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Z. Zhang
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P2.03 - Poster Session/ Treatment of Locoregional Disease – NSCLC (ID 213)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P2.03-032 - Prognostic Impact of EGFR and KRAS Mutations in Patients with Lung Adenocarcinoma Treated with Definitive Radiation Therapy (ID 2422)
09:30 - 09:30 | Author(s): Z. Zhang
- Abstract
Background:
An association of EGFR and KRAS mutations with radiation sensitivity has been postulated in preclinical studies. Recent clinical studies reported longer local control and survival in patients (pts) harboring EGFR mutations treated with definitive radiotherapy (RT). Here, we sought to evaluate the prognostic impact of EGFR and KRAS mutations in 223 adenocarcinoma pts treated with definitive RT at our institution.
Methods:
Between 2004 and 2013, 466 inoperable pts with non-squamous lung cancer were treated with definitive RT ± chemotherapy. Mutational testing was performed in 223 pts. 44% were male, 56% female. 65% were former, 13% never, and 22% current smokers. Clinical stage was II in 5%, IIIA in 37% and IIIB in 58%. Median size of tumor was 3.8 cm (range 0.5-12.2 cm). 60% received concurrent, 31% sequential chemo-RT and 9% RT alone. The median RT dose was 63Gy (range 50-80Gy). OS was estimated by the Kaplan-Meier method. Cumulative incidence functions were used to estimate local failure (LF) and distal failure (DF), using death without failure as a competing risk. Association of factors with OS was analyzed by Cox regression and association with LF and DF by competing risk regression.
Results:
EGFR status was wild-type in 205 pts (92%) and mutated in 18 (8%). The most common EGFR mutations were exon 19 deletion (8 pts), followed by exon 21 L858R (7 pts), and exon 20 insertion (3 pts). KRAS status was wild- type in 142 pts (64%), mutated in 63 (28%), and not performed in 18 (8%). The most common mutations were G12C (13%), followed by G12V (5%) and G12A and G12D (3% each). With a median follow-up among survivors of 32.7 months (range 0.6-114), the median OS was 38 months for pts with EGFR mutation versus 26 months for pts without (p=0.96); 21 months for patients with KRAS mutation versus 31 months for pts without (p=0.24). 2-year LF was 37% and 46% for pts with and without EGFR mutation, and 48% and 46% for pts with and without KRAS mutation, respectively. 2-year DF was 80% and 64% for pts with and without EGFR mutation, and 62% and 64% for pts with and without KRAS mutation, respectively. On univariate analysis, factors significantly associated with improved OS included KPS ≥ 80 (p=0.01), increasing RT dose (p=0.04) and use of concurrent chemotherapy compared to RT alone (p=0.001). Factors associated with higher risk of LF included stage IIIB (p=0.04) and sequential rather than concurrent chemotherapy (p=0.05). Factors associated with a higher risk of DM included stage IIIB (p=0.03) and lower RT dose (p=0.003). Association of EGFR and KRAS mutations did not reach statistical significance on univariate analysis, thus we did not further investigate their effects by multivariable analysis.
Conclusion:
Despite analyzing the largest patient population to date, we did not identify a significant prognostic impact by EGFR or KRAS mutational status. The lack of an observed association could be related to the low rate of EGFR mutations identified. RT dose and use of concurrent chemotherapy were significantly associated with overall survival.
