Purpose: To analyze the outcome in all oropharynx cancer patients treated at the University of Wisconsin during 1995-2005 and highlight the methodologic challenge in comparing outcome after intensity-modulated radiotherapy (IMRT) with that of historical controls.
Methods and materials: Outcomes were compared in 195 oropharynx cancer patients after definitive radiotherapy with curative intent in the pre-IMRT era (pre-IMRT, n = 105), after IMRT (IMRT+, n = 52) or after non-IMRT techniques during the IMRT era (IMRT-, n = 38).
Results: With a median follow-up of 30.4 months, the 3-year overall survival rate in IMRT+, IMRT-, and pre-IMRT patients was 88.2%, 81.1%, and 67.7%, respectively; and for locoregional control was 96.1%, 78.1%, and 81.1%. Patients from the IMRT era more frequently received concurrent chemotherapy (67% vs. 6%, p < 0.001) and underwent adjuvant neck dissection (52% vs. 29%, p = 0.002). Patients with T3-4 disease and bilateral neck disease were significantly less likely to receive IMRT. Cox regression analysis identified IMRT as a significant prognostic factor (p = 0.04); however, after including T stage in the model, IMRT lost independent significance (p = 0.2). Analysis of a potential effect of IMRT on Grade 3+ mucositis or skin reaction was also hampered by the change in other treatment characteristics.
Conclusions: Outcomes in oropharynx cancer have improved at our institution since the introduction of IMRT. However, multiple factors have contributed to this improvement, and presentation of IMRT outcomes without the full context of historical and contemporary controls may yield data that overstate outcome after IMRT.