A Canadian study says radiologists often overlook catheter tract metastasis in people with pleural mesothelioma, even though as many as a quarter of patients with pleural catheters develop the problem.
Mesothelioma patients can develop excess fluid around the lungs that makes it hard to breathe. Doctors can treat the problem with pleural catheters that stay in place and drain to the outside.
But tiny tumors that spring up along the tract where the catheter was inserted are a risk with this treatment. These tiny tumors are called metastatic tumors. They are easy to miss on CT scans. But the new report says there are other tell-tale signs of catheter tract metastasis.
Pleural Catheters for Effusion in Mesothelioma
Pleural effusion is a common problem for pleural mesothelioma patients. Effusion is a build-up of fluid in the space between the pleural lining and the lungs. The fluid is a byproduct of the body’s effort to fight the cancer. As it fills the space, pleural effusion makes it harder for the lungs to expand when the patient inhales.
Draining the fluid or filling in the space can help mesothelioma patients feel better. Pleurodesis is a surgical procedure for filling in the space. An indwelling pleural catheter is a tool for draining the fluid. Both options have risks.
Catheter tract metastasis is a risk of indwelling pleural catheters. When the doctor inserts the catheter, it pierces the chest wall. At that time, or when it is removed, it may disturb mesothelioma tumor cells. These disturbed cells sometimes “seed” new mesothelioma tumors. These often occur at the catheter insertion spot.
Doctors may treat these new tumors with radiation. But first, they have to know they are there.
Spotting Catheter Tract Metastasis
In the new report in European Radiology, researchers analyzed the cases of 90 mesothelioma patients with pleural catheters. Twenty-three of them (26%) developed catheter tract metastasis. Most of these metastatic tumors appeared just under the skin at the spot where the catheter entered the body.
Metastatic tumors along the catheter tract grew at a median rate of 3.5 mm per month. They showed up a median of 408 days after catheter insertion. Eighty-three percent of cases of catheter tract metastasis happened after the catheter was removed.
But That was not the biggest surprise in the report. Even though more than a quarter of patients with pleural catheters develop metastatic disease on the catheter tract, radiologists spotted fewer than half of them.
“CTM is commonly overlooked and underreported by radiologists,” writes lead researcher Faisal Hamad. “Reporting radiologists described focal abnormality at the insertion site in only 9 out of 23 patients.”
But the report also showed that CT is not the only way to catch catheter tract metastasis in mesothelioma patients. Patients with these tumors also usually had enlarged chest muscles on that side of the chest.
“Ipsilateral muscle enlargement is a newly described CT finding that can assist in the detection and diagnosis,” concludes Dr. Hamad.
Watching for this symptom and paying close attention to the insertion site even after removal might help doctors find and treat more metastatic mesothelioma tumors.
Hamad, F, et al, “Tract metastasis in patients with long-term pleural catheter-computed tomography diagnosis and longitudinal assessment”, April 15, 2021, European Radiology, Online ahead of print, https://link.springer.com/article/10.1007/s00330-021-07867-0