Intensity-modulated radiation therapy reduces radiation-induced trismus in patients with nasopharyngeal carcinoma: a prospective study with >5 years of follow-up.
BACKGROUND
Intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC) provides better temporomandibular joint (TMJ) sparing and, thus, may reduce the incidence of radiation-induced trismus after radiotherapy. The objectives of this study were to evaluate radiation-induced trismus in patients with NPC who had received IMRT and to assess the pretreatment factors, relevant treatment factors, and dosimetry parameters associated with trismus.


METHODS
A prospective, single-arm measurement study with more than 5 years of follow-up was designed. Patients with newly diagnosed stage I through IVB NPC who received treatment with IMRT were eligible. Patients received 66 to 70 grays (Gy) to the gross tumor volume. The maximal interincisal distance (MID) was measured at baseline and 6 months, 1 year, 2 years, 3 years, 4 years, and 5 years after they completed IMRT.


RESULTS
The trial enrolled 211 consecutive patients from 2001 to 2004. The mean dose to the TMJ ranged from 6.18 Gy to 51.36 Gy (median dose, 29.88 Gy). Compared with baseline MID levels, normalized MID levels at 6 months, 1 year, 2 years, 3 years, 4 years, and 5 years after IMRT were 94.6% ± 9.9%, 92.5% ± 10.5%, 92% ± 10.6%, 92.2% ± 10.5%, 92.1% ± 10.2%, and 90.3% ± 11.4%, respectively (P < .001). According to a revised subjective-objective management-analytical (SOMA) scale, grade 1/2 trismus was identified in 12 of 211 patients (5.7%), and no grade 3/4 trismus was observed. There was an increasing risk of trismus after IMRT when the MID was <40.5 mm at baseline compared with an MID >40.5 mm (P = .007). No dosimetric parameter was associated with trismus.


CONCLUSIONS
IMRT was able to reduce the radiation dose to the TMJ and likely reduced the incidence and severity of radiation-induced trismus after radiotherapy.
Department of Radiation Oncology, State Key Laboratory of Oncology in Southern China, Cancer Center, Sun Yat-Sen University, Guangzhou, People's Republic of China.
Yuan-Yuan
YY
Chen
Chong
C
Zhao
Jin
J
Wang
Hong-Lian
HL
Ma
Shu-Zheng
SZ
Lai
Yuan
Y
Liu
Fei
F
Han
Li-Xia
LX
Lu
Yong
Y
Bao
Ming
M
Chen
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077274:Nasopharyngeal Carcinoma; D009303:Nasopharyngeal Neoplasms / Q000532:radiotherapy; D011832:Radiation Injuries / Q000453:epidemiology / Q000209:etiology*; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects; D013704:Temporomandibular Joint / Q000528:radiation effects*; D014313:Trismus / Q000453:epidemiology / Q000209:etiology*