The purpose of this study was to make a pathological evaluation of the tumor
response and the lung injury of non-small cell lung cancer (NSCLC) patients after
carbon ion therapy. We enrolled four NSCLC patients with chest wall invasion but
without nodal and distant metastasis (T3N0M0). Only primary lesions were
irradiated with carbon ions, followed by surgical resection. The patients
consisted of three males and one female varying by age from 54 to 73 (average
66.3). Total treatment dose was 59.4 and 64.8 GyE, respectively, administered in
18 fractions over 6 weeks, or 72.0 GyE in 16 fractions over 4 weeks. Resection
after radiation therapy was performed as a combination of lobectomy, lymph node
dissection and chest wall surgery. After fixation, the lung was sliced into thin
sections to match the CT image. Each slice was anatomically identified and the
slices were compared with each other subjected to pathological analysis. No tumor
cells were observed in two cases. The other two cases exhibited only a few tumor
cells sparsely distributed in the lung tissue. There was evidence of dense
pulmonary fibrosis in the limited space surrounding primary tumors, but its
density was found to rapidly decrease in the narrow area toward the outside. The
rate at which its density subsided mirrored the rapid decrease in the planning CT
dose distribution. Microscopy showed no evidence of fibrosis in any of the fields
irradiated with less than 15 GyE. Microscopy confirmed an outstanding tumor
response with limited pulmonary fibrosis. This substantiates the superior dose
localization and strong biological effect of carbon ion beams with a Bragg peak
in the lung. The pathological findings have thus provided evidence of the safety
and effectiveness of carbon beam therapy in the treatment of NSCLC.