ESTRO 2024 - Abstract Book

S1116

Clinical - Gynaecology

ESTRO 2024

The aim of this study was to evaluate the need for adaptive radiotherapy treatment and for re-planning by investigating changes in tumor volume throughout the course of radiation therapy treatment for cervical cancer, utilizing retrospective patient data and focusing on key factors, including initial tumor volume, tumor grade and concurrent chemotherapy and radiotherapy treatment.

Material/Methods:

This study utilized retrospective patient data obtained from the planning computed tomography (CT) and the cone beam computed tomography (CBCT) for 42 cervical cancer patients undergoing radiation therapy. The initial tumor volumes, as well as the intermediate and final tumor volumes, were registered. In addition, the numbers of fractions delivered, the tumor grades (i.e., G1, G2 and G3) and the use of concurrent chemo-radiation were accounted for during investigations. Furthermore, the number of fractions was normalized across all data entries to accurately evaluate the relationship between initial tumor volume and relative tumor volume change per fraction calculated using the volume difference method.

Results:

The analysis revealed a positive and statistically significant correlation (i.e., r > 0, P < 0.001) between the total number of fractions administered and the percentage decrease in tumor size (Figure 1). The mean percent volume changes per fraction were evaluated for three categories based on initial tumor volume: (i) less than 100 cm3, (ii) between 100 cm3 and 200 cm3, (iii) greater than 200 cm3, with corresponding values for decrease in tumor volume per fraction of 1.11%, 1.43% and 1.91%, respectively (Figure 2). In addition, the mean percent volume changes per fraction for patients categorized by tumor grade indicated a decrease in tumor volume of 1.4%, 1.41% and 1.62% for G1, G2 and G3, respectively. Furthermore, the analysis considered whether patients were undergoing concurrent chemo-radiation and found that the mean volume change per fraction decreased by 0.98% for patients not undergoing both treatments and by 1.61% for those undergoing chemo-radiotherapy. The data were further subdivided to examine the average volume tumor change per fraction for each combination of tumor grade and concurrent chemo-radiation. Data for patients with G1 tumors were available only for those undergoing both treatments concurrently, revealing a decrease in mean volume change per fraction of 1.42%. The mean tumor volume change per fraction for patients with G2 tumors that were undergoing only radiotherapy decreased by 0.98%, while for patients undergoing both treatments concurrently, the volume change per fraction decreased by 1.56%. For patients with G3 tumors undergoing only radiotherapy, the mean tumor volume change per fraction was 0.97%, while those undergoing both treatments concurrently showed a significantly higher decrease of 1.78%.

Figure 1. The positive slope of the trendline showed a positive correlation between percent decrease in tumor volume and number of fractions.