Impact of overall treatment time and dose escalation on local control in locally advanced cervical cancer treated by chemo-radiation and image-guided adaptive brachytherapy Renaud Mazeron # (abstract 1827) DPD 06. Digital Poster Discussion - GYN

GUSTAVE ROUSSYMazeron R ASTRO GYN PD6 Background Image-guided adaptive brachytherapy (IGABT) is becoming a standard in the treatment of locally advanced cervical cancer Local control rates reported in monocentric series are high, about 90% (Pötter et al., Nomden et al., Mazeron et al.) Objective: Identifying the prognosis factors for local control in a cohort a patients treated with concomitant chemo-radiation followed by IGABT 2

GUSTAVE ROUSSYMazeron R ASTRO GYN PD6 Material and Methods Consecutive patients Locally advanced cervical cancer (IB2-IVA) Curative intent GEC-ESTRO recommendations applied At the beginning of our experience, patients with stage I-II lesions went throughout post radiation hysterectomy. For them, local failure was considered in case of macroscopic remnant (1 cm in width) or in case of local relapse during their follow-up. In patients treated with definitive radiotherapy, local failure was defined as any relapse in the cervix, vagina, parametium, or uterus during the follow-up. 3

GUSTAVE ROUSSYMazeron R ASTRO GYN PD6 Note: Post radiation hysterectomy Patients included to warrant consecutive patients Treated at the beginning of our experience, with doses lower than nowadays. Important to study dose- response effect. 1cm as cutoff: strong prognosis factor reported in the literature Prognostic factors were analyzed using a linear regression model. Additional dose / effect correlations were done using the logit model. 4 Statistics

GUSTAVE ROUSSYMazeron R ASTRO GYN PD6 Results Tumor width at diagnosis (> 5 cm), initial tumor volume (>50 cm 3 ), D90% of the HR-CTV (high risk, > 85 Gy), the HR-CTV volume (> 30 cm 3 ) and overall treatment time (OTT, > 55days) appeared significantly correlated with local control in univariate analysis, but treatment duration remained the only significant factor in multivariate analysis (p=0.022, odds ratio=2.44). Logit models: positive for OTT, D90 HR and IR-CTV 5

GUSTAVE ROUSSYMazeron R ASTRO GYN PD6 Figure 1 6

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GUSTAVE ROUSSYMazeron R ASTRO GYN PD6 Take home messages OTT remains important with a loss of 0,5% of local control probability beyond 55 days This is less than reported 10 years ago (1%) but significant A dose-response for both HR-IR CTV has been shown similar to that demonstrated by Dimopoulos et al. for HDR brachytherapy, supporting the dose escalation concept (see oral presentation by Kari Tanderup) 8

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