Clinical investigation
Intensity-modulated radiation therapy for oropharyngeal carcinoma: impact of tumor volume

https://doi.org/10.1016/j.ijrobp.2003.08.004Get rights and content

Abstract

Purpose

To assess the therapeutic outcomes in oropharyngeal cancer patients treated with intensity-modulated radiotherapy (IMRT) and analyze the impact of primary gross tumor volume (GTV) and nodal GTV (nGTV) on survival and locoregional control rates.

Methods and materials

Between February 1997 and September 2001, 74 patients with squamous cell carcinoma of the oropharynx were treated with IMRT. Thirty-one patients received definitive IMRT; 17 also received platinum-based chemotherapy. Forty-three patients received combined surgery and postoperative IMRT. The median follow-up for all patients was 33 months (range, 9–60 months). Fifty-two patients (70.3%) had Stage IV disease, 17 patients (23%) had Stage III, 3 patients (4.1%) had Stage II, and 2 patients (2.7%) had Stage I tumors. The mean prescription dose was 70 and 66 Gy, respectively, for the definitive and postoperative cohorts. The daily fraction dose was either 1.9 or 2 Gy, five times weekly. The GTV and/or nGTV were determined and derived using the Computational Environment for Radiotherapy Research, a free software package developed at Washington University. The mean GTV was 30.5 ± 22.3 cm3, and the mean nGTV was 23.2 ± 20.6 cm3.

Results

Ten locoregional failures were observed. Six patients died of disease and three died of concurrent disease. Distant metastasis developed in 6 patients. The 4-year estimate of overall survival was 87%, and the 4-year estimate of disease-free survival was 81% (66% in the definitive vs. 92% in the postoperative RT group). The 4-year estimate of locoregional control was 87% (78% in the definitive vs. 95% in the postoperative RT group); the 4-year estimate of distant metastasis-free survival was 90% (84% in the definitive vs. 94% in the postoperative group). Multivariate analysis showed that GTV and nGTV were independent risk factors determining locoregional control and disease-free survival for definitive oropharyngeal IMRT patients. The worst late toxicities documented were as follows: 32 patients with Grade 1 and 9 with Grade 2 xerostomia; 2 with Grade 1 and 1 with Grade 2 skin toxicity; 3 with Grade 1 late mucositis; and 3 with Grade 1 trismus. Seventeen patients required gastrostomy tube placement.

Conclusion

IMRT is an effective treatment modality for locally advanced oropharyngeal carcinoma. The GTV and nGTV are the most important factors predictive of therapeutic outcome.

Introduction

Oropharyngeal carcinoma is usually squamous in origin. When tumor presents in advanced stages, the prognosis is poor (1). The management of primary oropharyngeal squamous cell carcinoma remains controversial. Surgery and postoperative radiotherapy (RT) is a commonly used strategy. Although this approach can yield satisfactory locoregional control, it may result in functional alteration and does not prevent distant metastasis. An alternative therapeutic modality, conventional RT, can also address the primary tumor site and the adjacent lymphatic drainage. However, conventional RT frequently impairs salivary gland function, causing permanent xerostomia. Recent technological advances have led to the successful clinical implementation of intensity-modulated RT (IMRT), an advanced form of three-dimensional RT. The initial results have been encouraging and suggest potential improvements in locoregional control rates and toxicity profiles 2, 3.

Patients with oropharyngeal carcinoma are ideally suited for IMRT, because this technique can conform to tumors with concave features, optimize tumor target coverage, and spare adjacent critical structures, most notably the salivary glands 4, 5, 6, 7. We previously showed that, compared with conventional RT, IMRT reduced late salivary toxicity without compromising tumor control in patients with oropharyngeal carcinoma (5). The objectives of this paper were to update our therapeutic outcomes with IMRT for oropharyngeal carcinoma and to analyze the impact of tumor volume on locoregional control and disease-free survival.

Section snippets

Patients and tumor characteristics

Between February 1997 and December 2001, 74 oropharyngeal cancer patients (13 women and 61 men; median age, 55 years; range, 35–76 years) were treated with IMRT either definitively (n = 31; 42%) or postoperatively (n = 43; 58%). The primary site was the tonsil in 50, base of tongue in 18, and soft palate in 6 patients. The American Joint Committee on Cancer (AJCC) staging system was used according to the primary tumor location (8). The T stage was T1 in 16, T2 in 25, T3 in 14, and T4 in 19

Results

Ten locoregional failures were found. Six patients died of disease and three died of concurrent disease. Distant metastasis developed in 6 patients. The 4-year estimate of overall survival was 87%, and the 4-year estimate of disease-free survival (DFS) was 81%. The 4-year estimate of locoregional control was 87%, and the 4-year estimate of distant metastasis-free survival (DMFS) was 90% (84% in the definitive vs. 94% in the postoperative group; Fig. 1).

Univariate analysis, taking gender,

Discussion

In the past few years, many studies dealing with the planning, delivery, and quality assurance of IMRT have been published. However, outcomes analyses validating the potential benefits and drawbacks of this novel technology are sparse. Because of the complexity of implementing IMRT, only a few reports benchmarking the treatment outcome of head-and-neck cancers have been published 2, 13. Lee et al.(13) reported excellent therapeutic results in nasopharyngeal carcinoma treated with IMRT without

Conclusion

Our results showed that IMRT for oropharyngeal cancers is clinically feasible and results in satisfactory locoregional control and survival rates. The GTV is an important parameter to predict survival and locoregional control.

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