Patterns of failure for hypopharynx cancer patients treated with limited high-dose radiotherapy treatment volumes.

Purpose
Optimal radiotherapy treatment volumes for patients with locally advanced hypopharynx squamous cell carcinoma should ensure maximal tumor coverage with minimal inclusion of normal surrounding structures. Here we evaluated the effectiveness of a direct 3-mm high-dose gross tumor volume to planning target volume expansion on clinical outcomes for hypopharynx cancers.


Materials and Methods
We performed a retrospective analysis of patients with hypopharynx carcinoma treated between 2004 and 2018 with primary radiotherapy using a direct high-dose gross tumor volume to planning target volume expansion and with or without concurrent systemic therapy. Diagnostic imaging of recurrences was co-registered with the planning CT. Spatial and volumetric analyses of contoured recurrences were compared with planned isodose lines. Failures were initially defined as in field, marginal, elective nodal, and out of field. Each failure was further classified as central high-dose, peripheral high-dose, central intermediate/low-dose, peripheral intermediate/low-dose, and extraneous. Clinical outcomes were analyzed by Kaplan-Meier estimation.


Results
Thirty-six patients were identified. At a median follow-up at 52.4 months, estimated 5-year overall survival was 59.3% (95% confidence interval [CI], 36.3%-74.1%), 5-year local and nodal control was 71.7% (95% CI, 47.1%-86.3%) and 69.9% (95% CI, 57.0%-82.6%), respectively. The most common failure was in the high-dose primary target volume. The gastrostomy tube retention rate at 1 year among patients without recurrence was 13.0% (95% CI, 3.2%-29.7%).


Conclusion
Minimal high-dose target volume expansions for hypopharynx cancers were associated with favorable locoregional control. This approach may enable therapy intensification to improve clinical outcomes.