Clinical Factors With Respect to Cervical Body Volume Reduction During Definitive External Beam Radiation Therapy for Hypopharyngeal Squamous Cell Carcinoma

Abstract

Substantial cervical body volume reduction (CBVR) occurs during fractionated external beam radiation therapy (EBRT) for head and neck cancer and could have dosimetric effects. Adaptive radiation therapy (ART) can address this issue, if necessary. However, it remains unclear whether all patients derive a significant benefit from routine ART. Our aim was to evaluate clinical factors affecting CBVR rates (CBVRR) during definitive conventional EBRT for hypopharyngeal squamous cell carcinoma (HSCC). We retrospectively studied 63 HSCC patients treated with definitive conventional EBRT to the primary tumor and metastatic lymph nodes (LN) between July 2006 and December 2012. This study included 60 men (95%) and 3 women (5%) with a median age of 63 years (range, 51-85 years). No patients received prior surgery for HSCC. The daily dose was either 1.8 or 2 Gy, five times weekly in 62 patients. The other patient received twice-daily 1.2-Gy fractions. For EBRT planning, computed tomography (CT) images were acquired before EBRT initiation and 3 to 5 weeks after the start of EBRT for re-planning in each patient. We examined CBVRR between the initial and re-planning CT images using a MATLAB program. Fifty-nine patients (94%) received concurrent chemotherapy (CC) using the following regimens: TPF [docetaxel (DOC), cisplatin (CDDP) and 5-fluorouracil (5-FU)] in 30 (47%); another CDDP-based regimen in 10 (16%); DOC in 17 (27%); DOC and 5-FU in 1 (2%); and TS-1 in 1 (2%). The remaining 4 patients (6%) did not receive CC. Eight patients were staged as T1 tumors (13%), 31 as T2 (49%), 15 as T3 (24%) and 9 as T4 (14%). Nineteen patients were staged as N0 (30%), 11 as N1 (18%), 2 as N2a (3%), 16 as N2b (25%), 6 as N2c (10%) and 9 as N3 (14%). Multiple linear regression was performed to explore clinical factors affecting CBVRR. The following clinical variables were assessed: age, gender, T stage, N stage, use of CC and the regimen. Backward stepwise regression was performed, and a P value greater than 0.20 was used for variable removal. P < 0.05 was defined as statistically significant. The institutional ethical review board approved this study. The median CBVRR was 6.5% (range, 1.2-23.7%). The final linear regression model identified N3 stage (95% confidence interval [CI] 1.333-7.775, P = 0.006) and TPF chemotherapy (95% CI 0.464-4.977, P = 0.019) as significant variables influencing CBVRR. Thus, intensive TPF-based CC and regional metastatic LN > 6 cm in greatest dimension were associated with substantial CBVRR. CBVRR appears to be associated with concurrent TPF chemotherapy and bulky regional LN metastasis in HSCC. HSCC patients with these factors may benefit from ART.