Usefulness of Follow-up MR Imaging in Lung Cancer Treatment

To evaluate the therapeutic effect of radiation therapy and chemotherapy in lung cancer patients, MR imaging was performed in 59 patients with lung cancer. Tumor size and signal intensity before and after treatment were discussed. MRI patterns of therapeutic effect were divided into 3 types. In 37 cases, mild tumor reduction was recognized, but there was no change in the signal intensity of the tumor after treatment (Type I). In 11 cases, high intensity areas considered to be tumor necrosis were observed inside the tumor on the T2-weighted image, and 9 of these (82%) were squamous cell carcinoma (Type II). In the remaining 11 cases, marked tumor reduction was observed on MRI, thus the signal intensity could not be compared, and 8 of these cases were small cell lung cancer (Type III). It was suggested that there was a certain correlation between these MRI patterns and histologic types. In 11 autopsied cases, comparison images and pathologic findings showed the MRI findings to be consistent with the pathologic findings. MR imaging can evaluate therapeutic effect not only by tumor size, but also by tissue characteristics. Furthermore tumors were clearly delineated from radiation pneumonitis in 5 of 8 cases (63%). Therefore, MRI was useful to evaluate therapeutic effect.