Prophylactic Irradiation of Tracts in Patients With Malignant Pleural Mesothelioma: An Open-Label, Multicenter, Phase III Randomized Trial

Bayman N, Appel W, Ashcroft L et al

J Clin Oncol 2019;37(14):1200-1208. ;

Abstract 

What is the key question?

  • Prophylactic irradiation of the chest wall has been used in patients with pleural mesothelioma on the basis of several small studies from many years ago.
  • The authors set out to investigate whether prophylactic irradiation was effective in preventing chest wall metastasis in patients with mesothelioma.

What is the bottom line?

  • 375 patients with MPM were recruited. All underwent either open lung biopsy, VATS, thoracoscopy or insertion of an ICC. 186 received prophylactic irradiation and 189 did not.
  • Radiotherapy to the area of the scar with 3cm margin and up to the 3rd rib above the scar was administered. All patients received chemotherapy at least one week after irradiation in the irradiation group and at the treating clinicians discretion in the control group with more than 90% receiving pemetrexed and platinum doublet.
  • Patients were reviewed at 6, 12, 26 and 52 weeks after randomization and contacted monthly by phone to assess for chest wall nodules. Patients were reviewed if there was any suspicion of chest wall nodules.
  • Primary end point was the presence of chest wall metastasis at 29 weeks from Secondary outcomes were incidence of CWM 12 months from randomization, time to CWM, position of CWM in those in the irradiation group, skin toxicity following irradiation and pain from CWM.
  • 2% of the Irradiation group and 5.3% of the control group developed CWM (6/186 and 10/189; OR 0.60; P=0.44). In total, 46 patients developed CWM, 17 in the irradiation group and 29 in the control group. The difference was not statistically significant (Hr .057;;P=.06).
  • 8 CWMs developed in the radiotherapy field in the irradiation group and 7 occurred outside the field (data was not recorded for 2 patients). Baseline pain scores were recorded in 38 patients with 20 patients (52.6%) recording the same level or less pain at the time of CWM diagnosis and 18 (47.4%) recording an increase in pain between baseline and diagnosis of CWM. Skin toxicity occurred in 116 with 96 being Grade 1 toxicity and only one having Grade 3 toxicity.

Why read on?

  • This is the largest trial to demonstrate that prophylactic irradiation does not significantly reduce the incidence of CWM in patients with mesothelioma and along with the Surgery for Mesothelioma After Radiation Therapy trial outlines significant toxicity associated with its use.