Stereotactic high dose fraction radiation therapy of extracranial tumors using an accelerator. Clinical experience of the first thirty-one patients

Escalated focal liver radiation and concurrent hepatic artery fluorodeoxyuridine for unresectable intrahepatic malignancies

PURPOSE

To evaluate the response, time to progression, survival, and impact of radiation (RT) dose on survival in patients with intrahepatic malignancies treated on a phase I trial of escalated focal liver RT.

PATIENTS AND METHODS

From April 1996 to January 1998, 43 patients with unresectable intrahepatic hepatobiliary cancer (HB; 27 patients) and colorectal liver metastases (LM; 16 patients) were treated with high-dose conformal RT. The median tumor size was 10 x 10 x 8 cm. The median RT dose was 58.5 Gy (range, 28.5 to 90 Gy), 1.5 Gy twice daily, with concurrent continuous-infusion hepatic arterial fluorodeoxyuridine (0.2 mg/kg/d) during the first 4 weeks of RT.

RESULTS

The response rate in 25 assessable patients was 68% (16 partial and one complete response). With a median potential follow-up period of 26.5 months, the median times to progression for all tumors, LM, and HB were 6, 8, and 3 months, respectively. The median survival times of all patients, patients with LM, and patients with HB were 16, 18, and 11 months, respectively. On multivariate analyses, escalated RT dose was independently associated with improved progression-free and overall survival. The median survival of patients treated with 70 Gy or more has not yet been reached (16.4+ months), compared with 11.6 months in patients treated with lower RT doses (P =.0003).

CONCLUSION

The excellent response rate, prolonged intrahepatic control, and improved survival in patients treated with RT doses of 70 Gy or more motivate continuation of dose-escalation studies for patients with intrahepatic malignancies.

Extracranial stereotactic radiation therapy: set-up accuracy of patients treated for liver metastases

PURPOSE

Patients with liver metastases might benefit from high-dose conformal radiation therapy. A high accuracy of repositioning and a reduction of target movement are necessary for such an approach. The set-up accuracy of patients with liver metastases treated with stereotactic single dose radiation was evaluated.

METHODS AND MATERIALS

Twenty-four patients with liver metastases were treated with single dose radiation therapy on 26 occasions using a self-developed stereotactic frame. Liver movement was reduced by abdominal pressure. The effectiveness was evaluated under fluoroscopy. CT scans were performed on the planning day and directly before treatment. Representative reference marks were chosen and the coordinates were calculated. In addition, the target displacement was quantitatively evaluated after treatment.

RESULTS

Diaphragmal movement was reduced to median 7 mm (range: 3-13 mm). The final set-up accuracy of the body was limited to all of median 1.8 mm in latero-lateral direction (range: 0.3-5.0 mm) and 2.0 mm in anterior-posterior direction (0.8-3.8 mm). Deviations of the body in cranio-caudal direction were always less than the thickness of one CT slice (<5 mm). However, a repositioning was necessary in 16 occasions. The final target shift was median 1.6 mm (0.2-7.0 mm) in latero-lateral and 2.3 mm in anterior-posterior direction (0.0-6.3 mm). The median shift in cranio-caudal direction was 4.4 mm (0.0-10.0 mm).

CONCLUSIONS

In patients with liver metastases, a high set-up accuracy of the body and the target can be achieved. This allows a high-dose focal radiotherapy of these lesions. However, a control CT scan should be performed directly before therapy to confirm set-up accuracy and possibly prompt necessary corrections.

Noninvasive patient fixation for extracranial stereotactic radiotherapy

PURPOSE

To evaluate the setup accuracy that can be achieved with a novel noninvasive patient fixation technique based on a body cast attached to a recently developed stereotactic body frame during fractionated extracranial stereotactic radiotherapy.

METHODS AND MATERIALS

Thirty-one CT studies (> or = 20 slices, thickness: 3 mm) from 5 patients who were immobilized in a body cast attached to a stereotactic body frame for treatment of paramedullary tumors in the thoracic or lumbar spine were evaluated with respect to setup accuracy. The immobilization device consisted of a custom-made wrap-around body cast that extended from the neck to the thighs and a separate head mask, both made from Scotchcast. Each CT study was performed immediately before or after every second or third actual treatment fraction without repositioning the patient between CT and treatment. The stereotactic localization system was mounted and the isocenter as initially located stereotactically was marked with fiducials for each CT study. Deviation of the treated isocenter as compared to the planned position was measured in all three dimensions.

RESULTS

The immobilization device can be easily handled, attached to and removed from the stereotactic frame and thus enables treatment of multiple patients with the same stereotactic frame each day. Mean patient movements of 1.6 mm+/-1.2 mm (laterolateral [LL]), 1.4 mm+/-1.0 mm (anterior-posterior [AP]), 2.3 mm+/-1.3 mm (transversal vectorial error [VE]) and < slice thickness = 3 mm (craniocaudal [CC]) were recorded for the targets in the thoracic spine and 1.4 mm+/-1.0 mm (LL), 1.2 mm+/-0.7 mm (AP), 1.8 mm+/-1.2 mm (VE), and < 3 mm (CC) for the lumbar spine. The worst case deviation was 3.9 mm for the first patient with the target in the thoracic spine (in the LL direction). Combining those numbers (mean transversal VE for both locations and maximum CC error of 3 mm), the mean three-dimensional vectorial patient movement and thus the mean overall accuracy can be safely estimated to be < or = 3.6 mm.

CONCLUSION

The presented combination of a body cast and head mask system in a rigid stereotactic body frame ensures reliable noninvasive patient fixation for fractionated extracranial stereotactic radiotherapy and may enable dose escalation for less radioresponsive tumors that are near the spinal cord or otherwise critically located while minimizing the risk of late sequelae.

Determining the optimal block margin on the planning target volume for extracranial stereotactic radiotherapy

PURPOSE

To determine the block margin that minimizes normal tissue irradiation outside of the planning target volume (PTV) for body stereotactic radiotherapy (Body-SRT) of lung and liver tumors.

METHODS AND MATERIALS

Representative patient cases of lung and liver tumors were chosen for analysis. A PTV was constructed for each case and plans were generated which employed an array of block margins ranging from -2.5 mm to 10 mm at isocenter. Plans were generated for cerrobend blocks and for a multileaf collimator. The prescription isodose coverage was renormalized for each case and dose-volume histograms (DVH) and normal tissue complication probabilities (NTCP) were determined for each plan.

RESULTS AND CONCLUSION

For the cases studied, the optimal block margin was in the 0.0 mm range. The ranking of plans was identical for both dose-volume based and biological based criteria. The method of blocking had no significant effect on treatment plans. The use of narrow margins for Body-SRT results in normal tissue sparing and creates significant target dose inhomogeneity which may be beneficial for tumor control.

Three-dimensional movement of a liver tumor detected by high-speed magnetic resonance imaging

OBJECTIVE

Three-dimensional (3D) movement of a spherical liver tumor during respiration was investigated with magnetic resonance imaging (MRI) using a high-speed sequence.

METHODS

A marker was placed on the surface of the patient as a reference of distance. Repetition time (TR) was 7.7 ms, echo time (TE) was 4.2 ms, flip angle was 20 degrees, section thickness was 8 mm, and a 256 x 128 matrix was used. The acquisition time was 1.0 s followed by an interval of 0.5 s. The 20 tumor contours extracted during 30 s were superimposed on sagittal and coronal MR images.

RESULTS

The maximum value of tumor edge location was 3.9 cm in the cranio-caudal direction, 2.3 cm in the ventro-dorsal direction, and 3.1 cm in the lateral direction. The mean length of tumor displacement observed was 2.1 cm in the cranio-caudal direction, 0.8 cm in the ventro-dorsal and 0.9 cm in the left-right direction, respectively. The locus of the center of the tumor contour in the sagittal cross section was inclined at 23 degrees and in the coronal cross section was inclined at 18 degrees to the cranio-caudal axis of body.

CONCLUSION

In conclusion, 3D movement of a spherical liver tumor was detected using rapid MRI sequential examinations. Magnetic resonance imaging has a potential to improve the accuracy of the planning target volume of a liver tumor.

[Stereotactic one-time irradiation (radiosurgery). The methods, indications and results]

BACKGROUND

Stereotaxy is a method to determine a point in the patient's body by an external coordinate system which is attached to the patient. Radiosurgery uses this method for precise delivery of a high single radiation dose to the patient. The aim is to destroy the tissue in the target and to spare surrounding unaffected normal tissue by a steep dose gradient.

METHODS

Three techniques of percutaneous radiosurgery are available: radiosurgery with ion beams with a cyclotron, spherical arrangement of cobalt-60 sources, the so-called gamma knife, and an adapted linear accelerator. The availability and the good clinical experience lead to a wide spread use of linear accelerator for radiosurgery in recent years. A subsequent development is fractionated stereotactic radiotherapy which combines the precision of radiosurgery with the radiobiological advantage of fractionation.

RESULTS

Only a few indications for radiosurgery are proven by statistically valid studies. One of these is the treatment of small arteriovenous malformation, where obliteration rates of 80% to 100% are reported with only minor toxicity. However, the obliteration rate is reduced significantly in large arteriovenous malformations. A local control rate of 90% is obtained after radiosurgery of brain metastases which is comparable to the results of microsurgical resection followed by adjuvant whole brain radiotherapy. An ongoing EORTC study evaluates the role of adjuvant whole brain radiotherapy after radiosurgery. The survival of the patients with brain metastases is limited by the existence of progressive extracerebral disease. The role of radiosurgery in the treatment of benign tumors is currently evaluated in clinical studies which include: vestibular schwannomas, meningiomas, chordomas and chondrosarcomas and pituitary adenomas. Most of the published studies include only small tumors because radiosurgery is limited by the risk of radionecrosis of adjacent normal tissue, which shows a steep dose volume response relationship. Recent developments of stereotactic radiotherapy include the use of mini-multileaf-collimators and clinical studies on stereotactic radiotherapy of extracranial targets.

CONCLUSIONS

Stereotactic irradiation is a well established treatment technique for intracranial tumors and arteriovenous malformations. Methods are available that allow optimization of dose distributions to irregularly shaped tumors for single dose as well as fractionated stereotactic irradiations by linear accelerator. Therefore the therapeutic potential of this technique has increased and enables also the extracerebral application in controlled clinical studies.

Managing geometric uncertainty in conformal intensity-modulated radiation therapy

The geometric precision of radiotherapy treatments must increase if the objectives of dose escalation and increased disease control are to be achieved. There are multiple strategies for increasing the geometric precision of a radiotherapy treatment system, including immobilization and setup aids for reducing random and systematic components of setup errors and organ motion alike. Alternatively, more complex strategies can be implemented based on additional information acquired over the course of treatment. Generally, these strategies can be divided into two categories: off-line and on-line. The strategies that are implemented in the clinic must consider the required geometric precision for a given treatment. From this specification, it is possible to select the appropriate strategies and approaches. The cost associated with each approach must also be considered. Once a system for delivery has been designed, the residual uncertainties must still be considered in the planning process. Parallel to the development of strategies for reducing uncertainty, progress is being made in better relating these residual uncertainties to margins for use in treatment planning. This article reviews advances in reducing uncertainty.

A dosimetric comparison of conventional vs conformal external beam irradiation of a stented coronary artery utilizing a new fluoroscopic imaging detector system

Purpose. To determine whether conformal external photon beam irradiation may prevent or reduce the rate of restenosis of a stented coronary artery following percutaneous transluminal coronary angioplasty (PTCA). Optimal conformal external beam irradiation with limited cardiac dose requires adequate visualization of the stented vascular segment. With existing image intensifiers, identification of a coronary stent is poorly localized. We propose using an amorphous silicon panel detector to observe the movement of the stent during the cardiac cycle.

BACKGROUND

Long-term radiation-induced coronary complications can be minimized by: (a) reducing the radiation field sizes, (b) fractionating the total dose over several days, and (c) applying multiple treatment beams. Localization of the movement of the stent during the cardiac cycle may allow for the design of radiation fields that conform to the stented vessel segment. This scheme may permit gating the radiation beam on or off relative to movement of the stent within or outside the radiation fields, respectively.

METHODS

Using a new solid-state amorphous silicon planar detector, with a dynamic range of 12 bits, fluoroscopic images of a Palmaz-Schatz coronary stent were obtained. The stent was centered in a polystyrene phantom 20 cm thick and imaged using a 90-kVp, 3.5-ma, source-detector and source stent distances of 114 and 100 cm, respectively. With the solid-state silicon detector, the stent was identified in a single video frame (1/30 s). This fast image acquisition should allow for mapping the motion of the stent during the cardiac cycle. The stent movement during the cardiac cycle may then be correlated with the QRS complex in the electrocardiogram.

CONCLUSIONS

The localization of a coronary stent during the cardiac cycle under fluoroscopy permits delivery of small conformal external radiation fields to treat stented coronary arteries, while minimizing radiation dose to surrounding normal cardiac tissue and vasculature. The best selection of treatment beam angles will be provided by high resolution fluoroscopic images of the stented region obtained from different beam directions. The three-dimensional movement of the stent, indexed in time with the QRS complex, will provide an important measure for gating radiation beams for conformal treatment delivery.

Focal, high dose, and fractionated modified stereotactic radiation therapy for lung carcinoma patients: a preliminary experience

BACKGROUND

Stereotactic radiation therapy is highly effective in the treatment of small brain metastases, regardless of the histology. This suggests that small extracranial malignancies may be curable with similar radiation therapy. The authors developed a novel treatment unit for administering such therapy.

METHODS

The unit consisted of a linear accelerator (linac), an X-ray simulator (X-S), computed tomography (CT), and a table. The gantry axes of the three machines were coaxial and could be matched by rotating the table. Patients were instructed to perform shallow respiration with oxygen. The motion of the tumor was monitored with the X-S. When the motion was slight enough, the table was rotated to the CT. To include all geometric movement on the CT images, each scan was made while the patient was performing shallow respiration. After the CT positioning, the table was rotated to the linac, and non-coplanar treatment was given. Beginning in October 1994, 45 patients with 23 primary or 43 metastatic lung carcinomas were treated. Radiation doses at the 80% isodose line were 30-75 gray in 5-15 fractions over 1-3 weeks with or without conventional radiation therapy.

RESULTS

The treatment was performed with no or minimal adverse acute symptoms. The daily treatment time was short. During a median follow-up of 11 months, local progression occurred in 2 of 66 lesions. Interstitial changes in the lung were limited.

CONCLUSIONS

With this unit and procedure, focal radiation therapy similar to stereotactic radiation therapy is possible for extracranial sites. The preliminary experience appeared safe and promising, and further exploration of this approach is warranted.

[The point of view of the radiotherapist]

During the last decade, stereotactic radiotherapy has widely improved in France. Thus one should study the present situation and its future trend. QUANTITATIVE NEED: Considering single dose radiotherapy, there are about 900 to 1,000 cases treated per year. However, the trend towards more fractionated treatment will disturb this temporary equilibrium; thus more machine time will be necessary. QUALITATIVE NEED: Stereotactic radiotherapy is practiced by multi-disciplinary teams including physicians, physicists and scientific specialists. Radiotherapists and physicist are responsible for treatment planning and evaluation as well as for clinical and methodological research. Accordingly, they should possess computers, treatment planning systems, etc. Such teams are necessary to carry out complex irradiations. GENERAL EVOLUTION: Fractionation of irradiation nowadays seems mandatory for most intracranial tumors except metastases and small regular arteriovenous malformations. Heterogeneity of lesion dose is related to the geometry and the physics of convergent fixed or mobile beams. It can be improved and the healthy tissue irradiation can be diminished using the multi-isocentric planning for complex lesion or with micro multi leaf collimators. MODALITIES OF STEREOTACTIC RADIOTHERAPY ACCORDING TO LESION TYPE: For neurinomas of the acoustic nerve, fractionated stereotactic radiotherapy yields few of the complications published after single dose stereotactic radiotherapy. The same can be said for meningiomas although some series reported very few complications after single dose stereotactic radiotherapy. Solitary metastases without systemic evolution, not situated on the mid-line, are favorable candidates for palliative single dose stereotactic radiotherapy. The conjunction with total brain irradiation seems to be useful. Small arteriovenous malformations will be treated with single dose stereotactic radiotherapy, whereas voluminous and/or geometrically complex nidus could benefit from protons or photon beams modulated by micro multi leaf collimators and a few fractions. EXTRA-CRANIAL STEREOTACTIC RADIOTHERAPY: Single dose stereotactic radiotherapy and fractionated stereotactic radiotherapy will be used as boost in various situations such as massif facial and in all sorts of tumors in the body specially when lesions are close to critical organs.