ESTRO 2023 - Abstract Book

S1074

Digital Posters

ESTRO 2023

Conclusion ILA may be an important risk factor for RP. RP can have severe manifestations, especially in patients with ILA-SF and influence prognosis. Therefore, these findings are important in decision-making prior to radiation therapy.

PO-1341 Failure patterns after stereotactic body radiotherapy for lung cancer according to the T stage

H. Doi 1 , T. Inagaki 1 , M. Inada 1 , N. Ishida 1 , A. Ri 1 , S. Tatsuno 1 , Y. Wada 1 , T. Uehara 1 , K. Nakamatsu 1 , M. Hosono 1 , Y. Nishimura 1

1 Kindai University Faculty of Medicine, Department of Radiation Oncology, Osaka-Sayama, Japan

Purpose or Objective Stereotactic body radiotherapy (SBRT) is a treatment option for early-stage lung cancer. The purpose of this study was to analyse the differences in failure patterns after SBRT for primary lung cancer according to the T stage, after accurately re examining the initial clinical T stage. Materials and Methods A total of 120 patients with early-stage lung cancer (T1-3N0M0) who underwent SBRT were analysed. The clinical stage in patients whose tumours were in contact with the chest wall was confirmed using four-dimensional computed tomography (4D-CT). Before restaging, 35 tumours in contact with the pleura were initially diagnosed as T2 with visceral pleural invasion. Local failure, regional node metastasis, and distant metastasis were confirmed from clinical charts. Results The median follow-up time was 27.5 months (range, 7–122) after SBRT. Thirteen patients were restaged from clinical T2 with visceral pleural invasion to T3 with chest wall invasion using 4D-CT analysis. There were no significant differences in dosimetric parameters for PTV among the T1, T2, and T3 groups. The volume of PTV was significantly smaller in T1 tumours than in T2 and T3 tumours (p < 0.001 and = 0.003, respectively). However, no significant differences were observed in the volume of PTV between T2 and T3 tumours (p = 0.967). Thirty-seven patients developed recurrences. The median progression free survival (PFS) was 38.1 months. The 1-, 3-, and 5-year PFS rates were 61.0%, 50.6%, and 34.6%, respectively. In the T1, T2, and T3 groups, the recurrence rates were 12% (8/69), 50% (18/36), and 73% (11/15), respectively. In addition, the 3-year PFS rates were 61.0%, 40.5%, and 22.9% for clinical stages T1, T2, and T3, respectively (p=0.001). In T1 tumours, three and five patients experienced local failure and regional nodal metastasis, respectively. In T2 tumours, oligo-metastasis and locoregional failures alone were observed in 28% (5/18) and 44% (8/18) of the patients with recurrences, respectively. In T3 tumours with chest wall invasion, recurrences were noted in 77% (10/13) of tumours. Forty-five of the 120 patients died during the follow-up period. The median overall survival (OS) was 53.8 months. The 1-, 3-, and 5-year OS rates were 88.1%, 60.8%, and 38.6%, respectively. The 3-year OS rates were 65.0%, 60.3%, and 47.5% in clinical T1, T2, and T3, respectively (p=0.213).

Conclusion