Is there any prognostic significance of the level of change in SUVmax after SBRT in patients with early stage NSCLC?

Background: Stereotactic body radiotherapy (SBRT) is a standard treatment for early stage non-small cell lung cancer (esNSCLC) patients who are not eligible for surgery. We aimed to evaluate the prognostic significance of the level of change in SUVmax (ΔSUVmax) between pre and post-treatment PET/CT in esNSCLC patients treated with SBRT. Methods: Between November 2009-February 2018, pathologically proven esNSCLC patients (T1-2N0M0) treated with CyberKnife as primary treatment alone and had pre and post-treatment PET/CT (in 3 weeks before and 12-16 weeks after SBRT) were retrospectively identified. The ΔSUVmax was calculated using formula ΔSUVmax. The area under the curve (AUC) was used to verify the accuracy; the product of maximum sensitivity and specificity was chosen as the cutoff value. Then, we stratified the study cohort above and below AUC and the survival data were estimated by Kaplan Meier method. Univariate and multivariate analyses were carried out by use of a Cox proportional hazards model. Results: All patients’ clinicopathological and treatment characteristics are presented in the table. Median dose was 45 Gy/3 fr (range: 45-60 Gy/3-5 fr). According to EORTC metabolic response criteria, 8 (16.7%) patients achieved complete, and 35 (72.9%) patients achieved partial response. AUC was calculated as 0.62 for cutoff ΔSUVmax (sensitivity 79%, specificity 45%). ΔSUVmax was ≥0.62 in 7 of 8 patients with complete response and <0.62 in progressive 2 patients. At a median follow-up of 23 (range: 6-92) months local, regional and distant relapse had developed in 16 (33.3%), 11 (22.9%), and 16 (33.3%) patients, respectively. 29 (60.4%) patients were still alive at the time of analysis. Median PFS was 15 vs 59 months (p=.012) and median OS was 36 vs 70 months (p=.045). In univariate analysis, we could not find any significant effect of sex, age, KPS, T stage, and BED10 on PFS, and OS. In both univariate and multivariate analysis, the lower ΔSUVmax (as both dichotomous and continuous variable) was determined as a negative prognostic factor on PFS (p=.02, .003 for univatiate and .013 and .003 for multivariate) and it has been showed that the lower ΔSUVmax (only as a dichotomous variable) is a negative prognostic factor on OS in multivariate analysis (p=.009).Table74P Clinicopathological and treatment characteristicsΔSUVmaxp<0.62 n (%)≥0.62 n (%)Gender Female Male2 (6.5) 29 (93.5)2 (11.8) 15 (88.2)NSDAge at diagnosis (years) Median Range67 54-8467 56-82NSDKPS Median Range90 60-10080 60-90NSDTumor Size (mm) Median Range27 15-4320 11-45NSDT stage T1 T221 (67.7) 10 (32.3)13 (76.5) 4 (23.5)NSDNSCLC histology Squamous Adenocarcinoma Other / unidentified13 (41.9) 8 (25.8) 10 (32.3)9 (52.9) 5 (29.4) 3 (17.6)NSDBED10 (Gy) Median Range112.5 100 - 180112.5 100 - 151NSDLocal Failure Yes No12 (38.7) 19 (61.3)4 (23.5) 13 (76.5)0.04Regional Failure Yes No9 (29.0) 22 (71.0)2 (11.8) 15 (88.2)0.02Distant Failure Yes No14 (45.2)) 17 (54.9)2 (11.8) 15 (88.2)0.02Last Situation Alive Exitus16 (51.6) 15 (48.4)13 (76.5) 4 (23.5)0.04 Open table in a new tab Conclusions: ΔSUVmax is a prognostic factor in esNSCLC patients treated with SBRT and patients with higher ΔSUVmax (≥0.62) have better PFS and OS. Legal entity responsible for the study: The authors. Funding: Has not received any funding. Disclosure: All authors have declared no conflicts of interest.