Clinical Investigation
Candidate Dosimetric Predictors of Long-Term Swallowing Dysfunction After Oropharyngeal Intensity-Modulated Radiotherapy

Presented in part at the annual meeting of the American Society of Therapeutic Radiology and Oncology, Boston, MA, September, 21-25 2008.
https://doi.org/10.1016/j.ijrobp.2009.10.002Get rights and content

Purpose

To investigate long-term swallowing function in oropharyngeal cancer patients treated with intensity-modulated radiotherapy (IMRT), and to identify novel dose-limiting criteria predictive for dysphagia.

Methods and Materials

Thirty-one patients with Stage IV oropharyngeal squamous carcinoma enrolled on a Phase II trial were prospectively evaluated by modified barium swallow studies at baseline, and 6, 12, and 24 months post-IMRT treatment. Candidate dysphagia-associated organs at risk were retrospectively contoured into original treatment plans. Twenty-one (68%) cases were base of tongue and 10 (32%) were tonsil. Stage distribution was T1 (12 patients), T2 (10), T3 (4), T4 (2), and TX (3), and N2 (24), N3 (5), and NX (2). Median age was 52.8 years (range, 42–78 years). Thirteen patients (42%) received concurrent chemotherapy during IMRT. Thirteen (42%) were former smokers. Mean dose to glottic larynx for the cohort was limited to 18 Gy (range, 6–39 Gy) by matching IMRT to conventional low-neck fields.

Results

Dose–volume constraints (V30 < 65% and V35 < 35% for anterior oral cavity and V55 < 80% and V65 < 30% for high superior pharyngeal constrictors) predictive for objective swallowing dysfunction were identified by univariate and multivariate analyses. Aspiration and feeding tube dependence were observed in only 1 patient at 24 months.

Conclusions

In the context of glottic laryngeal shielding, we describe candidate oral cavity and superior pharyngeal constrictor organs at risk and dose–volume constraints associated with preserved long-term swallowing function; these constraints are currently undergoing prospective validation. Strict protection of the glottic larynx via beam-split IMRT techniques promises to make chronic aspiration an uncommon outcome.

Introduction

Head-and-neck cancer severely quality of life. Although aggressive radiotherapy and chemoradiotherapy regimens have improved survival outcomes for this disease (1), this success has proved costly 2, 3, 4. Intensity-modulated radiotherapy (IMRT) techniques permit protection of normal tissues adjacent to tumors (5). It has been assumed that reducing dose to the uninvolved larynx and pharyngeal axis improves posttreatment rehabilitation. However, there are limited data to support this premise or to guide radiation oncologists to avoid specific organs at risk (OARs) important to swallowing. Eisbruch et al.6, 7 have recently associated dose to the superior pharyngeal constrictors and supraglottic larynx with post–radiation (RT) aspiration. Despite such early progress, data remain sparse for post-RT swallowing outcomes past 1 year, and published series lack quantifiable measures for swallowing function.

The purpose of this study was to identify specific candidate structures and dose–volume constraints for dysphagia-sparing oropharyngeal IMRT planning. Unique features of these data include uniform disease presentation and IMRT techniques, prospective collection of longitudinal functional outcomes beyond 12 months, and use of modified barium swallow outcome measures to objectively assess swallowing function in a quantitative fashion.

Section snippets

Methods and Materials

A total of 48 patients with Stage IV head and neck squamous cell carcinoma were enrolled onto an institutional review board–approved institutional Phase II chemoradiotherapy trial (Fig. 1). Swallowing outcomes were prospectively collected as an exploratory aim of this trial. We retrospectively correlated dosimetry with these swallowing outcomes in 31 patients with tonsil or base-of-tongue primary disease after treatment had been completed.

We delivered IMRT via a step-and-shoot, multileaf

Results

The patient, tumor, and treatment characteristics of our cohort (n = 31) are presented in Table 1 and summary statistics for OAR RT doses are listed in Table 2.

Discussion

Dysphagia is a key determinant of quality of life in patients treated with radiation for advanced head-and-neck cancer 3, 4 and is potentially more important than xerostomia (17). Efforts to study post-RT dysphagia have been complicated by a diverse spectrum of head-and-neck cancer presentations and treatment regimens as well as the recent transition from conventional to IMRT techniques. Recently published data specific to IMRT have implicated high-dose treatment of pharyngeal constrictor

Acknowledgments

We acknowledge Dr. Avraham Eisbruch for his assistance with the design of our candidate dysphagia-associated OARs.

References (31)

Cited by (160)

View all citing articles on Scopus

Supported by National Cancer Institute Grant CA132281.

Conflict of interest: none.

View full text