A retrospective dosimetry study of intensity-modulated radiotherapy for nasopharyngeal carcinoma: radiation-induced brainstem injury and dose-volume analysis

Abstract

BackgroundRadiation therapy is the standard radical treatment for nasopharyngeal carcinoma (NPC) but also causes transient as well as long-term complications. Patients who develop severe radiation-induced brainstem injuries have a poor prognosis due to the lack of effective medical therapies. However, the relationship between brainstem injury and radiation volume dose is unknown. In this study, we found that radiation-induced brainstem injury was significantly associated with brainstem dose per unit volume.MethodsA retrospective analysis was performed on a consecutive cohort of 327 patients with NPC receiving IMRT from May 2005 to December 2014. Dose-volume data and long-term outcome were analyzed.ResultsThe median follow-up duration was 56 months (range, 3–141 months), and six with T4 and two with T3 patients had radiation-induced brainstem injuries. The 3-year and 5-year incidences were 2.2% and 2.8%, respectively. The latency period of brainstem injury ranged from 9 to 58 months, with a median period of 21 months. The Cox regression analysis showed that brainstem radiation toxicity was associated with the T4 stage, D2% of gross tumor volume of nasopharyngeal primary lesions and their direct extensions (GTVnx), Dmax (the maximum point dose), D1%, D0.1cc (the top dose delivered to a 0.1-ml volume), and D1cc (the top dose delivered to a 1-ml volume) of the brainstem (p < 0.05). Receiver operating characteristic (ROC) curves showed that GTVnx D2% and the Dmax, D1%, D0.1cc, and D1cc of the brainstem were significant predictors of brainstem injury. The area under the ROC curve for these five parameters was 0.724, 0.813, 0.818, 0.818, and 0.798, respectively (p < 0.001), and the cutoff points 77.26 Gy, 67.85 Gy, 60.13 Gy, 60.75 Gy, and 54.58 Gy, respectively, were deemed as the radiation dose limit.ConclusionsRadiotherapy-induced brainstem injury was uncommon in patients with NPC who received definitive IMRT. Multiple dose-volume data may be the dose tolerance of radiation-induced brainstem injury.

Evolution and Dosimetric Analysis of Magnetic Resonance Imaging–Detected Brain Stem Injury After Intensity Modulated Radiation Therapy in Nasopharyngeal Carcinoma

“…latency of 21 months for patients with NPC treated with IMRT. 20 Thus, it appears that the latency of BSI in the modern RT era is quite similar to that in the conventional RT era, ranging from 6 months to 2 years. 21 In comparison, the latency of temporal lobe injury is reported to be between 2 and 5 years.…”

Lumbar vertebral osteoradionecrosis: a rare case report with 10-year follow-up and brief literature review

“…Anterior spinal surgery was also recommended owing to its advantages of excellent removal of necrotic bone, direct spinal cord decompression, and good fusion bed preparation in an irradiated surgical area. In the previous cervical ORN cases reported, the surgical rate for ORN was 52% (16/31), indicating that most patients with spinal ORN cannot be cured with conservative treatment [4,[7][8][9][10][11][12]. In our case, the patient was successfully treated conservatively.…”

“…ORN gradually progresses to the chronic phase, which includes vascular damage that leads to a combination of osteitis and discitis. ORN of the jaw has been reported to commonly present within 2 years after radiation treatment but has been described to present up to 20 to 30 years after the initial radiotherapy [8]. In addition, we reviewed that the mean time to onset of previous cervical ORN cases was 112 months, and the longest time was even up to 42 years [4,[7][8][9][10][11][12].…”

“…In this case, the patient had ORN 2 years after radiotherapy without a traumatic factor, so the classification of ORN was type 3 according this classification system. In the previous cervical ORN cases reported, type 3 ORN occurred most frequently (29/31, 93.5%), followed by type 1 ORN (2/31, 6.5%) [4,[7][8][9][10][11][12].…”

“…However, as ORN progresses, spinal kyphosis and instability can also lead to neurological compression and induced myelopathy or radiculopathy. In our review, most patients (18/31, 58%) with cervical ORN presented with symptoms of neurological injury at the end stage [4,[7][8][9][10][11][12]. Nevertheless, the common symptom of back pain is often overlooked as numerous etiological factors influenced.…”