The significance of apparent diffusion coefficient of MRI in early therapeutic response assessment in patients who undergo systemic treatment of renal cell carcinoma

Abstract

Existing criteria of the systemic treatment assessment in patients with renal cell carcinoma (RCC) do not allow to completely characterize profound changes in tumor tissues which appear due to target agents action, and to prognosticate degree of early therapeutic response.The objective was to define the role of the apparent diffusion coefficient (ADC) of the diffusion-weighted images (DWI) of MRI in early therapeutic response assessment in patients who undergo systemic therapy of advancer RCC.Material and methods. The study involved 32 patients with advanced RCC – main group, and 30 healthy volunteers - control group. In all patients with RCC as the first line of treatment, pazopanib 800 mg per os was administrated on daily basis. In all patients as a baseline (0-5 days prior to beginning of systemic treatment) and control (1 month after, mean 1,10±0,25 months) examination, contrast enhanced MRI with additionally included into scanning protocol DWI sequence with b-values 0 and 800 s/mm2 was performed.Results. We achieved significant difference in mean ADC values after 1 month of treatment in patients’ subgroups: in patients with partial response (PR) mean ADC value was 1,36±0,16×10-3 mm2/s, in cases with stabile disease (SD) it was 1,57±0,12×10-3 mm2/s and in patients with progressive disease (PD) – 1,77±0,06× mm2/s. In subgroup with PR we observed mean decrease of ADC by ↓19,11±10,64% (95% CI=12,35-25,87); in subgroup with SD mean ADC decrease was ↓7,66±6,72% (95% CI=2,86-12,47); in subgroup with PD conversely ADC increased by ↑1,11±2,46% (95% CI=-0,64-2,67), р<0,001. Conclusion. ADC unlike size of the primary tumor objectively reflects early changes which take place in tumor tissues of the advanced conventional RCC under the influence of the systemic treatment with pazopanib and can be used for the assessment of the early therapeutic response.