Partial stereotactic ablative boost radiotherapy in bulky non‐small cell lung cancer: a dosimetric comparison between proton and photon
Bai Yun1, Gao Xianshu1, Ma Mingwei1, Zhao Zhilei2, Liu Peilin1, Cao Xi1, Qin Shangbin1, Liu Siwei1, Gao Yan1, Ren Xueying1, Li Hongzhen1, Zhang Min1, Li Xiaomei1, Lyu Feng1, Li Xiaoying1, Qi Xin1, Chen Jiayan1, Xie Mu1
1Department of Radiation Oncology, Peking University First Hospital, Beijing 100034, China; 2Department of Radiation Oncology, Hebei Yizhou Cancer Hospital, Zhuozhou 072750, China
Abstract：Objective Partial stereotactic ablative boost radiotherapy(P‐SABR)is a method to deliver SABR boost to the gross tumor boost volume(GTVb), followed by conventionally fractionated radiotherapy to the whole tumor area(GTV). GTVb is the max volume receiving SABR while ensuring the critical organ‐at‐risk(OAR)falloff to 3 GyE/f. We investigated the potential advantage of proton therapy in treating bulky non‐small cell lung cancer(the tumor length greater than 8 cm). Methods Nine patients with bulky NSCLC treated with photon P‐SABR in our institute were selected. For the treatment planning of proton therapy, the GTVb target area was gradually outwardly expanded based on the photon GTVb target area until the dose to critical OARs reached 3 GyE/f. The GTV and CTV areas remained the same as photon plan. A proton intensity‐modulated radiation treatment plan(proton‐IMPT), a photon intensity‐modulated radiation treatment plan(photon‐IMRT)and a photon volumetric modulated arc therapy(photon‐VMAT)were created for each patient, respectively. The dosimetric parameters of different treatment plans were compared. Results The volume ratio of GTVb‐photon and GTVb‐proton to GTV was(25.4±13.4)% and(69.7±30.0)%,respectively(P<0.001). In photon‐IMRT, photon‐VMAT, and proton‐IMPT plan groups, the mean dose of CTV was(76.1±4.9)Gy, (78.2±3.6)Gy, and(84.7±4.9)Gy, respectively; the ratio of tumor volume with Biologic Effective Dose(BED)≥ 90 Gy to GTV volume was(70.7±21.7)%, (76.8±22.1)%,and(97.9±4.0)%,respectively. The actual dose and BED to the tumor area of the proton‐IMPT plan group were significantly higher than those of the photon plan group(both P<0.05). Besides, the OARs dose was significantly decreased in the proton‐IMPT group, with(49.2±22.0)%, (56.8±19.0)% and(16.1±6.3)% of the whole lung V5 for photon‐IMRT, photon‐VMAT and proton‐IMPT, respectively(all P<0.001). Conclusions Larger GTV boost target volume, higher BED and reduced OARs dose can be achieved in proton plans compared with photon plans. Proton P‐SABR is expected to further improve the local control rate of bulky NSCLC with fewer adverse effects.
Bai Yun,Gao Xianshu,Ma Mingwei et al. Partial stereotactic ablative boost radiotherapy in bulky non‐small cell lung cancer: a dosimetric comparison between proton and photon[J]. Chinese Journal of Radiation Oncology, 2022, 31(8): 710-715.
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