Discussion

This study examined the long-term effects of cancer treatment on episodic memory in BCS, using both narrative and standardized VPA tasks. Uniquely, it is the first to assess recall of verbatim, gist, and distortion details of narrative event memories in this population. As hypothesized, BCS showed impaired performance on the narrative memory task and reported greater cognitive workload compared to NC. In contrast, their performance on the VPA task was comparable to that of NC, with no reported increase in cognitive workload to complete this task. These findings were contrary to our expectations, and highlight an important limitation to standardized memory tasks that may contribute to an under-reporting of cognitive impairment following cancer treatment.

BCS recalled fewer verbatim and gist-based details on a naturalistic memory task compared to NC. Despite these differences, both groups performed similarly across immediate and delayed recall, suggesting similar patterns of forgetting even over a brief period of 20 min. These findings are noteworthy given that verbatim memory typically declines over time, even in healthy individuals [52]. Both groups recalled more gist details after a delay, consistent with memory becoming more gist-like and schematic over time [12], a finding that is also observed over longer periods of weeks and months. An unexpected finding was survivors reporting fewer gist details than NC, potentially indicating generally less accessible memory content [53]. Interestingly, only NC had a significant increase in memory distortions over time. These results support prior findings of cancer survivors recalling fewer narrative details [29], 54], 55], but contrast with studies showing no effects of chemotherapy [31], 56]. Accounting for memory distortions, BCS recalled fewer accurate gist and verbatim details than NC – a difference that remained consistent over time.

The present findings align with those of Taler et al. [37] who developed this narrative task to assess episodic memory quality in both healthy aging and in cases of mild cognitive impairment (MCI). Our results indicate that both BCS and NC groups reported fewer verbatim details following the delay, mirroring the pattern observed by Taler et al. when comparing healthy younger and older adults. Overall, younger adults produced more verbatim details than older adults, who in turn outperformed individuals with MCI. This pattern parallels our observation that NC participants reported more verbatim details than BCS participants, which potentially suggests that BCS may follow an accelerated trajectory of age-related memory changes, mirroring patterns seen in typical aging [57].

The finding that NC reported more memory distortions relative to BCS is counterintuitive but identifies an interesting distinction. Rather than reflecting superior memory accuracy, the lower distortion and gist scores among BCS likely indicate impairments in memory encoding [29], 31]. While memory naturally transforms over time, becoming less specific and more prone to distortion particularly for schema-consistent events, BCS may encode fewer details from the outset, leaving less information available for later recall or distortion [11], 12], 18]. This interpretation is reinforced by lower overall recall and supported by retrieval success scores, which account for both accuracy and completeness of memory.

In contrast to the narrative memory task, BCS and NC performed similarly on the VPA. This suggests that certain aspects of episodic memory, particularly simple associative learning, may remain relatively preserved following treatment. These findings align with prior findings that VPA performance lacks the sensitivity to detect subtle cognitive deficits, even in individuals with MCI [58].

BCS reported greater cognitive effort than NC during narrative recall, but not during the VPA task, suggesting that more complex, real-world memory tasks place higher cognitive demands on BCS. This pattern implies that BCS may recruit additional cognitive resources through compensatory mechanisms to perform narrative recall tasks [59], 60]. However, across both groups, higher subjective cognitive effort was associated with worse memory performance, indicating that these impressions likely reflect awareness of cognitive challenges [32]. BCS also reported greater subjective difficulties with both episodic and semantic memory, consistent with previous research identifying persistent perceived memory problems following treatment [61], 62].

Methodological variability likely contributes to inconsistencies in the literature on chemotherapy-related cognitive impairment, including differences in participants, treatment type and dosage, time since treatment, and measures. While many studies find that chemotherapy-treated cancer survivors perform worse on neuropsychological tests and report more memory and concentration difficulties, these subjective complaints often correlate more strongly with psychological distress than with objective impairment [38], 63]. Additionally, survivors who had above-average cognitive abilities before treatment may still score within normal ranges post-treatment but feel they have declined compared to their personal baseline. Thus, their concerns might reflect real changes that are not captured by standard population-based comparisons [38].

Both perceived and objective cognitive difficulties should be routinely addressed throughout cancer survivorship, with regular screening across different stages of recovery [64], 65]. Although clinical resources may be limited, comprehensive pre- and post-treatment neuropsychological assessments that incorporate standardized and ecologically valid measures, and subjective measures of cognitive functioning are recommended to define cognitive profiles and guide interventions [62], [66], [67], [68]. This ongoing approach can help validate patient experiences and support appropriate management of cognitive challenges over time [64].