New Radiation Therapy Techniques for the Treatment of Head and Neck Cancer

Dental Materials Effect in Neutron Contamination: Electron Mode of a Linac

BACKGROUND

Neutron contamination is produced in electron beams of linac when tooth or dental materials are located in the path of beam.

OBJECTIVE

This study aims to determine the neutron dose contamination from different dental restoration materials in electron mode of a linac.

MATERIAL AND METHODS

In this experimental study, the neutron dose contamination was calculated in the presence of tooth and tooth restored by Ceramco C3 veneer, Eclipse or amalgam. The electron mode included 8, 12, and 14 MeV electron beams of Siemens Primus linac at different depths before and after tooth. MCNPX code was used to simulate the linear accelerator and dental restoration materials. Tooth and tooth restoration materials were located in the beams' central axis and the neutron dose was scored in 3 × 3 × 1 cm³ voxels at different depths before and after the tooth.

RESULTS

The highest neutron dose contamination was observed for the combination of the tooth and Eclipse in 12 and 14 MeV beams and the maximum calculated relative neutron dose was 1.53 for tooth and Eclipse for 14 MeV electron beam.

CONCLUSION

Tooth and dental materials lead to neutron dose contamination production, therefore, in order to avoid having harmful effects on normal tissues due to the neutron beam in head and neck cancer, it is recommended that treatment planning performed should not place tooth with dental restoration materials in the path of the beam and lower energy electron beams be used.

The role of PET/CT in the management of patients affected by head and neck tumors: a review of the literature

The management of head and neck tumor (HNSCC) has been changing over the years, especially due to the aid of imaging techniques that help physicians to attain a correct diagnosis. These techniques represent a valuable tool to help tailor treatment and during follow-up of patients affected by malignancies. The aim of this review is to summarize the results of the most recent and relevant studies about the use of PET imaging in HNSCCs. This review is divided into six chapters: (1) The role of PET/CT in the pre-treatment phase; (2) PET/CT and radiotherapy planning; (3) PET/CT in the post-treatment setting; (4) PET/CT and SUVmax for prediction of prognosis; (5) miscellanea on the utility of PET in specific HNSCCs; (6) non-FDG PET tracers used in HNSCC. Promising results have been obtained so far. Despite the encouraging outcomes, more investigations are needed to warrant the value of this technique, especially in the pre-treatment setting.

Is FDG -PET-CT a valuable tool in prediction of persistent disease in head and neck cancer

OBJECTIVES

To evaluate accuracy of FDG-PET CT in prediction of persistent disease in head and neck cancer cases and to determine prognostic value of metabolic tumor response.

MATERIALS AND METHODS

Between 2009 and 2011, 46 patients with squamous cell carcinoma of head and neck receiving PET-CT were treated with definitive radiotherapy, with or without chemotherapy. There were 29 nasopharyngeal, 11 hypopharyngeal, 3 oropharyngeal and 3 laryngeal cancer patients, with a median age of 50.5 years (range 16-84), 32 males and 14 females. All patients were evaluated with PET-CT median 3-5 months (2.4-9.4) after completion of radiotherapy.

RESULTS

After a median 20 months of follow up, complete metabolic response was observed in 63% of patients. Suspicious residual uptake was present in 10.9% and residual metabolic uptake in 26.0% of patients. The overall sensitivity, specificity, positive predictive value and negative predictive value of FDG-PET-CT for detection of residual disease was 91% and 81%, 64% and 96% respectively. Two year LRC was 95% in complete responders while it was 34% in non-complete responders.

CONCLUSIONS

FDG PET CT is a valuable tool for assessment of treatment response, especially in patients at high risk of local recurrence, and also as an indicator of prognosis. Definitely more precise criteria are required for assessment of response, there being no clear cut uptake value indicating residual disease. Futhermore, repair processes of normal tissue may consume glucose which appear as increased uptake in control FDG PET CT.

Influence of irradiation and oncologic surgery on head and neck microsurgical reconstructions

Despite the refinement of microsurgical techniques, microsurgical free flap transfer in patients with a history of previous radiotherapy, neck dissection or free flaps remains a challenge in oncologic reconstructive surgery. Previous studies on the prognostic factors for postoperative complications have been largely retrospective and shown conflicting results. Our aim was to design a prospective study to identify negative outcome predictors of free flap surgery in previously treated oral cancer patients. Prospective study including all patients who required microsurgical free flap transfer for reconstruction of the oral cavity between July of 2007 and June of 2010 with subset analysis of those cases in whom previous surgical or nonsurgical oncological treatment for head and neck cancer had been carried out. A total of 360 free flaps were performed in 358 patients, of whom 61 had previous neck dissection and 58 had undergone radiation therapy. Operation time was significantly found to be longer in irradiated patients. The need for microsurgical revision, postoperative wound infection and free flap loss were significantly associated with the ASA score and a previous neck dissection. Wound infection was seen significantly more often after radiotherapy. Previous neck dissections and radiotherapy as well as the ASA score are significant negative predictors for success in free flap transfer. For patients with prior oncologic treatments in their medical history, we recommend detailed preoperative assessment of the vascular status and an intensified postoperative care to reduce complication rates to improve outcome in oncologic reconstructive surgery.

Lack of a correlation between γH2AX foci kinetics in lymphocytes and the severity of acute normal tissue reactions during IMRT treatment for head and neck cancer

PURPOSE

To investigate the phosphorylated histone H2A isoform X (γH2AX) foci kinetics as an indicator for the development of acute normal tissue complications during Intensity-Modulated Radiotherapy (IMRT) for head and neck cancer (HNC) patients.

MATERIALS AND METHODS

Microscopic scoring of the γH2AX foci was used to evaluate the DNA-double-strand-break repair capacity in from Ataxia-Telangiectasia (A-T) patients derived lymphoblastoid cell lines (LCL) and T-lymphocytes isolated from 31 IMRT treated HNC patients. Cells were irradiated in vitro with 0.5 Gy given at high-dose-rate (HDR) and examined at several times up to 24 h after irradiation. The patients were subdivided in three groups showing mild, moderate and severe acute normal tissue complications based on their Common Toxicity Criteria grades for dysphagia, mucositis and dermatitis during the radiotherapy course.

RESULTS

For the ATM (Ataxia-Telangiectasia-Mutated) defective LCL, a lower number of radiation-induced foci and a somewhat less efficient repair capacity was observed. No correlation was found between the γH2AX foci kinetics pattern and the risk for acute normal tissue complications among the three patient subgroups.

CONCLUSIONS

Scoring of γH2AX foci after in vitro irradiation of isolated T-lymphocytes of HNC patients cannot be applied to predict for the development of acute normal tissue complications.

Head and neck cancer

Most head and neck cancers are squamous cell carcinomas that develop in the upper aerodigestive epithelium after exposure to carcinogens such as tobacco and alcohol. Human papillomavirus has also been strongly implicated as a causative agent in a subset of these cancers. The complex anatomy and vital physiological role of the tumour-involved structures dictate that the goals of treatment are not only to improve survival outcomes but also to preserve organ function. Major improvements have been accomplished in surgical techniques and radiotherapy delivery. Moreover, systemic therapy including chemotherapy and molecularly targeted agents--namely, the epidermal growth factor receptor inhibitors--has been successfully integrated into potentially curative treatment of locally advanced squamous-cell carcinoma of the head and neck. In deciding which treatment strategy would be suitable for an individual patient, important considerations include expected functional outcomes, ability to tolerate treatment, and comorbid illnesses. The collaboration of many specialties is the key for optimum assessment and decision making. We review the epidemiology, molecular pathogenesis, diagnosis and staging, and the latest multimodal management of squamous cell carcinoma of the head and neck.

Posttreatment assessment of response using FDG-PET/CT for patients treated with definitive radiation therapy for head and neck cancers

PURPOSE

The goal of this study was to evaluate coregistered [18F] fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) for the detection of persistent disease after definitive radiation therapy in head and neck cancer.

METHODS AND MATERIALS

Posttreatment FDG-PET/CT was performed in 28 patients on average 8 weeks (range, 4 to 15.7 weeks) after completing definitive radiation therapy. FDG-PET/CT was visually analyzed for the entire patient group and at two time points (4-8 and >8 weeks) after treatment. The contrast-enhanced CT portion of PET/CT was separately analyzed blinded to the results of coregistered FDG-PET/CT and classified as negative or positive for residual locoregional disease. Pathologic findings and clinical follow-up served as the reference standard.

RESULTS

Follow-up data were available for all 28 patients (median, 17.6 months). Regarding the detection of residual disease, the overall sensitivity and specificity of FDG-PET/CT was 76.9% and 93.3%, respectively, compared with 92.3% and 46.7% for contrast-enhanced CT. The accuracy of FDG-PET/CT was 85.7%, compared with 67.9% for CT alone. All false-negative (n = 3) and false-positive (n = 1) FDG-PET/CT results occurred between 4 and 8 weeks after treatment. At 8 weeks or later after treatment, the specificity of CT was 28%, compared with 100% for FDG-PET/CT.

CONCLUSIONS

The metabolic-anatomic information from coregistered FDG-PET/CT provided the most accurate assessment for treatment response when performed later than 8 weeks after the conclusion of radiation therapy. FDG-PET/CT excelled by a higher specificity and overall diagnostic performance than CT imaging alone. These results support a potential clinical role of FDG-PET/CT in the early assessment of therapy response after definitive radiation therapy.