Prophylactic Intervention Site Radiation ‘Not Justified’ For Mesothelioma Patients

Radiotherapy does not prevent procedure-tract metastases in malignant pleural mesothelioma patients

medwireNews: Prophylactic radiotherapy should not be routinely offered to patients undergoing large-bore pleural intervention for malignant pleural mesothelioma, SMART trial researchers say on finding immediate receipt does not significantly reduce the likelihood of procedure-tract metastases (PTM).

PTM occurred in 9% of 102 patients who were given immediate radiotherapy, consisting of 21 Gy given in three fractions within 42 days of pleural intervention, versus 16% of 101 patients whose radiation was deferred until PTM diagnosis.

This gave a nonsignificant odds ratio of 0.51 for the primary intention-to-treat analysis of PTM incidence, report Nick Maskell, from the University of Bristol in the UK, and co-authors in The Lancet Oncology.

Median overall survival was similar between the immediate and deferred radiotherapy groups, at 357 versus 365 days. Morphine-equivalent dose requirement, visual analogue scores for chest pain and quality of life measures were also comparable between the treatment groups.

“Taken together with results from the three previous randomised controlled trials, prophylactic radiotherapy is ineffective in preventing PTMs in unselected patients with mesothelioma”, the SMART investigators conclude.

The authors of an accompanying comment agree that routine prophylactic radiotherapy is “not justified” in the overall patient population as the results suggest the treatment has “no effect on symptom control or on patients' perception of the natural history and progression of the disease.”

But they note that among patients who were not treated with first-line pemetrexed–platinum chemotherapy, immediate radiotherapy was associated with a significantly reduced risk of PTM, with an odds ratio of 0.16.

“These data seem to suggest a benefit of chemotherapy on loco-regional disease control in malignant pleural mesothelioma”, write Giovanni Luca Ceresoli and Vittorio Vavassori, from Cliniche Humanitas Gavazzeni in Bergamo, Italy.

“Although the data were derived from a subgroup analysis and should be confirmed by further studies, they are potentially relevant for clinical practice”, the commentators say, adding that these results together with those from the upcoming PIT trial will help “establish the standard of practice in this setting.”

References

Clive AO, Taylor H, Dobson L, et al. 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. Lancet Oncol 2016; Advance online publication 23 June. DOI: 10.1016/S1470-2045(16)30095-X

Ceresoli GL, Vavassori V. Radiotherapy to intervention sites in mesothelioma: no more? Lancet Oncol 2016; Advance online publication 23 June. DOI: 10.1016/S1470-2045(16)30132-2

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