PALM BEACH, FLA. — Helical multidetector computed tomography increases the detection of smaller segmental and subsegmental—but not central—pulmonary emboli following cancer surgery, according to the results of a database review.
In the study of almost 300 cancer surgery patients at a single center, MDCT increased the detection of PEs fourfold because of the ability to diagnose subsegmental PEs. MDCT did not increase the detection of central PEs.
“Diagnosis of pulmonary embolism in most major hospitals has changed, mostly because of the MDCT scan,” said Dr. Yuman Fong, chair of the department of surgery at Memorial Sloan-Kettering Cancer Center, New York, where the study was conducted. “There is increased sensitivity and the ability to get these scans much faster—in a single breath hold.”
MDCT has replaced ventilation/perfusion lung scans as the test of choice for detecting PE in most institutions, he noted at the annual meeting of the Southern Surgical Association.
Dr. Fong and his associates reviewed a prospective database of 47,601 patients who had abdominal, pelvic, thoracic, or soft-tissue major surgery at the cancer center. A total of 1,441 patients had a CT angiogram to rule out PE from January 2000 to December 2005. During this time, use of the contrast-enhanced, high-resolution MDCT scans of the chest within 30 days of surgery increased at the center from 5 per 1,000 patients in 2000 to 45 per 1,000 in 2005. The researchers sought to determine if patient outcomes changed as a result, said Dr. Fong, who is also vice chair of the technology department at the center.
They identified 311 patients who had a PE within 30 days of surgery. In all, 17 of the patients had a PE but no malignancy, and were excluded from the analysis; the remaining 294 cancer patients were assessed further.
The overall incidence of PE among cancer surgery patients increased from 2.3 per 1,000 patients in 2000 to 9.3 per 1,000 in 2005, a significant difference. This higher rate resulted from significantly greater diagnosis of subsegmental PEs, which increased from 0.1 per 1,000 patients in 2000 to 3 per 1,000 in 2005. At the same time, MDCT did not increase detection of central PEs, diagnosed in 0.7 per 1,000 patients in 2000 versus 0.6 per 1,000 in 2005.
Increased detection of subsegmental PEs with MDCT “makes sense because it's more sensitive,” Dr. Fong said. “Subsegmentals are harder to find with VQ [ventilation/perfusion] scan or single-detector CT.”
The researchers also looked at mortality. The annual incidence rate of fatal PE did not change during the study, remaining at 0.4 per 1,000. Not surprisingly, the 30-day mortality rate for patients with the more serious central PE was higher, at 44%, compared with 6% for patients with subsegmental PE. Those with central PE “were more likely to go to the ICU, have cardiopulmonary arrest, and die in the hospital,” Dr. Fong said.
More than half of the central PE group was symptomatic, whereas “only a few of the peripheral PEs were severely symptomatic,” Dr. Fong said. Shortness of breath, hypoxia, and an elevated heart rate (more than 100 beats per minute) were more common among central PE patients.
All 294 cancer patients with PE were treated with anticoagulants. Of these, 40 patients (14%) developed complications from the treatment. “Given a 14% complication rate with anticoagulation, are we putting some patients at increased risk?” asked Dr. Robert C.G. Martin, a surgical oncologist at the University of Louisville (Ky.).
“At Memorial Sloan-Kettering, when we discover a PE, whether or not it's central, we anticoagulate them,” Dr. Fong replied. “Surgeons put the patients on [anticoagulants,] and then the oncologists are generally afraid to take folks off anticoagulants, so they remain on semipermanent anticoagulation.” There is a balance to strike between a higher risk of complications and the lower likelihood of metastasizing cancer cells circulating in the blood “being able to stick,” he added.