Effect of time, dose and fractionation on local control of nasopharyngeal carcinoma

• Published in: Radiotherapy and oncology Vol. 36; no. 1; pp. 24 - 31
• Main Authors: Lee, Anne W.M., Chan, David K.K., Fowler, Jack F., Poon, Y.F., Foo, William, Law, Stephen C.K., O, S.K., Tung, Stewart Y., Chappell, Rick
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01-07-1995
• Subjects: Actuarial Analysis; Biological equivalent formulae; Carcinoma, Squamous Cell - pathology; Carcinoma, Squamous Cell - radiotherapy; Carcinoma, Squamous Cell - secondary; Disease-Free Survival; Dose; Female; Fractionation; Humans; Local control; Logistic Models; Lymph Nodes - radiation effects; Lymphatic Metastasis; Male; Multivariate Analysis; Nasopharyngeal carcinoma; Nasopharyngeal Neoplasms - pathology; Nasopharyngeal Neoplasms - radiotherapy; Neoplasm Recurrence, Local - pathology; Neoplasm Staging; Proportional Hazards Models; Radiotherapy Dosage; Radiotherapy, High-Energy; Relative Biological Effectiveness; Retrospective Studies; Time; Time Factors; Nasopharyngeal carcinoma; Fractionation; Time; Biological equivalent formulae; Local control; Dose
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/0167-8140(95)01579-6

To study the effect of radiation factors on local control of nasopharyngeal carcinoma, 1008 patients with similarly staged T1N0-3M0 disease (Ho's classification) were retrospectively analyzed. All patients were treated by megavoltage irradiation alone using the same technique. Four different fractionation schedules had been used sequentially during 1976–1985: with total dose ranging from 45.6 to 60 Gy and fractional dose from 2.5 to 4.2 Gy. The median overall time was 39 days (range = 38–75 days). Both for the whole series and 763 patients with nodal control, total dose was the most important radiation factor. The hazard of local failure decreased by 9% per additional Gy (
p < 0.01). Biological equivalents expressed in terms of Biologically Effective Dose or Nominal Standard Dose also showed strong correlation. Fractional dose had no significant impact. The effect of overall treatment time was insignificant for the whole series, but almost reached statistical significance for those with nodal control (
p = 0.06). Further study is required for elucidation, as 85% of patients completed treatment within a very narrow range (38–42 days), and the possible hazard is clinically too significant to be ignored.