Clinical outcomes after positron emission tomography/computed tomography-based image-guided brachytherapy for cervical cancer

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 D_90% ≥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.