Patterns of failure after salvage re-irradiation for recurrent head and neck cancer: implications for field design and consolidation therapy

Abstract

The complications as a result of re-irradiation (re-RT) for recurrent head and neck cancer (HNC) can be devastating to the already very ill patient. We sought to examine the pattern of failure with the goal of designing optimal re-RT fields for these patients. From July 1996 to April 2011, 47 HNC patients treated with fractionated re-RT developed locoregional failure. Recurrence sites were oropharynx (n = 12), neck (n = 11), oral cavity (n = 9), larynx (n = 5), paranasal sinuses (n = 5), parotid (n = 4), and hypopharynx (n = 1). Median initial radiation therapy (RT) dose was 65 Gy and median time between radiations was 32.2 months. Salvage surgery was performed in 21 patients (45 %), and 37 patients (79 %) received concurrent chemotherapy. Median re-RT dose was 60 Gy, and all patients received intensity-modulated RT. Patterns of failure were assessed by reviewing target volume delineation and compared slice-by-slice visually alongside axial imaging documenting locoregional recurrence. There was no intention to encompass prophylactic subclinical regions at risk. Coding of failures was either in-field (InF) or out-of-field (OutF). All others were marginal failures (margF). With a median follow-up of 24.5 months, the median time to locoregional progression-free survival (LRPFS) was 5.3 months and median overall survival (OS) was 12.5 months. Failures were documented as InF in 42 patients (89 %), OutF in three patients (6 %), and margF in two patients (4 %). Five patients died while undergoing re-RT. Patients who developed OutF occurred at sites beyond 2 cm from the tumor volume. In our series of recurrent HNC patients who underwent salvage re-RT, the vast majority of locoregional failures were InF. We feel that confining re-RT targets to the gross tumor volume or postoperative clinical target volume without treating the subclinical regions at risk for failure is sufficient. With current image guidance capabilities, reducing the planning target volume margin may further minimize toxicities.