Apparent diffusion coefficient as an effective index for the therapeutic efficiency of brain chemoradiotherapy for brain metastases from lung cancer

Abstract

Background: The potential of apparent diffusion coefficient (ADC) value alteration before and after chemoradiotherapy as a potential monitor for therapeutic efficiency of treatment for brain metastases from lung cancer were discussed.

Method: Thirty lung cancer patients with brain metastases, conventional magnetic resonance imaging (MRI) examination and diffusion weighted imaging (DWI) were performed one week before chemoradiotherapy and after one treatment cycle and two treatment cycles. 43 tumor lesions were divided into effective group and invalid group according to the changes of the tumor size. The differences in ADC values at different time points before and after treatment in each treatment group were analyzed.

Result: The maximum diameter of the tumor was no difference after one treatment cycle, but decreased after two treatment cycles. ADC values significantly increased after both one and two treatment cycles. In effective group, the ADC values were significantly increased after one and two treatment cycles. While, there are no difference in invalid group after one treatment cycle but decreased after two treatment cycles. ΔADC values in effective group after one and two treatment cycles were both significantly higher than those in the invalid group. ROC curve analysis then revealed that the area under the curve (AUC) of ΔADC after one treatment was 0.872.

Conclusion: ADC values in brain metastases from lung cancer can help monitor and dynamically observe the therapeutic efficiency of whole brain chemoradiotherapy.

Keywords: Apparent diffusion coefficient (ADC); Brain metastases; Magnetic resonance imaging (MRI); Therapeutic efficiency.

Fig. 1

ADC values indicate the tumor progression more sensitively than MRI (a) The maximum diameters of tumors for brain metastases from lung cancer before and after treatments. b ADC values of brain metastases from lung cancer before and after treatments. n = 43, p < 0.05 statistical significance compared to one week before treatment

Fig. 2

Two cases were shown below for example the group division: Case 1: Pathologically diagnosed as brain metastases from right lung adenocarcinoma. The maximum diameter of the lesion was 10 mm one week before treatment and the ADC value was 0.653 × 10^− 3 mm²/s; the maximum diameter of the lesion was 12 mm and the ADC value was 0.733 × 10^− 3 mm²/s after one treatment cycle; the maximum diameter of the lesion was 14 mm and the ADC value was 0.706 × 10^− 3 mm²/s after two treatment cycles. According to RECIST criteria, the patient belonged to the invalid group. Case 2: pathologically diagnosed as brain metastases from lung cancer. The lesions on the right occipital lobe were nodular with slightly higher signal intensity on T2WI, slightly lower signal intensity on T1WI, high signal intensity on DWI, and obviously enhanced lesions on contrast-enhanced T1WI. The maximum diameter was 17 mm before treatment and the ADC value was 0.759 × 10^− 3 mm²/s; after one treatment cycle, the maximum diameter of the lesion was reduced to about 16 mm, and the ADC value was 1.05 × 10^− 3 mm²/s; after two treatment cycles, the enhanced part of the lesion was obviously reduced, with a diameter of 3 mm, and the ADC value was 1.10 × 10^− 3 mm²/s, suggesting that the treatment was effective. According to RECIST criteria, this patient belongs to the effective group.

Fig. 3

ROC curve analysis of ΔADC values after one treatment cycle. The AUC was 0.872 (sensitivity = 81.8%, specificity = 85.7%)