P2.01-27 Apparent Diffusion Coefficient (ADC) Change on Repeated Diffusion-Weighted MRI During Chemotherapy for Stage IV Lung NSCLC

Diffusion-weighted magnetic resonance imaging (DWI) depicts the random Brownian movement of water molecules in biological tissues. The net displacement of these molecules diffusing across an area of tissue per second is the apparent diffusion coefficient (ADC). ADC has proven useful in detection, characterization and treatment response monitoring of malignant diseases and is used routinely in the investigation of cancer of the prostate. The role of MRI in the follow up of treated lung cancer remains unclear. Previous publications have suggested that it could function as a biomarker in chemoraditherapy treated NSCLC. Very little has been published about chemotherapy treated tumours. 20 patients with stage IV adenocarcinoma were enrolled between September 2014 and April 2017. They received treatment with carboplatin/placitaxel and bevacizumab (7,5mg/kg) with maintenance bevacizumab if response. Two patients, in whom the lesion proved to be too small to measure (<2 ml), were excluded. Characteristics of the remaining 18 patients: 8 f/10m, median age 69 (51 -77), median survival 9 month (1-NR, follow up 60months) and median time to treatment failure 6 month (1-37). DWI was performed at baseline, 2w, 4w and 16w. Four patients did not participate in the full study program. Two examinations were incomplete due to technical problems, and 8 MRI examinations were excluded due to the tumors becoming too small in size (<2 ml). A total of 57 MRI examinations were included. The ADC value at baseline varied between 950 and 1584mm2/s (median 1228). ADC values both increased and decreased during treatment (% change at week 2 range -11 to 24%, at w4 -14 to 34%, at 16 w -27 to 10%). The evolution of the ADC values at the different timepoints did not show any statistical significant increase or decrease (using Mean Comparison with Student t’s test, Prob>Chisq 0,2159). Proportion Hazard analysis did not show any statistical correlation between the baseline ADC value, the change in ADC value and overall survival, nor between ADC values, change in ADC values and time to treatment failure. Repeated MRI in lung cancer is feasible. The clinical value of ADC measurements in the follow up of chemotherapy treated lung cancer needs further investigations.