2343 - Treatment Outcomes of High-Dose Hypofractionated Palliative Radiotherapy (40 Gy in 10 daily fractions) for Non-Small Cell Lung Cancer

Purpose/Objective(s): Palliative thoracic radiotherapy is a crucial treatment modality for patients with non-small cell lung cancer (NSCLC), especially when the primary goal is local tumor control. Factors such as tumor size and location may limit the applicability of stereotactic ablative radiotherapy. This study aims to evaluate the efficacy and toxicity outcomes of a high-dose hypofractionated radiotherapy regimen of 40 Gy in 10 daily fractions, as a palliative local treatment for NSCLC.

Materials/Methods: This is a joint retrospective cohort study conducted in two tertiary oncology centers. Consecutive NSCLC patients who underwent palliative thoracic radiotherapy using the 40 Gy in 10 daily fractions regimen were identified from institutional databases. Treatment responses were evaluated using the RECIST criteria. Local tumor control rate was estimated using the cumulative incidence function with death assigned as a competing event. A sensitivity analysis was conducted, censoring data at the time of changes in systemic therapy. The rates of radiation pneumonitis and esophagitis were graded in accordance with CTCAE version 6.0.

Results: A total of 62 eligible patients were identified between January 2017 and December 2022, all of whom completed the 40 Gy in 10 daily fractions palliative regimen. The median age was 73.3 years. Adenocarcinoma (76%) and squamous cell carcinoma (18%) were the predominant histology types. Radiotherapy was given to 33 patients (53%) with inoperable primary NSCLC and 29 patients (47%) with oligopersistent or oligoprogressive NSCLC following systemic therapy. Most tumors were considered unsuitable for stereotactic ablative radiotherapy due to large tumor size (56%) or ultra-central location (31%). Volumetric modulated arc therapy was used for 54 patients (87%), while 3-dimensional conformal radiotherapy was used for 8 patients (13%). The median planning target volume was 174.5cc (IQR, 110.6cc – 279.0cc). The median V100 was 99.1% (IQR, 96.5% – 99.7%) with a median hotspot of 109.7% (IQR, 107.7% – 111.4%). With a median follow-up of 4.1 years, the overall response rate was 69.3%. The local control rates at 1-year and 3-year were 96.7% and 76.9% (sensitivity analysis, 96.7% and 73.4%), respectively. Over half of the patients (56%) developed subsequent distant progression. The crude incidences of grade 1 – 2 radiation pneumonitis and esophagitis were 46.7% and 8.1%, respectively. No high-grade adverse event was observed.

Conclusion: High-dose hypofractionated radiotherapy for NSCLC demonstrated a high local tumor control rate. The regimen of 40 Gy in 10 daily fractions is convenient and safe, making it a viable option for cases where tumor size or location renders stereotactic ablative radiotherapy unsuitable.