Association of long-term treatment outcomes with changes in PET/MRI characteristics and the type of early treatment response during concurrent radiochemotherapy in patients with locally advanced cervical cancer

Abstract

PURPOSE: We aimed to find predictive tumour characteristics as detected by interim positron-emission tomography/magnetic resonance imaging (PET/MRI) in cervical cancer patients. We also investigated the type of interim response. Furthermore, we compared the investigated parameters with disease-free (DFS) and overall survival (OS) outcomes. METHODS: We evaluated 108 patients treated between August 2015 and January 2023 with external-beam radiotherapy (EBRT) and image-guided adaptive brachytherapy (IGABT) who had undergone pretreatment staging, subsequent mid-treatment evaluation after completed EBRT and definitive restaging 3 months after completing the whole treatment using PET/MRI. Patients were then divided into two groups based on the RECIST and PERCIST criteria: responders (achieving complete metabolic response, CMR) and non-responders (non-CMR). These two groups were compared using selected parameters obtained at pre-PET/MRI and mid-PET/MRI. The early response to treatment as evaluated by mid-PET/MRI was categorized into three types: interim complete metabolic response, interim nodal response and interim nodal persistence. RESULTS: Mid-TLG-S (the sum of total lesion glycolysis for the primary tumour plus pelvic and para-aortic lymph nodes) parameter showed the best discriminatory ability for predicting non-CMR. The second factor with significant discriminatory ability was mid-MTV-S (the sum of the metabolic tumour volume of the primary tumour plus pelvic and para-aortic lymph nodes). The strongest factor, mid-TLG-S, showed a sensitivity of 40% and a specificity of 90% at a threshold value of 70. We found a statistically significant association of DFS and OS with the following parameters: number of chemotherapy cycles, early response type and CMR vs. non-CMR. CONCLUSION: We were able to identify thresholds for selected parameters that can be used to identify patients who are more likely to have worse DFS and OS. The type of early response during concurrent chemoradiotherapy (CCRT) was also significantly associated with DFS and OS. These aspects represent an important contribution to the possible stratification of patients for subsequent individualised adjuvant treatment.