ESTRO 2023 - Abstract Book

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ESTRO 2023

needed. Changes in volume and SUVpeak for GTV-T were calculated. Patients were divided into subgroups based on their relative volume- and SUVpeak-response (below/above median). Event was defined as progression at any site. Freedom from progression was calculated from the date of the pPCT and analyzed using the Kaplan Meier method. Cox proportional hazards model for progression was performed including performance status, stage, histology, gender, log of the baseline GTV-T volume, SUVpeak at baseline, and relative changes in volume- and SUVpeak -values from pre- to post-chemotherapy. Results Median follow-up time was 43 months. Baseline patient characteristics are shown in Table 1. Median change in volume was a decrease of 18% (IQR: -9.9%;-27.0%). Median change in SUVpeak was a decrease of 33.6% (IQR: -19.6%;-47.9%). Kaplan Meier curves for patients split by relative decrease in volume and SUVpeak (below/above median) are shown in figure 1. Two-year freedom from progression was 43.8% (95%-CI: [0.35-0.56]) for volume responders above median, and 21% (95%- CI: [0.14-0.31]) for volume responders below median. No significant correlation between freedom from progression and decrease in SUVpeak was observed (p=0.12). The Cox proportional hazards model showed poorer freedom from progression for patients with adenocarcinomas (HR: 1.52 [1.00-2.2.31], p=0.049), a significant impact of baseline GTV-T volume (HR: 1.26 [1.09-1.46], p<0.01) and improved outcome for patients with the most GTV-T volume reduction (above median) (HR: 0.53 [0.37-0.76], p<0.01).

Conclusion Patients with a large decrease in tumour volume after induction chemotherapy for locally advanced NSCLC have significantly better freedom from progression after treatment with cCRT. Patients with minor radiologic response to induction chemotherapy might benefit from treatment intensification.

PO-1307 SBRT of hilar lymph nodes from lung cancer: outcomes, toxicity and role of CTV

M. Rotondi 1 , I. Angelicone 1 , R.C. Sigillo 1 , D. Caivano 2 , M. Valeriani 1 , M.F. Osti 1

1 Università degli Studi di Roma "La Sapienza", A.O.U Sant'Andrea M-P, Radiation Oncology, Rome, Italy; 2 Santa Maria Goretti Hospital, Radiation Oncology, Latina, Italy Purpose or Objective To evaluate efficacy and tolerance of stereotactic body radiation therapy (SBRT) of mediastinal and hilar lymph nodes (LN) in patients (pts) with lung cancer, in terms of clinical outcomes, toxicities and relationship between clinical tumor volume (CTV) and prognosis. Materials and Methods From 2009 to 2020 forty-eight patients with lung cancer underwent SBRT on LN (56 lesions overall) including 82% (46 pts) were from non-small cell lung cancer (NSCLC), 7% (4 pts) were from small cell lung cancer (SCLC) and 10% (6pts) from others histologies. The state of patients at moment of treatment was classified as oligorecurrent (52%), oligoprogression (27%), oligometastatic (9%) and oligopersistent (12%). The median age was 69 years (range: 54-90 years) and the Performance Status was ≤ 2. Thirty-eight pts underwent Intensity Modulated Radiotherapy (IMRT), while eighteen pts