Correlation of locoregional treatment failures with radiotherapy target volumes after radiochemotherapy for esophageal cancer.

Abstract

166 Background: Radiotherapy is a mainstay in curative treatment concepts of esophageal cancer. Despite extensive treatment fields locoregional recurrences are frequent. We therefore aimed to evaluate the exact patterns of locoregional recurrence and correlate these recurrences with radiotherapy target volumes. Methods: Diagnostic PET-CT or CT imaging studies showing locoregional recurrences after preoperative or definitive radiochemotherapy for squamous or adenocarcinoma of the esophagus were matched with CT scans used for treatment planning. Distance of the recurrence from the Clinical Target Volume (CTV), Planning Target Volume (PTV) and the dose at the failure site were the determined. Target volume definition was in line with international standards. Results: We identified 104 patients treated with either definitive (n = 81) or preoperative radiochemotherapy (n = 23). After exclusion of patients with a history of second malignancies we found 25 locoregional recurrences in 20 patients. Median time to locoregional failure was 8 months (range 2-26 months). Six of 25 recurrences (24%) were located intraluminal in the initial Gross Tumor Volume (GTV), three of 25 (12%) were in-field nodal failures and five (20%) more than 1 cm distant from the PTV. Nine (36%) locoregional recurrences occurred within 1 cm of the cranial or distal end of the CTV, between the CTV and PTV or out-of-field adjacent to the PTV. Two patients developed anastomotic recurrence after surgery. Conclusions: Matching of diagnostic CTs showing local recurrences with radiotherapy planning CT data set allows the correlations of local recurrences with target volumes. Despite extensive safety margins, field margin recurrences remain a considerable problem in the treatment of esophageal cancer. The use of advanced radiotherapy techniques might facilitate larger treatment volumes without increasing toxicity.