ESTRO 2024 - Abstract Book

S2144

Clinical - Upper GI

ESTRO 2024

approval from the Institutional Review Board of Sichuan Cancer Hospital & Institute (SCCHEC-02-2020-015) and adhered to the principles outlined in the Declaration of Helsinki.

GTVp measurement and TTS: All participants underwent a chest spiral CT scan before and after receiving NCRT (Figure 2). Chest CT images taken before treatment were transmitted to an imaging biomarker explorer (IBEX). Two thoracic radiotherapists with over 10 years of clinical experience in ESCC treatment independently outlined the primary target lesions. The IBEX system was automatically re-established, and the GTVp measurements were computed by the system. The volume before and after NCRT was referred to as the pre-GTVp and post-GTVp, respectively. The tumor shrinkage rate was calculated as the difference between pre- and post- GTVp divided by pre-GTVp.

Results:

We collected data from 248 patients with resectable LA-ESCC who underwent computed tomography (CT) scans prior to the initiation of treatment. The median follow-up time was 37.7 months. The optimal cutoff of tumor shrinkage was 45%. In our univariate analysis, variables including ECOG status, stage, and tumor shrinkage rate showed significant correlations with PFS (p < 0.1). After adjusting for the effects of these significant variables in the multivariate analysis, the tumor shrinkage rate emerged as an independent prognostic factor of PFS (p < 0.05). An ROC curve was generated to identify the optimal threshold, which was established at a tumor shrinkage rate of 45%. Patients who were responders (tumor shrinkage rate >45%) had significantly better PFS than patients who were non- responders to NCRT (tumor shrinkage rate ≤45%) (adjusted hazard ratio [HR] = 0.45; 95% confidence interval [CI]: 0.28 – 0.73; p = 0.001; ). An ROC curve was plotted to determine the optimal cutoff for TTS, which was 42 days. Therefore, we denoted TTS < 42 days as short TTS, and TTS ≥ 42 days as long TTS. The baseline characteristics of the long and short TTS groups were balanced. For patients with response, In the univariate analysis of all categorical variables, longer TTS was significantly correlated with improved OS (adjusted HR = 0.36; 95% CI: 0.14 – 0.94; p = 0.037) and PFS (adjusted HR = 0.38; 95% CI: 0.25 – 1.01; p = 0.028), and no other variables with p < 0.05 were identified . The median OS was not achieved for patients in the long TTS group, whereas it was only 54.1 months in the short TTS group. Moreover, significant differences between the groups were not observed in terms of postoperative complication incidence. In non-responder patients, baseline clinicopathological characteristics were generally balanced between the long and short TTS groups . No significant difference was observed between the long and short TTS groups in terms of both OS and PFS.

Conclusion:

For patients with resectable LA-ESCC, the tumor shrinkage rate is an independent prognostic factor for PFS. Thus, for responders, prolonging TTS is recommended to obtain a better OS.

Keywords: ESCC ， NCRT ， tumor regression ， time to surgery

References:

1.Sung H, Ferlay J, Siegel RL, et al. Global Cancer Statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2021;71(3):209-249.