Xerostomia and its predictors following parotid-sparing irradiation of head-and-neck cancer

Intensity-modulated radiotherapy or volumetric-modulated arc therapy in patients with head and neck cancer: Focus on salivary glands dosimetry

BACKGROUND

Despite radiotherapy (RT) technical improvements, high salivary dysfunction rates are still reported in patients with head and neck squamous cell carcinoma (HNSCC). The purpose of the present study was to report salivary glands dosimetry with volumetric-modulated arc therapy (VMAT) and intensity-modulated RT (IMRT).

METHODS

Dosimetry of consecutive patients receiving IMRT or VMAT for proven HNSCC between 2007 and 2013 were retrospectively reviewed.

RESULTS

Data of 609 patients were studied. Mean dose, mean maximum dose, and mean percentage of salivary gland volume receiving at least 26 Gy (V26) of the contralateral parotid were 24.50 Gy (range, 0-70.4 Gy), 39.08 Gy (range, 0.38-76.45 Gy), and 40.92% (range, 0% to 100%), respectively. Mean and maximum dose on contralateral submandibular gland were 48.18 Gy (range, 0.19-70.73 Gy), and 61.25 Gy (range, 0-75.8 Gy), respectively.

CONCLUSION

Target volume coverage still has to be prioritized over organs at risk (OAR) sparing with new RT techniques. Submandibular glands are not sufficiently taken into account in guidelines. © 2016 Wiley Periodicals, Inc. Head Neck 38: 1028-1034, 2016.

Proton beam radiation therapy results in significantly reduced toxicity compared with intensity-modulated radiation therapy for head and neck tumors that require ipsilateral radiation

BACKGROUND

As proton beam radiation therapy (PBRT) may allow greater normal tissue sparing when compared with intensity-modulated radiation therapy (IMRT), we compared the dosimetry and treatment-related toxicities between patients treated to the ipsilateral head and neck with either PBRT or IMRT.

METHODS

Between 01/2011 and 03/2014, 41 consecutive patients underwent ipsilateral irradiation for major salivary gland cancer or cutaneous squamous cell carcinoma. The availability of PBRT, during this period, resulted in an immediate shift in practice from IMRT to PBRT, without any change in target delineation. Acute toxicities were assessed using the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

Twenty-three (56.1%) patients were treated with IMRT and 18 (43.9%) with PBRT. The groups were balanced in terms of baseline, treatment, and target volume characteristics. IMRT plans had a greater median maximum brainstem (29.7 Gy vs. 0.62 Gy (RBE), ​P < 0.001), maximum spinal cord (36.3 Gy vs. 1.88 Gy (RBE), ​P < 0.001), mean oral cavity (20.6 Gy vs. 0.94 Gy (RBE), ​P < 0.001), mean contralateral parotid (1.4 Gy vs. 0.0 Gy (RBE), P<0.001), and mean contralateral submandibular (4.1 Gy vs. 0.0 Gy (RBE), ​P < 0.001) dose when compared to PBRT plans. PBRT had significantly lower rates of grade 2 or greater acute dysgeusia (5.6% vs. 65.2%, P<0.001), mucositis (16.7% vs. 52.2%, P=0.019), and nausea (11.1% vs. 56.5%, P=0.003).

CONCLUSIONS

The unique properties of PBRT allow greater normal tissue sparing without sacrificing target coverage when irradiating the ipsilateral head and neck. This dosimetric advantage seemingly translates into lower rates of acute treatment-related toxicity.

Unilateral and bilateral neck SIB for head and neck cancer patients : Intensity-modulated proton therapy, tomotherapy, and RapidArc

AIM

To compare simultaneous integrated boost plans for intensity-modulated proton therapy (IMPT), helical tomotherapy (HT), and RapidArc therapy (RA) for patients with head and neck cancer.

PATIENTS AND METHODS

A total of 20 patients with squamous cell carcinoma of the head and neck received definitive chemoradiation with bilateral (n = 14) or unilateral (n = 6) neck irradiation and were planned using IMPT, HT, and RA with 54.4, 60.8, and 70.4 GyE/Gy in 32 fractions. Dose distributions, coverage, conformity, homogeneity to planning target volumes (PTV)s and sparing of organs at risk and normal tissue were compared.

RESULTS

All unilateral and bilateral plans showed excellent PTV coverage and acceptable dose conformity. For unilateral treatment, IMPT delivered substantially lower mean doses to contralateral salivary glands (< 0.001-1.1 Gy) than both rotational techniques did (parotid gland: 6-10 Gy; submandibular gland: 15-20 Gy). Regarding the sparing of classical organs at risk for bilateral treatment, IMPT and HT were similarly excellent and RA was satisfactory.

CONCLUSION

For unilateral neck irradiation, IMPT may minimize the dry mouth risk in this subgroup but showed no advantage over HT for bilateral neck treatment regarding classical organ-at-risk sparing. All methods satisfied modern standards regarding toxicity and excellent target coverage for unilateral and bilateral treatment of head and neck cancer at the planning level.

Comparisons of dysphagia and quality of life (QOL) in comparable patients with HPV-positive oropharyngeal cancer receiving chemo-irradiation or cetuximab-irradiation

PURPOSE

Compare functional outcomes of radiotherapy (RT) concurrent with cetuximab (cet-RT) or with chemotherapy (chemo-RT) for comparable, good prognosis patients with human papillomavirus related (HPV+) oropharyngeal cancer (OPC).

METHODS

Outcomes of patients with stage III/IV HPV+ OPC patients with minimal smoking history and non-T4/N3/N2C, treated on prospective protocol of RT concurrent with cetuximab (cet-RT), were compared to similar patients on prospective chemo-RT protocols. In both groups, videofluoroscopy (VF), observer rated dysphagia (ORD), and validated QOL questionnaires: xerostomia questionnaire (XQ), head and neck QOL, and University of Washington QOL, were performed periodically and compared to pretreatment. Mixed effects models with adjustment for baseline assessed differences between groups.

RESULTS

26 cet-RT patients were compared to 27 chemo-RT patients with similar baseline characteristics. In the chemo-RT group, no recurrences occurred. In the cet-RT group, 1 patient had persistent microscopic disease on salvage neck dissection and 1 distant failure. Both groups had mild VF-based swallowing dysfunction pre-treatment, worsened at 3 months (P<0.02) and persisted at 12 months, not differing between groups (P>0.11). For both groups ORD was very low pretreatment, worsened at 3 months and improved at 12 months, without differences between treatment groups (P=0.26). QOL Summary and domain scores for eating were good pretreatment, worse at 3 mo, and then improved to near baseline at 12 months, without differences between the groups in any QOL domains (P>0.10).

CONCLUSION

Both groups had excellent clinical outcomes without significant differences in objective or subjective functions. These data question using cetuximab instead of chemotherapy for treatment de-intensification for HPV+ OPC.

The management of head and neck tumors with high technology radiation therapy

Squamous cell carcinoma is responsible for 90% of the head and neck cancers affecting over 600,000 people worldwide. Radiation therapy, surgery and chemotherapy are the most important treatment modalities in head and neck squamous cell carcinoma. The aim of this review is to summarize the recent innovations in head and neck radiation therapy, which intends to appreciate the cutting-edge intensity-modulated radiation therapy strategies to mitigate long-term toxicities and evaluate promising technologies in the field as adaptive treatment, dose painting and proton therapy.

Is Pilocarpine Effective in Preventing Radiation-Induced Xerostomia? A Systematic Review and Meta-analysis

PURPOSE

To evaluate the efficacy of concomitant administration of pilocarpine on radiation-induced xerostomia in patients with head and neck cancers.

METHODS AND MATERIALS

The PubMed, Web of Science, Cochrane Library, and ClinicalTrials were searched to identify randomized, controlled trials studying the effect of concomitant administration of pilocarpine for radiation-induced xerostomia. Included trials were systematically reviewed, and quantifiable outcomes were pooled for meta-analysis. Outcomes of interest included salivary flow, clinician-rated xerostomia grade, patient-reported xerostomia scoring, quality of life, and adverse effects.

RESULTS

Six prospective, randomized, controlled trials in 8 articles were included in this systematic review. The total number of patients was 369 in the pilocarpine group and 367 in the control group. Concomitant administration of pilocarpine during radiation could increase the unstimulated salivary flow rate in a period of 3 to 6 months after treatment, and also reduce the clinician-rated xerostomia grade. Patient-reported xerostomia was not significantly impacted by pilocarpine in the initial 3 months but was superior at 6 months. No significant difference of stimulated salivary flow rate could be confirmed between the 2 arms. Adverse effects of pilocarpine were mild and tolerable.

CONCLUSIONS

The concomitant administration of pilocarpine during radiation increases unstimulated salivary flow rate and reduces clinician-rated xerostomia grade after radiation. It also relieves patients' xerostomia at 6 months and possibly at 12 months. However, pilocarpine has no effect on stimulated salivary flow rate.

Comparison of swallowing function after intensity-modulated radiation therapy and conventional radiotherapy for head and neck cancer

BACKGROUND

Intensity-modulated radiotherapy (IMRT) is hoped to protect structures important for swallow function. We compared posttreatment swallow function in 7 pairs of patients with head and neck cancer treated with either IMRT or conventional radiotherapy (RT).

METHODS

Patients were matched on tumor characteristics. Swallowing function was evaluated with the modified barium swallow procedure pretreatment and at 3 and 6 months postcancer treatment completion. Swallows were analyzed for bolus transit times, bolus residues, laryngeal closure (LAC) duration, cricopharyngeal opening (CPO) duration, and oropharyngeal swallow efficiency (OPSE). Data were analyzed using multifactor repeated measures analysis of variance and adjusted for baseline function.

RESULTS

Main effect of radiation type was significant for all measures on at least 1 bolus type. Patients treated with IMRT demonstrated shorter bolus transit times, less oral and pharyngeal residue, longer LAC, and larger OPSE.

CONCLUSION

Patients treated with IMRT demonstrated faster, more efficient swallows, and greater airway protection.

Radiation dose response simulation for biomechanical-based deformable image registration of head and neck cancer treatment

Biomechanical-based deformable image registration is conducted on the head and neck region. Patient specific 3D finite element models consisting of parotid glands (PG), submandibular glands (SG), tumor, vertebrae (VB), mandible, and external body are used to register pre-treatment MRI to post-treatment MR images to model the dose response using image data of five patients. The images are registered using combinations of vertebrae and mandible alignments, and surface projection of the external body as boundary conditions. In addition, the dose response is simulated by applying a new loading technique in the form of a dose-induced shrinkage using the dose-volume relationship. The dose-induced load is applied as dose-induced shrinkage of the tumor and four salivary glands. The Dice Similarity Coefficient (DSC) is calculated for the four salivary glands, and tumor to calculate the volume overlap of the structures after deformable registration. A substantial improvement in the registration is found by including the dose-induced shrinkage. The greatest registration improvement is found in the four glands where the average DSC increases from 0.53, 0.55, 0.32, and 0.37 to 0.68, 0.68, 0.51, and 0.49 in the left PG, right PG, left SG, and right SG, respectively by using bony alignment of vertebrae and mandible (M), body (B) surface projection and dose (D) (VB+M+B+D).

Sparing bilateral neck level IB in oropharyngeal carcinoma and xerostomia outcomes

OBJECTIVES

To assess whether sparing neck-level IB in target delineation of node-positive (N+) oropharyngeal carcinoma (OPC) can improve xerostomia outcomes without compromising locoregional control (LRC).

METHODS

A total of 125 N+ OPC patients with a median age of 57 years underwent chemoradiation between May 2010 and December 2011. A total of 74% of patients had T1-T2 disease, 26% T3-T4, 16% N1, 8% N2A, 48% N2B, 28% N2C; 53% base of tongue, 41% tonsil, and 6% other. Patients were divided into those who had target delineation sparing of bilateral level IB (the spared cohort) versus no sparing (the treated cohort). Sparing of contralateral high-level II nodes was also performed more consistently in the spared cohort. A prospective xerostomia questionnaire (patient reported) was given at each patient follow-up visit to this cohort of patients to assess late xerostomia. Clinical assessment (observer rated) at each patient follow-up visit was also recorded.

RESULTS

The 2-year LRC for the spared and treated cohorts was 97.5% and 93.8%, respectively (median follow-up, 23.2 mo). No locoregional failures occurred outside of treatment fields. The spared cohort experienced significant benefits in patient-reported xerostomia summary scores (P=0.021) and observer-rated xerostomia scores (P=0.006). In addition, there were significant reductions in mean doses to the ipsilateral submandibular gland (63.9 vs. 70.5 Gy; P<0.001), contralateral submandibular gland (45.0 vs. 56.2 Gy; P<0.001), oral cavity (35.9 vs. 45.2 Gy; P<0.001), and contralateral parotid gland (20.0 vs. 24.4 Gy; P<0.001).

CONCLUSIONS

Target delineation sparing of bilateral level IB nodes in N+ OPC reduced mean doses to salivary organs without compromising LRC. Patients with reduced target volumes had better patient-reported xerostomia outcomes.

Patient- and therapy-related factors associated with the incidence of xerostomia in nasopharyngeal carcinoma patients receiving parotid-sparing helical tomotherapy

We investigated the incidence of moderate to severe patient-reported xerostomia among nasopharyngeal carcinoma (NPC) patients treated with helical tomotherapy (HT) and identified patient- and therapy-related factors associated with acute and chronic xerostomia toxicity. The least absolute shrinkage and selection operator (LASSO) normal tissue complication probability (NTCP) models were developed using quality-of-life questionnaire datasets from 67 patients with NPC. For acute toxicity, the dosimetric factors of the mean doses to the ipsilateral submandibular gland (Dis) and the contralateral submandibular gland (Dcs) were selected as the first two significant predictors. For chronic toxicity, four predictive factors were selected: age, mean dose to the oral cavity (Doc), education, and T stage. The substantial sparing data can be used to avoid xerostomia toxicity. We suggest that the tolerance values corresponded to a 20% incidence of complications (TD20) for Dis = 39.0 Gy, Dcs = 38.4 Gy, and Doc = 32.5 Gy, respectively, when mean doses to the parotid glands met the QUANTEC 25 Gy sparing guidelines. To avoid patient-reported xerostomia toxicity, the mean doses to the parotid gland, submandibular gland, and oral cavity have to meet the sparing tolerance, although there is also a need to take inherent patient characteristics into consideration.

Evaluation of the Risk of Grade 3 Oral and Pharyngeal Dysphagia Using Atlas-Based Method and Multivariate Analyses of Individual Patient Dose Distributions

PURPOSE

The study aimed to apply the atlas of complication incidence (ACI) method to patients receiving radical treatment for head and neck squamous cell carcinomas (HNSCC), to generate constraints based on dose-volume histograms (DVHs), and to identify clinical and dosimetric parameters that predict the risk of grade 3 oral mucositis (g3OM) and pharyngeal dysphagia (g3PD).

METHODS AND MATERIALS

Oral and pharyngeal mucosal DVHs were generated for 253 patients who received radiation (RT) or chemoradiation (CRT). They were used to produce ACI for g3OM and g3PD. Multivariate analysis (MVA) of the effect of dosimetry, clinical, and patient-related variables was performed using logistic regression and bootstrapping. Receiver operating curve (ROC) analysis was also performed, and the Youden index was used to find volume constraints that discriminated between volumes that predicted for toxicity.

RESULTS

We derived statistically significant dose-volume constraints for g3OM over the range v28 to v70. Only 3 statistically significant constraints were derived for g3PD v67, v68, and v69. On MVA, mean dose to the oral mucosa predicted for g3OM and concomitant chemotherapy and mean dose to the inferior constrictor (IC) predicted for g3PD.

CONCLUSIONS

We have used the ACI method to evaluate incidences of g3OM and g3PD and ROC analysis to generate constraints to predict g3OM and g3PD derived from entire individual patient DVHs. On MVA, the strongest predictors were radiation dose (for g3OM) and concomitant chemotherapy (for g3PD).

The use of proton therapy in the treatment of head and neck cancers

External beam radiation therapy is a commonly utilized treatment modality in the management of head and neck cancer. Given the close proximity of disease to critical normal tissues and structures, the delivery of external beam radiation therapy can result in severe acute and late toxicities, even when delivered with advanced photon-based techniques, such as intensity-modulated radiation therapy. The unique physical characteristics of protons make it a promising option in the treatment of advanced head and neck cancer, with the potential to improve sparing of normal tissues and/or safely escalate radiation doses. Clinical implementation will require the continued development of advanced techniques such as intensity-modulated proton therapy, using pencil beam scanning, as well as rigorous methods of quality assurance and adaptive techniques to accurately adjust to changes in anatomy due to disease response. Ultimately, the widespread adaptation and implementation of proton therapy for head and neck cancer will require direct, prospective comparisons to standard techniques such as intensity-modulated radiation therapy, with a focus on measures such as toxicity, disease control, and quality of life.

RETRACTED: Laryngeal Function After Radiation Therapy

Laryngeal function after oncologic treatment is a key aspect and focus of interest in the contemporary management of head and neck cancers. Although historically the treatment of most locally advanced laryngeal cancers has been total laryngectomy, recent innovations in radiation therapy and combined chemotherapy and radiation therapy have shown that organ and function preservation can be achieved with good oncologic outcomes. Technical improvements, along with better understanding of tumor biology and dose tolerance of critical organs involved in speech and swallowing function, have paved the way for better outcomes. This article reviews in comprehensive detail the recent data of laryngeal function after radiotherapy.

Safety of contralateral submandibular gland sparing in locally advanced oropharyngeal cancers: A multicenter review

BACKGROUND

Previous groups have shown contralateral submandibular gland sparing to improve xerostomia with safe outcomes, but primarily in early-stage disease. In this study, we present a large cohort of patients with locally advanced head and neck cancer that underwent contralateral submandibular gland-sparing radiotherapy, to demonstrate feasibility and safety specifically in patients with locally advanced disease.

METHODS

We retrospectively analyzed patients who were treated prospectively with contralateral submandibular gland sparing. Only patients who underwent bilateral neck radiotherapy with contralateral submandibular gland doses <39 Gy were included.

RESULTS

We identified 71 patients. Approximately 80% of patients had ≥N2b disease. The contralateral submandibular gland mean dose was 33 Gy and, at a median follow-up of 27.3 months, no patients experienced treatment failure in the contralateral level IB lymph nodes.

CONCLUSION

Xerostomia remains a significant morbidity despite parotid sparing and can be minimized further by contralateral submandibular gland sparing. These data provide important preliminary evidence that contralateral submandibular gland sparing is feasible and may be safe even in locally advanced cancers.

Long-term quality of life after swallowing and salivary-sparing chemo-intensity modulated radiation therapy in survivors of human papillomavirus-related oropharyngeal cancer

PURPOSE

To evaluate long-term health-related quality of life (HRQOL) in 2 prospective studies of chemo-intensity modulated radiation therapy (chemo-IMRT) for oropharyngeal cancer (OPC).

METHODS AND MATERIALS

Of 93 patients with stage III/IV OPC treated on prospective studies of swallowing and salivary organ-sparing chemo-IMRT, 69 were eligible for long-term HRQOL assessment. Three validated patient-reported instruments, the Head and Neck QOL (HNQOL) questionnaire, the University of Washington quality of life (UWQOL) questionnaire, and the Xerostomia Questionnaire (XQ), previously administered from baseline through 2 years in the parent studies, were readministered at long-term follow-up, along with the Short-Form 36. Long-term changes in HRQOL from before treatment and 2 years were evaluated.

RESULTS

Forty patients (58%) with a median follow-up of 6.5 years participated, 39 of whom (97.5%) had confirmed human papillomavirus-positive OPC. Long term, no clinically significant worsening was detected in mean HRQOL scores compared with 2 years, with stable or improved HRQOL from before treatment in nearly all domains. "Moderate" or greater severity problems were uncommon, reported by 5% of patients for eating, 5% for swallowing, and 2.5% and 5% by HNQOL and UWQOL summary scores, respectively. Freedom from percutaneous endoscopic gastrostomy tube dependence and stricture dilation beyond 2 years was 97.5% and 95%, respectively. Eleven percent and 14% of patients reported "moderate" or "severe" long-term worsening in HNQOL Pain and Overall Bother domains, respectively, which were associated with mean dose to the cervical esophagus, larynx, and pharyngeal constrictors.

CONCLUSIONS

At more than 6 years' median follow-up, OPC patients treated with swallowing and salivary organ-sparing chemo-IMRT reported stable or improved HRQOL in nearly all domains compared with both before treatment and 2-year follow-up. New late toxicity after 2 years was uncommon. Further emphasis on sparing the swallowing organs may yield additional HRQOL gains for long-term OPC survivors.

Technique for comprehensive head and neck irradiation using 3-dimensional conformal proton therapy

Owing to the technical and logistical complexities of matching photon and proton treatment modalities, we developed and implemented a technique of comprehensive head and neck radiation using 3-dimensional (3D) conformal proton therapy. A monoisocentric technique was used with a 30-cm snout. Cervical lymphatics were treated with 3 fields: a posterior-anterior field with a midline block and a right and a left posterior oblique field. The matchline of the 3 cervical nodal fields with the primary tumor site fields was staggered by 0.5cm. Comparative intensity-modulated photon plans were later developed for 12 previously treated patients to provide equivalent target coverage, while matching or improving on the proton plans׳ sparing of organs at risk (OARs). Dosimetry to OARs was evaluated and compared by treatment modality. Comprehensive head and neck irradiation using proton therapy yielded treatment plans with significant dose avoidance of the oral cavity and midline neck structures. When compared with the generated intensity-modulated radiation therapy (IMRT) plans, the proton treatment plans yielded statistically significant reductions in the mean and integral radiation dose to the oral cavity, larynx, esophagus, and the maximally spared parotid gland. There was no significant difference in mean dose to the lesser-spared parotid gland by treatment modality or in mean or integral dose to the spared submandibular glands. A technique for cervical nodal irradiation using 3D conformal proton therapy with uniform scanning was developed and clinically implemented. Use of proton therapy for cervical nodal irradiation resulted in large volume of dose avoidance to the oral cavity and low dose exposure to midline structures of the larynx and the esophagus, with lower mean and integral dose to assessed OARs when compared with competing IMRT plans.

Regional radiation dose susceptibility within the parotid gland: effects on salivary loss and recovery

PURPOSE

Xerostomia is one of the most likely late toxic effects of radiotherapy treatment in patients with head-and-neck cancers. Modern treatment techniques can incorporate knowledge of complication risk into treatment plans. To this end, the authors attempt to quantify the regional radiotherapy dose-dependence of salivary output loss and recovery in a prospective study.

METHODS

Salivary output was collected from patients undergoing radiotherapy treatment for head-and-neck cancers at the BC Cancer Agency between February 2008 and May 2013. Regional dose-dependence (i.e., dose susceptibility) of loss and recovery is quantified using nonparametric (Spearman's rank correlation coefficients, local linear regression) and parametric (least-sum of squares, least-median of squares) techniques.

RESULTS

Salivary flow recovery was seen in 79 of 102 patients considered (p < 0.0001, Wilcoxon sign rank test). Output loss was strongly correlated with left- and right parotid combined dose φ = min (DL,  45 Gy) + min (DR,  45 Gy), and can be accurately predicted. Median early loss (three months) was 72% of baseline, while median overall loss (1 yr) was 56% of baseline. Fitting an exponential model to whole parotid yields dose sensitivities A3m = 0.0604 Gy(-1) and A1y = 0.0379 Gy(-1). Recovery was not significantly associated with dose. Hints of lateral organ sub-segment dose-response dimorphism were observed.

CONCLUSIONS

Sub-segmentation appears to predict neither loss nor recovery with any greater precision than whole parotid mean dose, though it is not any worse. Sparing the parotid to a combined dose φ of <50 Gy is recommended for a patient to keep ≈40% of baseline function and thus avoid severe xerostomia at 12 months post-treatment. It seems unlikely that a population's mean recovery will exceed 20%-30% of baseline output at 1 yr after radiotherapy treatment using current (whole-organ based) clinical guidelines.

Impact of Node Negative Target Volume Delineation on Contralateral Parotid Gland Dose Sparing Using IMRT in Head and Neck Cancer

There is considerable practice variation in treatment of the node negative (N0) contralateral neck in patients with head and neck cancer. In this study, we examined the impact of N0 neck target delineation volume on radiation dose to the contralateral parotid gland. Following institutional review board approval, 12 patients with head and neck cancer were studied. All had indications for treatment of the N0 neck, such as midline base of tongue or soft palate extension or advanced ipsilateral nodal disease. The N0 neck volumes were created using the Radiation Therapy Oncology Group head and neck contouring atlas. The physician-drawn N0 neck clinical target volume (CTV) was expanded by 25% to 200% to generate volume variation, followed by a 3-mm planning target volume (PTV) expansion. Surrounding organs at risk were contoured and complete intensity-modulated radiation therapy plans were generated for each N0 volume expansion. The median N0 target volume drawn by the radiation oncologist measured 93 cm(3) (range 71-145). Volumetric expansion of the N0 CTV by 25% to 200% increased the resultant mean dose to the contralateral parotid gland by 1.4 to 8.5 Gray (Gy). For example, a 4.1-mm increase in the N0 neck CTV translated to a 2.0-Gy dose increase to the parotid, 7.4 mm to a 4.5 Gy dose increase, and 12.5 mm to an 8.5 Gy dose increase, respectively. The treatment volume designated for the N0 neck has profound impact on resultant dose to the contralateral parotid gland. Variations of up to 15 mm are routine across physicians in target contouring, reflecting individual preference and training expertise. Depending on the availability of immobilization and image guidance techniques, experts commonly recommend 3 to 10 mm margin expansions to generate the PTV. Careful attention to the original volume of the N0 neck CTV, as well as expansion margins, is important in achieving effective contralateral gland sparing to reduce the resultant xerostomia and dysguesia that may ensue after radiotherapy.

A novel method for delineation of oral mucosa for radiotherapy dose-response studies

There is currently no standard method for delineating the oral mucosa and most attempts are oversimplified. A new method to obtain anatomically accurate contours of the oral mucosa surfaces was developed and applied to 11 patients. This is expected to represent an opportunity for improved toxicity modelling of oral mucositis.

Submandibular gland-sparing radiation therapy for locally advanced oropharyngeal squamous cell carcinoma: patterns of failure and xerostomia outcomes

Background

Saliva from submandibular glands (SMG) is necessary to minimize xerostomia. It is unclear whether SMG can be safely spared in patients undergoing bilateral neck radiotherapy for locally advanced oropharyngeal cancer without increasing the risk of marginal recurrence. We evaluated the outcomes of contralateral submandibular gland (cSMG) sparing intensity-modulated radiation therapy (IMRT).

Methods

All patients with stage III/IV oropharyngeal squamous cell carcinoma treated with bilateral neck IMRT from 2006–2012 at our institution were included. Appropriately selected patients with favorable primary tumor characteristics and no definite contralateral neck disease were treated with cSMG-sparing IMRT. Patterns of failure and xerostomia outcomes were retrospectively analyzed.

Results

114 patients were treated. 89% had stage IV disease and 89% received definitive radiation therapy. 76 patients (67%) received cSMG sparing IMRT. With a median follow-up of 30 months, there were 10 local, 9 regional, and 10 distant recurrences. 2-year overall survival was 86% and 2-year loco-regional control was 87%. In cSMG spared patients, the mean cSMG dose was 30.7 Gy. Late grade 2+ xerostomia was significantly reduced in the cSMG spared group compared to those without SMG sparing (6 months: 23% vs. 72%, 12 months: 6% vs. 41%, 24 months: 3% vs. 36%, all p < 0.0007). There were no peri-SMG marginal recurrences in the cSMG-spared cohort.

Conclusions

cSMG sparing IMRT did not increase marginal failures in this series of locally advanced oropharyngeal SCC patients. Xerostomia was significantly reduced in cSMG spared patients.

Submandibular gland-sparing intensity-modulated radiotherapy

Xerostomia is one of the most debilitating late effects of head and neck radiotherapy (RT) and significantly impacts quality of life. The submandibular gland (SMG) provides approximately 70% of the unstimulated saliva that accounts for about 95% of the salivary flow during a 24-hour period. Intensity-modulated RT (IMRT) has been used in recent years to lower the RT dose to the parotid gland(s) to reduce long-term xerostomia. There is little experience with SMG-sparing IMRT. Mean RT doses to the SMG exceeding 39 Gy cause permanent ablation of both stimulated and unstimulated salivary flow. Limited data suggest that SMG-sparing IMRT in selected patients results in reduced long-term xerostomia without increasing the risk of a local-regional recurrence.

Automated segmentation of the parotid gland based on atlas registration and machine learning: a longitudinal MRI study in head-and-neck radiation therapy

PURPOSE

To develop an automated magnetic resonance imaging (MRI) parotid segmentation method to monitor radiation-induced parotid gland changes in patients after head and neck radiation therapy (RT).

METHODS AND MATERIALS

The proposed method combines the atlas registration method, which captures the global variation of anatomy, with a machine learning technology, which captures the local statistical features, to automatically segment the parotid glands from the MRIs. The segmentation method consists of 3 major steps. First, an atlas (pre-RT MRI and manually contoured parotid gland mask) is built for each patient. A hybrid deformable image registration is used to map the pre-RT MRI to the post-RT MRI, and the transformation is applied to the pre-RT parotid volume. Second, the kernel support vector machine (SVM) is trained with the subject-specific atlas pair consisting of multiple features (intensity, gradient, and others) from the aligned pre-RT MRI and the transformed parotid volume. Third, the well-trained kernel SVM is used to differentiate the parotid from surrounding tissues in the post-RT MRIs by statistically matching multiple texture features. A longitudinal study of 15 patients undergoing head and neck RT was conducted: baseline MRI was acquired prior to RT, and the post-RT MRIs were acquired at 3-, 6-, and 12-month follow-up examinations. The resulting segmentations were compared with the physicians' manual contours.

RESULTS

Successful parotid segmentation was achieved for all 15 patients (42 post-RT MRIs). The average percentage of volume differences between the automated segmentations and those of the physicians' manual contours were 7.98% for the left parotid and 8.12% for the right parotid. The average volume overlap was 91.1% ± 1.6% for the left parotid and 90.5% ± 2.4% for the right parotid. The parotid gland volume reduction at follow-up was 25% at 3 months, 27% at 6 months, and 16% at 12 months.

CONCLUSIONS

We have validated our automated parotid segmentation algorithm in a longitudinal study. This segmentation method may be useful in future studies to address radiation-induced xerostomia in head and neck radiation therapy.

Eliminating radiotherapy to the contralateral retropharyngeal and high level II lymph nodes in head and neck squamous cell carcinoma is safe and improves quality of life

BACKGROUND

Radiation treatment volumes in head and neck squamous cell carcinoma (HNSCC) are controversial. The authors report the outcomes, patterns of failure, and quality of life (QOL) of patients who received treatment for HNSCC using intensity-modulated radiation therapy (IMRT) that eliminated the treatment of contralateral retropharyngeal lymph nodes (RPLNs) in the clinically uninvolved neck.

METHODS

A prospective institutional database was used to identify patients who had primary oral cavity, oropharyngeal, hypopharyngeal, laryngeal, and unknown primary HNSCC for which they received IMRT. There were 3 temporal groups (generations 1-3). Generation 1 received comprehensive neck IMRT with parotid sparing, generation 2 eliminated the contralateral high level II (HLII) lymph nodes, and generation 3 further eliminated the contralateral RPLNs in the clinically uninvolved neck. Patterns of failure and survival analyses were completed, and QOL data measured using the MD Anderson Dysphagia Inventory were compared in a subset of patients from generations 1 and 3.

RESULTS

In total, 748 patients were identified. Of the 488 patients who received treatment in generation 2 or 3, 406 had a clinically uninvolved contralateral neck. There were no failures in the spared RPLNs (95% confidence interval, 0%-1.3%) or in the high contralateral neck (95% confidence interval, 0%-0.7%). QOL data were compared between 44 patients in generation 1 and 51 patients in generation 3. QOL improved both globally and in all domains assessed for generation 3, in which reduced radiotherapy volumes were used (P < .007).

CONCLUSIONS

For patients with locally advanced HNSCC, eliminating coverage to the contralateral HLII lymph nodes and contralateral RPLNs in the clinically uninvolved side of the neck is associated with minimal risk of failure in these regions and significantly improved patient-reported QOL.

Role of perfusion computed tomography in assessing submandibular gland radiochemotherapy-induced injury

OBJECTIVE

We aimed to detect changes in the volume and perfusion parameters of the submandibular glands during and after radiochemotherapy.

STUDY DESIGN

Twelve patients underwent computed tomography (CT) and perfusion CT before radiochemotherapy, after 40 Gy, after 70 Gy, and 3 months after radiochemotherapy. Submandibular gland volume, blood volume, permeability surface area product, and blood flow were quantified.

RESULTS

Submandibular gland volumes during and after therapy were significantly lower compared with the baseline value (P < .001). Blood volume, blood flow, and permeability surface area product values showed statistically significant reduction during and 3 months after therapy. A significant linear correlation was found between changes in submandibular gland volume and of the perfusion parameter blood volume in the period between baseline and 3 months after therapy (P = .012; RP = -0.697).

CONCLUSIONS

Changes in submandibular gland volume and dynamics of perfusion parameters imply that radiation-induced injury of submandibular glands develops early during radiochemotherapy.

Developing an adaptive radiation therapy strategy for nasopharyngeal carcinoma

Adaptive radiotherapy (ART) has recently been introduced to restore the planned dose distribution by accounting for the anatomic changes during treatment. By quantifying the anatomic changes in nasopharyngeal carcinoma (NPC) patients, this study aimed to establish an ART strategy for NPC cases. A total of 30 NPC patients treated with helical tomotherapy were recruited. In the pretreatment megavoltage CT images, the anatomic changes of the posterolateral wall of nasopharynx (P-NP), neck region and parotid glands were measured and assessed. One-way repeated measure ANOVA was employed to define threshold(s) at any time-point. The presence of a threshold(s) would indicate significant anatomical change(s) such that replanning should be suggested. A pragmatic schedule for ART was established by evaluating the threshold for each parameter. Results showed the P-NP, parotid gland and neck volumes demonstrated significant regressions over time. Respectively, the mean loss rates were 0.99, 1.35, and 0.39 %/day, and the mean volume losses were 35.70, 47.54 and 11.91% (all P < 0.001). The parotid gland shifted medially and superiorly over time by a mean of 0.34 and 0.24 cm, respectively (all P < 0.001). The neck region showed non-rigid posterior displacement, which increased from upper to lower neck. According to the threshold occurrences, three replans at 9th, 19th and 29th fractions were proposed. This ART strategy was able to accommodate the dosimetric consequences due to anatomic deviation over the treatment course. It is clinically feasible and would be recommended for centers where an adaptive planning system was not yet available.

Using multivariate regression model with least absolute shrinkage and selection operator (LASSO) to predict the incidence of Xerostomia after intensity-modulated radiotherapy for head and neck cancer

Purpose

The aim of this study was to develop a multivariate logistic regression model with least absolute shrinkage and selection operator (LASSO) to make valid predictions about the incidence of moderate-to-severe patient-rated xerostomia among head and neck cancer (HNC) patients treated with IMRT.

Methods and Materials

Quality of life questionnaire datasets from 206 patients with HNC were analyzed. The European Organization for Research and Treatment of Cancer QLQ-H&N35 and QLQ-C30 questionnaires were used as the endpoint evaluation. The primary endpoint (grade 3⁺ xerostomia) was defined as moderate-to-severe xerostomia at 3 (XER_3m) and 12 months (XER_12m) after the completion of IMRT. Normal tissue complication probability (NTCP) models were developed. The optimal and suboptimal numbers of prognostic factors for a multivariate logistic regression model were determined using the LASSO with bootstrapping technique. Statistical analysis was performed using the scaled Brier score, Nagelkerke R², chi-squared test, Omnibus, Hosmer-Lemeshow test, and the AUC.

Results

Eight prognostic factors were selected by LASSO for the 3-month time point: Dmean-c, Dmean-i, age, financial status, T stage, AJCC stage, smoking, and education. Nine prognostic factors were selected for the 12-month time point: Dmean-i, education, Dmean-c, smoking, T stage, baseline xerostomia, alcohol abuse, family history, and node classification. In the selection of the suboptimal number of prognostic factors by LASSO, three suboptimal prognostic factors were fine-tuned by Hosmer-Lemeshow test and AUC, i.e., Dmean-c, Dmean-i, and age for the 3-month time point. Five suboptimal prognostic factors were also selected for the 12-month time point, i.e., Dmean-i, education, Dmean-c, smoking, and T stage. The overall performance for both time points of the NTCP model in terms of scaled Brier score, Omnibus, and Nagelkerke R² was satisfactory and corresponded well with the expected values.

Conclusions

Multivariate NTCP models with LASSO can be used to predict patient-rated xerostomia after IMRT.

Clinical observation of submandibular gland transfer for the prevention of xerostomia after radiotherapy for nasopharyngeal carcinoma: a prospective randomized controlled study of 32 cases

BACKGROUND

The aim of this study was to evaluate the clinical efficacy of submandibular gland transfer for the prevention of xerostomia after radiotherapy for nasopharyngeal carcinoma.

METHODS

Using the randomized controlled clinical research method, 65 patients with nasopharyngeal carcinoma were randomly divided into an experimental group consisting of 32 patients and a control group consisting of 33 patients. The submandibular glands were averted to the submental region in 32 patients with nasopharyngeal carcinoma before they received conventional radiotherapy; a lead block was used to shield the submental region during therapy. Prior to radiotherapy, the function of the submandibular glands was assessed using imaging. Submandibular gland function was measured using 99mTc radionuclide scanning at 60 months after radiotherapy. The data in the questionnaire regarding the degree of xerostomia were investigated and saliva secretion was measured at 3, 6, 12, and 60 months after radiotherapy. In addition, the 5-year survival rate was calculated.

RESULTS

After follow-up for 3, 6, and 12 months, the incidence of moderate to severe xerostomia was significantly lower in the experimental group than in the control group. The average amount of saliva produced by the experimental and control groups was 1.60 g and 0.68 g, respectively (P<0.001). After follow-up for 60 months, the uptake and secretion functions of the submandibular glands in the experimental group were found to be significantly higher than in the control group (P<0.001 and P<0.001, respectively). The incidence of moderate or severe xerostomia was significantly lower than in the control group (15.4% and 76.9%, respectively; P<0.001). The 5-year survival rates of the experimental group and the control group were 81.3% and 78.8%, respectively, and there was no significant difference between the two groups (P=0.806).

CONCLUSIONS

After a 5 year follow-up period involving 32 patients who had their submandibular glands transferred for the prevention of xerostomia after radiotherapy for nasopharyngeal carcinoma, we found that clinical efficacy was good. This approach could improve the quality of life of nasopharyngeal carcinoma patients after radiotherapy and would not affect long-term treatment efficacy.

Late Toxicities after Conventional Radiotherapy for Nasopharyngeal Carcinoma: Incidence and Risk Factors

Background. To determine the incidence and analyze the factors affecting late toxicity for nasopharyngeal carcinoma patients treated with conventional radiotherapy. Patients and Methods. Retrospective analysis was performed on 239 NPC patients treated between 1993 and 2004 in our institution. One hundred and fifty-seven patients were treated with conventional fractionation (2 Gy per fraction, 5 fractions per week) and eighty-two patients with hyperfractionated radiotherapy (1.6 Gy per fraction twice a day, 5 days per week). One hundred fifty nine patients underwent neoadjuvant cisplatin based chemotherapy. Late toxicity was evaluated according to the RTOG/EORTC score. Results. Xerostomia was the most common related complication (98.7%). Neoadjuvant chemotherapy and hyperfractionated radiotherapy did not increase late toxicities. Multivariate analyses showed that radiation dose was a significant factor for hearing impairment, younger age for trismus, initial node status for neck fibrosis, and initial dental hygiene for dental complications. Female gender was associated with significantly higher incidence of trismus and hearing impairment. Conclusion. Conventional radiotherapy was associated with a high rate of late toxicities which affect patients’ quality of life. With the development of three-dimensional conformal radiotherapy and intensity modulated radiotherapy, a reduced incidence of radiation related complications could be expected.

Improved survival using intensity-modulated radiation therapy in head and neck cancers: a SEER-Medicare analysis

BACKGROUND

Intensity-modulated radiation therapy (IMRT) is a technologically advanced, and more expensive, method of delivering radiation therapy with a goal of minimizing toxicity. It has been widely adopted for head and neck cancers; however, its comparative impact on cancer control and survival remains unknown. The goal of this analysis was to compare the cause-specific survival (CSS) for patients with head and neck cancers treated with IMRT versus non-IMRT from 1999 to 2007.

METHODS

CSS was determined using the Surveillance, Epidemiology, and End Results (SEER)-Medicare database and analyzed regarding treatment details, including the use of IMRT versus non-IMRT, using claims data. Hazard ratios (HRs) were estimated by the frailty model with a propensity score matching cohort and instrumental variable analysis.

RESULTS

A total of 3172 patients were identified. With a median follow-up of 40 months, patients treated with IMRT had a statistically significant improvement in CSS compared with those treated with non-IMRT (84.1% versus 66.0%; P < .001). When each anatomic subsite was analyzed separately, all respective subgroups of patients treated with IMRT had better CSS than those treated with non-IMRT. In multivariable survival analyses, patients treated with IMRT were associated with better CSS (HR = 0.72, 95% confidence interval = 0.59 to 0.90 for propensity score matching; HR = 0.60, 95% confidence interval = 0.41 to 0.88 for instrumental variable analysis).

CONCLUSIONS

Patients with head and neck cancers who were treated with IMRT experienced significant improvements in CSS compared with patients treated with non-IMRT techniques. This suggests there may be benefits to IMRT in cancer outcomes, in addition to toxicity reduction, for this patient population.

Late oral complications following radiotherapy for head and neck cancers

Radiotherapy is an important treatment modality for head and neck cancers, both as definitive treatment and as adjunct treatment after surgery. Complications are common after radiotherapy for head and neck cancer owing to irradiation of many normal tissues and structures with important functions related to daily activities. Of these, late oral complications are of particular concern because of their effect on many basic functions, such as speech and swallowing. Although late complications following radiotherapy have been recognized for many years, recent developments in the treatment of head and neck cancers may have a significant impact on the incidence and severity of late complications. This article examines the current issue of late oral complications after radiotherapy, with an emphasis on the impact of recent advances in cancer treatment.

Oral complications and management strategies for patients undergoing cancer therapy

With cancer survival rate climbing up over the past three decades, quality of life for cancer patients has become an issue of major concern. Oral health plays an important part in one's overall quality of life. However, oral health status can be severely hampered by side effects of cancer therapies including surgery, chemotherapy, radiotherapy, and hematopoietic stem cell transplantation. Moreover, prevention and treatment of these complications are often overlooked in clinical practice. The present paper aims at drawing health care professionals' attention to oral complications associated with cancer therapy by giving a comprehensive review. Brief comments on contemporary cancer therapies will be given first, followed by detailed description of oral complications associated with cancer therapy. Finally, a summary of preventive strategies and treatment options for common oral complications including oral mucositis, oral infections, xerostomia, and dysgeusia will be given.

Xerostomia in patients treated for oropharyngeal carcinoma: comparing linear accelerator-based intensity-modulated radiation therapy with helical tomotherapy

BACKGROUND

In comparison to sliding-window intensity-modulated radiation therapy (sw-IMRT), we hypothesized that helical tomotherapy (HT) would achieve similar locoregional control and, at the same time, decrease the parotid gland dose, thus leading to a xerostomia reduction.

METHODS

The association between radiation techniques, mean parotid dose, and xerostomia incidence, was reviewed in 119 patients with advanced oropharyngeal carcinoma treated with concurrent chemoradiation using sw-IMRT (n = 59) or HT (n = 60).

RESULTS

Ipsilateral and contralateral parotid mean doses were significantly lower for patients treated with HT versus sw-IMRT: 24 Gy versus 32 Gy ipsilaterally and 20 Gy versus 25 Gy contralaterally. The incidence of grade ≥2 xerostomia was significantly lower in the HT group than in the sw-IMRT group: 12% versus 78% at 6 months, 3% versus 51% at 12 months, and 0% versus 25% at 24 months. Total parotid mean dose <25 Gy was strongly associated to a lower incidence of grade ≥2 xerostomia at 6, 12, and 24 months.

CONCLUSION

This retrospective series suggests that using HT can better spare the parotid glands while respecting quantitative analysis of normal tissue effects in the clinic (QUANTEC)'s criteria.

Intensity-modulated radiation therapy for head and neck cancer: systematic review and meta-analysis

BACKGROUND AND PURPOSE

Intensity-modulated radiation therapy (IMRT) provides the possibility of dose-escalation with better normal tissue sparing. This study was performed to assess whether IMRT can improve clinical outcomes when compared with two-dimensional (2D-RT) or three-dimensional conformal radiation therapy (3D-CRT) in patients with head and neck cancer.

METHODS AND MATERIALS

Only prospective phase III randomized trials comparing IMRT with 2D-RT or 3D-CRT were eligible. Combined surgery and/or chemotherapy were allowed. Two authors independently selected and assessed the studies regarding eligibility criteria and risk of bias.

RESULTS

Five studies were selected. A total of 871 patients were randomly assigned for 2D-RT or 3D-CRT (437), versus IMRT (434). Most patients presented with nasopharyngeal cancers (82%), and stages III/IV (62.1%). Three studies were classified as having unclear risk and two as high risk of bias. A significant overall benefit in favor of IMRT was found (hazard ratio - HR=0.76; 95% CI: 0.66, 0.87; p<0.0001) regarding xerostomia scores grade 2-4, with similar loco-regional control and overall survival.

CONCLUSIONS

IMRT reduces the incidence of grade 2-4 xerostomia in patients with head and neck cancers without compromising loco-regional control and overall survival.

Evaluating the impact of patient, tumor, and treatment characteristics on the development of jaw complications in patients treated for oral cancers: a SEER-Medicare analysis

BACKGROUND

Jaw complications, including osteoradionecrosis, are significant sequelae of radiation therapy (RT) for oral cancers. This study identifies the impact of patient, tumor, and treatment characteristics on the development of jaw complications in patients treated with RT.

METHODS

The Surveillance, Epidemiology, and End Results (SEER)-Medicare database was used to identify patients treated with RT for oral cancers from 1999 to 2007. Jaw complications were identified by International Classification of Diseases 9th revision (ICD-9) diagnosis codes and/or related procedures using Current Procedural Terminology (CPT) and ICD-9 codes.

RESULTS

A total of 1848 patients were identified. With a median follow-up of 2.5 years, 297 patients (16.1%) developed jaw complications: 226 patients had a diagnosis, 41 patients had a procedure, and 30 patients had both. On multivariate analysis, female sex, lack of chemotherapy use, and fewer comorbidities were associated with a statistically significant increase in jaw complications.

CONCLUSIONS

Even with modern techniques, jaw complications are a notable and potentially devastating side effect of RT for oral cancers.

A novel setup approach for helical tomotherapy in head and neck cancer: A case report

Head and neck cancers that are associated with high-risk factors have a poor prognosis. In such patients, post-operative radiochemotherapy is mandatory. The present study describes the case of a 71-year-old high-risk head and neck cancer patient who was not able to tolerate the supine position for the radiotherapy setup. A lateral immobilization with a head mask and a vacuum cushion was performed. The patient underwent daily computed tomography (CT)-guided radiation therapy [image-guided radiation therapy (IGRT)]. At nine months post-radiotherapy, the patient had no xerostomia and no swallowing dysfunction. However, the patient suffered a local recurrence and succumbed due to bleeding of the tumor a number of weeks after the recurrence. A recalculation of the actual delivered dose, taking the daily delivered dose into account, was performed. The recurrence occurred within the high-dose region. In selected cases of patients with head and neck cancers who are unable to tolerate the supine position, lateral positioning and high precision treatment is possible using daily IGRT.

Survey of advanced radiation technologies used at designated cancer care hospitals in Japan

OBJECTIVE

Our survey assessed the use of advanced radiotherapy technologies at the designated cancer care hospitals in Japan, and we identified several issues to be addressed.

METHODS

We collected the data of 397 designated cancer care hospitals, including information on staffing in the department of radiation oncology (e.g. radiation oncologists, medical physicists and radiation therapists), the number of linear accelerators and the implementation of advanced radiotherapy technologies from the Center for Cancer Control and Information Services of the National Cancer Center, Japan.

RESULTS

Only 53% prefectural designated cancer care hospitals and 16% regional designated cancer care hospitals have implemented intensity-modulated radiotherapy for head and neck cancers, and 62% prefectural designated cancer care hospitals and 23% regional designated cancer care hospitals use intensity-modulated radiotherapy for prostate cancer. Seventy-four percent prefectural designated cancer care hospitals and 40% regional designated cancer care hospitals employ stereotactic body radiotherapy for lung cancer. Our multivariate analysis of prefectural designated cancer care hospitals which satisfy the institute's qualifications for advanced technologies revealed the number of radiation oncologists (P = 0.01) and that of radiation therapists (P = 0.003) were significantly correlated with the implementation of intensity-modulated radiotherapy for prostate cancer, and the number of radiation oncologists (P = 0.02) was correlated with the implementation of stereotactic body radiotherapy. There was a trend to correlate the number of medical physicists with the implementation of stereotactic body radiotherapy (P = 0.07). Only 175 (51%) regional designated cancer care hospitals satisfy the institute's qualification of stereotactic body radiotherapy and 76 (22%) satisfy that of intensity-modulated radiotherapy. Seventeen percent prefectural designated cancer care hospitals and 13% regional designated cancer care hospitals had a quality assurance committee.

CONCLUSIONS

The numbers of radiation oncologists and other operating staff might be essential factors in the implementation of advanced radiotherapy technologies. Small proportions of regional designated cancer care hospitals satisfy the institute's qualifications of advanced technologies.