

METHODS

Fifty-seven pulmonary lesions from 33 patients suspected of malignancy in computed tomography, were assessed by (99m)Tc-depreotide and (201)Tl early and delayed SPET imaging. Images were visually assessed and the tumour-to-normal (T/N) lung activity ratio for early (ER) and delayed (DR) scans and the retention index (RI), were calculated in every lesion. A final diagnosis was reached for all lesions, based either on histology or prolonged clinical and radiological follow-up.

RESULTS

Twenty-three lesions were characterized as malignant and 34 benign. In visual analysis, all malignant lesions accumulated both tracers resulting in sensitivity and negative predictive values of 100%. However, false positive interpretations resulted in a specificity of 64.7% and 67.6% for (99m)Tc-depreotide and (201)Tl, respectively. ER and DR of both agents and the RI of (99m)Tc-depreotide were significantly higher in malignant, compared to benign lesions. In defining thresholds of abnormality from ROC analysis, a significant increase in specificity was observed for both tracers in both scan phases (91.2% for all), as compared to visual analysis (P<0.01). There was no significant difference in the diagnostic performance between (99m)Tc-depreotide DR and (201)Tl DR, although the former provided the highest T/N ratio.

CONCLUSION

This study demonstrates that (99m)Tc-depreotide and (201)Tl SPET are equally effective and may be useful in the non-invasive determination of lung malignancy. The specificity of both techniques is significantly improved by quantifying radiopharmaceutical accumulation in pulmonary lesions.

Evaluation of breath-hold201Tl SPECT in the differential diagnosis of solitary pulmonary nodules

The aim of this study was to evaluate the usefulness of deep inspiration breath-hold SPECT (BrST, a method for 201Tl SPECT) in the diagnosis of solitary pulmonary nodules (SPN).

METHODS

Ten patients with malignant lesions and five with benign lesions were enrolled in this study. Early SPECT acquisition was performed 15 min after injection of 201Tl, while delayed SPECT images were acquired 3 h after injection. The first 15-sec acquisition was done using the BrST technique, and the second with the conventional free breathing (FB) method. We performed this technique alternately, and therefore, the odd data were from BrST and the even data were from FB. We referred to the T/N ratio of the early images as the ER and to the T/N ratio of the delayed images as the DR. To semi-quantitatively evaluate the degree of retention in the lesion, the retention index (RI) was calculated.

RESULTS

The RI of BrST indicated greater accuracy than that of FB in the differential diagnosis of SPN. For the benign and malignant lesions, the RI of BrST was -3.07 +/- 31.51 and 29.86 +/- 25.01, respectively (p < 0.05). The sensitivity, specificity, and accuracy of BrST (80%, 80%, and 80%, respectively) were significantly higher than those of FB (p < 0.05).

CONCLUSION

The BrST method is more accurate than that of the conventional FB method in the differential diagnosis of SPN.

Thallium-201 SPECT in advanced non-small cell lung cancer: in relation with chemotherapeutic response, survival, distant metastasis and p53 status

PURPOSE

The aim of this study was to evaluate the relationship between 201Tl tumor uptake, chemotherapeutic response, metastasis, p53 status and survival in non-small cell lung cancer (NSCLC).

METHODS

A total of 23 patients underwent 201Tl SPECT. In 9 patients, 2nd 201Tl SPECT study were performed 1 week after the 3rd cycle of chemotherapy (ChT), and early (ER) and delayed (DR) tumor/normal lung ratios and retention indices (RI) were obtained. In 15 patients p53 status was assayed with immuno-histochemical staining. The patients were divided into subgroups after the 3rd cycle of ChT; responders [R(+) (n = 10)] and non-responders [R(-) (n = 13)], distant metastasis [(M1) n = 11] and [(M0) n = 12], and mutant p53 status [p(+) n = 7, p53(-) n = 8].

RESULTS

The differences for ER, DR and RI values between all of the subgroups were not statistically significant. ER and DR of responders decreased significantly after ChT; from to 2.46 to 1.36 (p = 0.04) and 2.29 to 1.53 (p = 0.04), respectively. In the non-responder group, both ER and DR slightly increased after ChT (p > 0.05).

CONCLUSION

Our results suggest that in NSCLC, there was a weak correlation between higher 201Tl ratios and positive response to chemotherapy, absence of distant metastasis, and p53(-) status. Significant 201Tl uptake decrease after chemotherapy indicates that delayed 201Tl uptake can be used in evaluating the chemotherapeutic response.

Thallium-201 SPECT with triple-headed gamma camera for differential diagnosis of small pulmonary nodular lesion 20 mm in diameter or smaller

AIM

Although thallium-201 (201Tl) has been used for the diagnosis of lung cancer, its detectability of small pulmonary nodules is not known. The aim of this study was to evaluate the ability of 201Tl SPECT for the differential diagnosis for the pulmonary nodules 20 mm in diameter or smaller.

METHODS

201Tl SPECT was performed in 31 patients suspected of having primary lung cancer. The final diagnosis was established by histology, and tumor size was 10 to 20 mm in diameter. Twenty of 31 patients had malignant tumors, including squamous cell lung cancer (n = 5), adenocarcinoma (n = 14) and small cell lung cancer (n = 1), but in none of them was there mediastinal lymphnode involvement.

RESULTS

Ten of 20 malignant tumors and 1 of 11 benign lesions demonstrated significant 201Tl uptake, so that the positive predictive value, negative predictive value, sensitivity and specificity for the diagnosis of lung cancer were 90.9% (10/11), 50.0% (10/20), 50.0% (10/20) and 90.9% (10/11), respectively.

CONCLUSION

These data suggest that sensitivity for detecting lung cancer 20 mm or less in diameter may be insufficient, but even in patients with small pulmonary nodules, a positive 201Tl result is highly predictive of lung cancer.

Thallium-201 SPECT of orbital tumors

Thallium-201 ((201)Tl) SPECT is utilized as a diagnostic imaging tool for a variety of tumors, such as lung cancer, brain tumors, etc., but there is hardly any literature on this type of imaging in orbital lesions. We examined 22 patients with orbital lesions and unilateral exophthalmos to evaluate the usefulness of (201)Tl-SPECT in the diagnosis of orbital tumors. All 22 cases had a confirmed histopathological diagnosis. The patients underwent (201)Tl-SPECT imaging before therapy. Early images were obtained 15 minutes after the intravenous administration of 74 MBq (201)Tl-chloride, and delayed images were taken 3 hours later. The intensities of (201)Tl accumulation in the early and delayed images were measured. Three out of four patients with cavernous hemangiomas, one of two with neurinomas, all three with pleomorphic adenomas, one with lipoma, and one with dermoid cyst had negative scans, but the other 13 patients all displayed ( 201)Tl accumulation in the area of the tumor. Four malignant lymphomas, two reactive lymphoid hyperplasias, one meningioma, one neurinoma, one adenoid cystic carcinoma and one plasmacytoma showed increased uptake, especially in the early phase. The most intense uptake was seen in the metastic renal cell carcinoma, in both early and delayed phases. We conclude that (201)Tl-SPECT can be useful in predicting the histopathological diagnosis of orbital tumors, especially by comparing the accumulation rate in the early and delayed phases.

Differential uptake of TI-201 by small-cell lung cancer in a patient with pneumoconiosis-related pulmonary nodules

A 68-year-old man with pneumoconiosis was thought to have small-cell lung cancer based on the results of a biopsy of a bone tumor. Three pulmonary nodules were observed on a chest radiograph. Compared with a chest radiograph taken 4 months earlier, one of the nodules had grown. It was difficult to differentiate this nodule from pneumoconiosis-related benign pulmonary nodules from the appearance on the chest radiograph and CT. Ga-67 scintigraphy and TI-201 lung SPECT were performed to characterize these nodules. TI-201 SPECT showed differential high uptake in the enlarged nodule, whereas Ga-67 scintigraphy showed equally intense uptake in all these nodules. Transbronchial biopsy of the nodule that showed high TI-201 uptake revealed cancer cell nests against a background of interstitial fibrosis. The pathologic diagnosis was small-cell lung cancer that had developed in lung scar tissue. This case suggests the utility of TI-201 in scintigraphic assessments of pneumoconiosis-related pulmonary nodules when lung cancer is suspected.

Thallium and FDG uptake by atelectasis with bronchogenic carcinoma

We report a case of bronchogenic carcinoma with atelectasis studied by T1-SPECT and FDG-PET. In the carcinoma, abnormally high uptake of T1 and FDG were detected, but in the region of atelectasis, an abnormally high uptake of T1 with a relatively low uptake of FDG were observed. On quantitative analyses, the T1 retention indexes of the tumor and atelectasis were 29.7 and 42.0. The mean SUVs of FDG of the tumor and the atelectasis were 8.92 and 1.28. T1-SPECT could not distinguish the atelectasis from the carcinoma. FDG-PET was superior to T1-SPECT in this case in detecting malignancy and distinguishing it from atelectasis.

Pulmonary Tc-99m tetrofosmin imaging: clinical experience with detecting malignant lesions and monitoring response to therapy

The authors prospectively investigated the uptake and kinetics of Tc-99m tetrofosmin (Tetro) in benign and malignant lung lesions and the effect of radiotherapy, chemotherapy, or both on Tc-99m Tetro uptake in malignant lung tumors. Dynamic and planar Tetro imaging were performed in 45 patients with pulmonary lesions during a period of 28 months (34 untreated malignant tumors, 11 benign lesions). Tetro uptake was visibly increased in 26 of 34 malignant tumors, with a mean lesion to contralateral normal tissue ratio of 1.44 +/- 0.29 and a tumor washout rate of 28.4 +/- 6.6% 30 minutes after injection. In 3 of 11 benign lesions, Tetro uptake was observed. Of the 26 patients with malignant tumors and positive Tetro uptake, nine had repeated imaging 6 to 8 weeks after therapy. The patients were treated with radiotherapy, chemotherapy, or both. Reduction in radiological tumor size was used as the clinical response parameter. In five of nine patients, the course of Tetro uptake in follow-up imaging was in accordance with that of radiological tumor size. Two of four remaining patients had only slight discordance between the alteration of Tetro uptake and radiological tumor size. The sensitivity of Tetro to detect malignant lung lesions in our patients was 77%. The specificity and accuracy of the method were 73% and 76%, respectively. Tetro has limited diagnostic value in detecting lung cancer. It may be useful to monitor the response to therapy in malignant lung tumors with initial tracer uptake. Broader trials on this matter are needed for further clarification.

Intense and prolonged Tl-201 accumulation in a slow growing bronchioloalveolar carcinoma

Thallium-201 SPECT was performed to evaluate a pulmonary lesion in a 73-year-old male which had been considered to be an inflammatory lesion for two years. The lesion has slowly increased in size on x-CT. Tl-201 was intensely taken up and retained in the lesion, suggesting a malignant lesion. Histological examination revealed that the lesion was bronchioloalveolar carcinoma. This case suggested that Tl-201 uptake of pulmonary carcinoma would not be necessarily related to cell growth rate.

Temporal trends in the prevalence of malignancy in resected solitary pulmonary lesions

STUDY OBJECTIVE

To determine whether there has been an increase in the prevalence of malignancy among resected, indeterminate solitary pulmonary lesions (SPL) over the past 14 years.

DESIGN

A retrospective review of all thoracotomies for indeterminate SPLs from 1981 through 1994.

SETTING

A university-affiliated VA Medical Center.

PATIENTS

Three-hundred seventy resected indeterminate SPLs (all < or = 6 cm) in 360 patients.

MEASUREMENTS AND RESULTS

Virtually all patients were men with an average age of 63 +/- 9 years. The average lesion size was 2.5 +/- 1.4 cm; 71% were 3 cm or less. Overall, 79% of resected lesions were malignant; 94% of these were bronchogenic carcinomas. Granulomas accounted for more than 50% of benign lesions. The proportion of malignant diagnoses increased from 55 to 60% in 1981 to 1983 to 90 to 100% in 1990 to 1994 (p < 0.005). The increasing proportion of malignancy over time was independent of age at time of operation and lesion size. There was no significant difference in survival among patients with a malignant lesion resected in 1981 to 1983 compared with 1990 to 1994.

CONCLUSION

We conclude that there has been a striking increase in the prevalence of malignancy among resected indeterminate SPLs over the past 14 years in our institution. We suspect that this trend reflects improvements in our ability to diagnose benign SPLs preoperatively, primarily through the use of CT. Our results should prompt other institutions to review their recent experience with the diagnosis of indeterminate SPLs to provide more timely information to physicians and their patients who are contemplating resection of SPLs.