Treatment of Liver Metastases Using an Internal Target Volume Method for Stereotactic Body Radiotherapy

Summary

Stereotactic body radiotherapy (SBRT) requires rigorous accuracy and precision for delivering high radiation doses per fraction to small treatment volumes to improve tumor control and simultaneously reduce toxicity. Herein, we present a noninvasive and clinically convenient respiratory motion management protocol for SBRT for liver metastases.

Abstract

The prognosis of patients with metastatic cancers has improved in the past decades due to effective chemotherapy and oligometastatic surgery. For inoperable patients, local ablation therapies, such as stereotactic body radiotherapy (SBRT), can provide effective local tumor control with minimal toxicity. Because of its high precision and accuracy, SBRT delivers a higher radiation dose per fraction, is more effective, and targets smaller irradiation volumes than does conventional radiotherapy. In addition, steep dose gradients from target lesions to surrounding normal tissues are achieved using SBRT; thus, SBRT provides more effective tumor control and exhibits fewer side effects than conventional radiotherapy. The use of SBRT is prevalent for treating intracranial lesions (known as stereotactic radiosurgery); however, it is now also used for treating spinal and adrenal metastases. Because of advancements in image-guided assistance and respiratory motion management, several studies have investigated the use of SBRT for treating lung or liver tumors, which move as a patient breathes. The results of these studies have suggested that SBRT favorably controls tumors in the case of moving lesions.

Four-dimensional computed tomography (4D-CT) with an abdominal compressor (AC) is clinically convenient for effective respiratory motion management. Because this method is noninvasive and allows free breathing, its use reduces complications. Furthermore, patients consider this method convenient. Moreover, it is considered more efficient than other methods of respiratory motion management by physicians and therapists. The use of 4D-CT with an AC for treating pulmonary lesions has also been widely investigated, and the technique is gaining acceptance for treating hepatic lesions. However, the protocols for using 4D-CT with an AC for treating hepatic lesions are different from those used for treating pulmonary lesions. In this article, we describe a new protocol for SBRT with 4D-CT and an AC for treating liver metastases.

Introduction

Conventionally, metastasis is considered the terminal stage of cancer and is associated with poor prognosis and survival. However, Mountain et al. in 1984 reported that according to their 20-year experience, complete surgical removal of pulmonary metastasis results in a relatively higher survival rate if the primary tumor site is under systemic control at the time of surgery¹. Hellman and Weichselbaum in 1995 first proposed oligometastases, an intermediate stage between localized lesions and systemic disease with polymetastases, which can be cured using additional local treatment^2,3<....

Protocol

Taipei Medical University Joint Institutional Review Board approval was obtained for this study.

1. SBRT Consultation

1. Assess patient eligibility for SBRT for the treatment of liver metastases by consulting a multidisciplinary tumor board.
   NOTE: The need for local ablation as well as operation and other treatment options must be evaluated by the tumor board. Our selection criteria were as follows: 1) adult patients with a good performance status (Eastern Cooperative Oncology Group 0-1), 2) controlled cancer status through anticancer medication and with only oligometastases in the liver, 3) number of hepatic lesions ≤....

Results

SBRT can be implemented by intense-modulated radiotherapy (IMRT) (with 6 radiation beams) or volumetric arc radiotherapy (VMAT) (with continuous dose delivery and gantry rotation) to cover all targets in a single treatment because a single surgery may not achieve removal of all the tumors. A represe.......

Discussion

Respiration-induced liver deformity and organ motion contribute to the difficulties associated with radiation delivery, as well as contouring (target delineation) problems. Improvements in the techniques used for organ motion management have led to improvements in treatment accuracy and precision, which is fundamental to SBRT. Several image-guided techniques and respiratory motion management systems are currently available. Fiducial marker implantation is a common technique for target localization. A fiducial marker is u.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
CT scan	Philips	Brilliance Big Bore 16 Slice CT, 7387	Acquire CT images for contouring and planning
CT contrast	GE Healthcare	Omnipaque 350 mg L/mL	Enhence lesion in CT images
Linear accelerator	Elekta	Synergy	Deliver radiotherapy
Palnning system	Pinnacle	Pinnacle 9.8	Implement radiotherapy planning
Immobilization: BlueBag BodyFix	Elekta	900 mm x 2325 mm, P10104840	Immobilize the patient
Immobilization: BodyFix Cover sheet	Elekta	2700 mm x 1400 mm, P10102-304	Immobilize the patient
Immobilization: BodyFix abdominal compressor	Elekta	diaphragm control, P10102-149	Restrict breath motion and organ/lesion motion
Immobilization: vacuum pump	Elekta	vacuum pump, p2 120V, P10102-110	Shape body bag and cover sheet according to the patient