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 acute toxicity (peak scores) with field size was undertaken in 286 patients irradiated 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 endpoints.

RESULTS

For Grade-3 to -4 toxicity, the risk increased from 0.06 for 5 x 5 cm2 to 0.68 for 17 x 17 cm2 fields and conventional radiotherapy, and from 0.33 for 5 x 5 cm2 to 0.94 for 17 x 17 cm2 and multiple daily fractionation. For > 5% weight loss, the risk ranged from 0.07 for 5 x 5 cm2 to 0.94 for 17 x 17 cm2 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 into account may help to improve preventive and treatment measures.