Increased recurrences using intensity-modulated radiation therapy in the postoperative setting

To determine the pattern of failures following intensity modulated radiation therapy for head and neck cancer.

A retrospective single institution study. Between May 2001 and June 2008, 176 patients with head and neck cancer were treated with intensity modulated radiation therapy at Fox Chase Cancer Center. Ninety-five (54%) were squamous cell carcinoma treated with curative intent. Tumor and nodal stage, tobacco history, definitive versus postoperative therapy (PORT), addition of chemotherapy and RT duration were analyzed for association with patterns of failure. In patients treated with definitive radiation, high-risk PTV (PTV1) was prescribed to 70 Gy and low-risk PTV (PTV2) to 56 Gy. In the PORT setting, PTV1 was prescribed to 60 to 66 Gy and PTV2 to 54 Gy. Patterns of failure were assessed. Local failure (LF) was defined as the persistence of disease or recurrence within PTV1, marginal failure as recurrence at the region of high-dose falloff, and regional failure as nodal recurrence within PTV2.

Median follow-up was 20 months (range: 1-117). Median age was 60 years (range: 28-88), with 80% smokers and 81% stage III or IV. PORT was given to 29% and 71% were treated definitively, with concurrent Cisplatin used in the majority. Three-year local and locoregional (LR) failure rates were 9% and 16%, respectively. Failures occurred in 14 patients: 8 local, 3 regional, 1 LR, and 2 distant. Five of the 8 LF and all 3 marginal failures were observed in PORT cohort. On univariate analysis, the only predictor of LF was the use of PORT (P = 0.06). LR control was 66% for PORT versus 87%, 97% for definitive RT and chemoRT.

Local, regional failures were more common following PORT related to an increased risk of marginal failures.