Thin-slice CT tags subsegmental pulmonary emboli in oncology patients

Oncology patients have a fourfold risk above the general population of developing pulmonary embolism. If the patient is receiving chemotherapy, the risk is even greater. Irish radiologists have found that imaging these patients with thin-slice CT during routine staging or restaging can pinpoint clinically unsuspected pulmonary embolism.

Dr. Michelle Browne and colleagues from the University Hospital and the National University of Ireland, both in Galway, enrolled 280 consecutive oncology patients in their study. The most common type of cancer in this population was breast (79), followed by colorectal (37), and lymphoma (36).

The patients underwent contrast-enhanced CT scans of the thorax. Contiguous thin-slice (1 mm) reformatted images of the pulmonary arteries were acquired in addition to routine images acquired at 5-mm slice thickness. Exams were done on a 64-slice scanner and each study was prospectively read by two diagnostic radiologists. Referring physicians were notified of the results within 24 hours, according to Browne's poster.

Clinically unsuspected pulmonary emboli were detected in 15 patients (5.4%), according to the results. In six of these 15, the emboli could be seen only on thin-slice CT studies. Follow-up CT scans showed that a failure to treat with anticoagulation medication was associated with recurrent pulmonary emboli, Browne's group wrote.

Advantages of thin-slice CT include a faster acquisition time and reduced section thickness, the authors explained. In addition, thinner slices avoid volume-average pitfalls and offer superior visualization of subsegmental pulmonary arteries.

While Browne's group did not discuss whether a particular type of cancer carried a greater incidence of pulmonary emboli in their patient population, previous research has indicated that unsuspected pulmonary embolism results in an increase in symptoms (shortness of breath, chest pain, and limb pain) and a reduction in quality of life for the cancer patient.

A study by Dr. Casey L. O'Connell and colleagues at the University of Southern California-Keck School of Medicine in Los Angeles, found that 75% of oncology patients had signs or symptoms of pulmonary embolism (J Clin Oncol 2006;24(30):4928-4932).

"The delineation of fatigue as a manifestation of PE could represent an inability of patients to differentiate fatigue from other symptoms such as dyspnea with exertion.

However, these symptoms should increase the level of suspicion in medical oncologists for PE in their cancer patients," O'Connell's group wrote.