Irradiation-induced atherosclerosis: a factor in therapeutic planning.

Early primary head and neck cancers (stages I and II) and occult metastatic neck disease have caused debate regarding the choice between surgery and irradiation. The arguments for each are reviewed with a new consideration: the acceleration and/or induction of carotid atherosclerosis in irradiated patients. We present clinical case reports (n = 9), a retrospective clinical evaluation for the occurrence of carotid atherosclerosis in irradiated head and neck cancer patients (n = 57) and a comparison study of the extent and distribution of atherosclerosis in irradiated (n = 29) and nonirradiated head and neck cancer patients controlled for age, blood pressure, and tobacco use. The results show that carotid atherosclerosis is found in a wider anatomic distribution and to a greater extent in irradiated than in nonirradiated patients. We conclude that carotid atherosclerosis is induced and/or accelerated by neck irradiation. The implications as they relate to choice of treatment, to pretreatment evaluations, and to long-term follow-up are discussed.     

A prospective study of the effects of irradiation on the carotid artery

OBJECTIVES/HYPOTHESIS: To prospectively assess the effects of irradiation on the carotid artery in patients with head and neck cancer, as a possibly relevant factor in cancer treatment planning. STUDY DESIGN: Prospective study from a tertiary care academic setting on university (22 patients) and Veterans Affairs (14 patients) hospital patients; 1-year follow-up, including comparison of study data with age-matched and sex-matched control subjects from epidemiological studies. METHODS: Thirty-six patients with head and neck cancer who underwent therapeutic neck irradiation were examined by high-resolution ultrasound before and 1 year after treatment. Twelve patients were also studied at 2 years. Measurements included the intima-media thickness (IMT) of the carotid artery wall, the degree of stenosis as estimated from velocity measurements, and the presence and size of plaque. RESULTS: The pretreatment carotid IMT at baseline was 0.68 mm and was comparable to age-matched and sex-matched control subjects. Significant increase in the IMT was observed on both the left (0.67 vs. 0.84 mm) and the right (0.7 vs. 0.87 mm) sides (P < .001) 1 year after irradiation. In 12 patients who completed 24 months of follow-up the carotid IMT continued to significantly increase statistically compared with that at the first year after treatment (left side, 0.79 vs. 0.85 mm, P = .037; right side, 0.79 vs. 0.95 mm, P = .014). Statistically significant thickening of the carotid wall developed in all 36 patients by 1 year. Two patients experienced post-treatment neurological events and an area of stenosis greater than 75%. CONCLUSIONS: Neck irradiation significantly increases the thickness of the carotid wall during the first year after treatment--on average, 21 times more than in epidemiologically matched control volunteers. This phenomenon should be taken into consideration when planning treatment for the node-negative (NO) neck.     

Nuclear magnetic resonance spectroscopy of plasma for the detection of head and neck cancer

The plasma of 15 normal volunteers, four patients with benign head and neck disease, and 12 patients with biopsy proven head and neck malignancies were evaluated using water-suppressed nuclear magnetic resonance (NMR) spectroscopy. While the mean full width at half height (HHLW) of the NMR spectra showed a significant difference between groups (P less than .05), the predictive value of a positive test was only 57% the sensitivity was only 33%, and individual values in all groups demonstrated considerable overlap. The mean HHLW of the control group was 38.5 Hz +/- 3.5 compared with 35.2 Hz +/- 4.7 for the cancer group and 35.0 Hz +/- 10 for the benign disease group. This method was not able to distinguish patients with malignancy from those with benign disease or controls. Its use as a specific screening method for head and neck malignancy cannot be recommended.     

The role of image-guidance systems for head and neck surgery.

BACKGROUND: Although image-guidance systems have gained widespread acceptance for neurosurgical procedures, their role for extracranial surgery of the head and neck is yet to be defined. OBJECTIVES: To describe the authors' experience with image-guidance systems and to measure the effects of image-guided technology on the performance of minimally invasive otolaryngological procedures. DESIGN: Prospective cohort study. METHODS: Optical- and electromagnetic-based image-guidance systems were used during the performance of endoscopic surgery on patients with disease of the paranasal sinuses, orbit, skull base, and temporal bone (n = 79). Results were compared with those in control patients who underwent similar surgery without image guidance during the same period (n = 42). RESULTS: Intraoperative anatomical localization was accurate to within 2 mm at the start of surgery in all cases. Accuracy degraded by 0.89 +/- 0.20 mm (mean +/- SE) during the operative procedure. The use of an image-guidance system increased operating room time by a mean of 17.4 minutes per case (image-guidance group, 137.3 +/- 6.0 minutes [mean +/- SE]; control group, 119.9 +/- 5.7 minutes; P=.006) and increased hospital charges by approximately $496 per case. Intraoperative blood loss (image-guidance group, 178.4 +/- 18.0 mL [mean +/- SE]; control group, 149.4 +/- 20.1 mL) and complication rates (image-guidance group, 2.7%; control group, 4.7%) did not differ significantly between groups. CONCLUSIONS: Image-guidance systems can provide the head and neck surgeon with accurate information regarding anatomical localization in cases with poor surgical landmarks caused by extensive disease or prior surgery; however, the use of such systems is associated with increased operative time and expense.     

Microsurgical free flap reconstruction outcomes in head and neck cancer patients after surgical extirpation and intraoperative brachytherapy

OBJECTIVES: The management of recurrent or persistent head and neck cancer poses a challenging problem. Salvage surgery for these individuals consists of ablative surgery, interstitial brachytherapy, and microsurgical free flap reconstruction. This study reviews complications after such reconstruction. METHODS: We reviewed 139 consecutive head and neck cancer patients undergoing free flap reconstruction from January 1994 to May 2002. These included 66 patients with recurrent head and neck cancer undergoing intraoperative brachytherapy (IOBT) and free flap reconstruction and 73 undergoing free flap reconstructions only. A total of 142 reconstructions were performed, with three patients in IOBT group receiving two free flap reconstructions per patient, giving us a total of 69 reconstructions in the IOBT group versus 73 in the non-IOBT group. Nine patients were excluded from the IOBT group because of nonsynchronous use of brachytherapy and reconstruction, and 10 patients were excluded from the other group because they had prior radiotherapy or surgical treatment, leaving us with a total of 123 reconstructions, 60 in the IOBT group and 63 in the non-IOBT group. The IOBT group patients received iodine Vicryl seed implants, palladium seed implants, or both, to deliver an average dose of 79.3 +/- 31.8 Gy (mean +/- 1SD) to the surgical bed. RESULTS: All patients were followed for evidence of local wound complications. The IOBT group showed multiple complications in 23 (38.33%) of 60 reconstructions, the most common being wound dehiscence in 11. This, when compared with the non-IOBT group complications (15.87%), was found to be statistically significant (chi test, P <.01). CONCLUSION: IOBT increases the rate of complications in patients undergoing microvascular free tissue transfer. This, however, should not deter or alter the aggressiveness of cancer therapy used for managing recurrent head and neck cancer.     

Natural killer cell response to regional lymph node metastases

A determination of natural killer cell activity was performed in 67 individuals with advanced head and neck cancer. The mean activity of 28 patients clinically staged T3 NO or T4 NO was 81 +/- 11 lytic units (LU), significantly higher than 39 patients with palpable lymph node metastases (54 +/- 5 LU). Assessing patients by extent of nodal disease revealed that activity actually increased, though not significantly, with progressive N-staging. A major determinate of increased natural killer cell cytotoxicity in patients with lymph node metastases was extranodal cancer within the neck. The mean activity of nine patients whose tumor was fixed to underlying structures or adherent to skin was 87 +/- 15 LU, significantly higher than the 45 +/- 4 LU mean value of the remaining patients with clinically determined regional nodal disease. The potential clinical implications of these findings are discussed.     

Outcome of carotid artery resection for neoplastic disease: a meta-analysis.

PURPOSE: To determine the neurologic morbidity and oncologic effectiveness of carotid resection in patients with advanced squamous cell carcinoma of the head and neck. METHODS: A retrospective review of all published cases of squamous cell carcinoma of the head and neck treated by carotid resection was performed. RESULTS: A major neurologic complication occurred in 17% of patients. Neurologic morbidity was not associated with the method of carotid artery reconstruction. Two-year disease-free survival was 22%. The majority of recurrences were local or regional. Comparison of survival of this group to a similarly staged control group demonstrated no significant difference in survival. CONCLUSION: This review of the literature suggests that elective carotid resection achieves significant local/regional control of disease and that carotid artery involvement is not a poor prognostic factor in patients with advanced head and neck cancer.     

Head and neck cancer in cardiothoracic transplant recipients

INTRODUCTION: There is an increased incidence of cancer in patients after organ transplantation. We reviewed a large series of cardiothoracic transplant recipients to determine the incidence and natural history of head and neck malignancy. METHODS: A total of 1069 heart (n = 855), heart/lung (n = 111), and lung (n = 103) transplants were performed at Stanford University from January 1968 to February 1998. Demographic data, risk factors, and disease course were evaluated in patients who developed cancer. The mean length of follow-up was 8.9+/-5.2 years. RESULTS: One hundred twenty patients (11.2%) developed 547 non-lymphomatous malignancies. The mean number of malignancies per cancer patient was 4.6. The average time from transplantation to development of cancer was 63.1 months. A total of 50.5% of malignancies presented in the head and neck; 96.4% of these were cutaneous in origin and 3.6% were noncutaneous. Of cutaneous malignancies, 79.3% were squamous cell carcinoma and 15.9% were basal cell carcinoma Cutaneous malignancies most commonly presented on the scalp, cheek, lip, and neck. Noncutaneous malignancies involved the oral cavity (5), thyroid (4), and parotid (1). Thirteen percent of cutaneous head and neck cancers behaved aggressively, requiring extensive management including radical surgery, radiation, and/or chemotherapy. A total of 34.2% of cancer patients developed metastases and 54.9% of cancer patients died as a direct result of cancer. A total of 68% of cancer patients were smokers and 23.8% had significant alcohol use. CONCLUSION: Transplant recipients have an increased incidence of cancer presenting in the head and neck. Malignancies in transplant patients behave more aggressively than in the general population. Recognition of this aggressive biological behavior and heightened cancer surveillance should result in improved outcomes.     

Diagnosis of cervical lymph node metastases in head and neck cancer with ultrasonic measurement of lymph node volume

ObjectiveThe purpose of this study was to evaluate the usefulness of ultrasound (US) volume measurement of the cervical lymph nodes for diagnosing nodal metastasis in patients with head and neck cancer using a node-by-node comparison.MethodsThirty-four consecutive patients with head and neck cancer from one tertiary university hospital were prospectively enrolled from 2012 to 2017. Patients with histologically proven squamous cell primary tumors in the head and neck region scheduled to undergo a therapeutic neck dissection were eligible. For each patient, 1–4 target lymph nodes were selected from the planned neck dissection levels. Lymph nodes with thickness >20 mm or in a cluster were excluded. Node-by-node comparisons between the pre-operative US assessment, the post-operative actual measurements and histopathological results were performed for all target lymph nodes. Quantitative measurements, such as three diameters, ratios of the three diameters and volume were analyzed in this study. Lymph node volume was calculated using the ellipsoid formula.ResultsPatients comprised 28 men and 6 women with a mean age of 60.0 years (range, 29–80 years) at the time of surgery. In total, 67 target lymph nodes were analyzed in this study and the thickness ranged from 3.9 to 20.0 mm (mean 8.0 mm). There was a strong correlation between the US volume and post-operative actual volume (ρ = 0.87, p < 0.01). The US volume measured 2156 ± 2156 mm³ for the tumor positive nodes, which was significantly greater than the US volume of 512 ± 315 mm³ for tumor negative nodes (p < 0.01). Significant differences between tumor positive and tumor negative nodes were found in five variables (volume, thickness, major axis, minor axis and ratio of minor axis to thickness) for total lymph nodes. To identify predictors of lymph node metastasis, ROC curves of the US variables of target lymph nodes were compared, of which 4 variables were considered acceptable for predicting the lymph node metastasis: volume (AUC 0.86), thickness (AUC 0.86), major axis (AUC 0.79), and minor axis (AUC 0.79) for total lymph nodes. The optimal cut-off level for US volume in total lymph nodes was found to be 1242 mm³, whereby a 62% sensitivity and 98% specificity was reached (likelihood ratio: 25.2).ConclusionPre-operative ultrasonic volume measurement of the cervical lymph nodes was useful for early detection of cervical nodal metastasis in head and neck cancer.     

正常血压OSAS患者血清胎球蛋白A、颈动脉硬化指数和动脉内膜中层厚度的相关性分析

目的 探讨血压正常阻塞性睡眠呼吸暂停综合征(OSAS)患者血清胎球蛋白A、颈动脉硬化指数及动脉内膜中层厚度的关系。方法 选取血压正常OSAS患者64例作为病例组,健康体检人员30例作为对照组。检测并比较两组患者血清胎球蛋白A、颈动脉硬化指数(CSI)及动脉内膜中层厚度(cIMT)的差异。睡眠监测仪检测患者睡眠呼吸暂停低通气指数(AHI),分析病例组患者AHI与颈动脉硬化指数及动脉内膜中层厚度的相关性,分析胎球蛋白A与颈动脉硬化指数及动脉内膜中层厚度的相关性。结果 病例组患者颈动脉硬化指数及动脉内膜中层厚度显著高于对照组,而血清胎球蛋白A显著低于对照组(P＜0.05)。病例组AHI评分显著高于对照组;病例组最低血氧饱和度仅为(68.42±11.65)%,显著低于对照组的(92.55±4.64)%(P＜0.05)。经Pearson相关分析,病例组患者AHI与cIMT及CSI之间均存在正相关(r=0.421, r=0.502; P＜0.05),胎球蛋白A与cIMT及CSI之间均存在负相关(r=-0.515, r=-0.404; P＜0.05)。结论 低血清胎球蛋白A水平与正常血压OSAS患者亚临床颈动脉硬化显著相关。     

Dynamic contrast-enhanced magnetic resonance imaging in radiotherapeutic efficacy in the head and neck tumors

PURPOSE: The purpose to this study is to identify correlations between pathology and dynamic contrast-enhanced magnetic resonance imaging (MRI) and to assess the utility of this technique in the evaluation of radiation response for head and neck cancer. MATERIALS AND METHODS: MRI was prospectively performed after radiotherapy in 27 patients with various head and neck tumors. After bolus injection of contrast material, a dynamic study was performed using a spoiled gradient-recalled imaging sequence. The maximum slope of increase (MSI) on the time-intensity curve was displayed as a color-coded image. The ratio of MSI (MSIR) was obtained for tumor and normal muscles. Pathological specimens were obtained after MRI in all cases. Histological grading of irradiation changes was classified into 5 grades (0-4). Correlations between MSIR and histological grade were examined. RESULTS: Histologically, 18 tumors were classified as grade 2 (presence of viable tumor cells), 4 were grade 3 (nonviable tumor cells), and 5 were grade 4 (no tumor cells). Although the mean +/- SD of MSIR in patients with histological grade 2 or 3 was 7.4 +/- 7.9, MSIR in patients with grade 4 was 1.8 +/- 0.73, representing a significant difference ( P < .05). Every patient with grade 4 displayed an MSIR of 2.5 or less, although 5 of 22 patients with grade 2 or 3 had an MSIR of 2.5 or less. CONCLUSIONS: MSI quantitatively reflects response to radiotherapy for head and neck cancer. Color-coded MSI display is feasible for depicting permeability changes after radiotherapy.     

Clinical evaluation of a commercially available oral moisturizer in relieving signs and symptoms of xerostomia in postirradiation head and neck cancer patients and patients with Sjögren's syndrome

A major complication of irradiation therapy for head and neck cancer is salivary gland dysfunction and xerostomia. The purpose of this clinical investigation was to evaluate the effects of a commercially available oral moisturizer (Optimoist) on salivary flow rate, symptoms of xerostomia, oral pH, oral microflora, and swallowing in postirradiation head and neck cancer patients (XRT) and patients with Sj?gren's syndrome (SS). Subjects who were post-XRT and subjects with SS (n = 24; mean age = 54.1) discontinued their use of any salivary substitute or moisturizer for 2 weeks prior to entering the study. Baseline whole unstimulated saliva was collected for 5 minutes using a standard sialometric technique. Candida albicans and Lactobacillus cultures were performed using kits from Orion Diagnostica, Inc., and a pH analysis was performed on the salivary sample using a Markson (model 00663) pH meter. Swallowing was assessed by clinical measures by videofluoroscopic techniques. Several subjective assessments were performed to evaluate symptoms of xerostomia. Subjects were instructed in the use of a daily diary and to use only the provided article ad libitum for a period of 2 weeks. After the 2-week period, the results indicated significant subjective and objective improvements in signs and symptoms of xerostomia. Whole unstimulated salivary flow rate improved from (mean +/- SEM) 0.1150 +/- 0.02 to 0.2373 +/- 0.09 mL/min. Salivary pH did not change. Global subjective improvement in xerostomia improved in 58% of the subjects. Candida colonization decreased in 43% of the subjects. There was no change in Lactobacilli colonization. Swallowing objectively improved in 75% of subjects. These results indicate significant improvement in both signs of hyposalivation and symptoms of xerostomia with the use of Optimoist in postirradiation head and neck cancer patients and patients with SS.     

Carotid artery resection for head and neck cancer.

Occasionally, the head and neck surgeon encounters a patient whose malignancy involves the carotid artery. In these patients, curative or palliative surgery may require excision of the common or the internal carotid artery. However, the high complication and death rates dissuade many surgeons from undertaking carotid artery resection. This study reviews the outcomes in 20 patients treated between 1979 and 1985 at the Department of Otolaryngology-Head and Neck Surgery, The University of Iowa Hospitals and Clinics, with resection of the carotid artery for head and neck cancer. The carotid artery was electively resected in 16 patients, while 4 patients underwent emergent carotid artery ligation. In the group of patients studied the stroke rate was 25%, the death rate 20%, and the combined stroke and death rate 30%. Of the patients who survived the procedure, all but 1 died of complications caused by tumor recurrence. These results are discussed, and compared with results from other studies.     

Reliability of frozen section in determining tumor thickness intraoperatively in laryngeal cancer

OBJECTIVES: The relationship between locoregional lymph metastasis and tumor thickness in head and neck cancer has been well documented in recent years. Determining tumor thickness by frozen section may help the surgeon decide intraoperatively whether to perform elective neck dissection, whereas paraffin section results could be obtained at a later time for this decision. The aim of this study was to evaluate the accuracy of tumor thickness measurements obtained by macroscopic measurement and by frozen section intraoperatively in laryngeal cancer. STUDY DESIGN: Prospectively we compared the tumor thickness results obtained by gross visual examination, by frozen section, and by paraffin section in 20 total, near-total, and horizontal supraglottic laryngectomy specimens. METHODS: The sections were stained with hematoxylin and eosin and tumor thickness was measured under a light microscope with an ocular micrometer. RESULTS: A strong correlation was found between frozen section and paraffin section tumor thickness measurements (Pearson correlation coefficient = 0.993, P <.001). Paired t test showed a 4.59 mm mean difference between macroscopic and paraffin section measurements, and a 0.76 mm mean difference between frozen and paraffin section measurements. CONCLUSION: Assessment of tumor thickness in laryngeal cancer intraoperatively by frozen section is a reliable method.     

MRI-derived tumor thickness: an important predictor of outcome for T4a-staged tongue carcinoma

The objectives of this paper are to evaluate the heterogeneity of magnetic resonance imaging (MRI)-derived tumor thickness within tumors of the same T4a-staged tongue carcinoma and to elucidate the effects of tumor thickness on treatment outcomes. A sequential and prospectively maintained head and neck cancer database was retrospectively searched for newly diagnosed tongue carcinoma treated with surgery between 2003 and 2006. Fifty-eight patients with newly diagnosed T4a-staged tongue carcinoma were included in this study. Tumor thickness was obtained from preoperative magnetic resonance imaging. The mean MRI-derived tumor thickness was 22.29 mm. The patients with long tumor thickness (>26 mm) were associated with a significantly poor disease-specific survival (P = 0.015). The 2-year disease-specific survival rates were 72% in patients with short tumor thickness and only 27% in patients with long tumor thickness within the same T4a-staged disease. A substantial variation in MRI-derived tumor thickness was present within the same T4a-staged tongue carcinoma, and tumor thickness represented an important prognostic factor.     

Carotid rupture and tissue coverage

Carotid rupture following the treatment of head and neck malignancy is the most dreaded complication faced by the head and neck surgeon. Tissue coverage of the carotid artery has been advocated as the method of protection likely to prevent carotid rupture. A retrospective study was carried out to assess the benefit of carotid coverage and whether such protection plays a role in decreasing mortality and morbidity. A brief history of carotid protection is presented. A series of 194 head and neck cancer patients who underwent resection of their mucosal primary in continuity with radical neck dissection over a ten-year period was reviewed. No coverage was used in 120 cases, while 72 cases received carotid coverage. There was a 13% fistula rate and a 15% rate of wound complication without fistula. Six patients without recurrence who had carotid rupture or ligation for imminent rupture were identified. This group was scrutinized with regard to several parameters. Three received tissue coverage of the carotid system, while the other three were left unprotected. There was a 50% mortality rate and 25% rate of neurologic sequelae amongst the survivors. This review tends not to support the premise that tissue coverage is a major factor in the prevention of carotid rupture.     

Driving performance in patients with cancer in the head and neck region: a pilot study

OBJECTIVE: To investigate actual driving performance in a group of patients with cancer in the head and neck region. DESIGN: A nonrandomized controlled trial. PARTICIPANTS: Ten patients with cancer in the head and neck region participated in a driving evaluation using a virtual reality driving simulator. Driving performance from the simulator and observer ratings on participants' driving behaviors were compared between a group of patients with cancer in the head and neck region and a group of 50 community control subjects. MAIN OUTCOME MEASURES: Average speed, mean brake reaction time, steering variability, the total number of (fatal and nonfatal) collisions during the 12-minute evaluation course on the driving simulator, and the score of the 18-item Simulator Driving Performance Scale. RESULTS: Using Mann-Whitney U tests, the brake reaction time and the steering variability in the cancer group were significantly longer and larger, respectively, than those in the control group (P = .04) and (P = .02). However, no significant differences were found between the 2 groups in the mean rank scores for average speed, total number of collisions, and Simulator Driving Performance Scale (P >.05 for all). CONCLUSIONS: This pilot study provides preliminary evidence indicating inferior driving performance in a group of patients with cancer in the head and neck region when compared with a community control group. Further study is needed to investigate factors attributing to the difference.     

Use of preoperative erythropoietin in head and neck surgery

OBJECTIVE: To determine whether preoperative erythropoietin can raise the hemoglobin levels of head and neck cancer patients prior to major ablative surgery. STUDY DESIGN: Prospective, consecutive series. METHODS: Ten patients who were to undergo major head and neck surgery were scheduled to receive subcutaneous doses of erythropoietin (600 IU/kg) on days 21, 14, 7, and 1 prior to surgery. Serial hemoglobin levels and reticulocyte counts were obtained throughout the course of treatment. RESULTS: Eight patients experienced a significant increase in hemoglobin. There were two nonresponders. The mean preoperative hemoglobin level for all 10 patients increased 12.6 g/L, from 135.5 +/- 16.2 g/L (baseline) to 148.1 +/- 23.7 g/L (1 day preoperatively, p < .0001). CONCLUSIONS: Erythropoietin significantly increases hemoglobin levels in patients awaiting major head and neck oncologic surgery. It can be viewed as an important adjunct to other well-established blood conservation techniques aimed at reducing perioperative transfusion rates.     

Swallowing and tongue function following treatment for oral and oropharyngeal cancer.

This study examined tongue function and its relation to swallowing in 13 subjects with oral or oropharyngeal cancer treated with primary radiotherapy +/- chemotherapy and 13 age- and sex-matched control subjects. Measures of swallowing and tongue function were obtained using videofluoroscopy, pretreatment and 2 months posttreatment. Maximum isometric strength and endurance at 50% of maximum strength were obtained with the Iowa Oral Performance Instrument (IOPI). Control subjects were tested once. All subjects with head and neck cancer were evaluated pretreatment and 2 months posttreatment. No significant differences were found for the tongue function measures pre- and 2 months posttreatment in the group with head and neck cancer. Significantly higher tongue strength was observed in the control than in the group with head and neck cancer both pre- and posttreatment. No significant differences were found for the 2 groups for tongue endurance measures. Significant correlations of tongue strength and endurance and some swallow measures were found pre- and posttreatment for the group with head and neck cancer and for the control group. These correlations included oral and pharyngeal temporal swallow measures and oropharyngeal swallow efficiency. Pretreatment differences between the 2 groups in tongue strength were likely related to tumor bulk, pain, and soreness. Two-month posttreatment differences were likely related to radiation +/- chemotherapy changes to the oral and pharyngeal mucosa. This study provides support for the hypothesis that tongue strength plays a role in oropharyngeal swallowing, particularly related to the oral phase of the swallow.     

Estimating DNA repair by sequential evaluation of head and neck tumor radiation sensitivity using the comet assay

BACKGROUND: The alkaline comet assay is a microelectrophoretic technique for detecting single-strand DNA breaks, and may be used as an indirect measure of hypoxia by determining the radiation sensitivity of individual cells. OBJECTIVE: To assess the ability of the comet assay to estimate the rate of DNA repair after irradiation in patients with head and neck cancer. METHODS: The comet assay was used to evaluate DNA damage in fine-needle aspirates of lymph nodes containing metastatic squamous cell carcinoma in patients with head and neck cancer 1, 2, and 3 minutes after treatment with 500 rad (5 Gy) of irradiation. The amount of DNA damage (measured as the "tail moment" of the comet) is proportional to the number of DNA single-strand breaks after irradiation, which in turn depends on the oxygen concentration in each cell. RESULTS: The mean +/- SD of the median tail moment of the 1-minute postirradiation comets was 29.4 +/- 14.2 (n = 27). After 2 minutes, the mean median tail moment decreased to 25.4 +/- 13.6 (n = 25), representing a mean decrease of 11.9% in those patients with both 1- and 2-minute comet assays. Assuming a linear rate of repair, this decrease in DNA damage corresponds to a repair half-life of 4.2 minutes. A 3-minute assay was also performed on samples from a smaller number of patients (n = 9), with a mean value not significantly different from that of the 2-minute assay of the samples from this group. CONCLUSIONS: The comet assay is a promising tool for evaluating radiation sensitivity in individual cells. The rate of DNA repair early after irradiation is consistent with data in the literature.