Radical dose radiotherapy (RT) is frequently used in thoracic malignancies, both for early stage primary non-small cell lung cancer (NSCLC) and for secondary lesions from other primary tumors, particularly in the setting of oligometastatic patients. Although development of distant metastases is the predominant pattern of failure after treatment with radical RT, isolated local recurrences, defined as a tumor recurrence overlapping the 50% isodose field, are still observed and are becoming more and more frequent along with the prolongation of life expectancy in cancer patients. Salvage options for isolated post-radiation local failures are limited, with surgery or retreatment with radiotherapy as potential modalities.
While salvage surgical resection after previous thoracic irradiation has shown encouraging results, most patients experiencing post-radiation local relapse are not surgical candidates. Therefore, reirradiation may be the only viable salvage option for many patients. Retreatment with CFRT has been reported for locoregional failures, with generally-poor outcomes. Although, salvage SBRT after initial CFRT has been described in select small series of heterogeneous patient groups ranging from early stage to locally-advanced and metastatic, few data exist to guide us on the role of reirradiation with SBRT for isolated recurrences after initial SBRT for early-stage NSCLC. Due to the heterogeneity and the low numerosity of these experiences, important questions regarding the safety and efficacy in this setting are still largely unanswered. Particularly, the possibility of delivering a second course of ablative dose RT (BED 100 Gy) is almost unexplored.
Based on this background, we designed a prospective phase I study to evaluate the maximum tolerated dose (MTD) of SBRT for thoracic re-irradiation. Dose limiting toxicity will be pneumonitis G3. The potential advantage of the dose escalation planned in this study is the delivery of an ablative dose to radically treat patients with inoperable local relapse, without unacceptable toxicity.
