2047 - Pretreatment Maximum Standard Uptake Value (SUV max) on Positron Emission Tomography (PET) and the Risk of Distant Failure for Patients with Stage I Non-Small Cell Lung Cancer (NSCLC) Receiving Stereo

N. Haldar¹, A. L. Fekete², S. Jain³, P. A. Brower⁴, J. Martin⁵, L. N. McLean¹, and M. Werner-Wasik¹; ¹Department of Radiation Oncology, Sidney Kimmel Medical College of Thomas Jefferson University, Philadelphia, PA, ²Philadelphia College of Osteopathic Medicine, Philadelphia, PA, ³Drexel University College of Medicine, Philadelphia, PA, ⁴Jefferson Abington Hospital, Abington, PA, ⁵Thomas Jefferson University Hospital, Philadelphia, PA

Purpose/Objective(s): Characterization of tumor metabolism may help predict response to treatment and future treatment selection. Positron-emission tomography (PET) is used to identify hypermetabolic tissue by measuring the uptake of radioactive fluorodeoxyglucose as a surrogate marker of tumor invasiveness. Here we report a retrospective cohort study looking at rates of distant and locoregional failure based on pre-treatment standard-uptake-value maximum (SUV max) or SUV max change post-treatment for tumors < 5cm in size receiving stereotactic-body-radiation-therapy (SBRT). Materials/

Methods: Patients with T1-2 N0 M0 NSCLC treated definitively with SBRT from 2016-2022 at our institution were identified. Patients included in the study had available pre-treatment PET scans and at least 2 years of follow-up. All patients received SBRT with 6 MV photons. Two separate cohorts were created, one with patients with SUV max of their lesion >6.2 and one with SUV max <6.2. Of patients with available both pre-and post-treatment PET, another 2 cohorts were created, for those with a reduction or an increase in post-treatment SUV max. Comparisons between the two groups were conducted with a Fischer’s exact test. Demographic and treatment data were collected.
Results: A total of 60 patients were identified as having pre-treatment PET studies. The average age was 78 (67-98), 71%(n=43) were Caucasian, 20% were African American (n=12), 1.6% Asian (n=1), 1.6% Hispanic (n=1), 4.8% Other (n=3). Twenty percent of patients (n=11) received a prescription dose of 60Gy delivered in 5 fractions, 25% (n=15) received 54 Gy in 3 fractions, 13% (n=8) received 55Gy in 5 fractions, 32% (n=15) received 50 Gy in 5 fractions, 10% (n=6) received 48 Gy in 4 fractions. Sixteen pts had SUV maximum > 6.2 and 44 had SUV max <6.2. Of the 57 patients with both pre and post-treatment PET studies, sixty-three percent (n=36) of pts had a decrease in SUV max on post-treatment PET while 37% (n=21) of patients had an increase. Patients with pre-treatment SUV max > 6.2 did not have a significantly increased chance for locoregional recurrence: 44% (7/16) compared to those with SUV max < 6.2, 32% (14/44), p =0.29. However, patients with SUV max > 6.2 had an increased chance of distant failure compared to those with SUV max <6.2 (44% vs 16%, respectively, p=0.03). The correlation of locoregional recurrence between the cohorts with increase versus decrease in SUV max post-treatment did not reach statistical significance (52% vs 28%, respectively, p=0.058).
Conclusion: The SUV max of NSCLC tumors can predict response to ablative radiation treatment. An SUV max >6.2 prior to treatment was associated with an increased probability of distal failure. Increased risk of locoregional failure with an increase in SUV max post-treatment was not demonstrated but will be further explored in subsequent analyses.