Feasibility and safety of boost at 74 Gy based on interim FDG-PET during thoracic radio-chemotherapy for NSCLC patients

Prof Gerard Zalcman - Université de Paris, Paris, France

I presented yesterday the final results of a randomised phase II trial, RTEP7-IFCT1401, which is an academic trial of which the aim was to assess the PET CT as a means to personalise radiotherapy in stage 3 non-small cell lung cancer patients. So the design was a randomised, not comparative phase II. The standard arm patients received standard chemoradiotherapy up to 66Gy. They all had a PET CT at baseline and then at 42Gy but this PET CT did not help to modify the radiotherapy. In the experimental arm they also had at PET CT scan at baseline, they also had a PET CT at 42Gy but here the second PET CT helped to define the radiotherapy, meaning that patients with residual FDG uptake  at 42Gy had a boost of radiotherapy in the volume still metabolically active up to 74Gy.

We randomised 77 patients in the standard arm, 68 patients in the experimental arm of whom 48 received the boost based on the intermediate PET CT. The primary endpoint was local regional control rate at one year and this endpoint had to be over 66% and actually was met since it was 77.6% in the experimental arm and 71% in the standard arm. So the primary endpoint was met.

But the most important thing is that, contrary to the US phase III trial, RTOG 0617, we did not observe any supplemental toxicity induced by radiotherapy nor more toxicity in the cardiac, oesophageal or pulmonary areas. The local control was improved since the PFS was 22 months in the experimental arm versus 12 months in the standard arm with standard radiation.

So, the conclusion is that it can be a way to personalise radiotherapy, to give a boost to patients with radioresistant tumours which deserve such a boost and to spare radiotherapy in patients with radiosensitive tumours which do not deserve such a radiotherapy boost and sparing toxicity.