Dose-volume analysis of radiation dermatitis among nasopharyngeal carcinoma patients treated with comcurrent cetuximab-cisplatin and intensity-modulated radiotherapy

Abstract

17015 Background: To investigate the impact of dose-volume parameters of skin on the severity of radiation dermatitis in a cohort of nasopharyngeal carcinoma (NPC) patients treated with concurrent cetuximab (C225), cisplatin, and intensity-modulated radiotherapy (IMRT). Method: 20 stage III-IVb NPC patients were treated with a loading dose of C225 (400 mg/m2), followed by IMRT (74 Gy to primary, 70 Gy to involved nodes, 62 Gy to subclinical region, 35 fractions) plus weekly cisplatin (30 mg/m2) and C225 (250 mg/m2) for 6–7 cycles during radiotherapy. The different level of worst skin toxicity (Grade 0–2 vs. 3–4) within 90 days from start of RT (NCI CTCAE v 3.0), and hyperpigmentation (mild or moderate) were compared with respect to various dose-volume parameters: total skin volume within radiation portal (Vt), volume of skin irradiated to different dose levels (Vdose), maximum (Dmax) and mean (Dmean) skin dose using Mann-Whitney test. Result: The incidence of grades 1, 2, 3 and 4 radiation dermatitis were 30%, 45%, 20% and 5%, respectively. Duration of ≥grade 3 toxicity was less than 2 weeks in all patients. 5 patients (25%) developed moderate hyperpigmentation at irradiated skin, which improved gradually over time. The range of Dmax, Dmean, and Vt are 70–80 Gy, 21–28 Gy, and 758–1415 c.c., respectively. There was no significant difference in Dmax, Dmean, Vt, V70 Gy, V60 Gy, V50 Gy, V40 Gy, V30 Gy, V20Gy or V10Gy between patients with <grade 3 or ≥grade 3 skin toxicity. Likewise, there was no significant difference in these dose-volume parameters between patients with or without moderate skin hyperpigmentation. Conclusion: The current study suggests that triple therapy (IMRT, cisplatin, C225) does not significantly increase the severity of radiation dermatitis as compared to bimodality treatment (either radiotherapy plus C225 or chemoradiation). Within the range of irradiated skin dose and volume in this study, there is no association between dosimetry factors and skin toxicity implying that radiation dermatitis may be dominated by other physical or genetic risk factors that influence individual’s normal tissue sensitivity. No significant financial relationships to disclose.