Lung Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_31_3625 - Patterns of Failure After 5 Fraction Stereotactic Ablative Radiation Therapy in Early Stage Non-Small Cell Lung Cancer

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Patterns of Failure After 5 Fraction Stereotactic Ablative Radiation Therapy in Early Stage Non-Small Cell Lung Cancer
J. T. Mendel1, K. Ward2, K. D. Westover3, R. D. Timmerman4, H. Choy5, P. Iyengar3, L. A. Nedzi3, and D. J. Sher4; 1UTSW, dallas, TX, 2Paul L Foster School of Medicine, El Paso, TX, 3University of Texas Southwestern Medical Center, Dallas, TX, 4Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 5University of Texas – Southwestern Medical Center, Department of Radiation Oncology, Dallas, TX

Purpose/Objective(s): Stereotactic Ablative Radiotherapy (SABR) is an effective alternative to surgery in patients with early stage non-small cell lung cancer (NSCLC). We retrospectively reviewed patients with early stage NSCLC treated with common 5 fraction SABR regimens (50 vs 60 Gy) to evaluate failure patterns and outcomes.

Materials/Methods: Ninety-six patients with T1-2 NSCLC and follow up of at least 6 months were treated between July 2008 and July 2017 with definitive 5 fraction SABR at a single institution. All patients received either 50 or 60 Gy in 5 fractions and clinical response was evaluated using RECIST 1.1 criteria. Local failure over time was modeled using cumulative incidences with death as a competing risk.

Results: Median follow-up was 15.5 months (IQR = 7.6-30.8). 12.5% of patients were noted to have local failure and 25% of patients developed either LF, RF, or DM. Incidence of LF for the entire cohort was 14% at 2 years. Incidence of LF was 17% and 13% (NS) for patients treated with 50 and 60 Gy, respectively. The only predictor of local failure was T stage with an incidence at 2 years of 3% for T1 and 15% for T2 tumors (p = 0.01). Marginal failures were noted in 4 of the 12 failures. Of the 8 T2 patients with local recurrence, 7 were in-field failures. Of the entire cohort, 4 patients had an RX IDL >90% and of these 2 exhibited in-field failures.

Conclusion: SABR with 50-60 Gy in 5 fractions provides excellent local control for T1 tumors. T2 tumors have greater rates of in-field failures and may benefit from further escalation or adjuvant therapy.

Author Disclosure: J.T. Mendel: None. K. Ward: Student; PLFSOM. K.D. Westover: None. R.D. Timmerman: Research Grant; Varian Medical Systems, Accuray, Inc, Elekta Oncology. H. Choy: Research Grant; Celegene. Advisory Board; Bayer, EMD. D.J. Sher: None.

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