Does salivary gland scintigraphy predict response to pilocarpine in patients with post-radiotherapy xerostomia?

Safety and efficacy of oral pilocarpine in radiation-induced xerostomia in oropharyngeal carcinoma patients

Context

Patients with head-and-neck cancers can develop salivary gland hypofunction after radiotherapy. Oral pilocarpine has been shown to be effective treatment for radiation-induced xerostomia, although its usefulness is being discussed.

Aims

We aimed to evaluate the efficacy and safety profile of oral pilocarpine in radiation-induced xerostomia.

Materials and Methods

Sixty patients with oropharyngeal carcinoma were planned for radiotherapy and divided into two arms randomly: Arm A (30 patients) received oral pilocarpine and Arm B (30 patients) received placebo tablets for 12 weeks after 3 months of completion of radiotherapy. Salivary gland scintigraphy and xerostomia questionnaire (XQ) were obtained from each patient at baseline and at 3 and 6 months of completion of radiotherapy.

Results

There was a marked decrease in uptake ratio (UR) and excretion fraction (EF) after 3 months of completion of radiotherapy. There was a statistically significant difference between both the arms in relation to UR, but no significant difference was observed between the two arms in relation to EF after 6 months of completion of radiotherapy. A statistically significant difference was found comparing the XQ results in both the arms. The XQ results did not correlate with salivary gland dysfunction observed by means of salivary scintigraphy. Adverse effects due to xerostomia were generally mild and occasionally of moderate severity.

Conclusion

The use of oral pilocarpine did not significantly improve salivary gland excretory function, despite better results on salivary uptake at 6 months. However, oral pilocarpine significantly improved symptoms of xerostomia with minor side effects that were predominantly limited to sweating.

Parasympathomimetic drugs for the treatment of salivary gland dysfunction due to radiotherapy

BACKGROUND

This is an updated version of the original Cochrane review on parasympathomimetic drugs for the treatment of salivary gland dysfunction due to radiotherapy (published in Issue 3, 2007). Salivary gland dysfunction is a predictable side effect of radiotherapy to the head and neck region. Pilocarpine hydrochloride (a choline ester) is licensed in many countries for the treatment of radiation-induced salivary gland dysfunction. Other parasympathomimetics have also been used 'off licence' in the treatment of this condition.

OBJECTIVES

To determine the efficacy and tolerability of parasympathomimetic drugs in the treatment of radiation-induced salivary gland dysfunction (specifically radiation-induced xerostomia).

SEARCH METHODS

For this update, we ran searches of the Cochrane Oral Health Group Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 6), MEDLINE, EMBASE, and CINAHL in July 2015. We checked the reference lists of retrieved articles for additional studies, contacted experts in the field for unpublished and ongoing trials, and contacted relevant pharmaceutical companies for unpublished and ongoing trials.

SELECTION CRITERIA

The selection criteria for the review were: 1) randomised controlled trials; 2) people suffering from radiation-induced salivary gland dysfunction; 3) people treated with parasympathomimetic drugs; and 4) assessable data available on primary outcome measure.

DATA COLLECTION AND ANALYSIS

The two review authors independently collected data from the full-text version of relevant papers including: 1) citation details; 2) participants; 3) interventions; 4) assessments; 5) outcomes (that is efficacy, tolerability); and 6) quality issues.Due to a lack of appropriate data, we were unable to perform a meta-analysis.

MAIN RESULTS

In the original review, three studies, including a total of 298 participants, fulfilled the inclusion criteria. All three studies involved the use of pilocarpine hydrochloride. We have included no additional studies in the update of the review; we have excluded eight additional studies.The data suggest that pilocarpine hydrochloride is more effective than placebo and at least as effective as artificial saliva. The response rate was 42% to 51%. The time to response was up to 12 weeks. The overall side effect rate was high, and side effects were the main reason for withdrawal (6% to 15% of participants taking 5 mg three times a day had to withdraw). The side effects were usually the result of generalised parasympathomimetic stimulation (for example sweating, headaches, urinary frequency, vasodilatation). Response rates were not dose dependent, but side effect rates were dose dependent.

AUTHORS' CONCLUSIONS

There is limited evidence to support the use of pilocarpine hydrochloride in the treatment of radiation-induced xerostomia. Currently, there is little evidence to support the use of other parasympathomimetic drugs in the treatment of radiation-induced xerostomia. Available studies suggest that approximately half of patients will respond, but side effects can be problematic. The conclusions of the update are the same as the conclusions of the original review, since no new relevant studies have been published in the interim.

Assessment of post-radiotherapy salivary glands

Salivary glands are usually irradiated during radiotherapy for head and neck cancers, which can lead to radiation-induced damage. Radiation-induced xerostomia (oral dryness) is the most common post-radiotherapy complication for head and neck cancer patients and can reduce the patient's quality of life. Accurate and efficient salivary gland assessment methods provide a better understanding of the cause and degree of xerostomia, and may help in patient management. At present, there are different methods for the assessment of salivary gland hypofunction; however, none of them are considered to be standard procedure. This article reviews the value of common methods in the assessment of post-radiotherapy salivary glands.

Parasympathomimetic drugs for the treatment of salivary gland dysfunction due to radiotherapy

BACKGROUND

Salivary gland dysfunction is a predictable side effect of radiotherapy to the head and neck region. Pilocarpine hydrochloride (a choline ester) is licensed in many countries for the treatment of radiation-induced salivary gland dysfunction. Other parasympathomimetics have also been used 'off licence' in the treatment of this condition.

OBJECTIVES

To determine the efficacy and tolerability of parasympathomimetic drugs in the treatment of radiation-induced salivary gland dysfunction.

SEARCH STRATEGY

A detailed search strategy was developed for MEDLINE, and adapted for other databases (Cochrane Pain, Palliative and Supportive Care Group Register; Cochrane Oral Health Group Register; The Cochrane Controlled Trials Register; EMBASE; CINAHL; SIGLE; Dissertation Abstracts). The reference lists of identified studies, review articles and radiotherapy textbooks were checked for additional studies. Relevant pharmaceutical companies, clinical investigators, and professional organizations/journals were also contacted about additional studies.

SELECTION CRITERIA

The selection criteria for the review were: 1) randomised controlled trials; 2) patients suffering from radiation-induced salivary gland dysfunction; 3) patients treated with parasympathomimetic drugs; and 4) assessable data available on primary outcome measures.

DATA COLLECTION AND ANALYSIS

The two review authors independently collected data from the full text version of relevant papers including: 1) citation details; 2) patients; 3) interventions; 4) assessments; 5) outcomes (i.e. efficacy, tolerability); and 6) quality issues. We were unable to perform a meta-analysis, due to a lack of appropriate data.

MAIN RESULTS

Only three studies, involving a total of 298 patients, fulfilled the entry criteria for the review. All three studies involved the use of pilocarpine hydrochloride. The data suggest that pilocarpine hydrochloride was more effective than placebo, and at least as effective as artificial saliva in those participants that responded. The response rate was 42 to 51%. The time to response was up to 12 weeks. The side effect rate was high, and side effects were the main reason for withdrawal (six to 15% patients taking 5 mg tds). The side effects were usually the result of generalised parasympathomimetic stimulation (e.g. sweating, headaches, urinary frequency, vasodilatation). Response rates were not dose dependent, but side effect rates were dose dependent.

AUTHORS' CONCLUSIONS

There is limited evidence to support the use of pilocarpine hydrochloride in the treatment of radiation-induced salivary gland dysfunction. Currently, there is little evidence to support the use of other parasympathomimetic drugs in the treatment of this condition. Available studies suggest approximately half of patients will respond, but side effects to responders can be problematic. Adverse effects are dose dependent therefore it is important to keep dose to 5 mg tds.

The efficacy of pilocarpine and bethanechol upon saliva production in cancer patients with hyposalivation following radiation therapy

PURPOSE

Pilocarpine and bethanechol have been reported as potentially effective sialogogues for xerostomic patients. The purpose of the present study was to compare the efficacy of bethanechol to that of pilocarpine in patients with dry mouth following cancer therapy.

STUDY DESIGN

Patients with documented hyposalivation were provided pilocarpine or bethanechol for 2-3 weeks in an open-label randomized crossover study. Baseline and weekly whole resting saliva (WRS) and whole stimulated saliva (WSS) were obtained for 5 minutes. Subjective response and side effects were recorded.

RESULTS

Forty-two xerostomic patients who had received radiation therapy to the head and neck participated. The increase in the WRS and WSS with each medication independently was limited. Statistically significant increase in WRS was seen for both medications when all patients using either agent were analyzed, but no statistically significant increase in WSS was found.Twenty-seven patients completed the crossover protocol. No significant difference in the effect was noted between each of the 2 drugs whether they were prescribed as the first or second drug in the crossover. Statistically significant improvement in subjective report of saliva production/mouth wetness was seen for patients on either medication. This study suggests that subjective improvement in symptoms of dry mouth may be related to resting saliva production, and not to stimulated saliva production. No statistically significant differences in adverse side effects were reported between the medications prescribed. The most common side effects were minor and included frequent urination, dizziness, and increased sweating.

CONCLUSIONS

The findings indicate that head and neck radiation-treated patients with established hyposalivation will respond minimally to systemic sialagogues and while they may experience an increase in resting saliva little change in stimulated saliva may occur. It is not known whether relatively small increases in saliva are beneficial in maintaining oral health; however, subjective improvement suggests improved quality of life. While it is not known if prolonged use of a sialagogue will have increased effects, the limited increase in saliva seen following the second drug of the crossover suggests that prolonged use of a sialagogue may further increase saliva production.

An update of the etiology and management of xerostomia

Salivary gland disease gives rise to salivary gland enlargement, pain, and prolonged xerostomia (dry mouth). Xerostomia is the most common long-standing problem for the majority of affected patients. There are many causes of dry mouth, with long-standing xerostomia being a particular problem in Sjögren's syndrome and after radiation to the head and neck region. Xerostomia is usually managed with saliva substitutes, but a large number of potential systemic therapies of long-standing xerostomia now exist. Some-particularly immunosuppressants-are of fundamental interest for the potential reduction of gland damage in Sjögren's syndrome but as yet are of limited clinical usefulness. Others, particularly pilocarpine and cevimeline, are, or have the potential to be, clinically useful in stimulating salivation by virtue of their action on cholinergic receptors.

Utilidad de la pilocarpina como profiláctico de xerostomía en pacientes con cáncer de cabeza y cuello tratados con radioterapia. Valoración mediante gammagrafía y flujo salivar

AIM

To assess the utility of salivary gland scintigraphy and salivary flow to quantify salivary function and to evaluate the usefulness of pilocarpine in the treatment of radiation-induced xerestomia in head and neck cancer patients.

METHOD

Thirty two patients with head and neck tumor treated with radiotherapy (RDT) were studied. Patients were classified into two groups: pilocarpine group (P), that received prophylactic pilocarpine before RDT and during the first year after treatment. No pilocarpine group (NP) that received RDT without pilocarpine. Salivary gland scintigraphy and salivary flow were performed before RDT and during one year after treatment. Parotid and submaxillary uptake and excretion were calculated. Salivary flow after stimulation during five minutes was also obtained.

RESULTS

Uptake and excretion in both salivary glands decreased after RDT. There were no statistical differences comparing P and NP groups (p < 0.001). However, in group P a trend to recovery was observed in parotid uptake values at 12 months after treatment, but it was not statistically significant. In both groups the salivary flow decreased after RDT and a good correlation (r = 0.8) between salivary flow and submaxillary excretion and parotid excretion was found.

CONCLUSIONS

Salivary gland scintigraphy and salivary flow could be useful to evaluate salivary gland function in patients with head and neck irradiated tumors. Although better results on the salivary uptake at 12 months were noted, pilocarpine did not significantly improve salivary gland function.

Effect of pilocarpine mouthwash on salivary flow

Pilocarpine is a cholinergic agonist that increases salivary flow and has been used to treat xerostomia. Oral intake is the most frequent route of administration. Adverse effects are dose-dependent and include sudoresis, facial blushing and increased urinary frequency. The objective of the present study was to evaluate the effects of topical pilocarpine solutions as mouthwashes on salivary flow and their adverse effects on healthy subjects. Forty volunteers received 10 ml 0.5, 1 and 2% pilocarpine solutions or 0.9% saline in a randomized, double-blind, placebo-controlled manner. Salivation was measured before and 45, 60 and 75 min after mouth rinsing for 1 min with 10 ml of saline or pilocarpine solutions. Vital signs were measured and ocular, gastrointestinal and cardiovascular symptoms, anxiety and flushing were estimated using visual analog scales. There was a dose-dependent increase in salivation. Salivation measured after 1 and 2% pilocarpine (1.4 +/- 0.36 and 2.22 +/- 0.42 g, respectively) was significantly (P<0.001) higher than before (0.70 +/- 0.15 and 0.64 +/- 0.1 g), with a plateau between 45 and 75 min. Cardiovascular, visual, gastrointestinal and behavioral symptoms and signs were not changed by topical pilocarpine. Mouth rinsing with pilocarpine solutions at concentrations of 1 to 2% induced a significant objective and subjective dose-dependent increase in salivary flow, similar to the results reported by others studying the effect of oral 5 mg pilocarpine. The present study revealed the efficacy of pilocarpine mouthwash solutions in increasing salivary flow in healthy volunteers, with no adverse effects. Additional studies on patients with xerostomia are needed.

Salivary scintigraphy for assessing the protective effect of pilocarpine in head and neck irradiated tumours

Patients with head and neck cancers can develop salivary hypofunction after radiotherapy. The use of pilocarpine during radiotherapy treatment has been shown to be an effective treatment, although its usefulness is being discussed. The aim of this study was: (1) to determine the value of a semiquantitative scintigraphy method for measuring the uptake and excretory salivary function of patients with head and neck irradiated tumours; and (2) to study the usefulness of pilocarpine as a salivary gland protector during radiotherapy. We prospectively studied 49 patients (mean age 61 years, range 29-87 years) with head and neck cancer in need of radiotherapy. Patients were divided into two groups consecutively: group P (26 patients) received 5 mg of pilocarpine three times per day starting the day before radiation therapy, and group NP (23 patients) received radiotherapy without pilocarpine and were used as the control group. Salivary gland scintigraphy and a visual analogue scale (VAS) of mouth dryness were obtained from each patient before radiotherapy and during the first year after treatment. The most frequent finding after radiotherapy was a quick impairment in parotid and submaxillary excretion (P < 0.001). There were no statistical differences comparing the pilocarpine group against the non-pilocarpine group. Parotid and submaxillary uptake significantly decreased after radiotherapy in both groups (P < 0.001). However, a tendency to recover within the pilocarpine group was observed in both the parotids and the submaxillary glands at 12 months. No differences were found comparing the VAS results in both groups. Strikingly, VAS data did not correlate with salivary gland dysfunction observed by means of scintigraphy. In conclusion, salivary scintigraphy is a useful technique to evaluate objectively the salivary gland function of patients with head and neck irradiated tumours as well as to test the response to pilocarpine. However, despite better results on the salivary uptake at 12 months, pilocarpine did not significantly improve salivary gland function.

Stimulated salivary pertechnetate clearance revisited: correlation with dynamic scintigraphic indices in Sicca syndrome

PURPOSE

The stimulated salivary clearance of Tc-99m pertechnetate (SSCP) introduced in 1985 by Blue and Jackson is revisited here in patients with known or possible salivary disorders and correlated with most commonly cited and up-to-date quantitative indices obtained from standard dynamic salivary scintigraphy.

METHODS

An SSCP test was performed after dynamic salivary scintigraphy in 19 patients with oral or ocular dryness, among whom 7 had Sjögren's syndrome. Many scintigraphic indices were calculated: salivary to background ratio (S/B[t]), background-corrected uptake U[t]), maximal uptake (Umax), cumulative gland uptake (CGU), initial slope of the uptake curve (IS), stimulated excretion velocity (SEV), stimulated excretion fraction (SEF), and excreted activity (EA).

RESULTS

The SSCP test was well tolerated, except in two patients in whom it had to be interrupted. Clearance values ranged from 5 to 40 ml/minute, with a clear-cut bimodal distribution centered around 15 to 20 ml/ minute. Six of the seven patients with Sjögren's syndrome had values less than 15 ml/minute. SSCP was closely correlated with all uptake indices (S/B, U, Umax, CGU, and IS) and uptake-related indices (EA, ISxSEF) (P < 0.01). A poor correlation was found with the excretion index SEV (P = 0.06) and none with SEF.

CONCLUSIONS

SSCP is a quick and objective means to investigate the sicca syndrome that may be useful in most clinical situations. It reflects the parenchymatous salivary gland function and will provide a means to assess and predict salivary gland involvement. Dynamic salivary scintigraphy remains necessary in very early stages because of its high sensitivity rate and ability to locate the impaired gland, or in severe stages in which lemon juice could be deleterious.