Safety of differential radiation dosing in lymph node positive necks treated with IMRT

Purpose: When treating head and neck squamous cell carcinoma (HNSCC) with intensity modulated radiation therapy (IMRT), it is common to use several dose levels for a lymph node positive neck: full dose (66-70 Gy) to gross cancer, intermediate dose (59-63 Gy) to higher risk neck regions, and standard dose (50-54 Gy) to lower risk neck regions. There is no consensus regarding how much of the neck should receive intermediate versus standard dose, however.

Methods and materials: HNSCC patients treated with IMRT were identified from 2 academic medical centers between 2004 and 2016. Intermediate dose was restricted to a region of the neck 2 cm above and below the most superior and inferior involved lymph nodes; standard dose was delivered to more distal neck regions. Descriptive statistics were calculated for demographics and clinical characteristics as well as proportions for failures 2 years after treatment. Failure outside the intermediate dose region was determined by calculating confidence intervals from a modification of the Poisson distribution.

Results: Of the 57 necks included in this study, 17.5% experienced disease recurrence in the neck within 2 years of completing treatment. All failures were within the 2-cm margin above or below the most superior and inferior involved nodes; there were no failures outside this 2-cm margin (95% confidence interval, 0-7.7).

Conclusions: The results of this study support the feasibility of treating only the neck adjacent to gross neck disease to an intermediate dose, and treating the remainder of the neck to a lower, standard dose. Although these results are encouraging, additional study of this treatment paradigm is warranted.