The critical need for guidance in managing glycaemic control in patients with cancer

Glycosylated haemoglobin and prognosis in 10,536 people with cancer and pre-existing diabetes: a meta-analysis with dose-response analysis

AIMS

To assess whether glycaemic control is associated with prognosis in people with cancer and pre-existing diabetes.

METHODS

In this pre-registered systematic review (PROSPERO: CRD42020223956), PubMed and Web of Science were searched on 25th Nov 2021 for studies investigating associations between glycosylated haemoglobin (HbA1c) and prognosis in people with diabetes and cancer. Summary relative risks (RRs) and 95% Confidence Intervals (CIs) for associations between poorly controlled HbA1c or per 1-unit HbA1c increment and cancer outcomes were estimated using a random-effects meta-analysis. We also investigated the impact of potential small-study effects using the trim-and-fill method and potential sources of heterogeneity using subgroup analyses.

RESULTS

Fifteen eligible observational studies, reporting data on 10,536 patients with cancer and pre-existing diabetes, were included. Random-effects meta-analyses indicated that HbA1c ≥ 7% (53 mmol/mol) was associated with increased risks of: all-cause mortality (14 studies; RR: 1.14 [95% CI: 1.03-1.27]; p-value: 0.012), cancer-specific mortality (5; 1.68 [1.13-2.49]; p-value: 0.011) and cancer recurrence (8; 1.68 [1.18-2.38; p-value: 0.004]), with moderate to high heterogeneity. Dose-response meta-analyses indicated that 1-unit increment of HbA1c (%) was associated with increased risks of all-cause mortality (13 studies; 1.04 [1.01-1.08]; p-value: 0.016) and cancer-specific mortality (4; 1.11 [1.04-1.20]; p-value: 0.003). All RRs were attenuated in trim-and-fill analyses.

CONCLUSIONS

Our findings suggested that glycaemic control might be a modifiable risk factor for mortality and cancer recurrence in people with cancer and pre-existing diabetes. High-quality studies with a larger sample size are warranted to confirm these findings due to heterogeneity and potential small-study effects. In the interim, it makes clinical sense to recommend continued optimal glycaemic control.

Diabetes and Cancer - optimising glycaemic control

Diabetes and cancer are both common and increasingly prevalent conditions, but emerging epidemiological evidence confirms that the risk of developing a number of common cancers is increased in those with type 2 diabetes. The risk of cancer in type 1 diabetes is less clearly defined, and therefore this review will focus on type 2 diabetes. Emerging evidence also supports an influence of diabetes on outcomes of cancer treatment. However, this relationship is bi-directional, with cancer and its treatment impacting on glucose control, whilst there is also emerging evidence that diabetes care can deteriorate after a cancer diagnosis (summarised in Figure 1). Despite these clear links there is a lack of evidence to guide clinicians in how to manage patients with diabetes during their cancer treatment. Although recent UK guidelines have started to address this, with the development of guidance for the management of hyperglycaemia in cancer, there is a clear need for wider guidance on the management of multi-morbidity during cancer, including diabetes and obesity, to incorporate nutritional management We have therefore undertaken a narrative review of the evidence of links between type 2 diabetes and cancer incidence and outcomes, and discuss the challenges to diabetes care during cancer treatment. This article is protected by copyright. All rights reserved.