Re: does lemon candy decrease salivary gland damage after radioiodine therapy for thyroid cancer?

TO THE EDITOR: In their paper on salivary gland damage after high-dose radioiodine ablation therapy, Nakada et al. discuss an interesting and practical issue (1). The authors propose a radiation protection paradigm based on a concept of the dynamics of salivary gland function. The authors claim to have compared 2 radiation protection regimens in similar patients groups: a group that started sucking lemon candy straight after radioiodine treatment (group A), versus a group that started 24 h later (group B). Based on this comparison, the authors recommended that patients start sucking lemon candy no earlier than 24 h after radioiodine treatment. Some aspects of this study are puzzling. First, the authors state that “On encountering unexpectedly higher salivary gland side effects in group A, the patients in group B tended to be treated more intensively with steroids or nonsteroidal antiinflammatory drugs for sialoadenitis and with a drug containing zinc acetate or vitamin B12 for taste dysfunction” (1). Might these differences in medical treatment (which were not specified quantitatively) have contributed to the observed reduction of radiation damage in group B? Second, as cited by the authors, the reported incidence of salivary gland injury varies considerably depending on the diagnostic criteria (2–5). The incidence of sialoadenitis, dry mouth, and loss of taste was investigated. Which criteria were used to define these primary endpoints? Third, which criteria were used to consider including sialoscintigraphy in the assessment of salivary function? What was the total number of these procedures in each group, and what was the outcome? We believe that these data are relevant because of the reported disagreement between subjective symptoms and sialoscintigraphy. Fourth, the authors’ concept of salivary gland function has not been studied physically. It is uncertain whether at any time point there is indeed an imbalance of the salivary blood flow and the counteracting saliva flow. Whether delayed stimulation of the salivary glands has a radioprotective effect therefore remains a matter of debate. If delayed stimulation is indeed beneficial, why should the optimal starting point of sucking lemon candy be 24 h? If this extra information could be supplied, the clinical significance of this study would be greatly enhanced.