Longitudinal evaluation of hippocampal subfields volumes and episodic memory in breast cancer patients and healthy controls

Despite previous reports of hippocampal alterations in breast cancer patients, the structural evolution of hippocampal subfields in relationship with memory remains to be characterized in this population. We here aimed to measure hippocampal subfield volumes and their links with memory performances before and after chemotherapy in breast cancer patients compared to healthy controls. Forty-two middle aged women were evaluated, including 19 patients assessed before (T1), one-month (T2) and one-year (T3) after chemotherapy, and 23 controls assessed at T1 and T3. Using high-resolution MRI, hippocampal subfields were automatically segmented. Derived volumetric measures were compared within the patient group (T1, T2, T3), and between groups at T1 and T3. Both encoding and retrieval memory performances were measured using a dedicated task. At T1, patients had larger subiculum volume than controls. Longitudinal comparisons within the patients’ group did not yield significant changes, while CA4-DG volumes increased over time in controls but not in patients. Memory retrieval was globally lower in patients than in controls but did not differ over time. CA4-DG volumes at T1 were positively associated with memory scores at T3 in HCs only. Volumes were negatively associated with age in both groups, and positively with education level in patients. Our results suggest combined effects of cancer and chemotherapy on hippocampal structure of breast cancer patients, by specifically highlighting modifications in the subiculum and in the CA4-DG. We here propose that both neuroinflammation and blockade of neurogenesis may have driven such differences, in line with previous hypothesis in rodent models of cancer.