Prospective matched study on comparison of volumetric-modulated arc therapy and intensity-modulated radiotherapy for nasopharyngeal carcinoma: dosimetry, delivery efficiency and outcomes

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Abstract

Background: The purpose of this study is to assess the feasibility of volumetric-modulated arc therapy (VMAT) for nasopharyngeal carcinoma (NPC) patients by comparing the physical dosimetry, delivery efficiency and clinical outcomes with intensity-modulated radiotherapy (IMRT).

Methods: A prospective matched study was performed for patients with newly diagnosed NPC who underwent VMAT or IMRT. The patients in two groups were equally matched in terms of gender, age, tumor stage and chemotherapy. The target coverage, homogeneity index (HI) and conformity index (CI) of the planning target volume (PTV), organs at risk (OARs) sparing, average treatment time and clinical outcomes were analyzed.

Results: From June 2013 to August 2015, a total of 80 patients were enrolled in this study, with 40 patients in each group. The coverage of PTV was similar for both groups. D2 was observed slight difference only in early stage disease (T1-2) (VMAT vs. IMRT, 7494±109 cGy vs. 7564±92 cGy; p=0.06). The HI of VMAT group was better than that of IMRT group (p=0.001), whereas CI was slightly worse (p=0.061). The maximum doses received by the brain stem, spinal cord, and optic nerve of VMAT were higher than those of IMRT (p<0.05). But the irradiation volumes in healthy tissue were generally lower for VMAT group, with significant differences in V20, V25 and V45 (p<0.05). With regard to the delivery efficiency compared with IMRT (1160 ± 204s), a 69% reduction in treatment time was achieved by VMAT (363 ± 162s). Both groups had 5 cases of nasopharyngeal residual lesions after radiotherapy. The 2-year estimated local relapse-free survival, regional relapse-free survival and locoregional relapse-free survival, distant metastasis-free survival, disease-free survival and overall survival were similar between two groups, with the corresponding rates of 100%, 97.4%, 97.4%, 90.0%, 90.0% and 92.4% in VMAT group, and 100%, 100%, 100%, 95.0%, 95.0% and 97.5% in IMRT group, respectively.

Conclusions: Both VMAT and IMRT can meet the clinical requirements for the treatment of NPC. The short-term tumor regression rates and 2-year survival rates with the two techniques are comparable. The faster treatment time benefits of VMAT will enable more patients to receive precision radiotherapy.

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Most cited references 28

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Volumetric modulated arc therapy: IMRT in a single gantry arc.

Karl-Otto Bischoff (2007)

In this work a novel plan optimization platform is presented where treatment is delivered efficiently and accurately in a single dynamically modulated arc. Improvements in patient care achieved through image-guided positioning and plan adaptation have resulted in an increase in overall treatment times. Intensity-modulated radiation therapy (IMRT) has also increased treatment time by requiring a larger number of beam directions, increased monitor units (MU), and, in the case of tomotherapy, a slice-by-slice delivery. In order to maintain a similar level of patient throughput it will be necessary to increase the efficiency of treatment delivery. The solution proposed here is a novel aperture-based algorithm for treatment plan optimization where dose is delivered during a single gantry arc of up to 360 deg. The technique is similar to tomotherapy in that a full 360 deg of beam directions are available for optimization but is fundamentally different in that the entire dose volume is delivered in a single source rotation. The new technique is referred to as volumetric modulated arc therapy (VMAT). Multileaf collimator (MLC) leaf motion and number of MU per degree of gantry rotation is restricted during the optimization so that gantry rotation speed, leaf translation speed, and dose rate maxima do not excessively limit the delivery efficiency. During planning, investigators model continuous gantry motion by a coarse sampling of static gantry positions and fluence maps or MLC aperture shapes. The technique presented here is unique in that gantry and MLC position sampling is progressively increased throughout the optimization. Using the full gantry range will theoretically provide increased flexibility in generating highly conformal treatment plans. In practice, the additional flexibility is somewhat negated by the additional constraints placed on the amount of MLC leaf motion between gantry samples. A series of studies are performed that characterize the relationship between gantry and MLC sampling, dose modeling accuracy, and optimization time. Results show that gantry angle and MLC sample spacing as low as 1 deg and 0.5 cm, respectively, is desirable for accurate dose modeling. It is also shown that reducing the sample spacing dramatically reduces the ability of the optimization to arrive at a solution. The competing benefits of having small and large sample spacing are mutually realized using the progressive sampling technique described here. Preliminary results show that plans generated with VMAT optimization exhibit dose distributions equivalent or superior to static gantry IMRT. Timing studies have shown that the VMAT technique is well suited for on-line verification and adaptation with delivery times that are reduced to approximately 1.5-3 min for a 200 cGy fraction.

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Intensity-modulated radiotherapy in the treatment of nasopharyngeal carcinoma: an update of the UCSF experience.

Nancy Lee, Ping Xia, Jeanne Quivey … (2002)

To update our experience with intensity-modulated radiotherapy (IMRT) in the treatment of nasopharyngeal carcinoma (NPC). Between April 1995 and October 2000, 67 patients underwent IMRT for NPC at the University of California-San Francisco (UCSF). There were 20 females and 47 males, with a mean age of 49 (range 17-82). The disease was Stage I in 8 (12%), Stage II in 12 (18%), Stage III in 22 (33%), and Stage IV in 25 (37%). IMRT was delivered using three different techniques: 1) manually cut partial transmission blocks, 2) computer-controlled auto-sequencing segmental multileaf collimator (SMLC), and 3) sequential tomotherapy using a dynamic multivane intensity modulating collimator (MIMiC). Fifty patients received concomitant cisplatinum and adjuvant cisplatinum and 5-FU chemotherapy according to the Intergroup 0099 trial. Twenty-six patients had fractionated high-dose-rate intracavitary brachytherapy boost and 1 patient had gamma knife radiosurgery boost after external beam radiotherapy. The prescribed dose was 65-70 Gy to the gross tumor volume (GTV) and positive neck nodes, 60 Gy to the clinical target volume (CTV), 50-60 Gy to the clinically negative neck, and 5-7 Gy in 2 fractions for the intracavitary brachytherapy boost. Acute and late normal tissue effects were graded according to the Radiation Therapy Oncology Group (RTOG) radiation morbidity scoring criteria. The local progression-free, local-regional progression-free, distant metastasis-free rates, and the overall survival were calculated using the Kaplan-Meier method. With a median follow-up of 31 months (range 7 to 72 months), there has been one local recurrence at the primary site. One patient failed in the neck. Seventeen patients developed distant metastases; 5 of these patients have died. The 4-year estimates of local progression-free, local-regional progression-free, and distant metastases-free rates were 97%, 98%, and 66% respectively. The 4-year estimate of overall survival was 88%. The worst acute toxicity documented was as follows: Grade 1 or 2 in 51 patients, Grade 3 in 15 patients, and Grade 4 in 1 patient. The worst late toxicity was Grade 1 in 20 patients, Grade 2 in 15 patients, Grade 3 in 7 patients, and Grade 4 in 1 patient. At 3 months after IMRT, 64% of the patients had Grade 2, 28% had Grade 1, and 8% had Grade 0 xerostomia. Xerostomia decreased with time. At 24 months, only one of the 41 evaluable patients had Grade 2, 32% had Grade 1, and 66% had Grade 0 or no xerostomia. Analysis of the dose-volume histograms (DVHs) showed that the average maximum, mean, and minimum dose delivered were 79.3 Gy, 74.5 Gy, and 49.4 Gy to the GTV, and 78.9 Gy, 68.7 Gy, and 36.8 Gy to the CTV. An average of only 3% of the GTV and 3% of the CTV received less than 95% of the prescribed dose. Excellent local-regional control for NPC was achieved with IMRT. IMRT provided excellent tumor target coverage and allowed the delivery of a high dose to the target with significant sparing of the salivary glands and other nearby critical normal tissues.

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Treatment results for nasopharyngeal carcinoma in the modern era: the Hong Kong experience.

Anne Lee, W M Sze, Joseph Au … (2005)

To analyze the treatment results achievable for nasopharyngeal carcinoma in the modern era to identify the key failures for future improvement and to provide an updated baseline for future trials. The results of 2687 consecutive patients treated at all public oncology centers in Hong Kong during 1996-2000 were retrospectively analyzed. The stage distribution (by American Joint Committee on Cancer and International Union Against Cancer staging system, 1997) was 7% Stage I, 41% Stage II, 25% Stage III, and 28% Stage IVA-B. All patients were irradiated with 6-MV photons and the median total dose was 66 Gy. Only 23% of patients had additional treatment with chemotherapy. The 5-year local, nodal, and distant failure-free rates were 85%, 94%, and 81%, respectively; patients with local failure had significantly higher risk of nodal and distant failures. The 5-year progression-free, overall, and cancer-specific survival rates were 63%, 75%, and 80%, respectively. The presenting stage was the most important prognostic factor for all endpoints: with overall survival decreasing from 90% for Stage I to 58% for Stage IVA-B. The results achieved by the 2070 patients treated by radiotherapy alone were almost identical to that of the whole series, the distant failure-free rate among patients with locoregional control was 89% for Stage I-II and 75% for Stage III-IVB. The 860 patients (32%) staged with magnetic resonance imaging achieved significantly better results than those staged by computed tomography, the overall survival being 93% vs. 83% for Stages I-II, and 72% vs. 63% for Stages III-IVB (p = 0.001). Treatment results for nasopharyngeal carcinoma have substantially improved in the modern era; future trials should be based on updated baseline results. Further reduction of distant failure is important for future breakthrough, particularly for patients with advanced disease.

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Author and article information

Journal

Journal ID (nlm-ta): J Cancer

Journal ID (iso-abbrev): J Cancer

Journal ID (publisher-id): jca

Title: Journal of Cancer

Publisher: Ivyspring International Publisher (Sydney )

ISSN (Electronic): 1837-9664

Publication date Collection: 2018

Publication date (Electronic): 28 February 2018

Volume: 9

Issue: 6

Pages: 978-986

Affiliations

[1 ]Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in Southern China, Collaborative Innovation Center for Cancer Medicine, People's Republic of China.

[2 ]Department of Medical Oncology, The Fifth Affiliated Hospital of Sun Yat-sen University, Zhuhai, People's Republic of China.

Author notes

✉ Corresponding author: Fei Han, MD, Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in Southern China, Collaborative Innovation Center for Cancer Medicine, 651 Dongfeng Road East, Guangzhou 510060, People's Republic of China. Telephone: +86-20-87343543; Fax: +86-20-87343372; E-mail: hanfeisysucc@ 123456163.com

^* These authors contributed equally to this work.

Competing Interests: The authors declare no competing financial interests.

Article

Publisher ID: jcav09p0978

DOI: 10.7150/jca.22843

PMC ID: 5868165

PubMed ID: 29581777

SO-VID: f280b874-98b0-4d9c-ad17-f33b6ae2b1c1

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This is an open access article distributed under the terms of the Creative Commons Attribution (CC BY-NC) license ( https://creativecommons.org/licenses/by-nc/4.0/). See http://ivyspring.com/terms for full terms and conditions.

Prospective matched study on comparison of volumetric-modulated arc therapy and intensity-modulated radiotherapy for nasopharyngeal carcinoma: dosimetry, delivery efficiency and outcomes

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Most cited references 28

Volumetric modulated arc therapy: IMRT in a single gantry arc.

Intensity-modulated radiotherapy in the treatment of nasopharyngeal carcinoma: an update of the UCSF experience.

Treatment results for nasopharyngeal carcinoma in the modern era: the Hong Kong experience.

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