LAUSR

Objectives: Computed tomography (CT) and positron emitted tomography (PET) are used to assess disease response to chemoradiotherapy in locally advanced cervical cancer (LACC), however inconclusive imaging leads to repeat studies, biopsies and added cost. This study aimed to determine optimal timing of post-treatment imaging to optimize detection of residual disease and lower cost without impairing outcomes. Methods: We performed a retrospective review of 260 patients (pts) with LACC who received primary chemoradiotherapy or radiation at a single institution between 2009 and 2020. Demographic and clinical information was abstracted from medical records. Pts had at least one post-treatment CT or PET. Primary outcome was accuracy of post-treatment imaging as measured by Area Under the Curve (AUC) with AUC = 1 indicating perfect prediction. Pts were grouped by imaging timing: 0-2 months (mos), 2-4 mos, 4-6 mos, or >6 mos. Statistical tests were analysis of variance, chi-square, and Cox proportional hazards. Results: 156 pts were included. Median age at diagnosis was 51 yrs, 57% were White, and 35% had private insurance. 78% had squamous histology, 60% had stage III disease, 78% underwent PET and 22% underwent CT. The most common timing for imaging was 2-4 mos (43%), followed by 4-6 mos (22%), >6 mos (22%), and 0-2 mos (13%). A trend toward later imaging was seen in Black pts (37% Black vs 53% White 0-2 mos, 16% Black vs 66% White 2-4 mos, 31% Black vs 57% White 4-6 mos, 46% Black vs 43% White, >6 mos p=0.15). A similar trend occurred comparing uninsured and insured pts (0-2 mos 21% vs 58%, 2-4 mos 28% vs 39%, 4-6 mos 29% vs 37%, >6 mos 31% vs 14%, p=0.08). Post-treatment imaging, regardless of timing, was an accurate indicator of complete response (negative predictive value 99%). Imaging performed between 0-2 mos had the highest AUC, 1.0 (p 6 mos (AUC 0.94, p=0.007), 4-6 mos (AUC 0.8, p=0.77), and 2-4 mos (AUC 0.78, ref). Pts with imaging at 2-4 mos were more likely to need repeat imaging (0% (0-2 mos), 22% (2-4 mos), 6% (4-6 mos), and 6% (> 6 mos) [p Conclusions: Though limited by sample size and retrospective design, these data suggest that imaging 2-4 mos post-treatment for LACC leads to increased need for repeat imaging likely due to indeterminate results. We suspect the high performance of 0-2 mo and >6 mo scans were influenced by selection bias; pts who received imaging 6mo group had surpassed the time during which post-treatment effect was evident on PET, and also likely had high concordance with concerning exam findings. While no survival differences were noted, further study is needed to determine timing of post-treatment imaging that optimizes assessment of treatment response while avoiding unnecessary interventions and preserving patient outcomes.