title: Dose-response relationship of nasopharyngeal carcinoma above conventional tumoricidal level: a study by the Hong Kong nasopharyngeal carcinoma study group (HKNPCSG).
abstract: OBJECTIVE
  To define the dose-response relationship of nasopharyngeal carcinoma (NPC) above the conventional tumoricidal dose level of 66 Gy when the basic radiotherapy (RT) course was given by the 2D Ho's technique.
  
  
  METHODS
  Data from all five regional cancer centers in Hong Kong were pooled for this retrospective study. All patients (n = 2426) were treated with curative-intent RT with or without chemotherapy between 1996 and 2000 with the basic RT course using the Ho's technique. The primary endpoint was local control. The prognostic significance of dose-escalation ('boost') after 66 Gy, T-stage, N-stage, use of chemotherapy, sex and age (< or =40 years vs >40 years) was studied. Both univariate and multivariate analyses were performed.
  
  
  RESULTS
  On multivariate analysis, T-stage (P < 0.01; hazard ratio [HR], 1.58) and optimal boost (P = 0.01; HR, 0.34) were the only significant factors affecting local failure for the whole study population, and for the population of patients treated by radiotherapy alone, but not for patients who also received chemotherapy. The following were independent determinants of local failure for patient groups with different T-stages treated by radiotherapy alone: use of a boost in T1/T2a disease (P = 0.01; HR, 0.33); use of a boost (P < 0.01; HR, 0.60) and age (P = 0.01; HR, 1.02) in T3/T4 tumors. Among patients with T2b tumors treated by radiotherapy alone and given a boost, the use of a 20 Gy-boost gave a lower local failure rate than a 10 Gy-boost. There was no apparent excess mortality attributed to RT complications.
  
  
  CONCLUSIONS
  Within the context of a multi-center retrospective study, dose-escalation above 66 Gy significantly improved local control for T1/T2a and T3/4 tumors when the primary RT course was based on the 2D Ho's technique without additional chemotherapy. 'Boosting' in NPC warrants further investigation. Caution should be taken when boosting is considered because of possible increase in radiation toxicity.
authors.affiliation: Department of Clinical Oncology, The Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, China.
authors.forename: Peter M L
authors.initials: PM
authors.lastname: Teo
authors.forename: Sing Fai
authors.initials: SF
authors.lastname: Leung
authors.forename: Stewart Y
authors.initials: SY
authors.lastname: Tung
authors.forename: Benny
authors.initials: B
authors.lastname: Zee
authors.forename: Jonathan S T
authors.initials: JS
authors.lastname: Sham
authors.forename: Anne W M
authors.initials: AW
authors.lastname: Lee
authors.forename: Wai Hon
authors.initials: WH
authors.lastname: Lau
authors.forename: Wing Hong
authors.initials: WH
authors.lastname: Kwan
authors.forename: To Wai
authors.initials: TW
authors.lastname: Leung
authors.forename: Daniel
authors.initials: D
authors.lastname: Chua
authors.forename: Wai Man
authors.initials: WM
authors.lastname: Sze
authors.forename: Joseph S K
authors.initials: JS
authors.lastname: Au
authors.forename: Kwok Hung
authors.initials: KH
authors.lastname: Yu
authors.forename: Sai Ki
authors.initials: SK
authors.lastname: O
authors.forename: Dora
authors.initials: D
authors.lastname: Kwong
authors.forename: Tsz Kok
authors.initials: TK
authors.lastname: Yau
authors.forename: Stephen C K
authors.initials: SC
authors.lastname: Law
authors.forename: Wing Kin
authors.initials: WK
authors.lastname: Sze
authors.forename: Gordon
authors.initials: G
authors.lastname: Au
authors.forename: Anthony T C
authors.initials: AT
authors.lastname: Chan
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D002277:Carcinoma / Q000188:drug therapy / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D017024:Chemotherapy, Adjuvant; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006723:Hong Kong; D006801:Humans; D008499:Medical Records; D009303:Nasopharyngeal Neoplasms / Q000188:drug therapy / Q000401:mortality / Q000473:pathology / Q000532:radiotherapy*; D009367:Neoplasm Staging; D018714:Radiotherapy, Adjuvant; D012189:Retrospective Studies; D016019:Survival Analysis; D016896:Treatment Outcome