197PD - Identifying dosimetric predictors of toxicity in multiple lung tumors treated with stereotactic ablative radiotherapy (SABR)

Date 14 April 2016
Event European Lung Cancer Conference 2016 (ELCC) 2016
Session Predictive models for chemo- and radiotherapy
Topics Complications/Toxicities of treatment
Thoracic malignancies
Surgical oncology
Therapy
Radiation oncology
Presenter Hilâl Tekatli
Citation Journal of Thoracic Oncology (2016) 11 (supplement 4): S57-S166. S1556-0864(16)X0004-4
Authors H. Tekatli1, S. Tetar1, A. Warner2, D. Palma2, W. Verbakel1, T. Nguyen2, F. Spoelstra1, S. Gaede2, B. Slotman1, S. Senan1
  • 1Radiation Oncology, Vrije University Medical Centre (VUMC), 1081 HZ - Amsterdam/NL
  • 2Radiation Oncology, London Regional Cancer Center, London Health Science Center, University of Western Ontario, ON N6A 5W9 - London/CA

Abstract

Background

Stereotactic radiotherapy (SABR) is increasingly used for treating multiple synchronous lung lesions. Previous studies for solitary lesions revealed that contralateral lung doses predict the risk of radiation pneumonitis (RP). As dosimetric predictors for toxicity of SABR in patients with multiple lung lesions are unknown, we performed a multi-center retrospective study in this patient subgroup, and report on clinical outcomes and dosimetric parameters.

Methods

Patients undergoing SABR using Volumetric Modulated Arc Therapy for ≥2 synchronous parenchymal lung lesions within 1 month between 2009 and 2014, were identified from the VU University Medical Center and London Health Sciences Centre. All lesions received a BED10 of ≥100 Gy. Patients with prior or subsequent non-SABR thoracic radiotherapy were excluded. A recursive partitioning analysis was performed on survival and toxicity outcomes (CTCAE v4.03) using the hazard function and binary function respectively, based on baseline patient factors and treatment characteristics, including lung doses (V5 Gy–V50 Gy in 5 Gy intervals).

Results

84 patients treated for 187 lesions were identified. 46% were treated for multiple lung metastases and 54% for multiple primary NSCLC lesions. Median age was 69.4 years, 97% of patients were treated for 2–3 lesions, and 56% had bilateral lesions. Most plan optimizations severely constrained the V5 Gy of contralateral lung. After a median follow-up time of 28 months, median OS was 35 months, and 5 year survival was 39%. Grade ≥2 toxicity was recorded in 20% of patients at ≥6 weeks after start of treatment: RP (n = 9), chest wall pain (n = 5), rib fracture (n = 2), and dyspnea (n = 1). A total of 33 deaths were observed, including 1 treatment-related death from RP, 17 due to progressive disease, and 15 due to other causes. Multivariable analysis showed that total lung minus PTV V35 Gy ≥6.5% (in 2 Gy/fraction equivalent) best predicted for grade ≥2 RP (p = 0.007).

Conclusions

To the best of our knowledge, this is the first report on predictors of toxicity after SABR for multiple lung lesions. However, these findings should be further investigated in other patient populations, and using other delivery techniques for SABR.

Clinical trial identification

Legal entity responsible for the study

N/A

Funding

N/A

Disclosure

W. Verbakel, B. Slotman, S. Senan: The Department of Radiation Oncology of the VU University Medical Center has a research agreement with Varian Medical Systems. Honoraria and travel support received from Varian Medical Systems. All other authors have declared no conflicts of interest.