Learning curve of lung dose optimization in intensity-modulated radiotherapy for locally advanced non-small cell lung cancer

Abstract

Background: Intensity-modulated radiotherapy (IMRT) has been increasingly used for patients with locally advanced non-small cell lung cancer (LA-NSCLC). However, there are some barriers to implementing IMRT for LA-NSCLC, including the complexity of treatment plan optimization. This study aimed to evaluate the learning curve of lung dose optimization in IMRT for LA-NSCLC and identify the factors that affect the degree of achievement of lung dose optimization.

Methods: We retrospectively evaluated 40 consecutive patients with LA-NSCLC who received concurrent chemoradiotherapy at our institution. These 40 patients were divided into two groups: 20 initially treated patients (earlier group) and 20 subsequently treated patients (later group). Patient and tumor characteristics were compared between the two groups. The dose-volume parameter ratio between the actually delivered IMRT plan and the simulated three-dimensional conformal radiotherapy plan was also compared between the two groups to determine the learning curve of lung dose optimization.

Results: The dose-volume parameter ratio for lung volume to receive more than 5 Gy (lung V5) and mean lung dose (MLD) significantly decreased in later groups. The spread of the beam path and insufficient optimization of dose coverage of planning target volume (PTV) might cause poor control of lung V5, MLD.

Conclusions: A learning curve for lung dose optimization was observed with the accumulation of experience. Appropriate techniques, such as restricting the beam path and ensuring dose coverage of PTV during the optimization process, are essential to control lung dose in IMRT for LA-NSCLC.

Keywords: intensity-modulated radiotherapy; learning curve; lung cancer; lung dose; optimization.

FIGURE 1

Lung V5 ratio between intensity‐modulated radiotherapy (IMRT) and simulated three‐dimensional conformal radiation therapy (3D‐CRT) are shown. Circle dot represents individual patients and black bar represents mean value for each group. Mean V5_IMRT/V5_sim3D‐CRT was 1.61 in the earlier group while it was 1.29 in the later group which was significantly different (p < 0.001).

FIGURE 2

Mean lung dose ratio between intensity‐modulated radiotherapy (IMRT) and simulated three‐dimensional conformal radiation therapy (3D‐CRT) are shown. Circle dot represents individual patients and the black bar represents mean value for each group. Mean MLD_IMRT/MLD_3D‐CRT was 1.04 in the earlier group while it was 0.93 in the later group (p = 0.048).