核医学と放射線治療

Clinical Factors Relating to Cervical Body Volume Reduction during Curative External Beam Radiation Therapy for Head and Neck Cancer

Abstract

Ken Takeda, Suguru Dobashi, Shinya Komori, Koichi Chida, Noriyuki Kadoya, Satoshi Kida, Kengo Ito, Toshiyuki Sugawara, Masaki Kubozono, Rei Umezawa, Yojiro Ishikawa, Takaya Yamamoto, Maiko Kozumi, Noriyoshi Takahashi, Yu Katagiri, Yusuke Onozato, Takayuki Kanai, Kiyokazu Sato, Kazuma Kishi, Haruo Matsushita, Takenori Ogawa, Yukio Katori and Keiichi Jin

Purpose/Objectives: Substantial cervical body volume reduction (CBVR) occurs during fractionated external beam radiation therapy (EBRT) for head-and-neck cancer (HNC) and could have potential dosimetric influences. This study aims to investigate measurable clinical factors before treatment initiation correlating with CBVR during curative EBRT in HNC patients, and to determine which patients receive the great benefit from routine adaptive radiation therapy (ART).

Materials/Methods: Fifty-six patients with oropharyngeal squamous cell carcinoma (OSCC) and 67 patients with hypopharyngeal squamous cell carcinoma (HSCC) had received curative EBRT between 2006 and 2013 were enrolled. For EBRT planning, computed tomography (CT) images were acquired before EBRT initiation and between two to seven weeks after the start of EBRT for replanning in each patient. A MATLAB program was used to evaluate the CBVR rate (CBVRR) between the initial and replanning CT imaging. The following factors were assessed for correlation with CBVRR: the T and N stage, induction and concurrent chemotherapy, the initial gross tumor volume (GTV), the GTV reduction rate (GTVRR) between the initial and replanning CT imaging, the initial body weight (BW) and the BW loss rate (BWLR) during the EBRT course.

Results: In the OSCC group, the CBVRR ranged from 1.8 to 17.1% (median, 6.8%). In the HSCC group, the CBVRR ranged from 1.2 to 23.7% (median, 6.5%). In non-parametric univariate analysis, the N3 stage demonstrated a greater trend with the CBVRR than the N2c≥ stage in the HSCC group (p=0.023), whereas marginal inclination (p=0.096) was found in the OSCC group. The CBVRR was substantially related to the GTVRR (p=0.001) in the HSCC group.