| Objective To compare the dosimetric parameters and normal tissue complication probability (NTCP) of intensity modulat-ed proton therapy (IMPT) and intensity modulated radiation therapy (IMRT) for non-small cell lung cancer (NSCLC), and to explore the feasibility and optimal model of combined proton-photon radiotherapy in NSCLC.Methods The IMPT and IMRT plans were made for8 NSCLC patients in the Radiotherapy and Oncology Department of the Ion Medicine Center of The First Affiliated Hospital of Universi-ty of Science and Technology of China from November 2020 to April 2022 who underwent radical radiotherapy, respectively. The rela-tive biological effectiveness (RBE) of the IMPT plan was 1.1, and the prescription dose was 60 GyE/30 fractions. The two plans wereevaluated and compared according to the dosimetric parameters, and evaluated the NTCP of radiation pneumonia, esophageal toxicity,and 2-year mortality. Finally, the NTCP results were analyzed and selected the appropriate combined proton-photon radiotherapy mod-els.Results All NSCLC patients met the requirements, and the dose volume histogram dosimetric parameters showed no statisticallysignificant differences in the conformity index [1.28 (1.13, 1.43) vs. 1.12 (1.05, 1.18), P=0.068] and homogeneity index [0.09 (0.08, 0.15) vs. 0.11 (0.08, 0.16), P=0.327] of the IMPT and IMRT plans. There was a statistically significant decrease in IMPT compared to the IMRT plan for mean lung dose [9.38 (4.28, 13.78)Gy vs. 12.27 (7.95, 15.41)Gy,P=0.012], mean heart dose [5.59 (1.01,8.50)Gy vs. 8.23 (6.61, 15.82)Gy,P=0.012], and esophageal mean dose [10.53 (0.04, 21.62)Gy vs. 13.05 (3.84, 23.69). In addition, the IMPT plan showed significant reductions in bilateral lung V5 Gy, bilateral lung V20 Gy, bilateral lung V30 Gy, ipsilateral lung V5 Gy, ipsilateral lung V20 Gy,heart V30 Gy, heart V40 Gy and spinal cord D2% (P<0.05). IMPT can significantly reduce the NTCP of radiation pneumonia [8.35 (3.36, 15.80) % vs. 12.80 (6.51, 19.53) %, P=0.012], esophageal toxicity [20.43 (0.21, 42.58) % vs. 26.03 (5.43, 46.30) %,P=0.036] and 2-year mortality [43.28 (34.58, 48.27) % vs. 48.78 (42.74, 56.20) %,P=0.012], and the . NTCP values were 3.33 (3.08, 4.42) %, 5.22(1.51, 9.17) % and 5.96 (3.02, 11.13)%, respectively. Finally, two methods were chosen: NTCP thresholds or . NTCP threshold for ob-servation indicator, to select the combined proton-photon radiotherapy models.Conclusions The combined proton-photon radiothera-py plan is feasible. The threshold value of . NTCP can be set according to the patient, to increase the treatment benefit of NSCLC pa-tients and the accessibility of proton therapy. |
