[Irradiation field design according to locoregional relapse sites after radiotherapy of nasopharyngeal carcinoma].
OBJECTIVE
The lateral faciocervical field, lateral facial field, and cerrobent blocks were employed conventionally in radiotherapy of nasopharyngeal carcinoma (NPC) in Cancer Center of Sun Yat-sen University since 1990s. This study was to explore rationality of irradiated area of lateral faciocervical field and lateral facial field through analyzing the data of some patients presenting locoregional recurrence after conventional radiotherapy.


METHODS
Clinical data of the patients, treated in 1999 and presented locoregional failure and had reports of CT examinations before and after radiotherapy and after recurrence, were reviewed. The regions of recurrent lesions were analyzed. Dosimetric analysis of recurrent regions was performed for the patients with available data of irradiating fields. If no less than 95% of the volume of local recurrent lesion was within 95% isodose curve, it was defined as in-field failure; 20% to less than 95% of the volume was within 95% isodose curve as marginal failure; less than 20% of the volume was within 95% isodose curve as out-field failure.


RESULTS
Clinical data of 40 patients could be analyzed, and dosimetric analysis of recurrent regions was performed for 15 patients. Local recurrences mainly occurred in the nasopharyngeal cavity and the skull base bone. Dosimetric analysis showed 9 cases of in-field failure, 4 cases of marginal failure, and 2 cases of out-field failure. For the 6 cases of marginal and out-field failure, the main reasons of recurrence were low dose area in target volume due to not strictly following the guidelines of defining field limit, or inappropriately estimating the involved regions of lesions.


CONCLUSIONS
Irradiated area of lateral faciocervical field and lateral facial field employed conventionally in radiotherapy of NPC is rational.
Luo
Wei
W
State Key Laboratory of Oncology in South China, Guangzhou, Guangdong 510060, P. R. China. gzluowei@163.net
Tang
Yi-Qiang
YQ
Huang
Ying
Y
Lu
Li-Xia
LX
Lu
Tai-Xiang
TX
D000328:Adult; D000368:Aged; D002294:Carcinoma, Squamous Cell / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis; D008297:Male; D008875:Middle Aged; D009303:Nasopharyngeal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D009305:Nasopharynx / Q000473:pathology; D009364:Neoplasm Recurrence, Local; D009367:Neoplasm Staging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D019291:Skull Base / Q000473:pathology; D017211:Treatment Failure