The influence of field size and other radiotherapy parameters on acute toxicity in pharyngolaryngeal cancers

Background: Accelerated radiotherapy and/or chemo-radiotherapy of the head and neck region decrease the tolerance of acute responding tissues. Tissue tolerance is also field size dependent. Patients and Method: An attempt to retrospectively quantify the risk of acu te toxicity (peak scores) with field size was undertaken in 286 patients ir radiated for unresected head and neck tumors with or without chemotherapy, and with or without accelerated radiotherapy between 1979 and 1990. A Grade -3 to -4 acute toxicity score (RTOG) and > 5% weight loss were chosen as en dpoints. Results: For Grade-3 to -4 toxicity, the risk increased from 0.06 for 5 x 5 cm(2) to 0.68 for 17 x 17 cm(2) fields and conventional radiotherapy, and from 0.33 for 5 x 5 cm(2) to 0.94 for 17 x 17 cm(2) and multiple daily frac tionation. For > 5% weight loss, the risk ranged from 0.07 for 5 x 5 cm(2) to 0.94 for 17 x 17 cm(2) fields. Conclusions: The size of the cervical fields receiving the first 50 Gy was an indicator for severe acute toxicity and weight loss. Taking these data i nto account may help to improve preventive and treatment measures.