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Electrical stimulation of post-irradiated head and neck squamous cell carcinoma to improve xerostomia.

INTRODUCTION

Xerostomia is characterized by the symptom of oral dryness. There are numerous causes of xerostomia which include medications, systemic medical disorders, radiation therapy to the head and neck area, and psychiatric disorders. These situations may result in hypofunctioning salivary gland tissues with resultant xerostomia. Chronically decreased levels of saliva can pose difficulties with chewing, eating, swallowing, increased caries and infection, pain, avoidance of foods/medications and ultimately lead to a decreased quality of life. The incidence of xerostomia following ionizing radiation treatment for head and neck cancers has been reported as 64%. (1)

The current treatment options for xerostomia include salivary substitutes, artificial saliva, and saliva stimulating medications. Parotid-sparing ionizing radiation protocols have also emerged in an attempt to decrease post-radiation therapy xerostomia. These treatments are limited to preventing dental caries, oral candidiasis, and replacing saliva with substitutes. However, most efforts to improve xerostomia are temporary at best and have met with limited success. In the past, electrical stimulation (E-Stim) had been utilized and approved in the treatment of post-radiation dysphagia. The improvement in dysphagia has been reported as high as 75% of the treated patients. Interestingly, we have noted that a significant number of the patients being treated for dysphagia at our institution were also reporting an improvement in their xerostomia. In a review of the literature, we noted there are scarce reports for using E-Stim for post-irradiated head and neck cancer patients as a method to treat xerostomia.

The objective of our study was to determine the feasibility, efficacy, and complications of noninvasive neuromuscular E-stim in increasing salivation in post-irradiated head and neck cancer patients with xerostomia. This is a novel pilot study, in which, we were able to quantify the salivary production and provide objective data in measuring the effects of E-Stim on xerostomia.

MATERIALS AND METHODS

This a prospective pilot study performed on five patients. The study was approved and consent was granted by the local Institutional Review Board at Louisiana State University Health Sciences Center, Shreveport, Louisiana. Inclusion criteria for enrollment in the study included diagnosis of a head and neck cancer which required single modality radiation therapy or combination of radiation with chemotherapy and/or surgery. Exclusion criteria for the study were as follows: prior E-Stim therapy, use of sialagogic agent/saliva substitute, signs of recurrence of cancer, any established contraindication for use of E-Stim.

We enrolled five patients who met the above criteria in our study to receive 20 one-hour sessions of E-Stim therapy by our speech pathologists. Patients were enrolled in the study only after determining complete response to treatment at least two months after treatment was complete. Written informed consent was obtained from all of the patients. A transcutaneous electrical nerve stimulation (TENS) unit was employed for this study (Figure 1). The subjects were told not to eat or drink the morning of their scheduled treatment. The TENS unit electrode pads were placed externally on the skin overlying the parotid glands bilaterally. The electrode placement was in a square pattern with 2 (+ and -) above the thyroid notch and 2 (+ and -) below, approximately two inches apart (Figure 2). The setting of the TENS unit was increased in increments until the patient indicated a "grabbing" sensation and acceptable comfort levels for the patient. The settings ranged from 55-80mA (maximum setting). This defined the optimal intensity for the patients. The duration of treatment was 60 minutes per session.

[FIGURE 1 OMITTED]

Saliva was collected using dental rolls at three intervals: prior to treatment, after the patient had received ten sessions, and then two weeks after the 20 session protocol was completed. The dental rolls were weighed using a calibrated laboratory scale after collection and recorded to provide objective data. All of the subjects completed the above mentioned protocol.

We also obtained subjective data by requiring patients to complete the Dysphagia and Xerostomia Index Questionnaire pre-treatment and then two weeks post-treatment. This questionnaire contained nine questions asking the patients to subjectively grade the degree of xerostomia. The questions were graded 0-4 for each question and a higher score indicated worse xerostomia.

RESULTS

All patients had received radiotherapy with the parotid gland in close proximity. One of the five patients had received intensity-modulated radiotherapy (IMRT) and the remaining patients had received conventional radiotherapy.The breakdown of the stage and site of the primary cancer is shown in Table 1. We had three T2-3 oropharynx squamous cell carcinoma patients, one T2-3 oral cavity squamous cell carcinoma patients, and one patient with an unknown primary. The treatment modality and the amount of radiation received are also displayed. The saliva was measured in grams on a calibrated lab scale and is shown in Table 2 as pre-treatment, post ten treatments, and two weeks post-completion of 20 treatments. The results obtained from the xerostomia questionnaire are also shown in Table 3 with a higher score depicting worse symptoms.

The saliva production results were then analyzed using a Wilcoxon signed rank test to determine if 20 sessions of E-Stim treatment would significantly increase the amount of saliva production. We were able to demonstrate a difference when comparing saliva production between the pre-treatment and post-treatment results which trended towards statistical significance (p-value: 0.063).

A paired t-test was then performed to evaluate the results of the Dysphagia and Xerostomia Index Questionnaire scores. This revealed a statistically significant difference in those patients who received E-Stim therapy (p-value: 0.002). All the patients were noted to have an improvement with significantly decreased scores post-treatment.

We also performed a Spearman rank correlation coefficient analysis to determine if the amount of radiation that the patients had received made a difference in saliva production. Our results demonstrated that the dose of radiation received did not affect the results of salivation in this cohort of patients and was not a confounding factor. Due to the small number of patients that received IMRT we were unable to make any conclusions regarding the type of radiation received.

[FIGURE 2 OMITTED]

No untoward side effects/complications were noted in the patients during or after completion of treatment.

DISCUSSION

Neuromuscular stimulation of salivary gland function through the oral mucosa has been previously reported to increase the production of saliva and decrease the symptoms of xerostomia due to several causes. In a randomized, double-blind, placebo-controlled trial, Weiss et al reported some degree of response after three stimulation sessions of three minutes each in 24 patients with xerostomia related to Sjogren's disease, radiation therapy, drugs or unknown etiology. (2) They had used an intraoral device with moderate improvements in 50% and substantial improvements in 30%. Steller et al conducted a double-blinded study on 29 patients with Sjogren's. (3) They used an intra-oral E-Stim device applied to the tongue and hard palate and used expectorated samples as the collection means. A mean increase in the post-treatment saliva flow rates was reported suggesting further investigations in the use of E-Stim for xerostomia. However, some subjects had not responded at all while others responded tremendously leading to significant outliers. In 1992, Talal et al reported a statistically significant increase in salivary function of patients with Sjogren's. (4) They also noted a significant improvement in other symptoms such as dysphagia. More recently, Strietzel et al published a multicenter trial on 23 patients which evaluated the effectiveness of E-Stim on xerostomia resulting from Sjogren's, medications, or idiopathic causes. (5) The E-Stim apparatus utilized in this study was applied in an intra oral fashion. The results suggested an improvement in salivary flow rates tested by a wetness sensor for the treatment group. The intraoral devices have caused concern in patients with head and neck cancer as there is a belief that it could result in progression of precancerous lesions,6 hence, it has not gained popularity in post radiated head and neck cancer patients. Studies using the extraoral TENS unit device, as in our study, have not been performed on cancer patients who have undergone radiation therapy. The study reported by Hargitai et al had evaluated the effects of E-Stim and salivary gland flow using an extraoral TENS unit on 22 normal patents. (7) The study revealed an increase in parotid gland salivary flow in 15 of the 22 patients. Wong et al conducted a randomized trial on 37 patients with radiation-induced xerostomia using an acupuncture-like TENS (ALTENS) unit which was placed preferentially on acupuncture points according to traditional Chinese medicine principles. (8) They performed a symptom questionnaire suing the Visual Analog Scale (VAS) and measured whole saliva production (WSP) by analyzing expectorated saliva samples over a five-minute period. They reported only a trend toward statistical significance in the WSP or in the quality of life assessment based on the VAS. They did note a statistically significant difference with the improvement of taste and consistency of saliva on the VAS. Thus far, the effects of E-Stim therapy have shown promising results for the treatment of xerostomia due to various causes. However, such reports are scarce in the literature. Furthermore, the effects of noninvasive E-Stim have not been clearly defined in previously radiated patients.

Patients who have undergone radiation therapy to the head and neck region experience an array of associated morbidities which can be further compounded by the addition of chemotherapeutic/radiosensitizing agents. Varying degrees of xerostomia are apparent in these patients and pose a challenge to the physicians for implementing the adequate treatment to alleviate such symptoms. This pilot study assessed the application of E-Stim through a noninvasive percutaneous approach on patients with xerostomia who had previously received single/multimodality radiation therapy. Our results demonstrated an increase in saliva production for the treatment group as well as an improvement in the subjective perception of xerostomia. The use of dental rolls for saliva collection allowed a quantitative analysis in determining an increase in the salivary production. Although these results demonstrated a trend in increased salivary production, the small sample size may have precluded them from reaching statistical significance. Through the administration of the Xerostomia Questionnaire we were able to show a beneficial effect on patients' subjective assessment at the end of the treatment sessions. The long-term effects of E-Stim need to be further elucidated.

There is some caution advised in the use of a TENS unit. This includes refraining from use on or near the eyes, transcerebrally, on areas of decreased sensation/numb skin, on broken skin areas or wounds, on areas with previous postherpetic neuralgia. We encountered no untoward side-effects or adverse reactions during or after the treatment period.

The TENS is readily accessible through a number of different companies who now manufacture the unit after the commercial success by Medtronic. The typical cost for the patient for a TENS unit ranges from $30-$50 and the single use electrodes range from $.50-$1.00 a piece ($20 for a pack of 20-40 electrodes). Because the presence of xerostomia results in dysphagia for most patients, the treatment can be performed for the treatment of the dysphagia with the additional benefit of increasing salivary flows. We found that Medicare will provide reimbursement for the health care provider prescribing E-Stim with the TENS unit for dysphagia. Health care providers can use the current procedural terminology (CPT) code "92526," which is the speech pathology code for "swallowing dysfunction treatment." An additional code that can be used is "97533" which is for Sensory Integration Therapy, "for sensory integrative techniques to enhance sensory processing and promote adaptive responses to environmental demands, direct (one-on-one) patient contact by the provider, each 15 minutes."

The mechanism of action of the TENS unit is unclear. The direct stimulation of the parasympathetic nerves, auriculotemporal nerve, has been suggested to produce copious amounts of watery saliva at low frequencies and may be most useful clinically. (7) The electrodes are strategically placed above the submaxillary glands bilaterally to exert these effects. Furthermore, the TENS unit provides a treatment option which is extraoral and not cost prohibitive. It is an already proven treatment for dysphagia (9) and hence the added benefit of stimulating salivary glands would further allow for improvement in swallowing. This permits the concomitant use of the TENS unit while eating. These results are encouraging enough to further investigate the treatment option with a larger cohort of patients.

CONCLUSION

In conclusion, previously irradiated patients with resultant xerostomia demonstrated a good response to noninvasive percutaneous electrical stimulation. The TENS unit offers a viable treatment option for patients with xerostomia and in patients for whom other treatments may have failed. Further investigations are warranted in determining the effects of this treatment option on a larger scale and to more clearly define the long-term impact.

REFERENCES

(1.) Wijers OB, Levendag PC, Braaksma MM, et al. Patients with head and neck cancer cured by radiation therapy: a survey of the dry mouth syndrome in long-term survivors. Head Neck 2002;24:737-747.

(2.) Weiss WW Jr, Brenman HS, Katz P, et al. Use of an electronic stimulator for the treatment of dry mouth. J Oral Maxillofac Surg 1986;44:845-850.

(3.) Steller M, Chou L, Daniels TE. Electrical stimulation of salivary flow in patients with Sjogren's syndrome. J Dent Res 1988;67:1334 1337.

(4.) Talal N, Quinn JH, Daniels TE. The clinical effects of electrostimulation on salivary function of Sjogren's syndrome patients. A placebo controlled study. Rheumatol Int 1992;12:43 45.

(5.) Strietzel FP, Martin-Granizo R, Fedele S, et al. Electrostimulating device in the management of xerostomia. Oral Dis 2007;13:206 213.

(6.) Baker LL, McNeal DR, Benton LA, et al. NeuroMuscular Electrical Stimulation: A Practical Guide. 3rd edition. Downey, CA: Los Amigos Research and Education Institute, Inc; 1993.

(7.) Hargitai IA, RG Sherman, JM Strother. The effects of electrostimulation on parotid saliva flow: a pilot study. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2005; 99:316-320.

(8.) Wong RK, Jones GW, Sagar SM, et al. A Phase I-II study in the use of acupuncture-like transcutaneous nerve stimulation in the treatment of radiation-induced xerostomia in head-and-neck cancer patients treated with radical radiotherapy. Int J Radiat Oncol Biol Phys 2003;57:472-480.

(9.) Huckabee ML, Doeltgen S. Emerging modalities in dysphagia rehabilitation: neuromuscular electrical stimulation. N Z Med J 2007;120:U2744.

Kavita M. Pattani, MD; Chad M. McDuffie, MD; Matthew Morgan, MS; Cynthia Armstrong, BS; and Cherie-Ann O. Nathan, MD, FACS

Drs. Pattani, McDuffie, Nathan, and Mr. Morgan and Ms. Armstrong are with the Department of Otolaryngology Head and Neck Surgery at the Louisiana State University Health Sciences Center in Shreveport, Louisiana. They are also affiliated with the Feist-Weiller Cancer Center.
Table 1. Individual patient stage, site of primary, treatment
modality and radiation dose is portrayed.

Patient    T Stage/Site     Treatment            Total Radiation

1          T3 Oropharynx    XRT                  72 Gy
2          T2 Oropharynx    Chemo/XRT/Left ND    72 Gy
3          T2 Oral Cavity   Sx/XRT               68 Gy
4          T2 Oropharynx    Chemo/XRT/Left ND    58 Gy
5          Tx Unknown       XRT/Left ND          50 Gy

XRT=radiation; Gy=grays; Chemo=chemotherapy; ND=neck dissection;
Sx=surgery.

Table 2. Saliva measurements were initially taken prior to
treatment. Measurements were also obtained after ten treatment
sessions 1 and then again after 20 treatment sessions of
E-Stim.

Patient    Saliva                         Weight (grams)
           Pre-Treatment
                            Post Ten Treatments    Two Weeks Post 20
                                                   Treatments

1          0.1352           0.6030                 0.767
2          0.0727           0.2320                 0.283
3          0.1808           1.8580                 2.001
4          0.0019           0.066                  0.920
5          0.294            1.012                  1.935

Table 3. An xerostomia questionnaire was administered by
the speech pathologists with a score ranging from 0-4 for each
question. A higher score indicated worse xerostomia.

Patient         Questionnaire Score

           Pre-treatment    Post-treatment

1          32               22
2          25               12
3          22               17
4          19                7
5          29               16
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Author:Pattani, Kavita M.; McDuffie, Chad M.; Morgan, Matthew; Armstrong, Cynthia; Nathan, Cherie-Ann O.
Publication:The Journal of the Louisiana State Medical Society
Article Type:Report
Date:Jan 1, 2010
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