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. 2025 Jan-Dec:24:15330338241311136.
doi: 10.1177/15330338241311136.

Dosimetric and Radiobiological Impact of Patient Setup Errors in Intensity-modulated Radiotherapy for Esophageal Cancer

Jia-Huan Cai  1 , Xun Peng  1 , Jia-Yang Lu  1
Affiliations

Dosimetric and Radiobiological Impact of Patient Setup Errors in Intensity-modulated Radiotherapy for Esophageal Cancer

Jia-Huan Cai et al. Technol Cancer Res Treat. 2025 Jan-Dec.

Abstract

Purpose: To evaluate the impact of patient setup errors on the dosimetry and radiobiological models of intensity-modulated radiotherapy (IMRT) for esophageal cancer.

Methods and materials: This retrospective study with 56 patients in thermoplastic mask (TM) and vacuum bag (VB) groups utilized real setup-error (RSE) data from cone-beam CT scans to generate simulated setup-error (SSE) data following a normal distribution. The SSE data were applied to simulate all treatment fractions per patient by shifting the plan isocenter and recalculating the dose. A simulated plan sum (SPS) was created by accumulating all simulated fraction plans. Comparisons of target dose, improved homogeneity index (iHI), conformity index (CI), tumor control probability (TCP) and normal tissue complication probability (NTCP) were conducted between SPSs and original treatment plans (OTPs). Correlations between RSE and TCP/NTCP were analyzed.

Results: Compared to OTPs in the TM group, the planning target volume (PTV) of SPSs showed reductions in D95%, D98%, iHI, CI and TCP by 1.2%, 2.2%, 2.3%, 7.3% and 1.2%, while D2% increased by 0.3%; D2% of clinical target volume (CTV) increased by 0.2% (P < .05). In the VB group, D95%, D98%, iHI, CI and TCP of PTV decreased by 2.5%, 4.5%, 4.2%, 15.6% and 2.0%, with D2% increasing by 0.5%; D2% of CTV increased by 0.5% while D98% decreased by 0.2% (P < .05). The dose of organs at risk (OARs) changed slightly in both groups. The mean and standard deviation of absolute RSE negatively correlated with the TCP of PTV, while the mean RSE positively correlated with the NTCP of lung and spinal cord.

Conclusions: Setup errors may reduce dose homogeneity and conformity, potentially reducing TCP of PTV and increasing NTCP, especially when mean RSE shifts the isocenter towards OARs. VB immobilization may result in relatively larger impacts of setup errors, but this needs future validation.

Keywords: esophageal cancer; intensity modulated radiotherapy (IMRT); radiation dosimetry; radiobiology; setup error.

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Conflict of interest statement

Declaration of Conflicting InterestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
Flow chart of simulated setup error (SSE) data generation.
Figure 2.
Figure 2.
Histograms of the real setup errors (RSE) and simulated setup errors (SSE) in the left-right (LR), cranio-caudal (CC) and anterior-posterior (AP) directions for 28 patients in the thermoplastic mask (TM) group.
Figure 3.
Figure 3.
Histograms of the real setup errors (RSE) and simulated setup errors (SSE) in the left-right (LR), cranio-caudal (CC) and anterior-posterior (AP) directions for 28 patients in the vacuum bag (VB) group.
Figure 4.
Figure 4.
Dose-volume histograms (DVHs) of the planning target volume (PTV) and clinical target volume (CTV) between the original treatment plan (OTP) and simulated plan sum (SPS) for a representative case in the thermoplastic mask (TM) group.
Figure 5.
Figure 5.
Dose-volume histograms (DVHs) of the planning target volume (PTV) and clinical target volume (CTV) between the original treatment plan (OTP) and simulated plan sum (SPS) for a representative case in the vacuum bag (VB) group.
Figure 6.
Figure 6.
Isodose curves of the original treatment plan (OTP) and simulated plan sum (SPS) for a representative case.
Figure 7.
Figure 7.
Dose-volume histograms (DVHs) of the lung, spinal cord, spinal cord planning organ at risk volume (SC-PRV), heart and normal tissue (NT) between the original treatment plan (OTP) and simulated plan sum (SPS) for a representative case in the thermoplastic mask (TM) group.
Figure 8.
Figure 8.
Dose-volume histograms (DVHs) of the lung, spinal cord, spinal cord planning organ at risk volume (SC-PRV), heart and normal tissue (NT) between the original treatment plan (OTP) and simulated plan sum (SPS) for a representative case in the vacuum bag (VB) group.
Figure 9.
Figure 9.
Scatter plots showing correlations between the mean absolute value of real setup errors (RSE) in the cranio-caudal (CC) direction and the tumor control probability (TCP) variation of the planning target volume (PTV) (a), the mean absolute value of RSE in the anterior-posterior (AP) direction and the TCP variation of the PTV (b), the standard deviation (SD) of RSE in the left-right (LR) direction and the TCP variation of the PTV(c), the SD of RSE in the CC direction and the TCP variation of the PTV (d), the SD of RSE in the AP direction and the TCP variation of the PTV (e), the mean RSE in the CC direction and the normal tissue complication probability (NTCP) variation of the lung (f), the mean RSE in the AP direction and the NTCP variation of the lung (g), the mean RSE in the AP direction and the NTCP variation of the spinal cord (h).
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