Carcinoma of the tonsil: the effect of dose-time-volume factors on local control

Between 1970 and 1979, 372 patients with squamous cell carcinoma of the tonsil were treated with primary irradiation therapy, with salvage surgery for failures. The median age was 60 years and the male to female ratio was 2:1. The staging system used was the 1974 UICC TNM system. There were 47 T1 lesions (13%), 161 T2 lesions (43%), and 164 T3 lesions (44%). Regional nodes were not palpable in 173 (46%); 122 had N1 nodes (33%), 6 had N2 nodes (2%) and 71 had N3 nodes (19%). All patients received external beam radiation which was supplemented in 68 patients with a radioactive implant for disease into adjacent tongue. The overall survival for all patients was 38% at 5 years and 54% when corrected for intercurrent disease. Local control was 87% for T1 lesions, 68% for T2 lesions and 50% for T3 lesions. Regional control was 96% for N0, 67% for N1 and 37% for N2-3. A detailed dose-time-volume analysis revealed that increasing volume improved local control in T1 and T2 lesions (77% had local control if the volume was greater than 80 cm2 versus 53% if the volume was less than 80 cm2, p = 0.014), except for T3 lesions. Increasing the dose in the range of 5000 to 6500 rad had no significant effect on primary control in any stage of disease. The addition of a radioactive implant did not increase local control if disease extended into the tongue (57% local control if implant, 52% if no implant). This study demonstrates the significance of adequate treatment volume in local control for carcinoma of the tonsil. No significant dose response was found and subsequent surgery was not compromised when a moderate dose of radiation was used.