Pattern of failure after helical tomotherapy in head and neck cancer

Abstract

Background and purpose: Helical tomotherapy (HT, Hi-Art TomoTherapy(®)) is a recently developed radiation device delivering highly conformal dose with a rotational gantry resulting in more uniform target doses and better avoidance of organs at risk. Treatment failure patterns in head and neck cancer (HNC) patients treated with HT were analyzed.

Patients and methods: 63 patients with a biopsy-proven HNC were treated with HT. In patients with locoregional failure, the volume of failure (Vf) was contoured and co-registered with the initial planning computed tomography scan. With the use of dose-volume histogram (DVH) analysis, the Vf was classified as "in-field" (InF), "marginal" (MF) or "outside-field" (OutF), if ≥ 95%, 20-94%, and < 20% of Vf, respectively, were within the 95% isodose.

Results: Median follow-up time was 25 months (95% confidence interval 19.4-28 months). 2-year overall survival, disease-free survival, and locoregional control were 66%, 54%, and 77%, respectively. 13 patients developed a locoregional failure (four local, eight regional, and one local and regional). After DVH analysis, there were ten InF and two MF recurrences as well as one OutF recurrence.

Conclusion: Target delineation and coverage were adequate. The majority of locoregional failures were InF, i.e., in the high-dose region. Future work on dose escalation to the highest risk regions is recommended.