Clinical study on the guidance of the time for the second positioning of radiotherapy for cervical cancer based on ADC values combined with tumor volume regression

Abstract Objective To explore the correlation between ADC value and tumor volume regression in concurrent chemo-radiotherapy for cervical cancer, and to investigate the feasibility of early secondary localization. Methods Retrospective analysis: 66 patients with locally advanced cervical cancer were collected. The correlations between clinical pathological factors and ADC-related parameters and tumor volume regression were analyzed. Nine patients with radiotherapy sensitivity were selected based on previous studies, and the volume and dosimeter differences of the target area and organs at risk were analyzed to explore the feasibility of early secondary localization. Results At the 20th radiotherapy session, the median tumor volume was significantly reduced compared to before treatment (4.33 cm³vs 27.55 cm³, P < 0.05), and the ADC value significantly increased (1.163×10 − ³mm²/s vs 0.860×10 − ³mm²/s, P < 0.05). The TVRR was 85.6%, and △ADC was 35.62%±7.04%; △ADC ≥ 35.62%, baseline SCC-Ag > 2.7 ng/ml, and hemoglobin ≥ 110 g/L were related factors for tumor volume regression (χ 2 = 15.64, 4.19, 4.364, P < 0.05); △ADC was an independent risk factor (OR = 9.751, P < 0.05), and the ROC curve showed that the optimal cutoff value of △ADC was 38.7%; The GTV volume of Plan1, Plan2, and Plan3 gradually decreased (F = 14.173, P < 0.05), the conformity index (CI) and homogeneity index (HI) of PTV significantly decreased (F = 10.75, 16.20, P < 0.05), and bladder V40 significantly increased (F = 17.932, P < 0.05). Conclusion △ADC can be used as an important indicator for predicting the sensitivity of cervical cancer to radiotherapy, and a cutoff value of 38.7% has clinical value. For patients with radiotherapy sensitivity (△ADC ≥ 38.7%), early secondary localization can improve the conformity and dose uniformity of the target area, reduce the bladder irradiated volume, and provide a new strategy for precise radiotherapy.