Circadian variations in flow rate and composition of human stimulated submandibular saliva

The role of the soft palate dose regarding normal tissue toxicities in older adults with head and neck cancer undergoing definitive radiotherapy

PURPOSE

The number of older adults with head and neck squamous cell carcinoma (HNSCC) is continuously increasing. Older HNSCC patients may be more vulnerable to radiotherapy-related toxicities, so that extrapolation of available normal tissue complication probability (NTCP) models to this population may not be appropriate. Hence, we aimed to investigate the correlation between organ at risk (OAR) doses and chronic toxicities in older patients with HNSCC undergoing definitive radiotherapy.

METHODS

Patients treated with definitive radiotherapy, either alone or with concomitant systemic treatment, between 2009 and 2019 in a large tertiary cancer center were eligible for this analysis. OARs were contoured based on international consensus guidelines, and EQD2 doses using α/ß values of 3 Gy for late effects were calculated based on the radiation treatment plans. Treatment-related toxicities were graded according to Common Terminology Criteria for Adverse Events version 5.0. Logistic regression analyses were carried out, and NTCP models were developed and internally validated using the bootstrapping method.

RESULTS

A total of 180 patients with a median age of 73 years fulfilled the inclusion criteria and were analyzed. Seventy-three patients developed chronic moderate xerostomia (grade 2), 34 moderate dysgeusia (grade 2), and 59 moderate-to-severe (grade 2-3) dysphagia after definitive radiotherapy. The soft palate dose was significantly associated with all analyzed toxicities (xerostomia: OR = 1.028, dysgeusia: OR = 1.022, dysphagia: OR = 1.027) in the multivariable regression. The superior pharyngeal constrictor muscle was also significantly related to chronic dysphagia (OR = 1.030). Consecutively developed and internally validated NTCP models were predictive for the analyzed toxicities (optimism-corrected AUCs after bootstrapping: AUCxerostomia=0.64, AUCdysgeusia=0.60, AUCdysphagia=0.64).

CONCLUSIONS

Our data suggest that the dose to the soft palate is associated with chronic moderate xerostomia, moderate dysgeusia and moderate-to-severe dysphagia in older HNSCC patients undergoing definitive radiotherapy. If validated in external studies, efforts should be undertaken to reduce the soft palate dose in these patients.

Development of NTCP models for head and neck cancer patients treated with three-dimensional conformal radiotherapy for xerostomia and sticky saliva: the role of dosimetric and clinical factors

PURPOSE

The purpose of this multicentre prospective study was to investigate the significance of the radiation dose in the major and minor salivary glands, and other pre-treatment and treatment factors, with regard to the development of patient-rated xerostomia and sticky saliva among head and neck cancer (HNC) patients treated with primary (chemo-) radiotherapy ((CH)RT).

METHODS AND MATERIALS

The study population was composed of 167 consecutive HNC patients treated with three-dimensional conformal (3D-CRT) (CH) RT. The primary endpoint was moderate to severe xerostomia (XER6m) as assessed by the EORTC QLQ-H&N35 at 6 months after completing (CH)RT. The secondary endpoint was moderate to severe sticky saliva at 6 months (STIC6m). All organs at risk (OARs) potentially involved in salivary function were delineated on planning-CT, including the parotid, submandibular and sublingual glands and the minor glands in the soft palate, cheeks and lips. Patients with moderate to severe xerostomia or sticky saliva at baseline were excluded. The optimum number of variables for a multivariate logistic regression model was determined using a bootstrapping method.

RESULTS

The multivariate analysis showed the mean parotid dose, age and baseline xerostomia (none versus a bit) to be the most important predictors for XER6m. The risk of developing xerostomia increased with age and was higher when minor baseline xerostomia was present in comparison with patients without any xerostomia complaints at baseline. Model performance was good with an area under the curve (AUC) of 0.82. For STIC6m, the mean submandibular dose, age, the mean sublingual dose and baseline sticky saliva (none versus a bit) were most predictive for sticky saliva. The risk of developing STIC6m increased with age and was higher when minor baseline sticky saliva was present in comparison with patients without any sticky saliva complaints at baseline. Model performance was good with an AUC of 0.84.

CONCLUSIONS

Dose distributions in the minor salivary glands in patients receiving 3D-CRT have limited significance with regard to patient-rated symptoms related to salivary dysfunction. Besides the parotid and submandibular glands, only the sublingual glands were significantly associated with sticky saliva. In addition, reliable risk estimation also requires information from other factors such as age and baseline subjective scores. When these selected factors are included in predictive models, instead of only dose volume histogram parameters, model performance can be improved significantly.

Evidence of a generalized defect of acinar cell function in Shwachman-Diamond syndrome

BACKGROUND

: Because the acinar cells of the exocrine pancreas in patients with Shwachman-Diamond syndrome (SDS) are severely depleted, we hypothesized that a similar deficiency may be present in acinar cells of the parotid gland.

PATIENTS AND METHODS

: We determined serum pancreatic isoamylase and parotid amylase activities in 16 patients with SDS, 13 healthy controls, and 13 disease controls (cystic fibrosis or fibrosing pancreatitis). Parotid amylase and electrolyte concentrations were measured in stimulated parotid gland secretions. Starch digestion was assessed by breath hydrogen testing in patients with SDS (with and without enzyme supplements) and healthy controls.

RESULTS

: Serum pancreatic and parotid isoamylase values were lower in the patients with SDS than in the healthy controls (P < 0.0001 and P = 0.0002, respectively). Serum pancreatic isoamylase, but not parotid isoamylase, was significantly lower in the disease controls than in the healthy controls (P < 0.0001 and P = 0.17, respectively). Secreted parotid gland amylase concentration (units per milligram of protein) in patients with SDS was lower than that in the healthy controls (P = 0.04), whereas the disease controls were comparable to the healthy subjects (P = 0.09). Secreted parotid chloride concentration was inversely correlated with amylase concentration in the patients with SDS (P = 0.01), but no correlation was seen in the healthy controls or disease controls. When patients with SDS ingested starch without enzyme supplementation, their breath hydrogen excretion was significantly higher than that in the healthy controls (P = 0.009). Following starch ingestion with enzymes, breath hydrogen in the patients with SDS was lower (P < 0.05) than with no enzyme treatment, and no different from controls (P = 0.37).

CONCLUSIONS

: Mutations in the SBDS gene cause a generalized functional abnormality of exocrine acinar cells.

Influence of oral characteristics and food products on masticatory function

Mastication is a complex process that involves activities of the facial muscles, the elevator and suprahyoidal muscles, and the tongue. These activities result in patterns of rhythmic mandibular movements, food manipulation, and the crushing of food between the teeth. Saliva facilitates mastication by moistening food particles, making a bolus, and assisting swallowing, whereas food consistency modifies masticatory forces, the mandibular jaw movements, the duration of the mastication cycle, and the number of cycles preceding the first swallow. Jaw elevator EMG activity research shows a clear relation between muscular activity and food properties. The teeth, masticatory muscles, and temporomandibular joints are also important because together they form the mechanism by which the food particles are fragmented. Hard and dry foods require more chewing cycles and a longer time in the mouth until swallowing for sufficient breakdown to take place and for enough saliva to be added to form a coherent bolus safe enough for swallowing. Product characteristics, the amount of saliva, dentition, and bite force affect the chewing performance. This study presents an update and synopsis of the effects of saliva, food, dentition, muscle force, and temporomandibular disorders on the masticatory process.

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.

The influence of product and oral characteristics on swallowing

The urge to swallow food could be triggered by a threshold level in both food particle size and lubrication of the food bolus. Thus, both oral physiology and product characteristics may influence the swallowing threshold. We quantified the swallowing threshold in a group of 266 healthy adult subjects (age 42 +/- 12 years) by counting the number of chewing cycles needed to prepare food for swallowing. The influence of oral physiology on the swallowing threshold was determined by measuring salivary flow rate, maximum bite force and masticatory performance. We used about 10 cm(3) of bread, toast, melba toast, breakfast cake, peanuts and cheese to determine the influence on the swallowing threshold of various food characteristics, e.g. hardness, moisture and fat. Furthermore, we tested the effect of buttering the bread, toast, melba toast and breakfast cake on the swallowing threshold. Salivary flow rates were significantly and negatively correlated with the number of chewing cycles of melba toast and breakfast cake. Hence, subjects with more saliva needed less chewing cycles for these dry products. Maximum bite force and masticatory performance had an influence on the swallowing threshold for the hard products only (carrot and peanut). Although significant, the correlation coefficients were less than 0.28. Thus, the oral physiology parameters explained less than 10% of the variance in the swallowing threshold. We found significantly different numbers of chewing cycles for the various foods, ranging from 17 for cake to 63 for carrot. Hard and dry products needed more chewing cycles until swallowing. Buttering the food significantly reduced the number of chewing cycles needed before swallowing. This was especially true for the dry products cake, melba toast and toast. Hard and dry products require more chewing cycles and longer time in mouth until swallowing for sufficient breakdown to take place and for enough saliva to be added to form a coherent bolus safe for swallowing. In spite of this, more saliva, higher maximum bite force and better masticatory performance were only weakly correlated with a smaller number of chewing cycles. Butter enhanced lubrication and bolus formation of dry products, thus reducing the number of chewing cycles until swallowing. In conclusion, product characteristics and to a lesser extent oral physiology significantly affect swallowing threshold.

Chewing behavior and salivary secretion

We determined the salivary flow rate in 16 healthy subjects in rest and while chewing artificial and natural foods (Parafilm, Melba toast with and without margarine, and three different volumes of breakfast cake and cheese). We also determined the duration of a chewing cycle, the number of chewing cycles until swallowing, and the time until swallowing. The physical characteristics of the foods were quantified from force-deformation experiments. The flow rates of the saliva as obtained without stimulation, with Parafilm stimulation, and with chewing on the various foods were significantly correlated. An increase in chewing cycle duration, number of chewing cycles until swallowing, and time until swallowing was observed as a function of the volume of the food. More chewing cycles were required for Melba toast than for an equal volume of cake or cheese. This may be caused by the low water and fat percentage of the Melba toast. The number of chewing cycles and the time until swallowing significantly decreased when the Melba toast was buttered. The decrease may be caused by facilitation in bolus formation and lubrication of the food due to buttering the toast. The number of chewing cycles until swallowing was not correlated to the salivary flow rate.

Human salivary gland-specific daily variations in histatin concentrations determined by a novel quantitation technique

Histatins constitute a distinct family of human salivary antimicrobial peptides, of which histatins 1, 3 and 5 are the most abundant. To evaluate salivary gland-specific differences in histatin secretion, we used the recently developed histatin-zinc precipitation method to quantify histatins and to assess daily variations in secretions. Stimulated pure secretions from parotid glands (HPS) and submandibular/sublingual glands (SMSL) were collected from 10 different subjects at four different times of the day (9:35 a.m.; 12:40 p.m.; 2:50 p.m. and 5:00 p.m.). Zinc precipitation and subsequent reversed phase HPLC analysis were performed to determine concentrations of histatins 1, 3 and 5 with reference to purified histatin standards. Both HPS and SMSL secretions displayed daily variations in histatin concentrations. HPS values showed a maximum at mid-day and SMSL samples showed a maximum in the morning. Mean daily histatin concentrations were almost three fold higher in SMSL than in HPS. Mean histatin 1, 3 and 5 concentrations in HPS from 10 subjects ranged from 0.7 to 2.8, 0.6 to 4.3 and 1.0 to 4.3mg%, respectively. The corresponding means in SMSL were 2.8-12.2, 1.5-7.5 and 2.6-9.0mg%, respectively. Remarkably, although histatins constitute only 3-10% of total protein in these secretions, an almost perfect correlation between total protein and total histatin concentrations was observed for both glands. Despite a broad range in histatin concentrations between individuals, this study demonstrated a hitherto unidentified daily variation in histatin concentrations in HPS and SMSL secretions and a differential expression pattern which might have functional implications.

The influence of pilocarpine and biperiden on pH value and calcium, phosphate, and bicarbonate concentrations in saliva during and after radiotherapy for head and neck cancer

OBJECTIVE

The purpose of the present study was to investigate the influence of parasympathomimetic pilocarpine and anticholinergic biperiden on salivation, pH value, and calcium, phosphate, and bicarbonate concentrations in saliva in patients irradiated for malignant tumors of the head and neck region.

STUDY DESIGN

Sixty-nine patients were randomly assigned into 3 groups. Group A consisted of patients receiving pilocarpine, group B of those who were receiving biperiden during radiotherapy and pilocarpine for 6 weeks after its completion, and group C comprised patients receiving neither of the mentioned drugs. The quantity of secreted unstimulated saliva, its pH value, as well as calcium, phosphate, and bicarbonate concentrations in saliva were measured before the beginning of radiotherapy, after 30 Gy of irradiation, at completed irradiation, and 3, 6, and 12 months after completion of radiotherapy.

RESULTS

Saliva secretion was found to be the least affected in the group of patients receiving biperiden throughout the course of radiotherapy. One year after completion of therapy, the quantity of secreted saliva could only be measured in the patients receiving biperiden during radiotherapy; it amounted to 16% of the average initial quantity of saliva secreted before the beginning of irradiation. In all 3 groups of patients, mean pH value decreased during radiotherapy and started to increase again after completion of irradiation. In group B the decrease in pH value after radiotherapy was statistically significantly smaller than that in group C (P =.01). During and after irradiation, calcium concentration was increased in all 3 groups of patients. Phosphate concentration decreased during radiotherapy in all 3 groups. In group B it started to increase again 3 months after completion of radiotherapy. Bicarbonate concentration showed a slight increase during radiotherapy and started to decrease again after completion of irradiation.

CONCLUSION

The results of our study indicate that the inhibition of saliva secretion during radiotherapy and its stimulation after completion of treatment can contribute not only to some preservation of the quantity of saliva but also to at least partial preservation of its quality in terms of pH value and calcium, phosphate, and bicarbonate concentrations.

Determination of variation of stimulated salivary flow rates

Salivary hypofunction is associated with oral and pharyngeal disorders and requires early diagnosis and intervention. Large variability in salivary flow rates within and between individuals has been reported, which has impaired the establishment of standard values. The objective of this study was to determine variations in stimulated parotid and submandibular flow rates over 6 hours and to define salivary hypofunction. Pooled mean, standard deviation, and coefficient of variation values for four collection time periods were obtained from 36 healthy males and females (18 young, ages 20-38; 18 older, ages 60-77). The results demonstrated 27-44% variation in salivary flow rates over time. Overall, there were no significant age or gender differences in variability between and within salivary flow rates at all collection time periods. The results suggest that a 45% range in salivary flow rates could be considered normal salivary variation, and values below 45% of normal levels could be used to define salivary hypofunction.

Effects of two types of clothing on the day-night variation of core temperature and salivary immunoglobulin A

Circadian variations in core temperature, skin temperatures, heart rate, and salivary immunoglobulin A (IgA) were compared in subjects wearing two different types of clothing that covered, or left uncovered, their extremities. The experiments were carried out on six female subjects at an ambient temperature of 24 +/- 0.5 degrees C and relative humidity of 50 +/- 5%. One type of clothing consisted of long-sleeved shirts, full-length trousers, and socks (Type L: 1042 g, 1.048 clo); the other was half-sleeved shirts and knee-length trousers (Type H: 747 g, 0.744 clo). The main results were as follows: (i) The level of rectal temperature during night sleep was significantly lower with Type H than Type L clothing, and cosinor analysis indicated a significantly higher circadian amplitude with Type H clothing. (ii) Skin temperatures in the lower extremities increased significantly more on retiring to sleep with Type H than Type L clothing. (iii) Heart rate was significantly lower with Type H than Type L clothing during the sleep period. (iv) The day-night variation of salivary IgA showed a pattern that was the inverse of that of rectal temperature (i.e., low in the daytime and high in the nighttime), and the concentration of salivary IgA was significantly higher with Type H than Type L clothing at 02:30. (v) Subjectively, the self-assessed sleep quality was better with Type H clothing. These results suggest that clothing that leaves the extremities uncovered might be regarded as favorable at the moderate temperature since it induces good sleep and activates the immune response.

Xerostomia: the missing diagnosis?

Xerostomia is a distressing condition which may be associated with a number of specific diseases, iatrogenically induced following the administration of drugs or radiotherapy, or the result of inflammatory processes affecting salivary gland tissue. In this article epidemiological background is briefly reviewed and aetiological conditions associated with xerostomic states are summarized. The oral sequelae of xerostomia are discussed and approaches to diagnosis demonstrated. Treatment of xerostomia is basically supportive and the main elements are presented.

The secretory characteristics of epidermal growth factor in human saliva

A series of unstimulated and stimulated saliva samples from healthy volunteers was tested for EGF by radioimmunoassay. Salivary EGF, like other salivary constituents, was secreted in a diurnal pattern. On stimulation the rate of EGF secretion doubled but the concentration fell by 70% because of dilution by salivary fluid. EGF secretion was positively related to saliva flow (p = 0.00001) but the coefficient of correlation was low (r = 0.47). Over a period of 30 min continual salivary stimulation, EGF was released in a bimodal pattern with peaks occurring at 3 and 12 min. Subsequently, EGF secretion remained stable at a rate of release that was approx. 80% of the initial peak value (7.4 ng/min). Chromatography indicated that both high and low molecular-weight forms of EGF were present in unstimulated and stimulated saliva and that the low-weight form predominated. However, the proportion of high molecular-weight EGF increased from 18 to 38% of the total on short-term (3 min) stimulation.

Hyposalivatory drug use, whole stimulated salivary flow, and mouth dryness in older, long-term care residents

Drug-induced hyposalivation has only been anecdotally related to various subjective and objective oral problems. The study described here of 157 residents of a long-term care facility reports data on whole masticatory-stimulated salivary flow rates, use of medications, and perceptions of symptoms associated with hyposalivation, including mouth and eye dryness, tooth sensitivity, chewing satisfaction, and taste and smell acuity. One hundred and twelve residents (71%) were taking one or more drugs that induced hyposalivation. Salivary flow rates were lower in persons who were taking such drugs, and lowest in persons who were taking such drugs for a protracted period. Flow was also lower in females than males, and lower in persons institutionalized for long periods than in persons institutionalized for short periods. Persons who were taking drugs that induce hyposalivation were institutionalized longer, used more medications, had more health problems, were dissatisfied with chewing, and had fewer teeth than persons who were not taking such drugs. Persons who reported having mouth dryness also reported eye dryness and were dissatisfied with their chewing ability. Perceived mouth dryness was not related to salivary flow.

Evaluation of submandibular salivary flow rate in different age groups

The production of unstimulated and citrate-stimulated submandibular saliva was examined in 90 male and female adults, aged 26-93 years. None was taking prescription medications for treatment of systemic disease. There was no diminution in submandibular gland fluid output, at rest or during stimulation, with increasing age. Similar findings, previously reported for the parotid glands, were also confirmed. These results demonstrate that major gland fluid secretion capacity is maintained in healthy older individuals.

Temporal variations of glandular kallikrein, protein and amylase in mixed human saliva

Variations in the level of glandular kallikrein in human saliva may reflect physiological changes. Diurnal or circadian variations of many salivary components are important in relating changes in such components to oral or systemic conditions especially as most clinical studies are conducted between 0800 and 1700 h. Whole saliva was collected from 14 healthy young subjects at 0800, 1100, 1400 and 1700 h on two Fridays. Samples were centrifuged at 10,000 g for 10 min at 4 degrees C and the supernatant fractions stored at -20 degrees C. The enzymic activity of kallikrein was measured with D-valylleucylarginine-p-nitro-anilide as substrate. The activity of alpha-amylase and the total protein concentration (biuret) were also determined. Results were analysed in a repeated-measures design: there were no significant differences in kallikrein levels either within days or across days. There were significant differences for total protein and alpha-amylase levels within days but, in general, not across days. Minimal individual levels for protein and alpha-amylase were mostly at 0800 h; maxima were generally at 1400 or 1700 h. Kallikrein levels had no marked pattern of maximal or minimal distribution.

Age-dependent decreases in human submandibular gland flow rates as measured under resting and post-stimulation conditions

Submandibular saliva samples were obtained with a new collection device, under resting and post-stimulation conditions, from 28 healthy individuals between 70 and 91 years of age, and from 30 healthy individuals between 18 and 39 years of age. The salivary flow rates were significantly decreased in the aged group compared with the control group. The mean resting and post-stimulation flow rates for the aged group averaged 22% and 39%, respectively, of control values.

Changes in the electrophoretic pattern of salivary peroxidase at the middle of the menstrual cycle

Salivary peroxidase activity is known to increase at the middle of the menstrual cycle, and we report changes in electrophoretic patterns of salivary peroxidase over the same period. Peroxidase during the early follicular and late luteal phases of the menstrual cycle has been resolved into three forms by polyacrylamide gel electrophoresis. An additional, low mobility peroxidase has been detected at midcycle when two electrophoretic forms occurring at other times are reduced; this is coincident with the peak in total peroxidase activity. Available evidence suggests that this ovulatory peroxidase represents a catalytically active aggregate of the peroxidases normally present in saliva.

The flow-rate-dependent excretion of ionized calcium in pilocarpine-stimulated human submandibular saliva

In 10 healthy male subjects the total calcium concentration in submandibular saliva varied between 2.05 +/- 0.12 mmol/l and 2.48 +/- 0.1 mmol/min, and did not show a dependency on the flow rate. The salivary-ionized calcium increased significantly at flow rates between 0.1 and 1.3 ml/min (from 0.74 +/- 0.05 to 1.41 +/- 0.04 mmol/l) and even reached plasma levels.