GSOR10 Presentation Time: 9:45 AM: Positron Emission Tomography (PET) versus Computed Tomography (CT)-Guided Intracavitary Brachytherapy for Locally Advanced Cervical Cancer: A Randomised Study

Abstract

<h3>Purpose</h3> This study compared early clinical outcomes in locally advanced cervical cancer (LACC) treated with PET-CT guided intracavitary brachytherapy (ICBT) versus 3D CT guided ICBT after external beam radiation therapy (EBRT). <h3>Materials and Methods</h3> From September 2019 to April 2021, 50 patients with newly diagnosed LACC (FIGO stage IIB to IIIB) who received EBRT (50.4Gy in 28 fractions over 5.5 weeks) with concurrent weekly chemotherapy were randomized into two arms: PET/CT- guided ICBT arm (25 patients) and CT- guided ICBT arm (25 patients). High-risk clinical target volume (HRCTV) in PET-CT arm included cervix along with FDG avid lesion and in CT arm included cervix along with residual disease based on CT scan findings. The prescribed dose of ICRT was 7.0 Gy X 3 fractions (once a week fraction). Rectum, bladder, and sigmoid colon were contoured as organs at risk in both arms. Local control, overall survival, and dosimetry comparison between two arms were evaluated. Common Terminology Criteria for Adverse Events v.4.03 (CTCAE v4.03) was used for reporting early toxicity. <h3>Results</h3> Clinical characteristics like age, stage etc. were comparable in the two arms. The 2- year local control rate was 79.1% in PET-CT arm and 72.7% in CT arm (p-value, 0.3). The 2-year overall survival was 89% in CT arm and 82.9% in PET-CT arm (p-value, 0.6). The mean dose to HRCTV D90 and HRCTV D95 in PET CT arm was 87.7Gy (s=6.1Gy) and 83.04Gy (s=5.5Gy) and in CT arm was 85.6Gy (s=6.4Gy) and 80.6Gy (s=5.7Gy) (p-value, 0.13).The mean dose to bladder, rectum and sigmoid colon in PET-CT arm were 80.3Gy (s=8.2Gy), 70Gy (s=6.1Gy) and 66.2Gy (s=7.4Gy) and in CT arm were 79 Gy (s=6.9Gy), 70.2Gy (s=7.2Gy) and 64.9Gy (s=6.3Gy), (p-value:0.58, 0.88 and 0.55). No Grade III/IV OAR toxicity were reported in both arms. <h3>Conclusion</h3> Though the limited sample size, the results of our randomized study show that PET-CT guided ICBT is feasible in patients with LACC. The clinical outcome (overall survival, local control, and OAR toxicity) and dosimetry parameters were comparable in both arms. Based on marginally better local control in the PET-CT arm, though not statistically significant, we suggest further studies with a larger sample size to evaluate the role of PET-CT in LACC.