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Background and Purpose: When treating patients for esophageal cancer (EC) with photon or proton radiotherapy (RT), breathing motion of the target and neighboring organs may result in deviations from the planned dose distribution. The aim of this study was to evaluate the magnitude and dosimetric impact of breathing motion. Results were based on comparing weekly 4D computed tomography (4D CT) scans with the planning CT, using the diaphragm as an anatomical landmark for EC., Material and Methods: A total of 20 EC patients were included in this study. Diaphragm breathing amplitudes and off-sets (changes in position with respect to the planning CT) were determined from delineated left diaphragm structures in weekly 4D CT-scans. The potential dosimetric impact of respiratory motion was shown in several example patients for photon and proton radiotherapy., Results: Variation in diaphragm amplitudes were relatively small and ranged from 0 to 0.8 cm. However, the measured off-sets were larger, ranging from -2.1 to 1.9 cm. Of the 70 repeat CT-scans, the off-set exceeded the ITV-PTV margin of 0.8 cm during expiration in 4 CT-scans (5.7%) and during inspiration in 13 CT-scans (18.6%). The dosimetric validation revealed under- and overdosages in the VMAT and IMPT plans., Conclusions: Despite relatively constant breathing amplitudes, the variation in the diaphragm position (off-set), and consequently tumor position, was clinically relevant. These motion effects may result in either treatments that miss the target volume, or dose deviations in the form of highly localized over- or underdosed regions.

Background: Clinical nodal (cN) staging is a key element in treatment decisions in patients with esophageal cancer (EC). The reliability of cN status regarding the effect on response and survival after neoadjuvant chemoradiotherapy (nCRT) with esophagectomy was evaluated in determining the up- and downstaged pathological nodal (pN) status after surgery alone. Material and methods: From a prospective database, we included all 395 EC patients who had surgery with curative intent with or without nCRT between 2000 and 2015. All patients were staged by a standard pretreatment protocol: 16-64 mdCT, 18 F-FDG-PET or 18 F-FDG-PET/CT and EUS ± FNA. After propensity score matching on baseline clinical tumor and nodal (cT/N) stage and histopathology, a surgery-alone and nCRT group (each N  = 135) were formed. Clinical and pathological N stage was scored as equal (cN = pN), downstaged (cN > pN) or upstaged (cN < pN). Prognostic impact on disease free survival (DFS) was assessed with multivariable Cox regression analysis (factors with p value <.1 on univariable analysis). Results: The surgery-alone and nCRT group did not differ in cT/N status. Pathologic examination revealed equal staging (32 vs. 27%), nodal up (43 vs. 16%) and downstaging (25 vs. 56%), respectively ( p  < .001). Nodal up-staging was common in cT3-4a tumors and adenocarcinomas in the surgery-alone group, while nodal downstaging was found in half of cT1-2 and cT3-4 regardless of tumortype after nCRT. Prognostic factors for DFS were pN ( p  = .002) and lymph-angioinvasion ( p  = .016) in surgery-alone, and upper abdominal cN metastases ( p  = .012) and lymph node ratio ( p  = .034) in the nCRT group. Conclusions: Despite modern staging methods, correct cN staging remains difficult in EC. Nodal overstaging (cN > pN) occurred more often than understaging impeding an adequate assessment of pathologic complete response and prognosis after nCRT.