Pharyngeal Constrictor Muscle (Pcm) Sparing And Dysphagia Toxicity In The Treatment Of Intensity Modulated Radiation Therapy For Nasopharyngeal Cancer (Npc)

Contouring of PCM as a risk organ was started in the treatment planning of IMRT for NPC from 2009. As PCM sparing was not intended before 2009, we compared the dysphagia toxicity with or without PCM sparing, retrospectively. For all patients with NPC, two-step method IMRT was used as followed. Computed tomography planning was done twice before the start of IMRT for initial plan of 46-50 Gy/23-25 fractions and at the third or fourth week of treatment for boost plan of 20-24 Gy/10-12 fractions to high risk CTV. A total radiation dose was 70 Gy/ 35 fractions. Chemotherapy (cisplatin 80 mg/ m2 /3-weeks × 3 cycles) was given concurrently with IMRT, followed by adjuvant chemotherapy (cisplatin 70 mg/ m2 with 5-FU 700 mg/m2for 5 days × 2-3 cycles). In the present study, middle and lower PCM was re-contoured for all cases including patients without PCM sparing. PCM was contoured from the C2/3-disc level to bottom end of the cricoid cartilage. Upper PCM was excluded from PCM at OAR because it was included in PTV for NPC. Mean dose of the PCM was calculated using a radiation therapy planning system. Dysphagia toxicity was scored according to CTCAE Ver.4. Between 2004 and 2015, 72 consecutive patients were evaluable. Of the 72 patients, 39 patients were treated without contouring of PCM (group A) between 2004 and 2012. The remaining 33 patients were treated with PCM sparing (group B) between 2009 and 2015. Means of mean dose of PCM in groups A and B were 31.8Gy (range, 10.0-51.3Gy) and 28.4Gy (10-68Gy), respectively (t-test, P = 0.09). Dysphagia toxicity of group A and B were G0/1/2/3/5 = 29/3/3/3/1 and G0/1/2/3 = 26/5/1/1, respectively. One patient in group A dead of suffocation without tumor progression. Dysphagia toxicity of grade 2 or more was noted in 7 patients (18%) of group A , while only two patients (6%) of group B showed that toxicity (χ2test, P = 0.13). Our present analysis suggests that PCM sparing for NPC can reduce the incidence of severe dysphagia toxicity with IMRT.Tabled 1Abstract 2940; Table 1. Grade of dysphagiaG0G1G2G3G5group A: no PCM sparing (n = 39)293331group B: with PCM sparing (n = 33)265110 Open table in a new tab