Hippocampal protection during preventive cranial irradiation and neurocognitive functions in patients with small cell lung cancer.

Background: In small cell lung cancer (SCLC), limiting the radiation dose in the hippocampus area during preventive cranial irradiation (PCI) can reduce nerve injury and cognitive decline. This study was done to compare changes in cognitive functions between hippocampal-protected (3D-H) and non-hippocampal-protected (3D) patients during PCI.

Materials and methods: the study group included 113 patients with SCLC qualified to PCI divided in two subgroups: 3D-H (n = 74) and 3D (n = 39). Two diagnostic and screening tests, Mini-Mental State Examination (MMSE) Short Scale and Montreal Cognitive Assessment (MoCA) Scale, have been applied before the start of irradiation, immediately after and 3 months after PCI.

Results: The doses delivered to the volume of the left and right hippocampus were similar and amounted to 12.00 Gy and 12.05 Gy, respectively. There were no differences between 3D-H and 3D groups in the MoCA and MMSE tests at any time point. In both groups the values in MoCA and MMSE scales differed between time points I, II and III. The patients in the 3D-H group were less likely than patients in 3D group to experience significant cognitive decline on the MoCA scale (p = 0.003), but not on the MMSE scale (p = 0.103).

Conclusions: Following PCI, SCLC patients experience significant cognitive decline, even when the radiation dose in the hippocampal area is reduced. This trend continues for at least 3 months following the PCI. In hippocampal-protected patients significant cognitive decline assessed on the MoCA scale is less common than in non-hippocampal-protected patients.