EVALUATING TOTAL METABOLIC TUMOR VOLUME (TMTV) ON PET/CT AS A DETERMINANT FOR PERSONALIZED RADIATION DOSE OPTIMIZATION IN HODGKIN LYMPHOMA PATIENTS

Abstract

Objective: To assess baseline total metabolic tumour volume (TMTV) measured by ¹⁸F-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) in patients with Hodgkin lymphoma (HL) undergoing radiotherapy and to explore its associations with disease characteristics, radiotherapy factors and treatment response and to determine an exploratory baseline TMTV cut-off for predicting non-complete response to radiotherapy in patients. Material and Methods: This prospective observational cohort study included 80 histopathologically confirmed HL patients treated at the Institute of Nuclear Medicine and Oncology Lahore. Pre-radiotherapy TMTV and PET/CT baseline characteristics were obtained. Non-parametric tests, analysis of variance and Pearson correlation were used to assess associations. Discrimination between complete and non-complete response was assessed using receiver operating characteristic (ROC) analysis. Results: Mean baseline TMTV was 137.6±108.8 cm³ (range, 18.0–580.9). TMTV differed significantly across Ann Arbor stages (H=50.173, p<0.001), bulky disease (U=1508.000, p<0.001), B-symptom status (U=1100.500, p<0.001), and lesion distribution (H=7.887, p=0.019). TMTV correlated positively with radiation dose (r=0.562, p<0.001) and number of fractions (r=0.562, p<0.001), but not radiation technique (H=3.682, p=0.451). There was a difference between the response groups in terms of TMTV (F=4.442, p=0.006). Forty-four patients (55.0%) achieved complete response. Baseline TMTV was negatively correlated with percentage reduction in TMTV (r=−0.354, p=0.001). ROC analysis yielded AUC 0.674 (95% CI, 0.556–0.792; p=0.004); an exploratory cutoff of 161.25 cm³ had 50.0% sensitivity and 77.3% specificity. Conclusion: Baseline TMTV was associated with disease burden, radiotherapy prescription, and treatment response. The exploratory cutoff needs to be validated before clinical use, but TMTV can be used in conjunction with the conventional parameters in HL radiotherapy planning.