Dental intervention for the irradiated patient: time to re-evaluate dental treatment algorithms?

Modern radiotherapy delivery systems and treatment strategies are aimed at limiting the irradiation of healthy structures in the head and neck. This seeks to mitigate post-treatment toxicities and complications such as osteoradionecrosis of the jaw. Given the changes to radiotherapy, conventional workflows for the management of patients requiring dentoalveolar surgery may no longer be suitable. It may therefore be appropriate to revisit current treatment algorithms for the management of patients with radiotherapy to the jaws who require dentoalveolar surgery. At present, there are poor data on this. Development of a randomised trial may be warranted to establish the true relative risk for extraction of teeth in the setting of modern radiation therapy delivery systems.

Submandibular Gland Transfer: A Potential Imaging Pitfall.

BACKGROUND AND PURPOSE: The Seikaly and Jha submandibular gland transfer surgery is performed to facilitate gland shielding during radiation therapy for head and neck tumors to circumvent radiation-induced xerostomia. It results in an asymmetric postsurgical appearance of the submandibular and submental spaces. Our purpose was to characterize the morphologic and enhancement characteristics of the transferred submandibular gland and identify potential pitfalls in postoperative radiologic interpretation. MATERIALS AND METHODS: This retrospective study identified patients with head and neck cancer who had undergone the submandibular gland transfer procedure at our institution. Chart reviews were performed to identify relevant oncologic histories and therapies. CT and MR neck imaging was reviewed to characterize morphologic and enhancement characteristics of the pre- and postoperative submandibular glands, as well as interpretive accuracy. RESULTS: Eleven patients with oropharyngeal and nasopharyngeal squamous cell carcinomas who underwent submandibular gland transfer were identified. The transferred glands were significantly lengthened in the anteroposterior dimension compared with contralateral glands (P < .001) and displaced anteriorly and inferiorly within the submandibular and submental spaces. Enhancement patterns of the transferred submandibular glands varied, depending on the time of imaging relative to the operation and radiation therapy. Submandibular gland transfer was acknowledged in the postoperative report in 7/11 cases. Errors in interpretation were present in 2/11 reports. CONCLUSIONS: After the submandibular gland transfer procedure, the submandibular and submental spaces lose their symmetric appearances as the transferred submandibular glands become lengthened and located more anteriorly and inferiorly, with variable enhancement characteristics. Familiarity with the postsurgical appearance of the transferred submandibular glands is key to accurate imaging interpretation.

Impact of Neuroradiology-Based Peer Review on Head and Neck Radiotherapy Target Delineation.

BACKGROUND AND PURPOSE: While standard guidelines assist in target delineation for head and neck radiation therapy planning, the complex anatomy, varying patterns of spread, unusual or advanced presentations, and high risk of treatment-related toxicities produce continuous interpretive challenges. In 2007, we instituted weekly treatment planning quality assurance rounds as a joint enterprise of head and neck radiation oncology and neuroradiology. Here we describe its impact on head and neck radiation therapy target delineation. MATERIALS AND METHODS: For 7 months, treatment planning quality assurance included 80 cases of definitive (48%) or postoperative (52%) head and neck radiation therapy. The planning CT and associated target volumes were reviewed in comparison with diagnostic imaging studies. Alterations were catalogued. RESULTS: Of the 80 cases, 44 (55%) were altered, and of these, 61% had clinically significant changes resulting in exclusion or inclusion of a distinct area or structure. Reasons for alteration included the following: gross or extant tumor, 26/44 (59%); elective or postoperative coverage, 25/44 (57%); lymph nodes, 13/44 (30%); bone, 7/44 (16%); skull base, 7/44 (16%); normal organs, 5/44 (11%); perineural, 3/44 (7%); distant metastasis, 2/44 (5%); and eye, 1/44 (2%). Gross tumor changes ranged from 0.5% to 133.64%, with a median change in volume of 5.95 mm3 (7.86%). Volumes were more likely to be increased (73%) than decreased (27%). CONCLUSIONS: A collaborative approach to head and neck treatment planning quality assurance has an impact. Cases likely to have challenging patterns of infiltrative, intracranial, nodal, orbital, or perineural spread warrant intensive imaging-based review in collaboration with a diagnostic neuroradiologist.

Prognostic significance of hyoid bone invasion in advanced base of tongue carcinoma treated by chemoradiation.

OBJECTIVES: To examine the prognostic influence of hyoid bone invasion in advanced base of tongue squamous cell carcinoma treated with chemoradiation. METHODS: We retrospectively reviewed pre-treatment imaging (CT/MRI) for the presence or absence of hyoid bone invasion in patients with advanced (clinical T3 or T4a stage) base of tongue squamous cell carcinoma treated with chemoradiation from January 2001 to January 2011. We compared patients with hyoid bone invasion to those without based on the following metrics: 1-, 2- and 5-year locoregional recurrence-free survival, disease-free survival, disease-specific survival and overall survival. RESULTS: Eleven of thirty-seven patients had hyoid invasion present on pre-treatment imaging. Average follow-up was 45 months. Patients with hyoid bone invasion were found to have lower percentages in all survival metrics measured compared to patients without, respectively, with statistical significance achieved in the following: 2-year locoregional recurrence-free survival: 36.4% versus 86.4% (P = 0.006), 5-year locoregional recurrence-free survival: 12.5% versus 63.6% (P = 0.05), 2-year disease-free survival: 36.4% versus 77.3% (P = 0.05), 5-year disease-free survival: 12.5% versus 63.3% (P = 0.05) and the Kaplan-Meier curve for locoregional recurrence-free survival (P = 0.0075). CONCLUSIONS: Hyoid bone invasion by base of tongue squamous cell carcinoma may indicate a poorer prognosis despite treatment. Hyoid bone invasion may be a possible indication for intensification of treatment and/or may indicate a necessity for increasing the degree of post-treatment surveillance monitoring and imaging.

Induction Hedgehog pathway inhibition followed by combined-modality radiotherapy for basal cell carcinoma.

Basal cell carcinoma (BCC), the most common cancer in the U.S.A., is treated primarily with local excision. In some cases, lesion size, location or extent prevent complete resection. Locally advanced BCC responds to systemic therapy with the Hedgehog pathway inhibitor vismodegib, but withdrawal of treatment may result in disease relapse. Here we present a case of locally advanced auricular BCC treated with induction vismodegib and radiation, resulting in durable local control and an acceptable level of acute toxicity.

Oropharyngeal carcinoma arising after methotrexate and etanercept therapy for rheumatoid arthritis.

Etanercept is an anti-tumor necrosis factor α receptor agent used to treat inflammatory conditions. Previous reports described rapid development of skin squamous cell carcinoma (SCC) after etanercept use. This report describes a novel case of oropharyngeal SCC associated with the use of etanercept. A 45-year-old man with rheumatoid arthritis developed oropharyngeal pain within 2 months after the start of etanercept therapy and was diagnosed with tonsillar carcinoma. This patient had other exposures that increase the risk of oropharyngeal cancer, such as tobacco and alcohol use. However, owing to the timing of onset of his initial symptoms, etanercept should be considered as a possible factor in the etiology or progression of his tumor, especially in the context of reported skin SCC after etanercept therapy in patients at risk for SCC. Clinicians should be alert to signs of malignancy in patients on etanercept, particularly those at high risk for skin or head and neck cancers.

SU-E-J-84: Investigating the Use of Deformable Algorithms to Register and Accumulate Dose to the Spinal Cord for Head-And-Neck Radiotherapy Patients.

PURPOSE: Mega-voltage cone-beam CT (MVCBCT) imaging can be used to monitor changes in neck flexion and calculate the true spinal cord dose during radiotherapy. To sum the dose over multiple fractions and compare with the planned dose requires deformable image registration. This study investigates the accuracy of deformable registration of the spine in kilovoltage CT (kVCT) to MVCBCT images for head-and-neck patients. METHODS: Head-and-neck kVCT and MVCBCT images were selected from five patients who exhibited large changes in neck flexion. The spinal canal was contoured in each image. MVCBCT images were rigidly registered to the kVCT image by aligning the C1-C2 vertebrae. Variations of a commercial deformable registration algorithm using the B-spline method were applied to a volume of interest surrounding the spine to deform the spinal cord structure from the kVCT to the MVCBCT. The Dice similarity index (DSI) was calculated between rigidly registered structures (DSI1), and compared against the DSI calculated between the MVCBCT structure and the structure deformed from kVCT to MVCBCT (DSI2). The difference between DSI2 and DSI1 was calculated to investigate the ability of the deformation algorithm to match the change in neck flexion. RESULTS: In this data set, a single-pass B-spline deformation algorithm was the most effective in deforming the kVCT spinal canal to the MVCBCT spinal canal, with a mean improvement in DSI (DSI2 - DSI1) of 0.134. The mean change in DSI for a single-pass algorithm with a contrast correction was 0.111; for a multiple-pass algorithm was 0.105; and for a multiple-pass algorithm with contrast correction was 0.075. CONCLUSIONS: Several versions of a commercially implemented B-spline deformation algorithm were found to improve the registration of the spinal canal in kVCT and MVCBCT head-and-neck images. The resulting accuracy in the calculation of the cumulative dose to the spinal cord is under investigation. We acknowledge Velocity for providing the registration software.

Sonographic examination of the neck after definitive radiotherapy for node-positive oropharyngeal cancer.

BACKGROUND AND PURPOSE: Radiographic determination of viable disease in cervical adenopathy following RT for head and neck cancer can be challenging. The purpose of this study was to evaluate the utility of US, with or without FNA, in regard to the postradiotherapy effects on documented metastatic adenopathy in patients with oropharyngeal cancer. MATERIALS AND METHODS: This study included 133 patients with node-positive oropharyngeal cancer who were irradiated from 1998 to 2004. Sonographic evaluation was performed within 6 months of completion of radiation. Posttreatment US results were compared with pretreatment CT images and were recorded as the following: progression, suspicious, indeterminate, posttreatment change, or regression (positive) versus nonsuspicious or benign (negative). FNAC was classified as nondiagnostic, negative, indeterminate, or positive. Results of US and US-guided FNAC were correlated with findings at neck dissection and disease outcome. RESULTS: Of 203 sonographic examinations, 90% were technically feasible and yielded a nonequivocal imaging diagnosis. Of 87 US-guided FNAs, 71% yielded a nonequivocal tissue diagnosis. The PPV and NPV of initial posttreatment US were 11% and 97%. Sensitivity and specificity were 92% and 28%. The PPV and NPV of US-guided FNA were 33% and 95%, and the sensitivity and specificity were 75% and 74%. On serial sonographic surveillance, of 33 patients with nonsuspicious findings, only 1 (3%) had neck recurrence. Of 22 patients with questionable findings on CT and negative findings on US, none had a neck recurrence. CONCLUSIONS: In experienced hands, serial US is an inexpensive noninvasive reassuring follow-up strategy after definitive head and neck RT, even when CT findings are equivocal.

A diamond target for megavoltage cone-beam CT.

PURPOSE: To determine the properties of a megavoltage cone-beam CT system using the unflattened beam from a sintered diamond target at 4 and 6 MV. METHODS: A sintered diamond target was used in place of a graphite target as part of an imaging beam line (an unflattened beam from a graphite target) installed on a linear accelerator. The diamond target, with a greater density than the graphite target, permitted imaging at the lower beam energy (4 MV) required with the graphite target and the higher beam energy (6 MV) conventionally used with the tungsten/stainless steel target and stainless steel flattening filter. Images of phantoms and patients were acquired using the different beam lines and compared. The beam spectra and dose distributions were determined using Monte Carlo simulation. RESULTS: The diamond target allowed use of the same beam energy as for treatment, simplifying commissioning and quality assurance. Images acquired with the diamond target at 4 MV were similar to those obtained with the graphite target at 4 MV. The slight reduction in low energy photons due to the higher-Z sintering material in the diamond target had minimal effect on image quality. Images acquired at 6 MV with the diamond target showed a small decrease in contrast-to-noise ratio, resulting from a decrease in the fraction of photons in the beam in the energy range to which the detector is most sensitive. CONCLUSIONS: The diamond target provides images of a similar quality to the graphite target. Diamond allows use of the higher beam energy conventionally used for treatment, provides a higher dose rate for the same beam current, and potentially simplifies installation and maintenance of the beam line.

Sci-Thurs PM: Delivery-12: Correction and calibration of megavoltage cone-beam CT images for the calculation of the dose of the day.

PURPOSE: To show that accurate dose calculations can be achieved with megavoltage cone-beam CT (MVCBCT) images of head-and-neck (H&N) and prostate sites, allowing the verification of the daily dose distribution received by these patients. METHOD AND MATERIALS: Corrections for the cupping and missing data artifacts seen on MVCBCT images were developed for both H&N and pelvic imaging. MVCBCT images of six H&N and two prostate patients were acquired weekly during the course of their treatment. Several regions of interest were contoured including: the prostate and rectum and the spinal cord and parotids. Dose calculation was performed with the MVCBCT images using the plan beams. Variations from treatment plan dosimetric endpoints were analyzed. RESULTS: Dose calculations with kVCT and corrected MVCBCT images of the H&N (pelvic) regions show standard deviations of 1.9% (0.6%). The mean dose to the right parotid of H&N patients had an average increase of 18% during treatment. The maximum dose to 1% of the spinal cord went up by 2% on average. For prostate patients on one fraction the dose received by 95% of the prostate diminished by 3%. One patient had an average increase of 3.6% of the maximum dose received by 1% of the rectum. CONCLUSION: MVCBCT can be used to verify daily dose distributions for H&N and prostate patients. An increase in the mean dose to normal tissues was observed during H&N treatment. Underdosage of the prostate and the dosimetric consequences of volume changes in rectum and bladder were observed. Research supported by Siemens.