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 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 between groups at T1 and T3 and within the patient group (T1, T2, T3). Both encoding and retrieval memory performances were measured using a dedicated task. At T1 and globally (i.e., T1 and T3 together), patients showed lower retrieval performance and larger subiculum and whole hippocampal volumes compared to controls. Volumes of the whole hippocampus and of the Cornu Ammonis (CA) 4-Dentate gyrus increased over time in controls. Longitudinal comparisons within the patients' group did not yield significant changes. Volumes were negatively associated with age in controls, and positively with education level in patients. Our results highlight structural differences in the subiculum and whole hippocampus of breast cancer patients both post-surgery and over the adjuvant treatment course. These modifications may reflect a combination of cancer-related and early perioperative factors, while the lack of subsequent longitudinal changes in patients prevents conclusions regarding the specific impact of chemotherapy. Additional studies with larger sample sizes will be of help to further our findings.