Hypoxia Imaging -Guided Radiotherapy of Nasopharyngeal Carcinoma

Overview

Nasopharyngeal carcinoma (NPC) differs from other head and neck malignancies in terms of its epidemiology, pathology, and treatment outcome . It is endemic in China and is one of the major public health problems. Concurrent radiotherapy and chemotherapy is the primary treatment for patients with NPC. Despite such aggressive treatment, many patients with locally advanced NPC still develop locally recurrent disease. Since local control is directly related to patient morbidity and mortality in NPC, there is a strong need to identify methods to further improve treatment outcome for NPC. One strategy to improve local control is to escalate the dose of radiotherapy. This is because local control has been shown to be directly related to the radiotherapy dose. Several different techniques, including brachytherapy, stereotactic radiosurgery, and dose-painting intensity modulated radiotherapy (IMRT), have been used to increase radiotherapy dose. However, due to the large number of critical anatomic structures near the nasopharynx, dose-escalation in NPC can also lead to increased toxicities. One technique that has achieved dose-escalation with minimal increase in toxicity is simultaneous modulated accelerated radiation therapy (SMART). The main challenge for such treatment is to identify the appropriate tumor volume to receive the high-dose radiotherapy. Conventional dose-escalation is conducted using computed tomography (CT) to identify the gross tumor volume (GTV). However, recent progress with F-18 fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG-PET/CT) in treatment planning allows more accurate tumor volume delineation. We hypothesize that the use of PET/CT in treatment planning can improve dose-escalation radiotherapy for NPC which in turn can improve therapeutic efficacy while reducing toxicity. PET/CT imaging of tissue hypoxia using \[F-18\]fluoromisonidazole (FMISO), the most widely used nitroimidazole imaging agent.Given that there has been no clinical trials directly comparing conventional chemoradiotherapy to CT-guided dose-escalation chemoradiotherapy or PET/CT guided dose-escalation chemoradiotherapy in locally advanced NPC.This was a study to evaluate the role of FMISO-PET hypoxia imaging for predicting survival in NPC,our study aims to compare the local control, overall survival and toxicities of the three treatment regimens..

Study Design Patients with previously untreated Stages III\~IVA (AJCC 6th Edition) of locally advanced NPC, Karnofsky performance status≥70, and good bone marrow, liver and kidney functions (white blood count ≥ 4.0×109/L, platelets ≥ 100×109/L, albumin ≥30 g/L , creatinine ≤100μmol/L) were enrolled on this study. Patients younger than 18, those with a prior (within 5 years) or synchronous malignancy were excluded. Pretreatment evaluations consisted of a history and physical, dental and laboratory studies. The clinical stage was determined based on all information provided by examinations including contrast enhanced CT and magnetic resonance imaging (MRI) of head and neck, Chest X-ray, liver sonography, bone scan, and 18F-FDG-PET. All tumors were histologically confirmed except those of distant sites. Patients who met the eligibility criteria were randomized 1:1:1 into the three treatment arms: conventional chemoradiotherapy (group A), FDG PET/CT -guided dose escalation chemoradiotherapy (group B) and FMISO PET/CT -guided dose escalation chemoradiotherapy (group C). All patients were given concurrent chemoradiotherapy within two weeks of diagnosis. Radiotherapy was delivered using the simultaneous modulated accelerated radiation therapy (SMART) IMRT technique in the dose-escalation treatment arms. Concurrent chemotherapy consisted of cisplatin (20mg / m2 ,iv, d1- 4) and docetaxel (75mg / m2, d1, d8) administered on the 1st and 4th week of treatment. All patients received adjuvant chemotherapy that ranged from 2 to 4 cycles. Follow-up and statistical analysis Planned patient assessment included physical examination and fiberoptic nasopharyngoscopy every 3 months to 3 years starting at 4 weeks post-treatment. A contrast-enhanced CT or MRI of the head and neck is also obtained at each follow up. After 3 years, the patients were followed yearly thereafter. Suspected recurrences were histologically proven. To assess for distant metastasis, CT of the chest and bone scan were obtained every half a year. During every follow-up visit, treatment toxicity were assessed. Radiotherapy-related toxicities were graded according to the Acute and the Late Radiation Morbidity Scoring Criteria of the Radiation Therapy Oncology Group (RTOG) and the European Organization for Research and Treatment of Cancer (EORTC). Chemotherapy-related toxicities (except nausea or alopecia) were graded by the criteria of the WHO. All events were measured from the date of randomization. OS was defined as the time from the date of radiotherapy to death or the latest date known to be alive. Durations were calculated from the end of treatment. The Kaplan-Meier method was used to calculate the actuarial rates of local control, DFS and OS. The χ2 test was used for comparing incidence rates and categorical variables and Student's t-test was used for comparing the means of continuous variables.