Abstract
BackgroundTo protect neurological tissues, underdosing occurs in most cases of T4 nasopharyngeal carcinoma (NPC) with intracranial extension. In this study, we aimed to evaluate the effect of dosimetric inadequacy on local control and late neurological toxicities for patients treated with intensity-modulated radiotherapy (IMRT) plus chemotherapy.MethodsWe prospectively enrolled patients who had non-metastatic T4 NPC with intracranial extension treated between January 2009 and November 2013. The prescribed dose was 66.0–70.4 Gy to the primary planning target volume (primary gross tumor volume [GTVp; i.e., the nasopharyngeal tumor] + 5.0 mm). Dose–volume histogram parameters were calculated, including minimum point dose (Dmin) and dose to 95% of the target volume (D95). All patients received chemotherapy with the cisplatin, 5-fluorouracil, and docetaxel regimen. Survivals were estimated using the Kaplan–Meier method and compared using the log-rank test.ResultsIn total, 41 patients were enrolled. The local partial response rate was 87.8% after induction chemotherapy. With a median follow-up of 51 months, 7 patients experienced failure in the nasopharynx; the 3-year local failure-free survival and overall survival rates of the 41 patients were 87.4% and 90.2%, respectively. The actual mean Dmin to the GTVp was 55.2 Gy (range 48.3–67.3 Gy), and D95 was 61.6 Gy (range 52.6–69.0 Gy). All doses received by neurological organs remained well within their dose constraints. No patients developed temporal lobe necrosis or other neurological dysfunctions.ConclusionsWith relative underdosed IMRT plus effective chemotherapy, the patients achieved satisfactory local control with few late toxicities of the central nervous system. Determining the acceptable extent of dosimetric inadequacy requires further exploration.
Highlights
To protect neurological tissues, underdosing occurs in most cases of T4 nasopharyngeal carcinoma (NPC) with intracranial extension
By imposing strict dose constraints for neurological structures, we aimed to explore the effect of dosimetric inadequacy on local control and treatment-induced toxicities for T4 NPC patients with intracranial extension when treating with intensity-modulated radiotherapy (IMRT) plus the TPF regimen
Dosimetric data Dosimetric data for critical neurological organs at risk (OARs) and gross tumor volume of the nasopharynx (GTVp) are summarized in Tables 2 and 3, respectively
Summary
To protect neurological tissues, underdosing occurs in most cases of T4 nasopharyngeal carcinoma (NPC) with intracranial extension. Owing to encouraging disease control results and the capacity for delivering a high radiation dose to the target while sparing adjacent organs, intensity-modulated radiotherapy (IMRT) is the standard treatment of nasopharyngeal carcinoma (NPC) [1, 2]. Because the tumor is located near neurological structures, such as the brain stem, temporal lobes, optic chiasm, and optic nerves, inadequate dose coverage of the target volumes often occurs. If dose constraints for the brain stem, optic chiasm, and optic nerves are prioritized, even the minimum tumoricidal dose to the entire target volume is not always achievable with the maximum tolerated dose of 54 Gy [8]
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