Purpose: To investigate the influence of induction chemotherapy (ICT) on dosimetric outcomes in patients with\ninoperable non-small cell lung cancer (NSCLC) treated with definitive chemoradiation (CRT).\nMaterials and methods: 30 patients with inoperable stage II-III NSCLC treated with 2ââ?¬â??4 cycles of ICT followed by\ndefinitive CRT to ? 60 Gy were selected. Tumor response to chemotherapy was scored by RECIST criteria. Treatment\nplans based on tumor extent prior to chemotherapy were generated based on equivalent planning constraints and\ntechniques as the original post-chemotherapy plans. Dosimetric parameters predictive of toxicity for lung, esophagus,\nheart, and spinal cord were compared amongst the pre- and post-ICT plans.\nResults: The majority of patients (70%) experienced an overall reduction in GTV size between the pre-ICT imaging and\nthe time of simulation. Comparing pre-and post-ICT diagnostic imaging, 5 patients met the RECIST criteria for response,\n23 were classified as stable, and 2 experienced disease progression on diagnostic imaging. Despite a significantly\nreduced GTV size in the post-ICT group, no systematic improvements in normal tissue doses were seen amongst the\nentire cohort. This result persisted amongst the subgroup of patients with larger pre-ICT GTV tumor volumes (>100 cc3).\nAmong patients with RECIST-defined response, a significant reduction in lung mean dose (1.9 Gy absolute, median 18.2\nGy to 16.4 Gy, p = 0.04) and V20, the percentage of lung receiving 20 Gy (3.1% absolute, median 29.3% to 26.3%, p = 0.04)\nwas observed. In the non-responding group of patients, an increased esophageal V50 was found post-chemotherapy\n(median 28.9% vs 30.1%, p = 0.02).\nConclusions: For patients classified as having a response by RECIST to ICT, modest improvements in V20 and mean\nlung dose were found. However, these benefits were not realized for the cohort as a whole or for patients with larger\ntumors upfront. Given the variability of tumor response to ICT, the a priori impact of induction chemotherapy to\nreduce RT dose to normal tissue in these patients is minimal in the setting of modern treatment planning
Loading....