![]() ![]() ![]() In the present study, the association between dose-volume histogram (DVH) parameters of normal tissues and late toxicities reported from patients enrolled in JCOG1015 were analyzed. The Japan Clinical Oncology Group (JCOG) study, a single-arm phase II trial, was conducted to investigate adaptive two-step IMRT for nasopharyngeal carcinoma (JCOG1015, UMIN-CTR: UMIN000005448) with more than 3 years’ follow-up and showed a 3-year overall survival rate of 88%. While much of the evidence forming this literature was based on clinical trials or clinical practice using 3D-CRT, these dose-volume constraints data should be revised in the era of IMRT. The Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) study, which reviewed and summarized normal tissue toxicity data from clinical trials, provided basic data of dose-volume constraints and clinical goals during radiation treatment planning for physicians and radiation oncologists. IMRT can deliver a more conformal dose to targets with reduced exposure to normal organs, which has improved xerostomia resulting from head and neck radiation therapy compared with 3D-conformal radiation therapy (3D-CRT). Intensity-modulated radiation therapy (IMRT), an advanced technique in external beam radiation therapy, has been widely used for head and neck carcinoma. The dose constraint criteria were appropriate for most OAR in this study, although more strict dose constraints might be necessary for the inner ear, PCM, and brainstem. The prevalence proportion of G2 xerostomia at 2 years was 17 versus 6% (contralateral parotid gland Dmean ≥ 25.8 Gy vs less). The optic nerve, pharyngeal constrictor muscle (PCM), and thyroid showed tendencies between DVH parameters and toxicity incidence. Significant associations between DVH parameters and incidences of toxicities were observed in the brainstem for myelitis (D1cc ≥ 55.8 Gy), in the brain for CNS necrosis (D1cc ≥ 72.1 Gy), in the eyeball for optic nerve disorder (Dmax ≥ 36.6 Gy), and in the ipsilateral inner ear for hearing impaired (Dmean ≥ 44 Gy). The 5-year cumulative incidences of Grade (G) 1 myelitis, ≥ G1 central nervous system (CNS) necrosis, G2 optic nerve disorder, ≥ G2 dysphagia, ≥ G2 laryngeal edema, ≥ G2 hearing impaired, ≥ G2 middle ear inflammation, and ≥ G1 hypothyroidism were 10%, 5%, 2%, 11%, 5%, 26%, 34%, and 34%, respectively. ROC analysis was used to estimate the optimal DVH cut-off value that predicted toxicities. The incidence of late toxicities was evaluated using the cumulative incidence method or prevalence proportion. Individual patient data and dose-volume histograms of organs at risk (OAR) were collected from 74 patients with nasopharyngeal carcinoma treated with IMRT who enrolled in JCOG1015. JCOG1015A1 is an ancillary research study to determine the organ-specific dose constraints in head and neck carcinoma treated with intensity-modulated radiation therapy (IMRT) using data from JCOG1015. ![]()
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