Talc Pleurodesis Simulating Pleural Metastases on FDG PET Imaging

Case Author(s): Gabriel De Simon, M.D. and Barry A. Siegel, M.D. , 02/01/01 . Rating: #D3, #Q4

Diagnosis: Talc pleurodesis simulating pleural metastases on FDG PET imaging.

Brief history:  Severe emphysema with several episodes of spontaneous pneumothorax, treated by pleurodesis. The patient also has a cecal mass suspicious for malignancy, on an abdominal CT scan.

Click here to view images.

Full history:  66-year-old woman with known severe emphysema due to smoking, who had several spontaneous right pneumothoraces, treated by chest tube placement and talc pleurodesis, approximately one year prior to the PET study. A CT scan of the chest, abdomen and pelvis performed prior to the PET scan demonstrated a lower lobe pulmonary mass suspicious for a primary bronchogenic cancer, and a mass in the cecum suggestive of a colonic neoplasm.

Radiopharmaceutical:  3.2 mCi F-18 Fluorodeoxyglucose i.v.

Findings:

WHOLE BODY TUMOR PET IMAGING:

1. Curvilinear areas of intensely increased FDG uptake on the pleural reflection of the right hemithorax, located predominantly on the mediastinal surface. Most of the increased uptake is on the inferior paravertebral pleural surface just above the right hemidiaphragm, and extends cephalad to involve more apical regions of the paravertebral pleura.
    

2. Focal region of moderately increased activity, with standardized uptake value of 1.8, in the posterior left lower lobe. FDG uptake is eqivocal for malignancy.
    

3. Midline anterior mediastinal focal uptake, just above the base of the ascending aorta.
    

4. Lobulated, intensely increased uptake in the cecum and proximal ascending colon, consistent with a colonic neoplasm. No features of abdominal lymphadenopathy or hepatic metastases.

CONTRAST-ENHANCED CT SCAN OF THE CHEST AND ABDOMEN:

1. Multiple right pleural-based masses with regions of focal high attenuation suggestive of calcium.
    

2. Left lower lobe spiculated pulmonary mass with central calcification, measuring approximately 2.5 cm, consistent with a primary bronchogenic carcinoma.
    

3. Circular calcification in the anterior mediastinum, just above the base of the ascending aorta.
    

4. 5-cm, enhancing mass in the cecum and ascending colon, likely a colonic malignancy.

Discussion:

Talc, a soft granular mineral composed of an acid metasilicate of magnesium (H2 Mg3 {SiO3}4), is more effective for pleurodesis than tetracyclines, quinacrine, mustine or bleomycin, with a reported success rate of approximately 91%. Talc was administered in this patient with emphysema subsequent to several recurrent spontaneous pneumothoraces, as a slurry by chest tube, twelve months prior to the FDG PET scan. Pathological studies have demonstrated that talc incites an intense granulomatous pleural inflammatory reaction, usually occurring within 24 hours, and often persisting many months.

Although the patient has a suspicious primary cecal malignancy by CT, substantiated by intensely increased FDG uptake, pleural inflammation due talc pleurodesis is presumed to be the cause of increased pleural activity rather than metastatic deposits, because the FDG distribution correlates almost exactly with that of the high density talc deposits on the CT scan. In addition, it would be very unlikely for colonic cancer metastases to involve the pleura so extensively on the right side without contralateral involvement, and metastases with calcification would likely have arisen from a mucinous colonic primary neoplasm, with tumoral low cellular density and mucin production expectedly resulting in less intense FDG activity than present in the cecal lesion or pleural surface of the patient.

The increased use of FDG PET to diagnose and stage thoracic malignancy, the usefulness of whole body imaging for staging neoplasms, and the increasing use of talc for pleurodesis, may result in more cases in which regions of intense pleural uptake caused by the inflammatory response to talc, are misinterpreted as malignancy. Correlation with the CT chest is mandatory to avoid diagnostic errors in patients with a known history of talc pleurodesis. The patient also has a left lower lobe mass with standardized uptake value of 1.8, which although equivocal for malignancy by FDG uptake, remains highly suspicious for a second primary bronchogenic cancer given the spiculated appearance on CT and backround of severe emphysematous changes.

Reference: Murray JG, Erasmus JJ, Bahtiarian EA and Goodman PC. Talc pleurodesis simulating pleural metastases on F18 FDG PET imaging. AJR 1997;

168:359-360.

Followup:

The patient underwent resection of a 23 cm segment of large intestine, with histological examination demonstrating multiple tubular villous adenomas, the largest measuring 9.8 cm, with focal high grade dysplasia but no evidence of malignancy or invasion at the resection margins. PET is not sufficiently specific in the differentiation of highly dysplastic villous adenomas and carcinomas, and the intense FDG uptake in the cecum is not surprising for this benign tumor. The patient was to undergo resection of the left lower lobe mass, but refused surgery and will thus have followup CT scans four monthly for re evaluation. A repeat CT scan performed on 2/23/01 demonstrated no interval growth or change in morphology of the left lower lobe mass.

** POSTED MAY 14, 2002 **

PET Scans Valuable Diagnostic Tool

By Merritt McKinney

NEW YORK (Reuters Health) - A scan that looks for cancerous activity throughout the body may help doctors decide on the best treatment for cancer patients, researchers in Hawaii report.

In two surveys, a whole-body scan called FDG-PET, or fluorodeoxyglucose positron emissiontomography, was useful in making treatment decisions in 89% to 96% of patients.

Besides helping doctors decide whether a suspicious mass or lump is cancerous, ``for those people who are already being treated for cancer, PET can change the course of care in most cases,'' the study's lead author, Dr. Robert Tucker of Queen's Medical Center in Honolulu, told Reuters Health. With the aid of a PET scan, doctors can choose the most appropriate drugs and procedures, which may improve patients' quality of life, he explained.

FDG-PET scans work by measuring the use of glucose, or sugar, in the body's cells. Since cancer cells consume more sugar than normal cells, the scan identifies cancerous cells in the body and shows whether cancerous cells have spread beyond the original location of a tumor.

In a group of 463 cancer patients who underwent FDG-PET, the scan was valuable in making or confirming treatment decisions in 89% of patients, Tucker and his colleagues report in the May 1st issue of the Journal of Clinical Oncology. And in 45% of the patients, doctors changed the recommended treatment based on what the scan showed.

The most common type of cancer in the survey was lung cancer, followed by head and neck cancer, and colorectal cancer.

In a sample of 53 mostly lung-cancer cases pulled from the larger group to be reviewed by a lung specialist and a cancer surgeon, FDG-PET scans were even more helpful, according to the report. The screens were judged useful in 96% of the cases. In 33% of patients, surgery was canceled after doctors reviewed the results of the scan. In 15% of patients, chemotherapy or radiation was added to the treatment plan afterwards, and one or more of the treatments was canceled in 7% of patients.

Based on the results of the surveys, Tucker said that FDG-PET ``should become an integral part of a physician's diagnostic work-up of a suspected cancer patient and a routine exam for those with cancer.''

Although FDG-PET scans are expensive to perform, Tucker and his colleagues suspect that the test is worth the extra cost, since it can rule out unnecessary treatment. Tucker's group is now conducting a 2-year study comparing the treatment costs of patients who have PET scans with other patients who do not undergo the tests.

SOURCEJournal of Clinical Oncology 2001;192504-2508.

** POSTED APRIL 30, 2001 **

PET Scans More Accurate at Detecting Lung Cancer Than Standard Methods

NEW YORK (Reuters Health) - A new technique could improve the detection of lung cancers that have spread to other parts of the body, researchers in the Netherlands report. Using the scan could reduce the number of tests and procedures that lung cancer patients have to undergo, they say.

Dr. Remge Pieterman and colleagues compared the standard method of detecting cancers throughout the body--which includes computed tomography (CT), ultrasound, bone scanning, and needle biopsies--to a newer technique called whole-body positron emission tomography (PET), in 102 patients with lung cancer. None of the patients had small-cell lung cancer, a form of the disease, which is more difficult to treat.

They found that PET was able to detect non-small-cell lung cancer and its spread with more sensitivity than the traditional methods. In 11 of 102 patients, PET detected secondary cancers that had not been found by the standard method.

``Our study confirms that, as compared with traditional staging methods, PET can result in a more accurate classification of the stage of disease in patients with...non-small-cell lung cancer,'' Pieterman's group writes in the July 27th issue of The New England Journal of Medicine.

Although they weren't looking specifically at whether the PET scan improved the chances of survival for the cancer patients, the researchers suggest that ``the increased accuracy may improve survival.''

They recommend that future studies examine survival in these patients. In the meantime, the researchers note that at present, the procedure is not cost effective due to the limited availability of the equipment needed to perform the scan.

In an accompanying editorial, Dr Salvatore Berlangieri and Dr Andrew Scott, both of Austin and Repatriation Medical Center, Melbourne, Australia note that many US insurers have approved reimbursement of PET for lung cancer. These results add to ``the accumulating body of evidence that PET...is more accurate than CT'' for lung cancer staging.

Lung cancer is the leading cause of cancer deaths in both men and women in the US and will claim about

160,000 lives in this year.

SOURCE: The New England Journal of Medicine 2000; 343; 254-261