Impact of cancer on use of glucoselowering drug t

Authors: Marjolein M J Zanders Harm R Haak Myrthe P P van HerkSukel Lonneke V van de PollFranse Jeffrey A Johnson

Publish Date: 2015/04/03

Volume: 58, Issue: 6, Pages: 1380-1381

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Abstract

To the Editor We thank Frans Pouwer for his comments on our study 1 exploring adherence to glucoselowering drugs following a cancer diagnosis among individuals with diabetes 2 Our findings revealed that there was a significant drop in the medication possession ratio at the time of cancer diagnosis with the largest drops among patients with stage IV disease and gastrointestinal or pulmonary cancers In his letter Pouwer describes two potential mechanisms that could explain these results 1As Pouwer indicates weight loss has been associated with improvements in beta cell function and insulin sensitivity among individuals with diabetes As a result glucose levels decline HbA1c values improve and less glucoselowering drug treatment may be required to obtain optimal metabolic control While weight loss is common among cancer patients especially among those with gastrointestinal lung or advanced cancer as described by Pouwer the impact of weight loss on metabolic control and thus on diabetes treatment among these cancer patients is to our knowledge unknown However according to our research HbA1c values improve before colorectal cancer diagnosis M M J Zanders M P P van HerkSukel R M C Herings L V van de PollFranse H R Haak unpublished data and it is possible that this might be the result of weight loss Although we might expect that the decisions made regarding diabetes treatment are similar for cancer patients and those without cancer ie improvement in HbA1c leads to reductions in glucoselowering drug dose we assume then that the attention of patient and physician is also on metabolic control and diabetes treatment around cancer diagnosis In addition in practice clinical decisionmaking regarding metabolic control is based on anticipating an interplay of factors besides weight loss such as food intake glucose values HbA1c risk of hypoglycaemia diarrhoea and presence of diabetesrelated complications such as kidney dysfunction and foot lesions 3 Finally physicians might decide to not change diabetes treatment among cancer patients if they find that HbA1c values increase ie worsen back to baseline after cancer diagnosis as our research suggests M M J Zanders M P P van HerkSukel R M C Herings L V van de PollFranse H R Haak unpublished data Nevertheless weight loss might be one of the multiple factors that make physicians decide to lower the dose or even discontinue diabetes treatment When weight loss causes physicians to verbally inform patients to change their daily regimen the same amount of treatment already in the patient’s possession might be distributed over a greater number of days giving the impression that adherence has declined when in fact it hasn’t If this was the most plausible and only explanation for the study findings then as suggested by Pouwer we should have used the words ‘medication use’ instead of ‘medication adherence’In our manuscript we briefly described that stress following a major event could have contributed to the observed decline in adherence Depressive symptoms might have a role in this since depression is related to stress and seems also to be associated with lower adherence rates as discussed in the comment of Pouwer 1 Consequently it would be very relevant and interesting to investigate in a future study whether the decline in adherence was modified by the presence of depression or depressive symptoms among patients with cancer and diabetesAs elaborated in our study 2 and in the contribution by Pouwer 1 we can conclude that the association between adherence to glucoselowering treatment and cancer is probably explained by an interplay of factors We thank Pouwer for his valuable additions regarding potential mechanisms to explain the complex association The explanation for the decline in adherence should be studied in more detail taking into account the discussed mechanisms and the type of cancer

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