Parotid Flow Rate Research Articles

Prospective Randomized Study of Intensity-Modulated Radiotherapy on Salivary Gland Function in Early-Stage Nasopharyngeal Carcinoma Patients

This randomized trial compared the rates of delayed xerostomia between two-dimensional radiation therapy (2DRT) and intensity-modulated radiation therapy (IMRT) in the treatment of early-stage nasopharyngeal carcinoma (NPC). Between November 2001 and December 2003, 60 patients with T1-2bN0-1M0 NPC were randomly assigned to receive either IMRT or 2DRT. Primary end point was incidence of observer-rated severe xerostomia at 1 year after treatment based on Radiotherapy Oncology Group /European Organisation for the Research and Treatment of Cancer late radiation morbidity scoring criteria. Parallel assessment with patient-reported outcome, stimulated parotid flow rate (SPFR), and stimulated whole saliva flow rate (SWSFR) were also made. At 1 year after treatment, patients in IMRT arm had lower incidence of observer-rated severe xerostomia than patients in the 2DRT arm (39.3% v 82.1%; P = .001), parallel with a higher fractional SPFR (0.90 v 0.05; P < .0001), and higher fractional SWSFR (0.41 v 0.20; P = .001). As for patient's subjective feeling, although a trend of improvement in patient-reported outcome was observed after IMRT, recovery was incomplete and there was no significant difference in patient-reported outcome between the two arms. IMRT is superior to 2DRT in preserving parotid function and results in less severe delayed xerostomia in the treatment of early-stage NPC. Incomplete improvement in patient's subjective xerostomia with parotid-sparing IMRT reflects the need to enhance protection of other salivary glands.

Protection of Salivary Function by Concomitant Pilocarpine During Radiotherapy: A Double-Blind, Randomized, Placebo-Controlled Study

To investigate the effect of concomitant administration of pilocarpine during radiotherapy for head-and-neck squamous cell carcinoma (HNSCC) on postradiotherapy xerostomia. A prospective, double blind, placebo-controlled randomized trial including 170 patients with HNSCC was executed to study the protective effect of pilocarpine on radiotherapy-induced parotid gland dysfunction. The primary objective endpoint was parotid flow rate complication probability (PFCP) scored 6 weeks, 6 months, and 12 months after radiotherapy. Secondary endpoints included Late Effects of Normal Tissue/Somatic Objective Management Analytic scale (LENT SOMA) and patient-rated xerostomia scores. For all parotid glands, dose-volume histograms were assessed because the dose distribution in the parotid glands is considered the most important prognostic factor with regard to radiation-induced salivary dysfunction. Although no significant differences in PFCP were found for the two treatments arms, a significant (p = 0.03) reduced loss of parotid flow 1 year after radiotherapy was observed in those patients who received pilocarpine and a mean parotid dose above 40 Gy. The LENT SOMA and patient-rated xerostomia scores showed similar trends toward less dryness-related complaints for the pilocarpine group. Concomitant administration of pilocarpine during radiotherapy did not improve the PFCP or LENT SOMA and patient-rated xerostomia scores. In a subgroup of patients with a mean dose above 40 Gy, pilocarpine administration resulted in sparing of parotid gland function. Therefore, pilocarpine could be provided to patients in whom sufficient sparing of the parotid is not achievable.

Gland size estimation and body mass index improve salivary flow rate assessment

Although some representative studies, each with over 100 subjects, have reported no significant differences in salivary flow rates between males and females, the majority of such studies have reported that flow rates are significantly higher in males. I am not aware of any studies which have reported higher salivary flow rates in females than in males. It would seem reasonable to expect that large salivary glands would be able to produce higher flow rates than small glands. This could not be tested until a method of estimating salivary gland size was developed. The first such method was described by Ericson and Hedin who showed, in 23 cadavers, a high correlation (r = 0.95) between the parotid gland volume and the area on a lateral sialogram. For the submandibular glands, the correlation was lower (0.68). Ericson then reported, for 92 subjects, a high correlation (r = 0.93) between the logarithm of parotid salivary flow rate in response to gustatory stimulation with 10% citric acid and the logarithm of gland area on a lateral sialogram. In a similar study on submandibular glands but using 6% citric acid in 28 subjects, the correlation coefficient was 0.52. The only study not carried out by Ericson’s group in which a sialographic technique was employed confirmed, in 30 subjects, Ericson’s finding of a positive correlation between the maximum parotid salivary flow rate and the size of the gland. A major disadvantage of the sialographic technique for estimating gland volume is that it gives only a two-dimensional view of the gland. In addition, it is expensive to carry out, it exposes the subject to radiation, and it cannot be employed on all the major salivary glands.

Oral health of people with dementia

Oral health of people with dementia

Recurrent pleomorphic adenoma of the parotid gland: Long-term outcome of patients treated with radiation therapy

To evaluate the role of radiation therapy in the management of recurrent pleomorphic adenoma of the parotid gland. Between 1960 and 2004, 34 patients were treated with postoperative radiation therapy for recurrent pleomorphic adenoma of the parotid gland to a median dose of 5000 cGy (range, 4,500-6,000 cGy). Median age was 48 years (range, 24-72 years). Gross total resection at the time of surgery before radiation was achieved in 30 patients (88%), and histologic analysis demonstrated multifocal disease in 16 patients (47%). Radiation was delivered for a first, second, third, fourth, fifth, and sixth local recurrence in 24%, 21%, 24%, 24%, 6%, and 3% of patients, respectively. With a median follow-up of 17.4 years (range, 2.3-28.9 years), 2 patients had local recurrences at a median of 3.4 years after completion of radiation. The 20-year actuarial local control rate was 94%. One patient developed a second malignancy at approximately 14 years after completion of therapy. The use of postoperative radiation therapy leads to excellent long-term local control for the treatment of recurrent pleomorphic adenoma with acceptable late toxicity. Although the incidence of second malignancy was low in this population, continued follow-up is warranted.

Intensity-modulated radiotherapy significantly reduces xerostomia compared with conventional radiotherapy

Xerostomia is a severe complication after radiotherapy for oropharyngeal cancer, as the salivary glands are in close proximity with the primary tumor. Intensity-modulated radiotherapy (IMRT) offers theoretical advantages for normal tissue sparing. A Phase II study was conducted to determine the value of IMRT for salivary output preservation compared with conventional radiotherapy (CRT). A total of 56 patients with oropharyngeal cancer were prospectively evaluated. Of these, 30 patients were treated with IMRT and 26 with CRT. Stimulated parotid salivary flow was measured before, 6 weeks, and 6 months after treatment. A complication was defined as a stimulated parotid flow rate <25% of the preradiotherapy flow rate. The mean dose to the parotid glands was 48.1 Gy (SD 14 Gy) for CRT and 33.7 Gy (SD 10 Gy) for IMRT (p < 0.005). The mean parotid flow ratio 6 weeks and 6 months after treatment was respectively 41% and 64% for IMRT and respectively 11% and 18% for CRT. As a result, 6 weeks after treatment, the number of parotid flow complications was significantly lower after IMRT (55%) than after CRT (87%) (p = 0.002). The number of complications 6 months after treatment was 56% for IMRT and 81% for CRT (p = 0.04). IMRT significantly reduces the number of parotid flow complications for patients with oropharyngeal cancer.

Secretion rate and amylase concentration of whole saliva after consumption of beer

Saliva is of paramount importance for the maintenance of oral health (1). Only a few studies have investigated the acute effects of alcohol consumption on salivary function. In rats, acute administration of a high dose of ethanol caused a significant reduction in stimulated parotid secretion (2) and reduced the protein synthesis in all major salivary glands (3). Ingestion of a high dose of ethanol by humans also caused a decrease in parotid salivary flow rate (4) and stimulated whole saliva flow rate (5), with a concomitant reduction in salivary amylase activity and output (5). In this study, we investigated the possible effects of a relatively small volume of beer on salivary function. Ten healthy volunteers (seven men and three women; mean age 32.1 ± 17.9 years) participated in this study. They were instructed to abstain from alcohol at least 12 h prior to the experiment and to abstain from smoking, eating, drinking caffeine containing beverages and toothbrushing at least 1 h prior to the experiment. All experiments took place between 09:30 and 12:30 hours. In a crossover design, the volunteers consumed either 300 ml top-fermented beer (Palm Breweries, Steenhuffel, Belgium, 5.2% alcohol) within 5 min. As a control, 300 ml non-alcoholic beer was used (Amstel Malt, Zoeterwoude, The Netherlands, <0.1% alcohol). The time interval between both experimental conditions was 1 week. Immediately before the consumption of beer and 15, 30, 45, 60, 90 and 120 min later, mechanically stimulated whole saliva was collected in preweighed tubes for 5 min by parafilm-chewing (6). The salivary flow rates were determined gravimetrically. SHORT COMMUNICATION

Variability of flow rate when collecting stimulated human parotid saliva

The aim of this study was to estimate the accuracy and reproducibility of citric-acid-stimulated parotid saliva sampling. In healthy volunteers a strong correlation (r2 = 0.79) between flow rates from the left and right parotid gland was observed. In patients with Sjögren's syndrome this correlation (r2 = 0.90) was even stronger. The intraindividual variation in healthy volunteers was 23.3 +/- 5.9%. Increasing the number of collections did not reduce this variation significantly. In head and neck cancer patients, to estimate whether repeated measurements result in more reliable baseline values for use in clinical studies, repeated collections did not result in a significant reduction of intrapatient variation, similar to the results with the healthy volunteers. Thus, notwithstanding the good agreement between left and right flow rates, a high variation in parotid flow rates has to be considered when planning clinical trials evaluating the effects of treatment on salivary gland functioning.

Significant Improvement of Parotid Flow of IMRT Compared to Conventional Radiotherapy in Oropharyngeal Cancer

Significant Improvement of Parotid Flow of IMRT Compared to Conventional Radiotherapy in Oropharyngeal Cancer

Structural and functional characteristics of irradiation damage to parotid glands in the miniature pig

To evaluate the effects of a solitary megadose protocol of ionizing radiation (IR) on the structure and function of the miniature pig (minipig) parotid gland. Fourteen minipigs were subjected to either 15 or 20 Gy to one parotid gland with a linear accelerator, whereas another four minipigs served as non-IR controls. Salivary flow rates and salivary chemistries were measured pre-IR and 4 and 16 weeks post-IR. A quantitative assessment of gland weight and acinar area and detailed serum chemistry and hematologic analyses were also performed. Parotid flow rates decreased by approximately 50% either with 20 Gy at 4 weeks, or 15 Gy at 16 weeks post-IR. In the 20 Gy group, salivary flow rates were reduced by approximately 80% at 16 weeks post-IR. A significant decrease in salivary calcium and amylase and an increase of salivary potassium levels were found in both IR groups. There were also transient alterations in serum chemistry and hematology parameters post-IR. Parotid gland weights were significantly decreased (-50%) in the 15 and 20 Gy groups at 4 and 16 weeks post-IR. Additionally, the acinar cell area in glands of both IR groups was significantly reduced from that in control glands at both the 4 and 16 weeks time points. Structural changes in salivary gland parenchyma occurred relatively early after IR, whereas the alterations in salivary output were relatively delayed. Further, reductions in salivary flow were not proportional to acinar cell area loss. Together, these findings suggest that nonparenchymal IR damage likely contributes to IR-induced salivary hypofunction.

Impact of intensity-modulated radiotherapy (IMRT) on salivary gland function in early-stage nasopharyngeal carcinoma (NPC) patients: A prospective randomized study

5501 Background: Severe xerostomia regularly occurs in NPC patients treated by 2-dimensional radiotherapy (2DRT). Although IMRT reduces parotid gland irradiation in NPC, randomized data supporting its use is lacking. Methods: Patients with T1–2bN0–2M0 NPC were randomized to receive either IMRT or 2DRT, both 66Gy, without chemotherapy. Primary endpoint was RTOG xerostomia at 1 year after treatment. Secondary endpoints included RTOG xerostomia at 6 weeks post treatment, stimulated parotid flow rate (SPFR) and stimulated whole saliva flow rate (SWSFR). Post-RT saliva flow rate was expressed as percentage of residual flow rate over pre-RT baseline. Planned sample size was 27 patients in each arm, to detect a 40% reduction in incidence of severe (RTOG >=grade 2) xerostomia (assumed to occur in >=80% of 2DRT-treated patients) with 80% power for alpha=0.05. Categorical and continuous variables were analyzed with chi-square test and wilcoxon rank-sum test, respectively. Results: 60 patients were recruited, and 56 patients were eligible (28 patients in each arm). Patients in IMRT arm had significantly less severe xerostomia than 2DRT at 6 weeks (13/28 vs 24/28, p=0.0019), and a borderline difference at 6 months (21/28 vs 26/28, p=0.0689) after RT. Post-RT SPFR was significantly higher in IMRT arm at 6 weeks (39% vs 9%, p<0.0001) and at 6 months (70% vs 4%, p<0.0001). Post-RT SWSFR was similar between both arms at 6 weeks and at 6 months. Analysis of 1-year data would be performed in March. No failure or death was observed in either arm. Conclusions: IMRT is superior to 2DRT in preserving parotid function and results in less severe xerostomia as early as 6 weeks post-RT. SPFR, but not SWSFR, shows progressive recovery over time with IMRT. (This study is supported by Hong Kong Research Grant Council CUHK4041/01M) No significant financial relationships to disclose.

Long-term parotid gland function after radiotherapy

Irradiation of the parotid glands causes salivary dysfunction, resulting in reduced salivary flow. Recovery can be seen with time; however, long-term prospective data are lacking. The objective of this study was to analyze the long-term parotid gland function after irradiation for head-and-neck cancer. A total of 52 patients with head-and-neck cancer and treated with radiotherapy (RT) were prospectively evaluated. Stimulated bilateral parotid salivary flow rates were measured before RT and 6 weeks, 6 months, 12 months, and at least 3.5 years after RT completion. A complication was defined as a stimulated parotid flow rate of <25% of the pre-RT flow rate. The normal tissue complication probability model proposed by Lyman was fit to the data. Multilevel techniques were used to model the patterns of flow rates with time. The mean stimulated flow rate of the parotid glands before RT was 0.31 mL/min (standard deviation [SD], 0.21). This was reduced to 0.14 mL/min (SD, 0.15) at 6 weeks after RT and recovered to 0.20 mL/min (SD, 0.22) at 6 months and 0.19 mL/min (SD, 0.21) at 12 months after RT. The mean stimulated flow rate was 0.25 mL/min (SD, 0.28) 5 years after RT. The mean dose to the parotid gland resulting in a 50% complication probability increased from 34 Gy at 6 weeks to 40 Gy at 6 months, 42 Gy at 12 months, and 46 Gy at 5 years after RT. Multilevel modeling indicated that both dose and time were significantly associated with the flow ratio. Salivary output can still recover many years after RT. At 5 years after RT, we found an increase in the salivary flow rate of approximately 32% compared with at 12 months after RT.

Salivary changes and dental caries as potential oral markers of autoimmune salivary gland dysfunction in primary Sjogren's syndrome.

Backgroundthe classification criteria for primary Sjögren's syndrome (pSS) include a number of oral components. In this study we evaluated if salivary flow and composition as well as dental caries are oral markers of disease severity in pSS.Methodsin 20 patients fulfilling the American-European Consensus criteria for pSS and 20 age-matched healthy controls whole and parotid saliva flow rates and composition, measures of oral dryness, scores of decayed, missing and filled tooth surfaces (DMFS), periodontal indices, oral hygiene, and dietary habits were examined.Resultsin pSS, salivary flow rates, pH, and buffer capacities were lower, and DMFS, salivary sodium and chloride concentrations higher than in the healthy controls. DMFS also correlated inversely to salivary flow rates and positively to oral dryness. Apart from slightly increased gingival index, and more frequent dental visits in pSS, the periodontal condition, oral hygiene or sugar intake did not differ between these two groups. In pSS, findings were correlated to labial salivary gland focus score (FS) and presence of serum-autoantibodies to SSA/SSB (AB). The patients having both presence of AB and the highest FS (>2) also had the highest salivary sodium and chloride concentrations, the lowest salivary phosphate concentrations, lowest salivary flow rates, and highest DMFS compared to those with normal salivary concentrations of sodium and chloride at a given flow rate.Conclusionthe salivary changes observed in some pSS patients reflect impaired ductal salt reabsorption, but unaffected acinar transport mechanisms, despite low salivary secretion. Our results suggest that changes in salivary flow and composition as well as dental caries may serve as potential markers of the extent of autoimmune-mediated salivary gland dysfunction in pSS. The study also indicates that the ductal epithelium is functionally affected in some pSS patients, which calls for future pathophysiological studies on the mechanisms underlying this impaired salt reabsorption.

Oral health condition and saliva flow in southern Chinese with Sjögren’s syndrome

To investigate the oral health condition and saliva flow of southern Chinese patients with Sjögren's syndrome (SS). 51 SS patients (26 primary and 25 secondary cases) and 29 controls took part in this cross-sectional study. Stimulated whole and parotid saliva flow rates, pH, and buffer capacity, and xerostomia, oral mucosal lesions, oral hygiene status, dental and periodontal conditions, prosthetic status were assessed and compared between groups. Stimulated whole saliva (SWS) flow was reduced in primary and secondary SS cases (p<0.001), pH and buffer capacity were also reduced in the primary SS group (p<0.05). SS patients had a greater prevalence of xerostomia than controls (p<0.001). Primary SS patients had a higher mean DMFT, more missing teeth, and more prostheses than secondary SS cases and controls (p<0.05). SWS flow correlated negatively with the number of filled teeth in both SS groups (p<0.05) and the number of decayed teeth in the primary SS group (p<0.05). Despite good oral hygiene and regular dental check-ups, the oral health of southern Chinese with primary SS was significantly compromised compared with secondary SS cases and controls, most probably due to the combined effect of impaired salivary gland function and poorer saliva buffer capacity.

Salivary gland function in persons with ectodermal dysplasias

Ectodermal dysplasias (EDs) constitute a group of conditions comprising developmental defects in two or more of the following tissues: hair, teeth, nails, and sweat glands. The aim of the present study was to contribute to a better understanding of salivary gland involvement in EDs. An ED group (n = 39, median age 12 yr; 24 males, 15 females) and a healthy age- and sex-matched control group were studied. Citric acid stimulated submandibular and parotid salivary flow rates and salivary concentrations, and output of total protein, acidic proline-rich proteins and histatins were analysed. The associations between quantitative and qualitative salivary parameters were also studied. In the ED group, 13 persons (33%) demonstrated a significantly reduced secretion of submandibular and/or parotid saliva, in addition to a low unstimulated and/or chewing-stimulated whole salivary flow. In the ED group as a whole, a reduced median secretory rate of submandibular saliva was found, whereas the median concentrations of some protein parameters were increased. However, the overall output of proteins was normal or reduced. Submandibular glands seemed to be more affected than parotid glands in EDs. In conclusion, salivary secretory tests are recommended in persons with known or suspected EDs.

Influence of parotid-sparing radiotherapy on xerostomia in head and neck cancer patients

Radiotherapy (RT) for head and neck cancers causes permanent salivary gland dysfunction (SGD) and xerostomia. We have previously demonstrated the effectiveness of parotid-sparing RT on salivary function. The aim of this was to characterize the relationship between radiation dosages to parotid glands, SGD, xerostomia, and impaired quality of life (QOL). Ninety-three patients received unilateral ( n=38) and bilateral ( n=44) neck RT with parotid-sparing techniques, or standard three-field technique RT ( n=11). Unstimulated and stimulated parotid saliva was collected pre-RT and 1 year post-RT. Assessment of QOL and xerostomia was conducted with three questionnaires. The results demonstrated that reduced radiation dosages to parotid glands were strongly associated with percentage of baseline parotid flow rates measured at 1 year post-RT. Unilateral and bilateral neck RT with parotid-sparing techniques were successful in preserving salivary output, compared to standard three beam RT techniques. Lower radiation dose to contralateral parotid glands was associated with greater percentage of baseline salivary flow rates at 1 year post-RT, fewer xerostomic complaints, and an enhanced QOL.

The influence of clinical factors on human stimulated parotid flow rate in cancer and other patients.

Reduced salivary secretion can produce a wide variety of complaints, having a negative impact on the daily life of a patient. Multiple causes of salivary hypofunction are described, however, there are no consistent data about the influence of clinical parameters on parotid gland function. We studied a group of patients with head and neck malignancies before treatment with radiotherapy. We used Lashley cups to collect stimulated parotid saliva simultaneously from both parotid glands. Sizes of the parotid gland, gender, age, tobacco and alcohol consumption, and tumour characteristics were related to the function of the parotid gland. A considerable variability in parotid output was found with a range of 0.03-1.66 ml/min (mean 0.34 ml/min). None of the variables were correlated with parotid flow. These results are important, especially when evaluating effects of radiation on parotid gland function.

Qantitative dose-volume response analysis of changes in parotid gland function after radiotheraphy in the head-and-neck region

Purpose: To study the radiation tolerance of the parotid glands as a function of dose and volume irradiated.Methods and Materials: One hundred eight patients treated with primary or postoperative radiotherapy for various malignancies in the head-and-neck region were prospectively evaluated. Stimulated parotid flow rate was measured before radiotherapy and 6 weeks, 6 months, and 1 year after radiotherapy. Parotid gland dose-volume histograms were derived from CT-based treatment planning. The normal tissue complication probability model proposed by Lyman was fit to the data. A complication was defined as stimulated parotid flow rate <25% of the preradiotherapy flow rate.Results: The mean stimulated preradiotherapy flow rate of 174 parotid glands was 0.34 mL/min. The mean flow rate reduced to 0.12 mL/min 6 weeks postradiotherapy, but recovered to a mean flow rate of 0.20 mL/min at 1 year after radiotherapy. Reduction in postradiotherapy flow rate correlated significantly with mean parotid dose. No threshold dose was found. Increasing the irradiated volume of parotid glands from 0%–40% to 90–100% in patients with a mean parotid dose of 35–45 Gy resulted in a decrease in flow ratio from, respectively, approximately 100% to less than 10% 6 weeks after radiation. The flow ratio of the 90%–100% group partially recovered to 15% at 6 months and to 30% at 1 year after radiotherapy. The normal tissue complication probability model parameter TD50 (the dose to the whole organ leading to a complication probability of 50%) was found to be 31, 35, and 39 Gy at 6 weeks, 6 months, and 1 year postradiotherapy, respectively. The volume dependency parameter n was around 1, which means that the mean parotid dose correlates best with the observed complications. There was no steep dose-response curve (m = 0.45 at 1 year postradiotherapy).Conclusions: This study on dose/volume/parotid gland function relationships revealed a linear correlation between postradiotherapy flow ratio and parotid gland dose and a strong volume dependency. No threshold dose was found. Recovery of parotid gland function was shown at 6 months and 1 year after radiotherapy. In radiation planning, attempts should be made to achieve a mean parotid gland dose at least below 39 Gy (leading to a complication probability of 50%).

Early to late sparing of radiation damage to the parotid gland by adrenergic and muscarinic receptor agonists.

Damage to salivary glands after radiotherapeutic treatment of head and neck tumours can severely impair the quality of life of the patients. In the current study we have investigated the early-to-late pathogenesis of the parotid gland after radiation. Also the ability to ameliorate the damage using pretreatment with adrenergic or muscarinic receptor agonists is studied. Rats were locally irradiated with or without i.p. pretreatment with phenylephrine (α-adrenoceptor agonist, 5 mg kg−1), isoproterenol (β-adrenoceptor agonist, 5 mg kg−1), pilocarpine (4 mg kg−1), methacholine (3.75 mg kg−1) (muscarinic receptor agonists) or methacholine plus phenylephrine. Parotid salivary flow rate, amylase secretion, the number of cells and gland histology were monitored sequentially up to 240 days postirradiation. The effects were described in 4 distinct phases. The first phase (0–10 days) was characterised by a rapid decline in flow rate without changes in amylase secretion or acinar cell number. The second phase (10–60 days) consists of a decrease in amylase secretion and is paralleled by acinar cell loss. Flow rate, amylase secretion and acinar cell numbers do not change in the third phase (60–120 days). The fourth phase (120–240 days) is determined by a further deterioration of gland function but an increase in acinar cell number, albeit with poor tissue morphology. All drug pretreatments used could reduce radiation effects in phase I and II. The protective effects were lost during phase IV, with the exception of methacholine plus phenylephrine pretreatment. The latter combination of drugs ameliorated radiation-damage throughout the entire follow-up time. The data show that combined pre-irradiation stimulation of muscarinic acetylcholine receptors with methacholine plus α-adrenoceptors with phenylephrine can reduce both early and late damage, possibly involving the PLC/PIP2 second messenger pathways. This opens perspectives for the development of clinical applicable methods for long-term sparing of parotid glands subjected to radiotherapy of head and neck cancer patients. © 2001 Cancer Research Campaignhttp://www.bjcancer.com

Early to late sparing of radiation damage to the parotid gland by adrenergic and muscarinic receptor agonists

Damage to salivary glands after radiotherapeutic treatment of head and neck tumours can severely impair the quality of life of the patients. In the current study we have investigated the early-to-late pathogenesis of the parotid gland after radiation. Also the ability to ameliorate the damage using pretreatment with adrenergic or muscarinic receptor agonists is studied. Rats were locally irradiated with or without i.p. pretreatment with phenylephrine (α-adrenoceptor agonist, 5 mg kg–1), isoproterenol (β-adrenoceptor agonist, 5 mg kg–1), pilocarpine (4 mg kg–1), methacholine (3.75 mg kg–1) (muscarinic receptor agonists) or methacholine plus phenylephrine. Parotid salivary flow rate, amylase secretion, the number of cells and gland histology were monitored sequentially up to 240 days postirradiation. The effects were described in 4 distinct phases. The first phase (0–10 days) was characterised by a rapid decline in flow rate without changes in amylase secretion or acinar cell number. The second phase (10–60 days) consists of a decrease in amylase secretion and is paralleled by acinar cell loss. Flow rate, amylase secretion and acinar cell numbers do not change in the third phase (60–120 days). The fourth phase (120–240 days) is determined by a further deterioration of gland function but an increase in acinar cell number, albeit with poor tissue morphology. All drug pretreatments used could reduce radiation effects in phase I and II. The protective effects were lost during phase IV, with the exception of methacholine plus phenylephrine pretreatment. The latter combination of drugs ameliorated radiation-damage throughout the entire follow-up time. The data show that combined pre-irradiation stimulation of muscarinic acetylcholine receptors with methacholine plus α-adrenoceptors with phenylephrine can reduce both early and late damage, possibly involving the PLC/PIP2 second messenger pathways. This opens perspectives for the development of clinical applicable methods for long-term sparing of parotid glands subjected to radiotherapy of head and neck cancer patients. © 2001 Cancer Research Campaign http://www.bjcancer.com