Preventive radiotherapy may not be the best way to keep new tumors from growing at the site of pleural interventions in people with malignant pleural mesothelioma.
That is the finding of a group of physician researchers in the UK, who tracked the outcomes of more than 200 mesothelioma patients from institutes across the country who had procedures that required the use of a large-bore pleural tube.
Pleural Interventions in Mesothelioma
Pleural mesothelioma is a virulent cancer that occurs on the membrane that encircles and encases the lungs. Any procedure or surgery that involves using medical equipment in this region constitutes a pleural intervention.
Mesothelioma patients may need all kinds of pleural interventions, from surgeries to remove the bulk of their tumor, to diagnostic procedures, to chest tubes to drain excess pleural fluid. For some of these procedures, it may be necessary to use a large-bore ( ≥ 20 French) chest tube.
While these procedures may be necessary, they also carry the risk of accidentally spreading mesothelioma to new areas of the chest. New mesothelioma tumors have been found to sometimes grow along the path where a pleural tube was inserted.
Preventing New Mesothelioma Tumors
One way to help prevent the formation of these new mesothelioma tumors, known as procedure-tract metastases (PTMs), is to irradiate the area where the large-bore tube was inserted.
By disturbing the DNA of cells along the insertion path, radiotherapy can help keep mesothelioma cells from gaining a foothold there.
But the new UK study suggests that performing this radiotherapy procedure before new mesothelioma tumors develop is no more effective at preventing the spread of mesothelioma than just treating them when they crop up.
Prophylactic Versus Treatment-Focused Radiotherapy
To compare the two approaches to PTMs, doctors led by a University of Bristol team randomly assigned 203 mesothelioma patients to receive either prophylactic radiotherapy immediately following their large-bore procedure or treatment-focused radiotherapy if and when tumors occurred.
The trial, nicknamed SMART, found no justification for performing radiotherapy when no new mesothelioma tumors are present.
“The patients were well matched at baseline. No significant difference was seen in PTM incidence in the immediate and deferred radiotherapy groups,” reports lead author Amelia O. Clive, PhD, in The Lancet Oncology.
There was also no significant difference between the two group of mesothelioma patients in side effects, which most commonly included skin toxicity and tiredness. Based on these findings, the team recommends against “routine use of prophylactic radiotherapy in all patients with mesothelioma after large-bore thoracic interventions”.
Clive, AO, “Prophylactic radiotherapy for the prevention of procedure-tract metastases after surgical and large-bore pleural procedures in malignant pleural mesothelioma (SMART): a multicentre, open-label, phase 3, randomised controlled trial”, June 23, 2016, The Lancet Oncology