Recurrence patterns after a decreased dose of 40 Gy to the elective treated neck in head and neck cancer

Purpose: To investigate the patterns of regional recurrences with emphasis on recurrences in the electively irradiated lymph node regions after dose de-escalation to 40 Gy (EQD2Gy) in head and neck cancer. Methods and materials: Two hundred thirty-three patients treated with radio(chemo)therapy using 40 Gy (EQD2Gy) to the elective lymph node regions were included. All regional recurrences were reconstructed and projected on the initial radiotherapy planning Computed Tomography studies to identify the localization of recurrence. Furthermore, patient and treatment characteristics were correlated with the regional recurrences to identify risk factors. Results: The median follow-up in our study was 26 months. Overall- and disease-specific survival at 2 years were 71.2% (95% CI 65.3–77.1) and 64.2% (95% CI 59.2–69.3), respectively. Local, regional and distant control at 2 years was 84.1% (95% CI 79.1–89.2), 89.2% (95% CI 84.3–94.1) and 83.2% (95% CI 76.3–90.1), respectively. Twenty-eight patients experienced a regional recurrence. Fourteen of these patients had a recurrence within the high dose volume (14 of 28). Nine had a recurrence in the electively irradiated lymph node regions (9 of 28) and 5 recurrences occurred outside the target volume. The actuarial rate of recurrence in the electively irradiated lymph node regions was 3.9% (95% CI 1.8–6.0) at 2 years. No significant associations could be observed between recurrence in electively irradiated lymph node regions and age, gender, tumor site, stage, or the presence of human papillomavirus in oropharyngeal cancers. Conclusions: The actuarial rate of recurrence in the electively irradiated lymph node regions was 3.9% (95% CI 1.8–6.0) at 2 years. This incidence is comparable to recurrence rates after standard dose of 50 Gy, suggesting that lower doses to the elective neck do not result in higher regional recurrences.