Correlation between pretreatment FDG-PET biological target volume and anatomical location of failure after radiation therapy for head and neck cancers.

BACKGROUND AND PURPOSE: To assess whether the pretreatment FDG-PET-defined biologic target volume (PET-BTV) correlates with the anatomical sites of loco-regional failure (LRF) after RT for head and neck cancer (HNC).

MATERIALS AND

METHODS

We retrospectively identified 61 HNC patients treated definitively with either 3-D CRT or IMRT who had a pre-therapy PET/CT. The GTV and high-risk CTV(1) definitions included composite data obtained from diagnostic CT, PET/CT, physical examination, and MRI when available. The median CTV(1) dose was 70Gy. 95% received chemotherapy. For patients with LRF, a recurrence volume (V(r)) was identified and was mapped to the pretreatment planning CT and pretreatment PET scan.

RESULTS

At a median follow-up of 22 months, 15% (9/61) patients had LRF. For patients with a LRF, 100% (9/9) of failures were inside the GTV. One of nine [11% (95% CI: 3-45%)] had V(r) which mapped outside of the pretreatment PET-BTV, while 8/9 patients had V(r) within the PET-BTV. Predictors of LRF in our series included GTV volume (p=0.003), but not mean SUV (p=0.13) or max SUV (p=0.25).

CONCLUSIONS

Following treatment in which the GTV was defined based on the composite of imaging and physical examination, the majority, but not all, LRF occurred within the PET-BTV. These results support an important, but not exclusive, role of FDG-PET in defining the GTV.