Elsevier

Practical Radiation Oncology

Volume 3, Issue 2, April–June 2013, Pages 124-129
Practical Radiation Oncology

Original Report
Four-dimensional versus 3-dimensional computed tomographic planning for gastric mucosa associated lymphoid tissue lymphoma

https://doi.org/10.1016/j.prro.2012.05.004Get rights and content

Abstract

Purpose

This study compares dosimetric parameters of 4-dimensional (4D) and 3-dimensional (3D) computed tomographic (CT) planning for gastric mucosa-associated lymphoid tissue (MALT) lymphoma in an attempt to identify any potential benefit of 4DCT planning.

Methods and Materials

We identified 18 patients who received definitive 4DCT radiation planning from September 2006 to September 2011 for gastric MALT lymphoma at our institution. In addition to the kidneys and liver, we contoured an internal target volume (ITV) and static clinical target volume (sCTV) for each patient based on the 4D and 3D images, respectively, to develop 3D conformal radiation plans. Using the static and motion plans, we measured the volume of ITV covered by at least 95% of the prescribed dose (V95), the minimum dose received by 95% of the ITV (D95), and the volume of organs receiving at least 20 Gy or 30 Gy (V20 or V30).

Results

Volumes of the ITV, motion liver, left kidney, and right kidney were significantly larger than their static counterparts. The static plan significantly lowered the ITV V95 and D95 compared with the motion plan. However, this undercoverage was significantly associated with the superior-inferior (SI) respiratory excursions. A V95 of > 98% was observed in 92% of patients with SI excursions < 15 mm versus 33% of patients with SI excursions > 15 mm (P = .02). When compared with the motion plan, the static plan also significantly lowered the liver V30 and left kidney V20.

Conclusions

The 3DCT planning can result in undercoverage of the ITV and altered estimation of doses to normal structures. However, in patients with limited respiratory excursions (< 15 mm), 4D and 3D images generated similar ITV coverage.

Introduction

Extranodal marginal zone B-cell lymphoma of mucosa associated lymphoid tissue (MALT), or MALT lymphomas, make up approximately 5% of all non-Hodgkin lymphoma.1 The stomach is the second most common site of MALT lymphoma, second only to the skin.2 The etiology of gastric MALT lymphoma has been linked to Helicobacter pylori (H pylori) infection, which is associated with over 90% of gastric MALT lymphomas. As a result, eradication of H pylori with antibiotics and a proton pump inhibitor is standard first-line therapy for gastric MALT lymphoma.3 With this treatment, H pylori is eradicated in up to 90% of cases,4., 5. resulting in a complete remission of gastric MALT lymphoma in 70%-80% of patients that can take up to 18 months to occur.6

However, there is a subset of patients with gastric MALT lymphoma who are not infected with H pylori or do not respond to treatment for H pylori. In particular, translocation t(11;18) or trisomy 3 within the lymphoma predict for a poor response to H pylori treatment.5 Although there is no consensus, and treatment options include radiation therapy, chemotherapy, or partial or total gastrectomy, patients with a poor response to H pylori treatment or H pylori-negative gastric MALT lymphoma are typically treated with local radiation therapy.7 Radiation therapy is a very effective treatment for gastric MALT lymphoma. Four-to-5-year disease-free survival ranges from 85% to 100%8 with doses of 30-35 Gy.5

In the modern era, abdominal computed tomography (CT) has become standard for radiation planning, and is used to define the target volume and normal tissue or avoidance structures. However, the stomach is known to move significantly with respiration. Four-dimensional CT (4DCT) radiation planning, which takes into account respiratory motion in determining the gross target volume and clinical target volume (CTV), has demonstrated significant tumor movement in a variety of other malignancies, including lung cancer,9., 10. esophageal cancer,11 breast cancer,12 and pancreatic cancer.13 Although it has been shown that 4DCT planning is dosimetrically superior to landmark-based field setups,14 only limited data are available comparing 4DCT radiation planning to conventional 3DCT radiation planning specifically for lymphoma of the stomach.15 This review investigates the potential benefits of 4DCT radiation planning for gastric MALT lymphoma, including improved coverage of the tumor and more accurate dose estimation to normal structures, and seeks to identify a subgroup of patients who may especially benefit from 4D planning.

Section snippets

Patients

Over 40 patients with gastric MALT lymphoma were treated at our institution between January 1995 and March 2011. Approximately in 2008, it became institution policy to use 4DCT radiation planning to account for respiratory motion of the stomach and nearby organs. A total of 19 patients with stage IE gastric MALT lymphoma have received 4DCT radiation planning at our institution from September 2006 to September 2011. Scans for 1 patient could not be retrieved for technical reasons. Therefore,

Results

Average stomach movement in the SI, AP, and LR dimensions were 10.2 mm (range, 4.0-19.0 mm), 4.4 mm (range, 1.0-9.0 mm), and 2.7 mm (range, 0-6.5 mm), respectively. Compared with their static counterparts, the volumes of the ITV, mLiver, mLeftKidney, and mRightKidney were significantly larger (Table 1). Mean differences in volumes between the static and motion CTV, liver, left kidney, and right kidney were 30.0%, 15.7%, 17.6%, and 23.6%, respectively.

Using the plan generated with 3DCT images,

Discussion

For patients with gastric MALT lymphoma that is negative for H pylori or is resistant to antibiotic therapy, radiation therapy is often the next logical step for eradication of the disease. Current standards of radiation planning employ CT simulation to more accurately identify target volumes and organs at risk. However, standard free-breathing CT scans do not take into account respiratory motion, which can be a significant issue for the stomach and surrounding organs.

Accounting for respiratory

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Conflicts of interest: None.

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