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Abstract
Introduction: Although positron-emission tomography (PET) plays an integral role in cervix cancer diagnosis, there are limited data on PET-based image-guided brachytherapy (IGBT). We aimed to report the long-term outcomes of PET-based IGBT.

Methods: We reviewed 151 patients treated with definitive radiotherapy (RT), including PET-based IGBT between 2009 and 2018. After median 45 Gy of external beam RT with the four-field technique, a median 24 Gy of high-dose-rate iridium-192 IGBT was delivered in six fractions with Fletcher-Suit tandem and ovoids. All patients underwent 18F-fluorodeoxyglucose-PET/computed tomography planning with a brachytherapy applicator. Multivariable analysis of local control (LC) was performed using Cox regression analysis.

Results: The median high-risk clinical target volume (HRCTV) and HRCTV D90% were 51.8 (interquartile range [IQR] 35.9-79.4) cm3 and 77.7 (IQR 74.7-81.2) Gy, respectively. With a median follow-up of 57 (IQR 24.3-81.4) months, the 5-year LC rate was 89.2%. HRCTV ≥72 cm3 was associated with inferior LC (hazard ratio, 3.72, p = .017) after multivariable analysis: the 5-year LC rates were 94.0% and 77.9% for HRCTVs ≥72 and < 72 cm3 , respectively (p = .002). The impact of HRCTV D90% ≥70 Gy on LC was significant in patients with an HRCTV ≥72 cm3 compared to that in those with HRCTV < 72 cm3 . Patients with adeno/adenosquamous carcinoma demonstrated inferior LC in both groups. There were 13 (8.6%) and 11 (7.3%) patients with acute and late severe toxicities after RT.

Conclusion: PET-based IGBT leads to favorable LC, and HRCTV ≥72 cm3 requires further dose escalation to improve outcomes.

Affiliations

Nalee Kim 1, Won Park 1, Won Kyung Cho 1, Young Seok Cho 2
1Department of Radiation Oncology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
2Department of Nuclear Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.