Abstract
•The potential role of DW-MRI for response assessment of radiotherapy of lung cancer.•ADC values depend on the definition of the region of interest.•ADC values increase during radiochemotherapy.•ADC value increase appears to be independent from tumor volume regression.
Serial diffusion-weighted magnetic resonance imaging (DW-MRI) during radiochemotherapy of non-small cell lung cancer (NSCLC) is analyzed to investigate the apparent diffusion coefficient (ADC) as a potential biomarker for tumor response.
Ten patients underwent DW-MRI prior to and at three and six weeks during radiochemotherapy. Three methods of contouring primary tumors (PT) were performed to evaluate the impact of tumor heterogeneity on ADC values: PTT: whole tumor volume; PTT-N: PTT-necrosis; PTL: small volume of presumed active tumor with low ADC value. Pretreatment and during-treatment absolute ADC values and ADC value changes were analyzed for PT and involved lymph nodes (LN).
ADC values for PTT, PTT-N, PTL and LN increased by 8–14% (PT) and 15% (LN) at three weeks, and 19–26% and 23% at 6 weeks post initial treatment (p=0.04–0.002). Average percent ADC value increase was smaller than tumor volume regression (p=0.06–0.0005). Patients with overall survival <12 months had a lower increase of ADC values compared to longer surviving patients (p=0.008 for PTT).
Significant ADC value increases during radiochemotherapy for non-small cell lung cancer were observed. ADC value change during treatment appears to be an independent marker of patient outcome and warrants further investigation.
