Lung Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_34_3659 - The Effect of SBRT Treatment Duration for Early Stage NSCLC on Control Rates, Survival and Toxicity

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

The Effect of SBRT Treatment Duration for Early Stage NSCLC on Control Rates, Survival and Toxicity
R. van Dams1, N. Shaverdian1, G. Raghavan1, S. Chan2, and P. Lee1; 1Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, CA, 2University of California, Irvine, Irvine, CA

Purpose/Objective(s): The optimal treatment delivery schedule for stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC) has not been established. There is data to support a biological effective dose (BED) threshold of >100 Gy (Onishi et al., JTO 2007), resulting in several fractionation schema that accomplish this goal, but there is a lack of data to support the ideal duration of therapy. We examined retrospective data of patients treated over a range of 2 to 9 days with lung SBRT regimens with BED >100 Gy to identify whether there were differences in outcomes between shorter versus longer durations of therapy.

Materials/Methods: We performed a single-institution retrospective review of 152 consecutive patients with 175 treated tumors who underwent SBRT for primary lung NSCLC from February 2009 to September 2014. Fractionation schema used were 54 Gy in 3 fractions or 50 Gy in 4-5 fractions. Treatment duration was defined as the number of elapsed days between the first and last fraction of radiation. Kaplan-Meier estimate of survival was used to identify time failure as well as overall survival (OS), and the log-rank test was used to test for differences between cohorts. The two-sample test of proportions was used to test for differences in the rates of toxicity.

Results: With a median follow-up of 41.6 months, the median OS for the cohort was 74.7 months. Treatment duration ranged from 2 days to 9 days, with a median of 4 days. When patients were stratified across the median (i.e. ≤4 days vs >4 days), we found no difference in median OS (74.7 months vs 82.5 months, p = 0.21). There were no differences in 3-year OS (72.5% vs 65%, p = 0.31), local control (95.7% vs 91%, p = 0.34), or distant control (91.1% vs 88.4%, p = 0.62). Although there was no difference in the rate of all toxicity (17.2% vs 13.3%, p = 0.69), there were significantly more grade 2-3 toxicities among patients treated in a shorter duration (11.1% vs 2.7%, p = 0.036).

Conclusion: We found that patients with early stage NSCLC treated with lung SBRT over a longer duration (>4 days) did not have significantly different time to local or distant failure or overall survival compared to patients receiving their SBRT over fewer days. This provides evidence that lung SBRT delivered over more protracted treatment schedules may have comparable control rates while also limiting excess toxicity. Additional randomized studies may be warranted to identify an optimal treatment duration.

Author Disclosure: R. van Dams: None. N. Shaverdian: None. S. Chan: None. P. Lee: Honoraria; Viewray. Commitee Co-Chair; Committee Co-Chair.

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