Late effects of radiation therapy in the head and neck region

Pilot study of subcutaneous amifostine in patients undergoing postoperative intensity modulated radiation therapy for head and neck cancer: preliminary data

The major salivary glands produce about 90% of salivary secretions; the minor salivary glands produce the remainder. Standard conventional radiation therapy for advanced oropharyngeal tumors typically involves administering high radiation dose to the major salivary glands bilaterally. In most cases, this causes a marked reduction in oral saliva output. Xerostomia is the most prevalent late side effect of radiation for head and neck malignancies and is cited by patients as the major cause of decreased quality of life. The degree of xerostomia has been reported to depend on the radiation dose and salivary gland volume irradiated. Several studies show dose volume response relationships in the salivary glands, suggesting the possibility of significant improvement in saliva production post radiation as well as quality of life if radiation techniques can spare the salivary glands. In recent years, conformal radiation techniques have evolved, which may allow radiation of tumor targets in the head and neck area while sparing substantial portions of salivary glands. It has been shown that in using these techniques, adequate irradiation of the targets while sparing major salivary glands is feasible. Early clinical experience showed substantial sparing of salivary flow following radiation and suggested an improvement of tumor control and of xerostomia over that achieved with standard radiation techniques. We hypothesize that the addition of a radioprotector may further improve salivary function over that obtained with intensity modulated radiation therapy alone. To test this hypothesis, we initiated a pilot clinical trial whose principal objective is to compare measurements of unstimulated and stimulated salivary flow rates 6 months after intensity modulated radiation therapy plus amifostine (Ethyol; MedImmune, Inc, Gaithersburg, MD) (study patients) with those obtained in historical controls treated with intensity modulated radiation therapy alone.

Effects of radiation on normal tissue: consequences and mechanisms

The use of radiation therapy to treat cancer inevitably involves exposure of normal tissues. As a result, patients may experience symptoms associated with damage to normal tissue during the course of therapy for a few weeks after therapy or months or years later. Symptoms may be due to cell death or wound healing initiated within irradiated tissue, and may be precipitated by exposure to further injury or trauma. Many factors contribute to risk and severity of normal tissue reactions; these factors are site specific and vary with time after treatment. Treatments that reduce the risk or severity of damage to normal tissue or that facilitate the healing of radiation injury are being developed. These could greatly improve the quality of life of patients treated for cancer.

Prevention and treatment of the consequences of head and neck radiotherapy

The location of the primary tumor or lymph node metastases dictates the inclusion of the oral cavity, salivary glands, and jaws in the radiation treatment portals for patients who have head and neck cancer. The clinical sequelae of the radiation treatment include mucositis, hyposalivation, loss of taste, osteoradionecrosis, radiation caries, and trismus. These sequelae may be dose-limiting and have a tremendous effect on the patient's quality of life. Most treatment protocols to prevent these sequelae are still based on clinical experience, but alternatives based on fundamental basic and clinical research are becoming more and more available. Many of these alternatives either need further study before they can be incorporated into the protocols commonly used to prevent and treat the radiation-related oral sequelae or await implementation of these protocols. In this review, the various possibilities for prevention and/or treatment of radiation-induced changes in healthy oral tissues and their consequences are discussed.

Oral sequelae of head and neck radiotherapy

In addition to anti-tumor effects, ionizing radiation causes damage in normal tissues located in the radiation portals. Oral complications of radiotherapy in the head and neck region are the result of the deleterious effects of radiation on, e.g., salivary glands, oral mucosa, bone, dentition, masticatory musculature, and temporomandibular joints. The clinical consequences of radiotherapy include mucositis, hyposalivation, taste loss, osteoradionecrosis, radiation caries, and trismus. Mucositis and taste loss are reversible consequences that usually subside early post-irradiation, while hyposalivation is normally irreversible. Furthermore, the risk of developing radiation caries and osteoradionecrosis is a life-long threat. All these consequences form a heavy burden for the patients and have a tremendous impact on their quality of life during and after radiotherapy. In this review, the radiation-induced changes in healthy oral tissues and the resulting clinical consequences are discussed.

Dosimetric predictors of xerostomia for head-and-neck cancer patients treated with the smart (simultaneous modulated accelerated radiation therapy) boost technique

PURPOSE

To evaluate the predictors of xerostomia in the treatment of head-and-neck cancers treated with intensity-modulated radiation therapy (IMRT), using the simultaneous modulated accelerated radiation therapy (SMART) boost technique. Dosimetric parameters of the parotid glands are correlated to subjective salivary gland function.

MATERIALS AND METHODS

Between January 1996 and June 2000, 30 patients with at least 6 months follow-up were evaluated for subjective xerostomia after being treated definitively for head-and-neck cancer with the SMART boost technique. Threshold limits for the ipsilateral and contralateral parotid glands were 35 Gy and 25 Gy, respectively. Dosimetric parameters to the parotid glands were evaluated. The median follow-up time was 38.5 months (mean 39.9 months). The results of the dosimetric parameters and questionnaire were statistically correlated.

RESULTS

Xerostomia was assessed with a 10-question subjective salivary gland function questionnaire. The salivary gland function questionnaire (questions 1, 2, 3, 4, 6, and 9) correlated significantly with the dosimetric parameters (mean and maximum doses and volume and percent above tolerance) of the parotid glands. These questions related to overall comfort, eating, and abnormal taste. Questions related to thirst, difficulty with speech or sleep, and the need to carry water daily did not correlate statistically with the dosimetric parameters of the parotid glands.

CONCLUSIONS

Questions regarding overall comfort, eating, and abnormal taste correlated significantly with the dosimetric parameters of the parotid glands. Questions related to thirst, difficulty with speech or sleep, and the need to carry water daily did not correlate statistically with the dosimetric parameters of the parotid glands. Dosimetric sparing of the parotid glands improved subjective xerostomia. IMRT in the treatment of head-and-neck cancer can be exploited to preserve the parotid glands and decrease xerostomia. This is feasible even with an accelerated treatment regimen like the SMART boost. More patients need to be evaluated using IMRT to identify relevant dosimetric parameters.

Xerostomia: etiology, recognition and treatment

BACKGROUND

Clinicians may encounter symptoms of xerostomia, commonly called "dry mouth," among patients who take medications, have certain connective tissue or immunological disorders or have been treated with radiation therapy. When xerostomia is the result of a reduction in salivary flow, significant oral complications can occur.

TYPES OF STUDIES REVIEWED

The authors conducted an Index Medicus--generated review of clinical and scientific reports of xerostomia in the dental and medical literature during the past 20 years. The literature pertaining to xerostomia represented the disciplines of oral medicine, pathology, pharmacology, epidemiology, gerodontology, dental oncology, immunology and rheumatology. Additional topics included the physiology of salivary function and the management of xerostomia and its complications.

RESULTS

Xerostomia often develops when the amount of saliva that bathes the oral mucous membranes is reduced. However, symptoms may occur without a measurable reduction in salivary gland output. The most frequently reported cause of xerostomia is the use of xerostomic medications. A number of commonly prescribed drugs with a variety of pharmacological activities have been found to produce xerostomia as a side effect. Additionally, xerostomia often is associated with Sjögren's syndrome, a condition that involves dry mouth and dry eyes and that may be accompanied by rheumatoid arthritis or a related connective tissue disease. Xerostomia also is a frequent complication of radiation therapy.

CONCLUSIONS AND CLINICAL IMPLICATIONS

Xerostomia is an uncomfortable condition and a common oral complaint for which patients may seek relief from dental practitioners. Complications of xerostomia include dental caries, candidiasis or difficulty with the use of dentures. The clinician needs to identify the possible cause(s) and provide the patient with appropriate treatment. Remedies for xerostomia usually are palliative but may offer some protection from the condition's more significant complications.

Complications of radiation therapy for head and neck cancers. The patient's perspective

Newer treatments for head and neck cancers, including altered fractionation and the use of concomitant radiotherapy and chemotherapy, may provide better local-regional tumor control rates; however, patients may experience more frequent and more severe acute toxicities that result in considerable suffering. Through this study, we sought a better understanding of patients' experiences when undergoing radiotherapy. Personal interviews were conducted with 33 individuals who had received radiotherapy for head and neck cancers. These individuals described their treatment experiences and identified the most troublesome and debilitating side effects of radiotherapy. Overall, lethargy and weakness, dry mouth, mouth sores and pain, taste changes, and sore throat were the most frequently reported troublesome or debilitating side effects. The single most debilitating side effect was oropharyngeal mucositis that was characterized by patients as sore throat, and mouth sores and pain; both negatively affected the patient's ability to eat and drink, causing many patients to experience significant weight loss. Trends toward more aggressive management of head and neck cancers underscore the need for new and effective therapies for oropharyngeal mucositis occurring in patients receiving radiotherapy.

Evaluation and management of oropharyngeal Dysphagia in head and neck cancer

BACKGROUND

Dysphagia is a common symptom of head and neck cancer or sequelae of its management. Swallowing disorders related to head and neck cancer are often predictable, depending on the structures or treatment modality involved. Dysphagia can profoundly affect posttreatment recovery as it may contribute to aspiration pneumonia, dehydration, malnutrition, poor wound healing, and reduced tolerance to medical treatments.

METHODS

The author reviewed the normal anatomy and physiology of swallowing and contrasted it with the commonly identified swallowing deficits related to head and neck cancer management. Evaluation methods and treatment strategies that can be used to successfully manage the physical and psychosocial effects of dysphagia are also reviewed.

RESULTS

Evaluation of dysphagia by the speech pathologist can be achieved with instrumental and noninstrumental methods. Once accurate identification of the deficits is completed, a range of treatment strategies can be applied that may return patients to safe oral intake, improve nutritional status, and enhance quality of life.

CONCLUSIONS

To improve safety of oral intake, normalize nutritional status, reduce complications of cancer treatment and enhance quality of life, accurate identification of swallowing disorders and efficient management of dysphagia symptoms must be achieved in an interdisciplinary team environment.

Pilot study of impedance-controlled microcurrent therapy for managing radiation-induced fibrosis in head-and-neck cancer patients

PURPOSE

To evaluate the effectiveness of impedance-controlled microcurrent therapy for managing treatment sequelae in head-and-neck cancer patients.

METHODS AND MATERIALS

Between January 1998 and June 1999, 26 patients who were experiencing late effects of radiotherapy were treated b.i.d. with impedance-controlled microcurrent therapy for 1 week. Objective range-of-motion measurements were made for cervical rotation, extension/flexion, and lateral flexion before therapy, at the end of each treatment day, and monthly for 3 months. In addition, each patient's subjective complaints were tabulated before treatment and reevaluated at the last follow-up visit. No additional physical therapy or electrical stimulation was permitted during the follow-up period.

RESULTS

At the end of the course of microcurrent therapy, 92% of the 26 patients exhibited improved cervical rotation, 85% had improved cervical extension/flexion, and 81% had improved cervical lateral flexion. Twenty-two patients returned for the 3-month follow-up visit. Of these, 91% had maintained a cervical rotation range of motion greater than their pretherapy measurements. Eighty-two percent maintained improved cervical extension/flexion and 77% maintained improved lateral flexion. When the range-of-motion measurements were stratified by pretreatment severity (severe, moderate, mild, or asymptomatic), the degree of improvement directly correlated with the severity. Thus, patients who had more severe initial symptoms experienced a higher percentage of improvement than did those with milder symptoms. For these patients, the cervical rotation range of motion changed from a baseline of 59 degrees +/- 12 degrees to 83 degrees +/- 14 degrees at 3 months; flexion/extension improved from 47 degrees +/- 10 degrees to 73 degrees +/- 13 degrees; and lateral flexion went from 31 degrees +/- 7 degrees to 48 degrees +/- 9 degrees. Some patients also reported symptom improvement for tongue mobility, facial asymmetry, xerostomia, cervical/facial muscle spasms, trismus, and soft tissue tenderness. No adverse effects were observed.

CONCLUSION

Impedance-controlled microcurrent therapy shows promise for remediation of range-of-motion limitations arising as late effects of radiotherapy for head-and-neck cancer. Additional studies are needed to validate these preliminary results and to optimize the microcurrent treatment protocol, particularly with respect to treatment schedules and combining microcurrent therapy with physical and/or drug therapy.

Patients with head and neck cancer cured by radiation therapy: a survey of the dry mouth syndrome in long-term survivors

BACKGROUND

Xerostomia can have a significant impact on the quality of life of patients treated by radiation therapy (RT) for cancer in the head and neck. The first aim of the study was to evaluate the degree of xerostomia in 39 long-term survivors treated between 1965-1995 by conventional two-dimensional radiation therapy and currently without evidence of disease. The second aim was to develop a concise instrument to evaluate the subjective aspects of xerostomia.

METHODS

A newly developed questionnaire and a visual analog scale (VAS) were used in analyzing the degree of dry mouth and xerostomia-related problems. The radiation dose received by the major salivary glands was estimated by analyzing two-dimensional simulation films.

RESULTS

Sixty-four percent of the patients experienced a moderate to severe degree of xerostomia. In the multivariate analysis, three questions regarding dry mouth, eating, and speech were particularly discriminatory for establishing the degree of xerostomia as expressed by the VAS score.

CONCLUSIONS

In this survey, 64% of the long-term survivors, after treatment by conventional two-dimensional radiation therapy for a malignancy in the head and neck region, still experienced a moderate to severe degree of permanent xerostomia. A simplified instrument to evaluate xerostomia subjectively can consist of the VAS score and three graded questions.

Comparison of radiosensitivity of rat parotid and submandibular glands after different radiation schedules

BACKGROUND AND PURPOSE

To investigate the radiosensitivity of rat parotid and submandibular gland functioning after local single dose, conventional fractionated and accelerated fractionated irradiation.

METHODS

The salivary glands of male albino Wistar rats were locally irradiated with a single dose (15 Gy) or a calculated (alpha/beta; 9.6) biological effective dose of fractionated irradiation equal to this, viz. conventional fractionation (32 Gy in 16 fractions of 2 Gy/day, five times/week) or accelerated fractionation (32 Gy in 16 fractions of 2 Gy, two fractions/day). Parotid and submandibular/sublingual saliva samples were collected by means of miniaturized Lashley cups before and up to 240 days after irradiation. Salivary flow rate, lag phase and amylase secretion were used as parameters for the assessment of salivary gland function. At the end of the experiments the animals were sacrificed and the glands processed for histopathological examination.

RESULTS

Up to 120 days after irradiation no differences were observed between the glands or between the different irradiation schedules. Beyond 120 days, however, the parotid gland performed better in flow rate and lag phase after fractionated irradiation, when compared to the submandibular gland. The observed differences in function corresponded with the observed late histopathological changes. The parotid gland contained more acinar cells and had a higher gland weight. No differences were observed between both fractionation schedules on each gland.

CONCLUSIONS

The main observation from this study is the higher radiosensitivity of the submandibular gland compared to the parotid gland for late effects after fractionated irradiation. This may have implications for the treatment planning in case of radiotherapy for head and neck cancer.

Objective assessment of swallowing dysfunction and aspiration after radiation concurrent with chemotherapy for head-and-neck cancer

PURPOSE

To objectively assess swallowing function after an intensive chemoradiation regimen for locally advanced head-and-neck cancer and to assess the clinical implications of swallowing dysfunction.

PATIENTS AND METHODS

Twenty-nine patients with nonresectable Stage IV head-and-neck cancer participated in a Phase I study of radiation, 70 Gy/7 weeks, concurrent with weekly gemcitabine. Because of a high rate of mucosal toxicity, reduced drug doses were delivered to subsequent patient groups: 300, 150, 50, and 10 mg/m(2)/week. Twenty-six of these patients underwent prospective evaluation of swallowing function with videofluoroscopy and esophagogram. Studies were performed pretherapy, early post-therapy (1-3 months), and late post-therapy (6-12 months).

RESULTS

Complete tests were performed pretherapy in 22 patients, early post-therapy in 20, and late post-therapy in 13. Twenty-five patients had at least one post-therapy study. Post-therapy dysfunction was characterized by reduced inversion of the epiglottis, delayed swallow initiation and uncoordinated timing of the propulsion of the bolus, opening of the cricopharyngeal muscle, and closure of the larynx, all of which promoted aspiration during and after the swallow. In addition, reduced base-of-tongue retraction with reduced contact to the posterior pharyngeal wall and incomplete cricopharyngeal relaxation resulted in pooling in the pyriform sinuses and vallecula of residue, which was frequently aspirated after the swallow. Post-therapy aspirations were typically "silent," eliciting no cough reflex, or the cough was delayed and noneffective in expelling the residue. Aspiration was observed in 3 patients (14%) in the pretherapy studies, in 13 (65%) in the early post-therapy studies, and in 8 (62%) in the late post-therapy studies (aspiration rates post-therapy vs. pretherapy: p = 0.0002). Six patients had pneumonia requiring hospitalization 1-14 months after therapy (median: 2.5 months), being the likely cause of death in 2 patients. Five cases of pneumonia occurred among 17 patients who had demonstrated aspiration in the post-therapy studies, compared with no cases of pneumonia among 8 patients who had not demonstrated aspiration (p = 0.1). Of the 4 patients who had not undergone any post-therapy study, 1 developed pneumonia. Mucositis scores, prolonged tube feeding, presence of tracheostomy tube, and gemcitabine doses were not found to be related to aspiration or pneumonia risk.

CONCLUSIONS

After intensive chemoradiotherapy, significant objective swallowing dysfunction is prevalent. It promotes aspiration, which may not elicit a cough reflex and may be associated with pneumonia. Aspiration pneumonia may be an underdocumented complication of chemoradiotherapy for head-and-neck cancer. Future studies should examine whether routine post-therapy videofluoroscopy and training aspirating patients in safe swallowing strategies can reduce this risk.

The enigmatic mechanism of irradiation-induced damage to the major salivary glands

Irradiation is a central treatment modality administered for head and neck malignancies. Its major and most devastating side-effect is an induced damage to the major salivary glands. This article aims at suggesting a comprehensive explanation for the underlying mechanism of this damage, which has been considered as enigmatic throughout the 90 years since it was first described in 1911. The mechanism suggested is based on the considerable literature concerning this enigma in rat salivary glands. According to this proposed mechanism, the irradiation results in a sublethal DNA damage, which manifests and becomes lethal at a delayed phase. Thus, when the acinar progenitor cells are going through a reproductive phase when parenchymal replenishment is required, they die. The injurious agents, which result in this delayed reproductive cell death, appear to be highly redox-active transition metal ions, such as iron and copper. These metal ions, which seem to be associated with secretion granules, are not necessarily contained within the granules as previously suggested, but rather are probably located at sites more proximal to the DNA.

Intensity-modulated radiotherapy in the treatment of nasopharyngeal carcinoma: an update of the UCSF experience

PURPOSE

To update our experience with intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma (NPC).

METHODS AND MATERIALS

Between April 1995 and October 2000, 67 patients underwent IMRT for NPC at the University of California-San Francisco (UCSF). There were 20 females and 47 males, with a mean age of 49 (range 17-82). The disease was Stage I in 8 (12%), Stage II in 12 (18%), Stage III in 22 (33%), and Stage IV in 25 (37%). IMRT was delivered using three different techniques: 1) manually cut partial transmission blocks, 2) computer-controlled auto-sequencing segmental multileaf collimator (SMLC), and 3) sequential tomotherapy using a dynamic multivane intensity modulating collimator (MIMiC). Fifty patients received concomitant cisplatinum and adjuvant cisplatinum and 5-FU chemotherapy according to the Intergroup 0099 trial. Twenty-six patients had fractionated high-dose-rate intracavitary brachytherapy boost and 1 patient had gamma knife radiosurgery boost after external beam radiotherapy. The prescribed dose was 65-70 Gy to the gross tumor volume (GTV) and positive neck nodes, 60 Gy to the clinical target volume (CTV), 50-60 Gy to the clinically negative neck, and 5-7 Gy in 2 fractions for the intracavitary brachytherapy boost. Acute and late normal tissue effects were graded according to the Radiation Therapy Oncology Group (RTOG) radiation morbidity scoring criteria. The local progression-free, local-regional progression-free, distant metastasis-free rates, and the overall survival were calculated using the Kaplan-Meier method.

RESULTS

With a median follow-up of 31 months (range 7 to 72 months), there has been one local recurrence at the primary site. One patient failed in the neck. Seventeen patients developed distant metastases; 5 of these patients have died. The 4-year estimates of local progression-free, local-regional progression-free, and distant metastases-free rates were 97%, 98%, and 66% respectively. The 4-year estimate of overall survival was 88%. The worst acute toxicity documented was as follows: Grade 1 or 2 in 51 patients, Grade 3 in 15 patients, and Grade 4 in 1 patient. The worst late toxicity was Grade 1 in 20 patients, Grade 2 in 15 patients, Grade 3 in 7 patients, and Grade 4 in 1 patient. At 3 months after IMRT, 64% of the patients had Grade 2, 28% had Grade 1, and 8% had Grade 0 xerostomia. Xerostomia decreased with time. At 24 months, only one of the 41 evaluable patients had Grade 2, 32% had Grade 1, and 66% had Grade 0 or no xerostomia. Analysis of the dose-volume histograms (DVHs) showed that the average maximum, mean, and minimum dose delivered were 79.3 Gy, 74.5 Gy, and 49.4 Gy to the GTV, and 78.9 Gy, 68.7 Gy, and 36.8 Gy to the CTV. An average of only 3% of the GTV and 3% of the CTV received less than 95% of the prescribed dose.

CONCLUSION

Excellent local-regional control for NPC was achieved with IMRT. IMRT provided excellent tumor target coverage and allowed the delivery of a high dose to the target with significant sparing of the salivary glands and other nearby critical normal tissues.

The role of intensity-modulated radiotherapy in the treatment of parotid tumors

PURPOSE

To compare intensity-modulated radiotherapy (IMRT) treatment plans with three-dimensional conformal radiotherapy (3D-CRT) plans to investigate the suitability of IMRT for the treatment of tumors of the parotid gland.

METHODS AND MATERIALS

One 3D-CRT treatment plan and 10 IMRT treatment plans with differing beam arrangements were produced for each of nine patient data sets. The plans were compared using regret analysis, dose conformity, dose to organs at risk, and uncomplicated tumor control probability (UTCP).

RESULTS

The target dose was comparable in the 3D-CRT and IMRT plans, although improvements were seen when seven and nine IMRT fields were used. IMRT reduced the mean dose to the contralateral parotid gland and the maximum doses to the brain and the spinal cord, but increased the ipsilateral lens dose in some cases. Each IMRT arrangement produced a higher UTCP than the 3D-CRT plans; the largest absolute difference was 9.6%.

CONCLUSIONS

IMRT is a suitable means for treating cancer of the parotid, and a five-field class solution is proposed. It produced substantial sparing of organs at risk and higher UTCPs than 3D-CRT and should enable dose escalation.

Modifying normal tissue damage postirradiation. Report of a workshop sponsored by the Radiation Research Program, National Cancer Institute, Bethesda, Maryland, September 6-8, 2000

Late effects that develop in normal tissues adjacent to the tumor site in the months to years after radiotherapy can reduce the quality of life of cancer survivors. They can be dose-limiting and debilitating or life-threatening. There is now evidence that some late effects may be preventable or partially reversible. A workshop, "Modifying Normal Tissue Damage Postirradiation", was sponsored by the Radiation Research Program of the National Cancer Institute to identify the current status of and research needs and opportunities in this area. Mechanistic, genetic and physiological studies of the development of late effects are needed and will provide a rational basis for development of treatments. Interdisciplinary teams will be needed to carry out this research, including pathologists, physiologists, geneticists, molecular biologists, experts in functional imaging, wound healing, burn injury, molecular biology, and medical oncology, in addition to radiation biologists, physicists and oncologists. The participants emphasized the need for developing and choosing appropriate models, and for radiation dose-response studies to determine whether interventions remain effective at the radiation doses used clinically. Both preclinical and clinical studies require long-term follow-up, and easier-to-use, more objective clinical scoring systems must be developed and standardized. New developments in biomedical imaging should provide useful tools in all these endeavors. The ultimate goals are to improve the quality of life and efficacy of treatment for cancer patients treated with radiotherapy.

Protection of salivary function by intensity-modulated radiation therapy in patients with head and neck cancer

The degree of xerostomia has been reported to depend on the radiation dose and the salivary gland volume irradiated. Sparing salivary function can be achieved by reducing radiation dose to the salivary glands or using a radiation protector, such as amifostine (Ethyol). In this report, the author reviews clinical experiences in intensity-modulated radiation therapy (IMRT) for head and neck cancer. In experiences, the dosimetric advantage of IMRT did translate into significant reduction of late salivary toxicity in patients with oropharyngeal carcinoma. The author has found no adverse impact on tumor control and disease-free survival in patients treated with IMRT. Further, when studying the dose response of parotid gland after irradiation, it was found that the stimulated saliva flow 6 months after IMRT treatment reduced at approximately 4% per Gy exponentially of the mean parotid dose. The authors also review existing clinical data on the combination of amifostine and radiation and the potential therapeutic gain in combining IMRT with amifostine.

Parotid and submandibular/sublingual salivary flow during high dose radiotherapy

It was studied whether differences in acute radiosensitivity exist between parotid and submandibular/sublingual glands. The results revealed that salivary flow rates decreased dramatically during the first 2 weeks of radiotherapy. Neither recovery nor significant differences were observed between the production of saliva from the parotid and submandibular/sublingual glands during the 13 weeks observation period.

F-18-fluoro-deoxy-glucose positron-emission tomography scanning in detection of local recurrence after radiotherapy for laryngeal/ pharyngeal cancer

BACKGROUND

The objective of this investigation was to determine whether F18-fluoro-deoxy-glucose (FDG) positron-emission tomography (PET) could differentiate between local recurrence and late radiation effects after radiotherapy for laryngeal/pharyngeal cancer.

METHODS

In a prospective study of 75 patients (67 larynx, eight oro/hypopharynx), 160 laryngoscopies and 109 FDG PET scans were performed on the head and neck region. The mean follow-up time after the first FDG PET scan was 23 months (minimum 1 year).

RESULTS

Local recurrence was diagnosed in 37 patients: 19 after the first biopsy and 18 after follow-up biopsies. For all of the negative initial FDG scans (27), the biopsies that were taken at the same time were negative and no recurrence was seen for at least 1 year. The first FDG scan was a true positive in 34 of 48 patients. In 12 of the 14 patients with false-positive results, FDG scans were repeated; a decreased FDG uptake was found in 9 of the 12. The sensitivity and specificity of the first scan were respectively 92% and 63%; including subsequent FDG scans, the rates were 97% and 82%, respectively.

CONCLUSIONS

When a local recurrence is suspected after radiotherapy for cancer of the larynx/pharynx, an FDG PET scan should be the first diagnostic step. No biopsy is needed if the scan is negative. If the scan is positive and the biopsy negative, a decreased FDG uptake measured in a follow-up scan indicates that a local recurrence is unlikely.

Extended-term effects of head and neck irradiation in a rodent

Radiotherapy to the head and neck is a common treatment for malignancies of the region. Unfortunately, exposure to irradiation often results in a variety of complications, most of which are localised and expressed in the short term following irradiation. However, prolonged and systemic effects may have greater clinical importance as the survival rate of head and neck irradiated patients is increasing yearly. Six groups of 18-20 rats were evaluated during a 1 year study. The non-irradiated control group was compared with 2.5 Gy, 5, 7.5, 10 and 15 Gy irradiated groups. We found a dose-dependent reduction in both survival and body weight in our rat models following a delayed, prolonged and chronic process. Dying animals were emaciated, dehydrated and starved, and many were blind and immunocompromised. While the exact underlying mechanism of this delayed, but devastating, phenomenon has not yet been determined, the delayed xerostomia inflicted on these animals may, at least partially, explain it. The clinical implications for head and neck patients require further evaluation, but our data should be considered, in the context of the available evidence for the long-term effects of head and neck irradiation in humans.

The effects of benzoate and fluoride on dental caries in intact and desalivated rats

The decline in prevalence of dental caries in some segments of the population has been attributed mainly to extensive exposure to fluoride. Over the past decades, the use of fluoridated products has increased. During the same period, the consumption of food preservatives such as benzoates and sorbates has also increased substantially. Benzoates, in vitro, possess antibacterial properties similar to those of fluoride and in combination with fluoride could affect caries development. In the present study we explored the effects of sodium benzoate and fluoride in combination and alone on dental caries in our animal model. The results showed a combination of benzoate and fluoride reduced caries activity more effectively in rodents fed a cariogenic diet ad libitum than fluoride alone (p = 0.038).

Role of areca nut in betel quid-associated chemical carcinogenesis: current awareness and future perspectives

Betel quid (BQ)-chewing is a popular oral habit with potential links to the occurrence of oral cancer. Many of the literature-based studies reveal that areca nut (AN) extract may demonstrate mutagenic and genotoxic effects, in addition to inducing preneoplastic as well as neoplastic lesions in experimental animals. Areca nut should, thus, be highly suspected as a human carcinogen. Toxicity studies relating to AN-contained polyphenols and tannins are not conclusive, with both carcinogenic and anti-carcinogenic effects being reported. The mutagenicity and genotoxicity of areca alkaloids has been detected by many short-term assays. However, their genotoxicity to oral fibroblasts and keratinocytes, the target cells of BQ, has not been identified. It would thus appear that AN toxicity is not completely due to its polyphenol, tannin and alkaloid content. The single agent which is responsible for AN carcinogenicity awaits further clarification. Reactive oxygen species produced during auto-oxidation of AN polyphenols in the BQ-chewer's saliva, are crucial in the initiation and promotion of oral cancer. Nitrosation of areca alkaloids also produces AN-specific nitrosamines, that have been demonstrated to be mutagenic, genotoxic and are capable of inducing tumors in experimental animals. Arecaidine and AN extract are further suggested to be tumor promoters. Antioxidants such as glutathione and N-acetyl-L-cysteine can potentially prevent such AN-elicited cytotoxicity. Further studies are needed to delineate the metabolism of AN ingredient and their roles in the multi-step chemical carcinogenesis, in order to enhance the success of the future chemoprevention of oral cancer and oral submucous fibrosis.

Mucositis reduction by selective elimination of oral flora in irradiated cancers of the head and neck: a placebo-controlled double-blind randomized study

PURPOSE

The aim of the study was to test the hypothesis that aerobic Gram-negative bacteria (AGNB) play a crucial role in the pathogenesis of radiation-induced mucositis; consequently, selective elimination of these bacteria from the oral flora should result in a reduction of the mucositis.

METHODS AND MATERIALS

Head-and-neck cancer patients, when scheduled for treatment by external beam radiation therapy (EBRT), were randomized for prophylactic treatment with an oral paste containing either a placebo or a combination of the antibiotics polymyxin E, tobramycin, and amphotericin B (PTA group). Weekly, the objective and subjective mucositis scores and microbiologic counts of the oral flora were noted. The primary study endpoint was the mucositis grade after 3 weeks of EBRT.

RESULTS

Seventy-seven patients were evaluable. No statistically significant difference for the objective and subjective mucositis scores was observed between the two study arms (p = 0.33). The percentage of patients with positive cultures of AGNB was significantly reduced in the PTA group (p = 0.01). However, complete eradication of AGNB was not achieved.

CONCLUSIONS

Selective elimination of AGNB of the oral flora did not result in a reduction of radiation-induced mucositis and therefore does not support the hypothesis that these bacteria play a crucial role in the pathogenesis of mucositis.

Calculation of the uncertainty in complication probability for various dose-response models, applied to the parotid gland

PURPOSE

Usually, models that predict normal tissue complication probability (NTCP) are fitted to clinical data with the maximum likelihood (ML) method. This method inevitably causes a loss of information contained in the data. In this study, an alternative method is investigated that calculates the parameter probability distribution (PD), and, thus, conserves all information. The PD method also allows the calculation of the uncertainty in the NTCP, which is an (often-neglected) prerequisite for the intercomparison of both treatment plans and NTCP models. The PD and ML methods are applied to parotid gland data, and the results are compared.

METHODS AND MATERIALS

The drop in salivary flow due to radiotherapy was measured in 25 parotid glands of 15 patients. Together with the parotid gland dose-volume histograms (DVH), this enabled the calculation of the parameter PDs for three different NTCP models (Lyman, relative seriality, and critical volume). From these PDs, the NTCP and its uncertainty could be calculated for arbitrary parotid gland DVHs. ML parameters and resulting NTCP values were calculated also.

RESULTS

All models fitted equally well. The parameter PDs turned out to have nonnormal shapes and long tails. The NTCP predictions of the ML and PD method usually differed considerably, depending on the NTCP model and the nature of irradiation. NTCP curves and ML parameters suggested a highly parallel organization of the parotid gland.

CONCLUSIONS

Considering the substantial differences between the NTCP predictions of the ML and PD method, the use of the PD method is preferred, because this is the only method that takes all information contained in the clinical data into account. Furthermore, PD method gives a true measure of the uncertainty in the NTCP.

The utility of SPECT in determining the relationship between radiation dose and salivary gland dysfunction after radiotherapy

Salivary gland scintigraphy (SGS) is used to depict salivary gland dysfunction after radiotherapy (RT). The aim of this study was to investigate the utility of SGS combined with single photon emission computed tomography (SPECT). Twenty-one patients with a carcinoma of head and neck underwent SGS before and 1 month after RT. After injection of 370 MBq 99Tcm-pertechnetate, a biplanar dynamic acquisition (12 x 1 min) was started, followed by a SPECT acquisition during 4 min. Carbachol was then injected and a second dynamic study (16 x 1 min) was performed, again followed by a SPECT acquisition. The salivary excretion fraction (SEF) was calculated both from the geometric mean planar image for each parotid and from the SPECT data for each transverse plane through the parotids. The RT-induced changes in the SEF (dSEF) were correlated with the mean radiation dose calculated using tomography-based dosimetry. The mean radiation dose to the parotids was 44 Gy (range 4.4-68.1 Gy). The mean range of the variation in radiation dose to the transverse slices within the parotids of a patient was 24 Gy (range 6.2-51.9 Gy). Considering all transverse planes through the parotids in all patients, a linear correlation was found between the dSEF calculated using SGS-SPECT and the radiation dose (r=0.45, P=0.0001). Thirteen patients had a variation in radiation dose within the parotids of more than 20 Gy. In nine of these a significant intra-individual correlation between radiation dose and the dSEF of the transverse parotid slices was found (r range 0.55-0.97; P value range 0.037-0.0001). In conclusion, SGS-SPECT can be used for monitoring radiation-induced parotid gland dysfunction. It offers the unique possibility for the assessment of intra-individual dose-dysfunction curves in patients with large variations in the radiation dose within the parotids.

Changing oral care needs in the United States: the continuing need for oral medicine

OBJECTIVE

The purpose of this article is to provide oral care providers evidence of oral conditions and medical compromise that is impacting the oral health and oral health needs of the public.

DESIGN

Data were analyzed based on current epidemiologic data, derived in large part from the Health and Nutrition Examination Surveys, the National Center for Health Statistics, National Health Interview Survey Series 1994-1997; American Cancer Society, National Cancer Institute Surveillance Examination and End Results data base, Morbidity and Mortality Weekly Reports, peer-reviewed publications, and surveys of oral medicine-related disorders.

RESULTS

Millions of Americans have medical conditions that complicate their oral health care. Oral health problems associated with age, medical health and treatment, and institutional setting are increasing. Chronic orofacial pain, persistent oral soft tissue lesions, and salivary gland and chemosensory disorders are common problems of modern society.

CONCLUSIONS

Evidence suggests that the next decade will bring a significantly increased demand for diagnosis and management of patients with oral conditions and patients with oral manifestations of systemic conditions, and an increase in general oral care needs of patients who are medically compromised. These increasing demands should be reflected in dental education and continuing education.

Three-dimensional intensity-modulated radiotherapy in the treatment of nasopharyngeal carcinoma: the University of California-San Francisco experience

PURPOSE

To review our experience with three-dimensional intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma.

METHODS AND MATERIALS

We reviewed the records of 35 patients who underwent 3D IMRT for nasopharyngeal carcinoma at the University of California-San Francisco between April 1995 and March 1998. According to the 1997 American Joint Committee on Cancer staging classification, 4 (12%) patients had Stage I disease, 6 (17%) had Stage II, 11 (32%) had Stage III, and 14 (40%) had Stage IV disease. IMRT of the primary tumor was delivered using one of the following three techniques: (1) manually cut partial transmission blocks, (2) computer-controlled autosequencing static multileaf collimator (MLC), and (3) Peacock system using a dynamic multivane intensity-modulating collimator (MIMiC). A forward 3D treatment-planning system was used for the first two methods, and an inverse treatment planning system was used for the third method. The neck was irradiated with a conventional technique using lateral opposed fields to the upper neck and an anterior field to the lower neck and supraclavicular fossae. The prescribed dose was 65-70 Gy to the gross tumor volume (GTV) and positive neck nodes, 60 Gy to the clinical target volume (CTV), and 50-60 Gy to the clinically negative neck. Eleven (32%) patients had fractionated high-dose-rate intracavitary brachytherapy boost to the primary tumor 1-2 weeks following external beam radiotherapy. Thirty-two (91%) patients also received cisplatin during, and cisplatin and 5-fluorouracil after, radiotherapy. Acute and late normal tissue effects were graded according to the Radiation Therapy Oncology Group (RTOG) radiation morbidity scoring criteria. Local-regional progression-free, distant metastasis-free survival and overall survival were estimated using the Kaplan-Meier method.

RESULTS

With a median follow-up of 21.8 months (range, 5-49 months), the local-regional progression-free rate was 100%. The 4-year overall survival was 94%, and the distant metastasis-free rate was 57%. The worst acute toxicity was Grade 2 in 16 (46%) patients, Grade 3 in 18 (51%) patients and Grade 4 in 1 (3%) patient. The worst late toxicity was Grade 1 in 15 (43%), Grade 2 in 13 (37%), and Grade 3 in 5 (14%) patients. Only 1 patient had a transient Grade 4 soft-tissue necrosis. At 24 months after treatment, 50% of the evaluated patients had Grade 0, 50% had Grade 1, and none had Grade 2 xerostomia. Analysis of the dose-volume histograms (DVHs) showed that the average maximum, mean, and minimum dose delivered were 79.5 Gy, 75.8 Gy, and 56.5 Gy to the GTV, and 78.9 Gy, 71.2 Gy, and 45.4 Gy to the CTV, respectively. An average of only 3% of the GTV and 2% of the CTV received less than 95% of the prescribed dose. The average dose to 5% of the brain stem, optic chiasm, and right and left optic nerves was 48.3 Gy, 23.9 Gy, 15.0 Gy, and 14.9 Gy, respectively. The average dose to 1 cc of the cervical spinal cord was 41.7 Gy. The doses delivered were within the tolerance of these critical normal structures. The average dose to 50% of the right and left parotids, pituitary, right and left T-M joints, and ears was 43. 2 Gy, 41.0 Gy, 46.3 Gy, 60.5 Gy, 58.3 Gy, 52.0 Gy, and 52.2 Gy, respectively.

CONCLUSION

3D intensity-modulated radiotherapy provided improved target volume coverage and increased dose to the gross tumor with significant sparing of the salivary glands and other critical normal structures. Local-regional control rate with combined IMRT and chemotherapy was excellent, although distant metastasis remained unabated.

Beam intensity modulation using tissue compensators or dynamic multileaf collimation in three-dimensional conformal radiotherapy of primary cancers of the oropharynx and larynx, including the elective neck

INTRODUCTION

The treatment of midline tumors in the head and neck by conventional radiotherapy almost invariably results in xerostomia. This study analyzes whether a simple three-dimensional conformal radiotherapy (3D-CRT) technique with beam intensity modulation (BIM) (using a 10-MV beam of the MM50 Racetrack Microtron) can spare parotid and submandibular glands without compromising the dose distribution in the planning target volume (PTV).

METHODS

For 15 T2 tumors of the tonsillar fossa with extension into the soft palate (To) and 15 T3 tumors of the supraglottic larynx (SgL), conventional treatment plans, consisting of lateral parallel opposed beams, were used for irradiation of both the primary tumor (70 Gy) and the elective neck regions (46 Gy). Separately, for each tumor a 3-D conformal treatment plan was developed using the 3-D computer planning system, CadPlan, and Optimize, a noncommercial program to compute optimal beam profiles. Beam angles were selected with the intention of optimal sparing of the salivary glands. The intensity of the beams was then modulated to achieve a homogeneous dose distribution in the target for the given 3D-CRT techniques. The dose distributions, dose-volume histograms (DVHs) of target and salivary glands, tumor control probabilities (TCPs), salivary gland volumes absorbing a biologically equivalent dose of greater than 40 or 50 Gy, and normal tissue complication probabilities (NTCPs) of each treatment plan were computed. The parameters of the 3D-CRT plans were compared with those of the conventional plans.

RESULTS

In comparison with the conventional technique, the dose homogeneity in the target volume was improved by the conformal technique for both tumor sites. In addition, for the SgL conformal technique, the average volumes of the parotid glands absorbing a BED of greater than 40 Gy (V40) decreased by 23%, and of the submandibular glands by 7% (V40) and 6% (V50). Consequently, the average NTCPs for the parotid and submandibular glands were reduced by 7% and 6%, respectively. For the To conformal techniques, the V40 of the parotid glands was decreased on average by 31%, resulting in an average reduction of the NTCP by 49%. Both the average V50 and the NTCP of the submandibular glands were decreased by 7%.

CONCLUSION

For primary tumors of the oropharynx, the parotid glands could be spared to a considerable degree with the 3D-CRT technique. However, particularly the ipsilateral submandibular gland could not be spared. For primary tumors of the larynx, the 3D-CRT technique allows sparing of all salivary glands to a considerable and probably clinically relevant degree. Moreover, the conformal techniques resulted in an increased dose homogeneity in the PTV of both tumor sites.

Measuring radiation fibrosis: the interobserver reliability of two methods of determining the degree of radiation fibrosis

PURPOSE

To compare the interobserver reliability of the palpation method with the method of measuring tissue compliance with a tissue compliance meter (TCM) on women who underwent breast-conserving surgery and radiotherapy for breast cancer.

METHODS AND MATERIALS

Thirty-eight patients and 30 controls were measured with the palpation method by two radiation oncologists and with the TCM by two physiotherapists. Measurements were taken on four locations of the breasts of all 68 women. Reliability coefficients were computed for both methods. A weighted kappa score was computed for the palpation method and this was compared with the intraclass correlation coefficient (ICC) computed for the TCM method. The conditions for direct comparison of these scores were met in this study.

RESULTS

A weighted kappa of 0.65 was computed for the palpation method and an ICC of 0.91 was computed for the TCM method. These scores differ significantly from each other (p < 0.01).

CONCLUSION

The interobserver reliability of the TCM method is superior to that of the palpation method. However, at locations where the TCM is not applicable, palpation is a good alternative.

CT-based parotid gland location: implications for preservation of parotid function

PURPOSE

The position of the parotid gland in relation to surrounding structures was investigated.

MATERIALS AND METHODS

Sixty-five patients with head and neck tumours were prospectively evaluated. Parotid position was determined using beam's eye views of CT images projected on simulator films. Distances between the different borders of the parotid gland and surrounding bony marks were quantitatively assessed.

RESULTS

The parotid gland volume ranged from 12.9 to 46.4 cm(3). The distance between the cranial border of the parotid gland and the tuberculum anterior of the atlas ranged between 0.7 and 4.8 cm. The position of the parotid gland was unaffected by the angle of the mandible.

CONCLUSIONS

The size and position of the parotid gland varies largely among patients. As the extent of radiation-induced salivary dysfunction depends on the volume of the gland tissue exposed, CT-based simulation of radiation fields is necessary.

Toxicity in head and neck cancer: a review of trends and issues

The quest for improved fractionation and combined modality regimens in head and neck cancer has also yielded progressively higher rates of toxicity. Time compression of dose delivery in accelerated fractionation has produced high rates of severe mucositis including the early stoppage of two randomized trials. The addition of chemotherapy has introduced systemic toxicity and can exacerbate local tissue reactions when used concurrent with radiotherapy. Mucositis is recognized as the principal impediment to efforts at further treatment intensification. The development and utilization of standardized toxicity grading criteria and accepted reporting standards has lagged toxicity production, impeding a full appreciation of the true extent of both acute and late toxicity. Objective data regarding acute and chronic effects on organ function are also sorely lacking. A better characterization of the frequency, severity, and duration of the various toxicities encountered in head and neck cancer will also allow the rational development of toxicity interventions. New methods are needed to summarize the global or aggregate toxicity of a treatment program. Further research into the assessment and analysis of toxicity is not only crucial to improvements in quality of life (QOL), but perhaps, improved rates of disease control as well.

Posterior fossa boost in medulloblastoma: an analysis of dose to surrounding structures using 3-dimensional (conformal) radiotherapy

PURPOSE

The purpose of this study was to compare three different techniques of delivering the posterior fossa boost in patients with medulloblastoma.

METHODS AND MATERIALS

Five patients underwent CT simulation for treatment planning of the posterior fossa boost. For each slice, the posterior fossa was contoured in addition to the cochlea, non-posterior fossa brain, pituitary gland, mandible, parotid glands, thyroid gland, pharynx, and cervical spinal cord. For each patient, plans for three techniques of delivering the posterior fossa boost were compared. Technique A utilized parallel-opposed lateral fields using bony landmarks (2-dimensional radiotherapy); the other two techniques were planned using 3-dimensional radiotherapy. Technique B utilized a pair of coplanar wedged posterior oblique beams, whereas Technique C utilized a pair of posterior oblique fields and a vertex field. Dose-volume histograms (DVH) were obtained for each of the organs contoured and for each technique and patient. The maximum, minimum, and mean dose to each organ were determined using the DVH program in our treatment planning system.

RESULTS

In 3 of 5 patients, the planning target volume (PTV) was not included in the treatment field with Technique A. The cochlea received 100%, 50%, and 42% of the prescribed posterior fossa dose using Techniques A, B, and C respectively. The mean dose to the non-posterior fossa brain was highest with Technique C, intermediate with Technique A, and lowest for Technique B. The mean dose to the non-posterior fossa brain with Technique B was comparable to the mean non-posterior fossa brain dose delivered using parallel-opposed lateral fields based on the CT definition of the PTV. Likewise, mean dose to the pituitary gland was lowest for Technique B. Both Techniques B and C were associated with a higher mean dose to the thyroid gland, mandible, parotid glands, and pharynx.

CONCLUSIONS

The use of Technique B minimized the radiotherapy dose to the cochlea, pituitary gland, and non-posterior fossa brain. Contrary to what one may expect, conformal radiotherapy using Technique B did not deliver a higher dose to the non-posterior fossa brain over standard parallel-opposed lateral fields. Other advantages of conformal techniques B and C over 2-dimensional radiotherapy are the inclusion of the PTV in all patients and a lower mean dose to the pituitary gland. The main disadvantage of conformal Techniques B and C employed in our patients is a higher mean dose to the thyroid gland and other tissues in the neck.

Dose, volume, and function relationships in parotid salivary glands following conformal and intensity-modulated irradiation of head and neck cancer

PURPOSE

To determine the relationships between the three-dimensional dose distributions in parotid glands and their saliva production, and to find the doses and irradiated volumes that permit preservation of the salivary flow following irradiation (RT).

METHODS AND MATERIALS

Eighty-eight patients with head and neck cancer irradiated with parotid-sparing conformal and multisegmental intensity modulation techniques between March 1994 and August 1997 participated in the study. The mean dose and the partial volumes receiving specified doses were determined for each gland from dose-volume histograms (DVHs). Nonstimulated and stimulated saliva flow rates were selectively measured from each parotid gland before RT and at 1, 3, 6, and 12 months after the completion of RT. The data were fit using a generalized linear model and the normal tissue complication probability (NTCP) model of Lyman-Kutcher. In the latter model, a "severe complication" was defined as salivary flow rate reduced to < or =25% pre-RT flow at 12 months.

RESULTS

Saliva flow rates data were available for 152 parotid glands. Glands receiving a mean dose below or equal to a threshold (24 Gy for the unstimulated and 26 Gy for the stimulated saliva) showed substantial preservation of the flow rates following RT and continued to improve over time (to median 76% and 114% of pre-RT for the unstimulated and stimulated flow rates, respectively, at 12 months). In contrast, most glands receiving a mean dose higher than the threshold produced little saliva with no recovery over time. The output was not found to decrease as mean dose increased, as long as the threshold dose was not reached. Similarly, partial volume thresholds were found: 67%, 45%, and 24% gland volumes receiving more than 15 Gy, 30 Gy, and 45 Gy, respectively. The partial volume thresholds correlated highly with the mean dose and did not add significantly to a model predicting the saliva flow rate from the mean dose and the time since RT. The NTCP model parameters were found to be TD50 (the tolerance dose for 50% complications rate for whole organ irradiated uniformly) = 28.4 Gy, n (volume dependence parameter) = 1, and m (the slope of the dose/response relationship) = 0.18. Clinical factors including age, gender, pre-RT surgery, chemotherapy, and certain medical conditions were not found to be significantly associated with the salivary flow rates. Medications (diuretics, antidepressants, and narcotics) were found to adversely affect the unstimulated but not the stimulated flow rates.

CONCLUSIONS

Dose/volume/function relationships in the parotid glands are characterized by dose and volume thresholds, steep dose/response relationships when the thresholds are reached, and a maximal volume dependence parameter in the NTCP model. A parotid gland mean dose of < or =26 Gy should be a planning goal if substantial sparing of the gland function is desired.

[CT densitometry for the grading of subcutaneous fibrosis after the photon-neutron therapy of malignant salivary gland tumors]

BACKGROUND

To evaluate alternative treatment regimen e.g. neutron therapy determination of treatment efficacy as well as side effects is important. Sensitivity of computed tomography (CT) in detecting changes of connective tissue after neutron therapy was examined.

PATIENTS AND METHODS

In the course of their follow-up period (median 45 months) 12 patients with malignant salivary gland tumors who had postoperatively received neutron (1/12) or photon/neutron therapy (11/12) were examined by means of CT densitometry on 3 representative scans in the area of radiotherapy. In 3 ROI (regions of interest) in subcutaneous fatty tissue the density at the irradiated and the non-irradiated side was determined according to Hounsfield units (HU) and the average density was calculated. The average density of both sides was compared and correlated with the clinical grade of fibrosis according to LENT SOMA.

RESULTS

All CT measurements (216 ROI, 18 ROI per patient) showed higher density levels on the irradiated side than on the non-irradiated side. The average density on the irradiated side was -57.7 +/- 4.7 HU and on the non-irradiated side -69.4 +/- 5.8 HU (p = 0.002). In 3/12 patients a clinical fibrosis was not seen; however, the relative density measured on the irradiated and non-irradiated side deviated by up to 8%. This could have been caused by minimal changes not being noticed by either patient and examiner. In patients with determined fibrosis Grade 1 (8/12) the relative density deviation was 4 to 39%. In 1/12 patients with determined fibrosis Grade 2 the relative density deviation was 50% (Figures 1a and 1b). Fibrosis Grade 3 and 4 did not occur (Table 1).

CONCLUSIONS

Fibrosis is correlated with an increasing value of HU of the tissue density in CT. With the described method it is possible to graduate radiation induced subcutaneous fibrosis in correlation to the clinical fibrosis grade according to LENT SOMA. In the patients we examined subcutaneous fibroses after photon/neutron therapy were moderate. Especially in characterising subclinical or slight changes of connective tissue after radiotherapy computed tomography is of value.

Management and long-term complications of pediatric cancer

The impact of recently intensified and novel therapies for the treatment of childhood cancer has been an increased number of survivors and an increase in the number of treatment complications among survivors. Thus, it is important for the primary care practitioner to be aware of not only acute but chronic complications of therapy, including the possibility of second malignancies. Long-term follow-up is essential, and continuous education of patients and health care personnel is an important aspect for the complete success of treatment. Primary care practitioners also need to incorporate other subspecialties in the management of these patients to ensure that they receive complete evaluation and treatment.

Toxicity antagonists in head and neck cancer

Clinical trials of altered fractionation and concurrent chemoradiation regimens have better elucidated the limits of both acute and late normal tissue toxicities in the head and neck. Acute effects on mucosal epithelium represent the principal barrier to intensification of radiation or chemoradiation schedules. Late soft tissue injury and organ dysfunction limit efforts to escalate radiation total dose. New insights into the cellular and molecular mechanisms of injury repair allow new strategies in the management and prevention of treatment-related toxicity. Toxicity antagonists are agents that directly interfere with the mechanism of toxicity or modulate the normal tissue response to injury. This article reviews 10 agents under development. Not only could such interventions reduce treatment-related morbidity, but they may also allow treatment intensification in advanced disease.

The effects of radiation on craniofacial skeletal growth: a quantitative study

To determine whether radiation delivered to children treated for head and neck cancer causes deformity, we performed a quantitative analysis for craniofacial asymmetry. A total of 42 patients, with either rhabdomyosarcoma or nasopharyngeal carcinoma, treated between 1980 and 1991, were analyzed. Exclusions included 16 subjects, leaving 26 children of mixed race and gender with a median age at diagnosis of 13 years (range: 2-18) and a median age at follow-up of 4 years (range: 3-37). Data from 14 measurements of the cranium and facial skeleton, for which normative data exist, were recorded. Symmetry of the face and head were determined and each measurement was compared to age specific standards. Deviation occurred in the cranial vault, the anterior and mid-interorbital distances and lateral orbital wall length. Asymmetry existed in the medial and lateral orbital wall lengths and the zygomatic arches. We conclude that, children irradiated for head and neck malignancies, have significant alterations in some skeletal measurements indicative of treatment induced asymmetry and potential deformity.

Transvascular drug delivery in solid tumors

The microvessel wall is a barrier for the delivery of various therapeutic agents to tumor cells. Tumor microvessels are, in general, more permeable to macromolecules than normal vessels. The hyperpermeability is presumably due to the existence of large pore structures in the vessel wall, induced by various cytokines. The cutoff pore size is tumor dependent, as determined by transport studies of nanoparticles. The vascular permeability is heterogeneous in tumors and dependent on physicochemical properties of molecules as well as the ultrastructure of the vessel wall. The ultrastructure is dynamic and can be modulated by the tumor microenvironment. The microenvironment itself can be altered by the transvascular transport because the transport may facilitate angiogenesis, reduce blood flow, and induce interstitial hypertension in tumors. Future studies of transport need to address mechanisms of the barrier formation and emphasize development of novel strategies for circumventing or exploiting the vascular barrier.

[Late effects of ionizing radiations on head and neck region tissues]

Numerous structures are included in the irradiated volume of patients presenting with head and neck cancer: skin, mucosa, bone, teeth, cartilage, muscles, salivary glands, etc. Curative intent treatment of such tumours requires aggressive approach which can lead to severe sequellae. These sequellae are in most cases dose-dependent and volume-dependent. However, an appropriate technique might decrease the severity of such sequellae. Details of these late changes are presented, including their pathophysiology, clinical syndromes, potential treatment, and prevention.

[Late effects of radiations on mature and growing bone]

The physiopathology of radiation-induced bone damage is no completely elucidated. Ionizing radiation may induce an inhibition or an impairment of growing bone. This fact is of particular importance in children, and represents one of the most important dose-limiting factors in the radiotherapeutic management of children with malignant diseases. Scoliosis, epiphyseal slippage, avascular necrosis, abnormalities of craniofacial growth may be observed after radiation. Child's age at the time of treatment, location of irradiated bone and irradiation characteristics may influence the radiation-related observed effects. In adults, pathological analysis of mature bone after ionizing radiation exposure are rare, suggesting that it is difficult to draw a clear feature of the action of radiation on the bone. Osteoporosis, medullary fibrosis and cytotoxicity on bone cells lead to fracture or necrosis. Various factors can influence bone tolerance to radiation such as bone involvement by tumor cells or infection, which is frequent is mandibulary osteoradionecrosis. Technical improvements in radiation techniques have also decreased radio-induced bone complications: the volume, fractionation and total dose are essential to consider. The absence of a consistent radiation-induced late effects evaluation scale has hampered efforts to analyze the influence of various therapeutic maneuvers and the comparison of results from different reported series. The currently proposed evaluation scale may help harmonizing the classification of radiation-induced bone late effects.

Comprehensive irradiation of head and neck cancer using conformal multisegmental fields: assessment of target coverage and noninvolved tissue sparing

PURPOSE

Conformal treatment using static multisegmental intensity modulation was developed for patients requiring comprehensive irradiation for head and neck cancer. The major aim is sparing major salivary gland function while adequately treating the targets. To assess the adequacy of the conformal plans regarding target coverage and dose homogeneity, they were compared with standard irradiation plans.

METHODS AND MATERIALS

Fifteen patients with stage III/IV head and neck cancer requiring comprehensive, bilateral neck irradiation participated in this study. CT-based treatment plans included five to six nonopposed fields, each having two to four in-field segments. Fields and segments were devised using beam's eye views of the planning target volumes (PTVs), noninvolved organs, and isodose surfaces, to achieve homogeneous dose distribution that encompassed the targets and spared major salivary gland tissue. For comparison, standard three-field radiation plans were devised retrospectively for each patient, with the same CT-derived targets used for the clinical (conformal) plans. Saliva flow rates from each major salivary gland were measured before and periodically after treatment.

RESULTS

On average, the minimal dose to the primary PTVs in the conformal plans [95.2% of the prescribed dose, standard deviation (SD) 4%] was higher than in the standard plans (91%, SD 7%; p = 0.02), and target volumes receiving <95% or <90% of the prescribed dose were smaller in the conformal plans (p = 0.004 and 0.02, respectively). Similar advantages of the conformal plans compared to standard plans were found in ipsilateral jugular nodes PTV coverage. The reason for underdosing in the standard treatment plans was primarily failure of electron beams to fully encompass targets. No significant differences were found in contralateral jugular or posterior neck nodes coverage. The minimal dose to the retropharyngeal nodes was higher in the standard plans. However, all conformal plans achieved the planning goal of delivering 50 Gy to these nodes. In the conformal plans, the magnitude and volumes of high doses in noninvolved tissue were significantly reduced. The main reasons for hot spots in the standard plans (whose dose calculations included missing tissue compensators) were photon/electron match line inhomogeneities, which were avoided in the conformal plans. The mean doses to all the major salivary glands, notably the contralateral parotid (receiving on average 32% of the prescribed dose, SD 7%) were significantly lower in the conformal plans compared with standard radiation plans. The mean dose to the noninvolved oral cavity tended to be lower in the conformal plans (p = 0.07). One to 3 months after radiation, on average 60% (SD 49%) of the preradiation saliva flow rate was retained in the contralateral parotid glands and 10% (SD 16%) was retained in the submandibular/sublingual glands.

CONCLUSIONS

Planning and delivery of comprehensive irradiation for head and neck cancer using static, multisegmental intensity modulation are feasible. Target coverage has not been compromised and dose distributions in noninvolved tissue are favorable compared with standard radiation. Substantial major salivary gland function can be retained.

Demonstration of increased collagen synthesis in irradiated human skin in vivo

Fibrosis is a common side-effect of radiation therapy. As a complex network of cytokines and other mediators plays a central role in the process leading to fibrosis, we used an in vivo method to measure skin collagen synthesis, taking into account the physiological conditions. We determined suction blister (i.e. interstitial) fluid concentrations of types I and III procollagen propeptides, reflecting types I and III collagen synthesis, in irradiated and unirradiated skin of breast cancer patients 1-5 years after surgery and radiation therapy, hence using the patients as their own controls. The mean concentrations of the measured collagen markers were approximately two times higher in the irradiated skin than in the unirradiated contralateral breast skin. The difference slowly diminishes with time. These results indicate that abundant collagen synthesis in the irradiated skin continues several years after discontinuation of the radiation therapy, leading to fibrosis. The method outlined here offers a new in vivo perspective to study events leading to radiation fibrosis.

[Risk factors of late complications after interstitial 192Ir brachytherapy in cancers of the oral cavity]

Brachytherapy has confirmed its prevailing role in conservative treatment of oral cavity carcinomas. To describe late toxicity in long-term surviving patients, comparisons with other series are necessary. Study of series of patients implanted for floor of the mouth or mobile tongue shows the need for more detailed data. Dental prophylaxy and lead protection of the mandibule, good indications and techniques of brachytherapy are necessary to avoid late complications. Some treatment factors have proved to be of good prognosis for late complications through multivariate analysis of large series treated with lr 192 wires, using the Paris system, eg, dose rate lower than 0.5 or 0.7 Gy/h, intersource spacing smaller than 1.2 or 1.5 cm, treated surface less than 12 cm2, lineic activity less than 1.5 mCi/cm, less than 1 cm diameter hyperdose, and use of mandibular lead protections. Tumor volume and location to the floor of mouth lead to higher risk of complications. Knowledge of treatment-related factors is important, with the development of new afterloading projectors allowing to control the dose rate and correct small inhomogeneities. High-dose rate exclusive brachytherapy is not recommended. More precise and reproducible classification should be used to report complications in series leading to publications in the future, thus allowing to compare results, reduce complication rates and improve the quality of life.