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

Deep-inspiration breath-hold kilovoltage cone-beam CT for setup of stereotactic body radiation therapy for lung tumors: Initial experience

We report our initial experience with deep-inspiration breath-hold (DIBH) cone-beam CT (CBCT) on the treatment table, using the kilovoltage imager integrated into our linear accelerator, for setting up patients for DIBH stereotactic body radiation therapy (SBRT) for lung tumors. Nine patients with non-small cell lung cancer (seven stage I), were given 60Gy in three fractions. All nine patients could perform a DIBH for 35s. For each patient we used a diagnostic reference CT volume image acquired during a DIBH to design an SBRT plan consisting of 7-10 noncoplanar conformal beams. Four patients were setup by registering DIBH kilovoltage projection radiographs or megavoltage portal images on the treatment table to digitally reconstructed radiographs from the reference CT. Each of the last 14 fractions out of a total of 27 was setup by acquiring a CBCT volume image on the treatment table in three breath-holds. The CBCT and reference CT volume images were directly registered and the shift was calculated from the registration. The CBCT volume images contained excellent detail on soft tissue and bony anatomy for matching to the reference CT. Most importantly, the tumor was always clearly visible in the CBCT images, even when it was difficult or impossible to see in the radiographs or portal images. The accuracy of the CBCT method was confirmed by DIBH megavoltage portal imaging and each treatment beam was delivered during a DIBH. CBCT acquisition typically required five more minutes than radiograph acquisition but the overall setup time was often shorter using CBCT because repeat imaging was minimized. We conclude that for setting up SBRT treatments of lung tumors, DIBH CBCT is feasible, fast and may result in less variation among observers than using bony anatomy in orthogonal radiographs.

Hypofractionated high-dose proton beam therapy for stage I non-small-cell lung cancer: preliminary results of a phase I/II clinical study

PURPOSE

To present treatment outcomes of hypofractionated high-dose proton beam therapy for Stage I non-small-cell lung cancer (NSCLC).

METHODS AND MATERIALS

Twenty-one patients with Stage I NSCLC (11 with Stage IA and 10 with Stage IB) underwent hypofractionated high-dose proton beam therapy. At the time of irradiation, patient age ranged from 51 to 85 years (median, 74 years). Nine patients were medically inoperable because of comorbidities, and 12 patients refused surgical resection. Histology was squamous cell carcinoma in 6 patients, adenocarcinoma in 14, and large cell carcinoma in 1. Tumor size ranged from 10 to 42 mm (median, 25 mm) in maximum diameter. Three and 18 patients received proton beam irradiation with total doses of 50 Gy and 60 Gy in 10 fractions, respectively, to primary tumor sites.

RESULTS

Of 21 patients, 2 died of cancer and 2 died of pneumonia at a median follow-up period of 25 months. The 2-year overall and cause-specific survival rates were 74% and 86%, respectively. All but one of the irradiated tumors were controlled during the follow-up period. Five patients showed recurrences 6-29 months after treatment, including local progression and new lung lesions outside of the irradiated volume in 1 and 4 patients, respectively. The local progression-free and disease-free rates were 95% and 79% at 2 years, respectively. No therapy-related toxicity of Grade > or =3 was observed.

CONCLUSIONS

Hypofractionated high-dose proton beam therapy seems feasible and effective for Stage I NSCLC. Proton beams may contribute to enhanced efficacy and lower toxicity in the treatment of patients with Stage I NSCLC.

Stereotactic body radiation therapy in multiple organ sites

INTRODUCTION

Stereotactic body radiation therapy (SBRT) uses advanced technology to deliver a potent ablative dose to deep-seated tumors in the lung, liver, spine, pancreas, kidney, and prostate.

METHODS

SBRT involves constructing very compact high-dose volumes in and about the tumor. Tumor position must be accurately assessed throughout treatment, especially for tumors that move with respiration. Sophisticated image guidance and related treatment delivery technologies have developed to account for such motion and efficiently deliver high daily dose. All this serves to allow the delivery of ablative dose fractionation to the target capable of both disrupting tumor mitosis and cellular function.

RESULTS

Prospective phase I dose-escalation trials have been carried out to reach potent tumoricidal dose levels capable of eradicating tumors with high likelihood. These studies indicate a clear dose-response relationship for tumor control with escalating dose of SBRT. Prospective phase II studies have been reported from several continents consistently showing very high levels of local tumor control. Although late toxicity requires further careful assessment, acute and subacute toxicities are generally acceptable. Patterns of toxicity, both clinical and radiographic, are distinct from those observed with conventionally fractionated radiotherapy as a result of the unique biologic response to ablative fractionation.

CONCLUSION

Prospective trials using SBRT have confirmed the efficacy of treatment in a variety of patient populations. Although mechanisms of ablative-dose injury remain elusive, ongoing prospective trials offer the hope of finding the ideal application for SBRT in the treatment arsenal.

Phase II study on stereotactic body radiotherapy of colorectal metastases

Surgical resection provides long term survival in approximately 30% of patients with colorectal carcinoma (CRC) liver metastases. However, only a limited number of patients with CRC-metastases are amendable for surgery. We have tested the effect of stereotactic body radiotherapy (SBRT) in the treatment of inoperable patients with CRC-metastases. Sixty-four patients with a total number of 141 CRC-metastases in the liver (n = 44), lung (n = 12), lymph nodes (n = 3), suprarenal gland (n = 1) or two organs (n = 4) were treated with SBRT with a central dose of 15 Gy x 3 within 5-8 days. Median follow-up was 4.3 years. After 2 years, actuarial local control was 86% and 63% in tumor and patient based analysis, respectively. Nineteen percent were without local or distant progression after 2 years and overall survival was 67, 38, 22, 13, and 13% after 1, 2, 3, 4 and 5 years, respectively. One patient died due to hepatic failure, one patient was operated for a colonic perforation and two patients were conservatively treated for duodenal ulcerations. Beside these, only moderate toxicities such as nausea, diarrhoea and skin reactions were observed. SBRT in patients with inoperable CRC-metastases resulted in high probability of local control and promising survival rate. One toxic death and few severe reactions were observed. For the majority of patients, the treatment related toxicity was moderate.

Factors important for efficacy of stereotactic body radiotherapy of medically inoperable stage I lung cancer. A retrospective analysis of patients treated in the Nordic countries

We reviewed results of SBRT treatment of 138 patients with medically inoperable stage I NSCLC treated during 1996-2003 at five different centres in Sweden and Denmark. Mean age was 74 years (range 56-90) with 69 men and 72 women. SBRT was delivered using a 3D conformal multifield technique and a stereotactic body frame. Doses delivered were 30-48 Gy (65% isodose at the periphery of planning target volume, PTV) in 2-4 fractions. Equivalent dose in 2 Gy fractions (EQD2) was in the range of 50-100 Gy. Mean gross tumour volume (GTV) was 39 cm3 (2-436), and planning target volume was 101 cm3 (11-719). Overall response rate (CR, PR) was 61% (84/138). SD was noted in 36% (50/138). During a median follow-up period of 33 months (1-107), 16 (12%) local failures occurred, ten of which also included distant metastases. Local failure was associated with tumour size, target definition and central or pleura proximity. Distant metastases occurred in 25% (35/138) of the patients. Ninety-one (65%) patients died during follow-up of which 55 patients (60%) died of other causes than lung cancer. Three- and 5-year overall survival was 52 and 26% respectively. Lung cancer specific 3- and 5-year overall survival was 66 and 40% respectively. Fifty nine percent (83/138) of the patients had no side effects. Fourteen patients experienced grade 3-4 toxicity according to radiation therapy oncology group (RTOG). EQD2 (> v.s.<55.6 Gy) showed a statistically significant benefit survival for the higher doses. SBRT for stage I NSCLC results in favourable local control not inferior to fractionated RT and with acceptable toxicity.

Internal movement, set-up accuracy and margins for stereotactic body radiotherapy using a stereotactic body frame

The aim of this study was to evaluate the uncertainty of patient immobilization within the Elekta body frame (SBF) used for stereotactic body radiotherapy (SBRT) and to suggest margins sufficient to ensure dose coverage to the gross target volume (GTV). The study was based on the evaluation of repeated CT-scans of 30 patients treated by SBRT. The overall uncertainty was divided between uncertainty related to internal movement of the tumor and uncertainty in the patient set-up. Standard deviations of the overall tumor displacement were 2 mm, 3 mm and 4 mm in medial-lateral (m-l), anterior-posterior (a-p), and cranio-caudal (c-c) directions, respectively. In a model based on the data, an ellipsoid planned target volume (PTV) corresponding to the standard deviations in the orthogonal directions and a scaling factor, K defined a 3-dimentional (3-D) probability density. According to the model, a 90% probability of full dose coverage of the GTV was secured using margins of 9 mm (m-l), 9 mm (a-p) and 13 mm (c-c), respectively. The overall uncertainty was dominated by internal tumor movements whereas the set-up uncertainty of the patient in the SBF was less pronounced. It was concluded that the Elekta SBF is useful for immobilisation of patients for SBRT. However, due to internal movement conventional margins of 5 mm in m-l and a-p and 10 mm in the c-c directions may be insufficient for full dose coverage.

Stereotactic body radiation therapy for primary and metastatic liver tumors: A single institution phase i-ii study

The feasibility, toxicity and tumor response of stereotactic body radiation therapy (SBRT) for treatment of primary and metastastic liver tumors was investigated. From October 2002 until June 2006, 25 patients not suitable for other local treatments were entered in the study. In total 45 lesions were treated, 34 metastases and 11 hepatocellular carcinoma (HCC). Median follow-up was 12.9 months (range 0.5-31). Median lesion size was 3.2 cm (range 0.5-7.2) and median volume 22.2 cm3 (range 1.1-322). Patients with metastases, HCC without cirrhosis, and HCC < 4 cm with cirrhosis were mostly treated with 3 x 12.5 Gy. Patients with HCC > or =4 cm and cirrhosis received 5 x 5 Gy or 3 x 10 Gy. The prescription isodose was 65%. Acute toxicity was scored following the Common Toxicity Criteria and late toxicity with the SOMA/LENT classification. Local failures were observed in two HCC and two metastases. Local control rates at 1 and 2 years for the whole group were 94% and 82%. Acute toxicity grade > or =3 was seen in four patients; one HCC patient with Child B developed a liver failure together with an infection and died (grade 5), two metastases patients presented elevation of gamma glutamyl transferase (grade 3) and another asthenia (grade 3). Late toxicity was observed in one metastases patient who developed a portal hypertension syndrome with melena (grade 3). SBRT was feasible, with acceptable toxicity and encouraging local control. Optimal dose-fractionation schemes for HCC with cirrhosis have to be found. Extreme caution should be used for patients with Child B because of a high toxicity risk.

Cone-beam CT based image-guidance for extracranial stereotactic radiotherapy of intrapulmonary tumors

Cone-beam CT (CB-CT) based image-guidance was evaluated for extracranial stereotactic radiotherapy of intrapulmonary tumors. A total of 21 patients (25 lesions: prim. NSCLC n = 6; pulmonary metastases n = 19) were treated with stereotactic radiotherapy (1 to 8 fractions). Prior to every fraction a CB-CT was acquired in treatment position, errors between planned and actual tumor position were measured and corrected. Intra- and inter-observer variability of manual evaluation of tumor position error was investigated and this manual method was compared with automatic image registration. Based on CB-CTs from 66 fractions the discrepancy (3-D vector) between planned and actual tumor position was 7.7 mm +/-1.3 mm. Tumor position error relative to the bony anatomy was 5.3 mm +/-1.2 mm, the correlation between bony anatomy and tumor position was poor. Intra-observer and inter-observer variability of manual evaluation of tumor position error was 0.9 mm +/-0.8 mm and 2.3 mm +/-1.1 mm, respectively. Automatic image registration showed highly reproducible results (<1 mm). However, compared with manual registration a systematic error was found in direction of predominant tumor breathing motion (2.5 mm vs 1.4 mm). Image-guidance using CB-CT was validated for high precision radiotherapy of intrapulmonary tumors. It was shown that both the planning reference and the verification image study have to consider tumor breathing motion.

A prospective Phase II trial of using extracranial stereotactic radiotherapy in primary and metastatic renal cell carcinoma

A retrospective study has indicated that stereotactic radiotherapy (SRT) has a value in treating both primary tumors and singular metastatic lesions that cause local symptoms. Here we present the results of a prospective study evaluating the safety and local efficacy of SRT in metastatic or inoperable primary renal cancer. Thirty patients with metastatic renal cell carcinoma (RCC) or inoperable primary RCC received high-dose fraction SRT. In total, 82 lesions were treated. Dose/fractionation schedules varied depending on target location and size. The most frequently used fractionations were 8 Gy x 4, 10 Gy x 4, 15 Gy x 2 or 15 Gy x 3 prescribed to the periphery of the PTV. Local control, defined as radiologically stable disease (SD) or partial/complete response (PR/CR) was obtained in 98% of treated lesions but 19% of lesions were in patients with a follow time of less than 6 months. CR was observed in 21% of the patients and 58% of the patients had a partial volume reduction or local stable disease after a median follow-up of 52 months (range 11-66) for patients alive and 18 months (range 4-57) for deceased patients. Local progression was seen in two lesions. Side effects were grade I-II in 90% of cases. The overall survival was 32 months. SRT for patients with primary and metastatic RCC resulted in high local control rate with generally low toxicity. The method can thus be considered a therapeutic option to surgery in patients with a limited number of metastases, as local treatment in RCC with an indolent presentation or as a method of reducing tumor burden prior to medical treatment.

Stereotactic radiotherapy of primary liver cancer and hepatic metastases

The purpose was to evaluate the clinical results of stereotactic radiotherapy in primary liver tumors and hepatic metastases. Five patients with primary liver cancer and 39 patients with 51 hepatic metastases were treated by stereotactic radiotherapy since 1997. Twenty-eight targets were treated in a "low-dose"-group with 3 x 10 Gy (n = 27) or 4 x 7 Gy (n = 1) prescribed to the PTV-encl. 65%-isodose. In a "high-dose"-group patients were treated with 3 x 12 - 12.5 Gy (n = 19; same dose prescription) or 1 x 26 Gy/PTV-enclosing 80%-isodose (n = 9). Median follow-up was 15 months (2-48 months) for primary liver cancer and 15 months (2-85 months) for hepatic metastases. While all primary liver cancers were controlled, nine local failures (3-19 months) of 51 metastases were observed resulting in an actuarial local control rate of 92% after 12 months and 66% after 24 months and later. A borderline significant correlation between dose and local control was observed (p = 0.077): the actuarial local control rate after 12 and 24 months was 86% and 58% in the low-dose-group versus 100% and 82% in the high-dose-group. In multivariate analysis high versus low-dose was the only significant factor predicting local control (p = 0.0089). Overall survival after 1 and 2 years was 72% and 32% for all patients and was impaired due to systemic progression of disease. No severe acute or late toxicity exceeding RTOG/EORTC-score 2 were observed. Stereotactic irradiation of primary liver cancer and hepatic metastases offers a locally effective treatment without significant complications in patients, who are not amenable for surgery. Patient selection is important, because those with low risk for systemic progression are more likely to benefit from this approach.

Individualized image guided iso-NTCP based liver cancer SBRT

A highly individualized stereotactic body radiotherapy (SBRT) strategy was developed to allow a wide spectrum of patients with liver cancer to be treated. This phase I/II study encompasses individualization of immobilization, radiation planning, PTV margin determination, image guidance strategy and prescription dose. Active breathing control breath hold is used to immobilize the liver when feasible. Image guidance strategies include orthogonal MV images and orthogonal kV fluoroscopy using the diaphragm for a surrogate for the liver, and kV cone beam CT using the liver or tumour for guidance. The prescription dose is individualized to maintain the same estimated risk of radiation-induced liver disease (RILD), based on a normal tissue complication probability (NTCP) model, with a maximum permitted dose of 60 Gy in 6 fractions. Since August 2003, 79 patients with hepatocellular carcinoma (33), intrahepatic cholangiocarcinoma (12) and liver metastases (34) were treated. The median tumour volume was 293 cm3 (2.9-3 088 cm3). The median prescribed dose was 36.6 Gy (24.0 Gy-57.0 Gy) in 6 fractions. The median effective liver volume irradiated was 45% (9-80%). Sixty percent of patients were treated with breath hold to immobilize their liver. Intra-fraction reproducibility (sigma) of the liver with repeat breath holds was excellent (1.5 mm); however inter-fraction reproducibility (sigma) was worse (3.4 mm). Image guidance reduced the residual systematic and random setup errors significantly.

A review on the clinical implementation of respiratory-gated radiation therapy

Respiratory-gated treatment techniques have been introduced into the radiation oncology practice to manage target or organ motions. This paper will review the implementation of this type of gated treatment technique where the respiratory cycle is determined using an external marker. The external marker device is placed on the abdominal region between the xyphoid process and the umbilicus of the patient. An infrared camera tracks the motion of the marker to generate a surrogate for the respiratory cycle. The relationship, if any, between the respiratory cycle and the movement of the target can be complex. The four-dimensional computed tomography (4DCT) scanner is used to identify this motion for those patients that meet three requirements for the successful implementation of respiratory-gated treatment technique for radiation therapy. These requirements are (a) the respiratory cycle must be periodic and maintained during treatment, (b) the movement of the target must be related to the respiratory cycle, and (c) the gating window can be set sufficiently large to minimise the overall treatment time or increase the duty cycle and yet small enough to be within the gate. If the respiratory-gated treatment technique is employed, the end-expiration image set is typically used for treatment planning purposes because this image set represents the phase of the respiratory cycle where the anatomical movement is often the least for the longest time. Contouring should account for tumour residual motion, setup uncertainty, and also allow for deviation from the expected respiratory cycle during treatment. Respiratory-gated intensity-modulated radiation therapy (IMRT) treatment plans must also be validated prior to treatment. Quality assurance should be performed to check for positional changes and the output in association with the motion-gated technique. To avoid potential treatment errors, radiation therapist (radiographer) should be regularly in-serviced and made aware of the need to invoke the gating feature when prescribed for selected patients.

The management of respiratory motion in radiation oncology report of AAPM Task Group 76

This document is the report of a task group of the AAPM and has been prepared primarily to advise medical physicists involved in the external-beam radiation therapy of patients with thoracic, abdominal, and pelvic tumors affected by respiratory motion. This report describes the magnitude of respiratory motion, discusses radiotherapy specific problems caused by respiratory motion, explains techniques that explicitly manage respiratory motion during radiotherapy and gives recommendations in the application of these techniques for patient care, including quality assurance (QA) guidelines for these devices and their use with conformal and intensity modulated radiotherapy. The technologies covered by this report are motion-encompassing methods, respiratory gated techniques, breath-hold techniques, forced shallow-breathing methods, and respiration-synchronized techniques. The main outcome of this report is a clinical process guide for managing respiratory motion. Included in this guide is the recommendation that tumor motion should be measured (when possible) for each patient for whom respiratory motion is a concern. If target motion is greater than 5 mm, a method of respiratory motion management is available, and if the patient can tolerate the procedure, respiratory motion management technology is appropriate. Respiratory motion management is also appropriate when the procedure will increase normal tissue sparing. Respiratory motion management involves further resources, education and the development of and adherence to QA procedures.

Dynamic targeting image-guided radiotherapy

Volumetric imaging and planning for 3-dimensional (3D) conformal radiotherapy and intensity-modulated radiotherapy (IMRT) have highlighted the need to the oncology community to better understand the geometric uncertainties inherent in the radiotherapy delivery process, including setup error (interfraction) as well as organ motion during treatment (intrafraction). This has ushered in the development of emerging technologies and clinical processes, collectively referred to as image-guided radiotherapy (IGRT). The goal of IGRT is to provide the tools needed to manage both inter- and intrafraction motion to improve the accuracy of treatment delivery. Like IMRT, IGRT is a process involving all steps in the radiotherapy treatment process, including patient immobilization, computed tomography (CT) simulation, treatment planning, plan verification, patient setup verification and correction, delivery, and quality assurance. The technology and capability of the Dynamic Targeting IGRT system developed by Varian Medical Systems is presented. The core of this system is a Clinac or Trilogy accelerator equipped with a gantry-mounted imaging system known as the On-Board Imager (OBI). This includes a kilovoltage (kV) x-ray source, an amorphous silicon kV digital image detector, and 2 robotic arms that independently position the kV source and imager orthogonal to the treatment beam. A similar robotic arm positions the PortalVision megavoltage (MV) portal digital image detector, allowing both to be used in concert. The system is designed to support a variety of imaging modalities. The following applications and how they fit in the overall clinical process are described: kV and MV planar radiographic imaging for patient repositioning, kV volumetric cone beam CT imaging for patient repositioning, and kV planar fluoroscopic imaging for gating verification. Achieving image-guided motion management throughout the radiation oncology process requires not just a single product, but a suite of integrated products to manipulate all patient data, including images, efficiently and effectively.

Conformal Radiotherapy of the Dominant Liver Metastasis

OBJECTIVES

To evaluate the safety and efficacy of conformal radiotherapy (RT) of the dominant liver metastasis as palliative treatment of patients with unresectable colorectal cancer liver metastases.

METHODS

We retrospectively reviewed the hospital and RT records of 17 patients with unresectable colorectal liver metastases who had been treated with palliative RT to the dominant liver metastasis at our institution.

RESULTS

The median size of the dominant liver metastasis was 10 cm (range, 3-19 cm). Twelve patients (71%) had evidence of extrahepatic disease. A median of 2 (range, 0-4) prior chemotherapy regimens had been administered. Median radiation dose was 42 Gy (range, 7.5-72 Gy). Concurrent chemotherapy included celecoxib in 1 (6%), capecitabine in 6 (35%), and both agents in 9 (53%) patients. Frequencies of acute diarrhea, nausea, vomiting, fatigue, hand-foot syndrome, and neutropenia were 29%, 47%, 6%, 29%, 7%, and 0%, respectively (all grade 2 or lower; no grade 3 toxicities). No late toxicities were noted. With a median follow-up time of 9.2 months, the median actuarial overall survival time from RT was 12.6 months (95% confidence interval [CI]: 3.3-40.9 months). The actuarial in-field local control rate was 62% at 6 months. The median actuarial time to in-field, out-of-field hepatic and distant progression were 6.8, 3.9, and 4.1 month, respectively (95% CIs, 3.9-15.8, 1.8-6.3, and 1.8-11.5 months, respectively).

CONCLUSIONS

Conformal RT to the dominant liver metastasis as palliative therapy for unresectable colorectal cancer liver metastases has an acceptable toxicity profile and may improve survival. This approach merits further exploration.

Comparison of helical, maximum intensity projection (MIP), and averaged intensity (AI) 4D CT imaging for stereotactic body radiation therapy (SBRT) planning in lung cancer

BACKGROUND AND PURPOSE

To compare helical, MIP and AI 4D CT imaging, for the purpose of determining the best CT-based volume definition method for encompassing the mobile gross tumor volume (mGTV) within the planning target volume (PTV) for stereotactic body radiation therapy (SBRT) in stage I lung cancer.

MATERIALS AND METHODS

Twenty patients with medically inoperable peripheral stage I lung cancer were planned for SBRT. Free-breathing helical and 4D image datasets were obtained for each patient. Two composite images, the MIP and AI, were automatically generated from the 4D image datasets. The mGTV contours were delineated for the MIP, AI and helical image datasets for each patient. The volume for each was calculated and compared using analysis of variance and the Wilcoxon rank test. A spatial analysis for comparing center of mass (COM) (i.e. isocenter) coordinates for each imaging method was also performed using multivariate analysis of variance.

RESULTS

The MIP-defined mGTVs were significantly larger than both the helical- (p=0.001) and AI-defined mGTVs (p=0.012). A comparison of COM coordinates demonstrated no significant spatial difference in the x-, y-, and z-coordinates for each tumor as determined by helical, MIP, or AI imaging methods.

CONCLUSIONS

In order to incorporate the extent of tumor motion from breathing during SBRT, MIP is superior to either helical or AI images for defining the mGTV. The spatial isocenter coordinates for each tumor were not altered significantly by the imaging methods.

Investigations of different kilovoltage x-ray energy for three-dimensional converging stereotactic radiotherapy system: Monte Carlo simulations with CT data

We are investigating three-dimensional converging stereotactic radiotherapy (3DCSRT) with suitable medium-energy x rays as treatment for small lung tumors with better dose homogeneity at the target. A computed tomography (CT) system dedicated for non-coplanar converging radiotherapy was simulated with BEAMnrc (EGS4) Monte-Carlo code for x-ray energy of 147.5, 200, 300, and 500 kilovoltage (kVp). The system was validated by comparing calculated and measured percentage of depth dose in a water phantom for the energy of 120 and 147.5 kVp. A thorax phantom and CT data from lung tumors (<20 cm3) were used to compare dose homogeneities of kVp energies with MV energies of 4, 6, and 10 MV. Three non-coplanar arcs (0 degrees and +/-25 degrees ) around the center of the target were employed. The Monte Carlo dose data format was converted to the XiO RTP format to compare dose homogeneity, differential, and integral dose volume histograms of kVp and MV energies. In terms of dose homogeneity and DVHs, dose distributions at the target of all kVp energies with the thorax phantom were better than MV energies, with mean dose absorption at the ribs (human data) of 100%, 85%, 50%, 30% for 147.5, 200, 300, and 500 kVp, respectively. Considering dose distributions and reduction of the enhanced dose absorption at the ribs, a minimum of 500 kVp is suitable for the lung kVp 3DCSRT system.

Excessive toxicity when treating central tumors in a phase II study of stereotactic body radiation therapy for medically inoperable early-stage lung cancer

PURPOSE

Surgical resection is standard therapy in stage I non-small-cell lung cancer (NSCLC); however, many patients are inoperable due to comorbid diseases. Building on a previously reported phase I trial, we carried out a prospective phase II trial using stereotactic body radiation therapy (SBRT) in this population.

PATIENTS AND METHODS

Eligible patients included clinically staged T1 or T2 (< or = 7 cm), N0, M0, biopsy-confirmed NSCLC. All patients had comorbid medical problems that precluded lobectomy. SBRT treatment dose was 60 to 66 Gy total in three fractions during 1 to 2 weeks.

RESULTS

All 70 patients enrolled completed therapy as planned and median follow-up was 17.5 months. The 3-month major response rate was 60%. Kaplan-Meier local control at 2 years was 95%. Altogether, 28 patients have died as a result of cancer (n = 5), treatment (n = 6), or comorbid illnesses (n = 17). Median overall survival was 32.6 months and 2-year overall survival was 54.7%. Grade 3 to 5 toxicity occurred in a total of 14 patients. Among patients experiencing toxicity, the median time to observation was 10.5 months. Patients treated for tumors in the peripheral lung had 2-year freedom from severe toxicity of 83% compared with only 54% for patients with central tumors.

CONCLUSION

High rates of local control are achieved with this SBRT regimen in medically inoperable patients with stage I NSCLC. Both local recurrence and toxicity occur late after this treatment. This regimen should not be used for patients with tumors near the central airways due to excessive toxicity.

Principe et mise en œuvre de la radiothérapie en conditions stéréotaxiques extracrânienne

We fully describe an innovative radiotherapy technique called Stereotactic Body Radiation Therapy (SBRT), and explain how this technique is commonly used for clinical purpose at the anticancer center Léon-Bérard (Lyon, France). In this technique, a non-invasive stereotactic body frame is used to locate the tumor site with a great precision. This frame is combined with a system, which enables to track the respiratory motions (Active Breathing Control (ABC) or diaphragmatic compression (DC)) in order to reduce the treatment margins for organ motion due to breathing. Thus, the volume of normal tissues that will be irradiated is considerably reduced. The dosimetry is realized with 3 CT exams performed in treatment conditions. The 3D patient "repositioning" is done with a volume CT acquisition (kV) combined with orthogonal images (kV and MV). The SBRT requires a system to limit the organ motions. Although the ABC seems to be more fastidious for patient, it would enable to use smaller margins than with DC technique. Nevertheless, the ABC is not compatible with volume CT acquisitions, which considerably improve the patient repositioning. In conclusion, the quality of repositioning and the high level of conformation enable to deliver high equivalent doses (>100 Gy) in hypofractionated mode, without increasing the treatment toxicity. The SBRT employs the last technologic innovations in radiotherapy and is therefore considered as a new efficient tool for solid tumors treatment.

Surgical robotics and image guided therapy in pediatric surgery: emerging and converging minimal access technologies

Minimal access surgery (MAS) is now commonplace in the armamentarium of the pediatric surgeon, and is being applied to a growing list of pediatric surgical diseases. Robot-assisted surgery and image guided therapy (IGT) have evolved as innovative minimal access approaches, and hold the promise of advancing MAS far beyond what is currently possible. The aims of this article are to describe the currently available robotic, and image guided therapy systems, review their present and potential applications, and discuss the future directions of these converging technologies.

Dosimetric verification in participating institutions in a stereotactic body radiotherapy trial for stage I non-small cell lung cancer: Japan clinical oncology group trial (JCOG0403)

A multicentre phase II trial of stereotactic body radiotherapy for T1N0M0 non-small cell lung cancer was initiated in Japan as the Japan Clinical Oncology Group trial (JCOG0403). Before starting the trial, a decision was made to evaluate the treatment machine and treatment planning in participating institutions to minimize the variations of the prescription dose between the institutions. We visited the 16 participating institutions and examined the absolute dose at the centre of a simulated spherical tumour of 3.0 cm diameter in the lung using the radiation treatment planning systems in each institution. A lung phantom for stereotactic body radiotherapy (SBRT) was developed and used for the treatment planning and film dosimetry. In the JCOG radiotherapy study group, the no model-based calculation algorithm or the model-based calculation algorithm with a dose kernel unscaled for heterogeneities were selected for use in the initial SBRT trials started in 2004, and the model-based calculation algorithm with a dose kernel scaled for heterogeneities was selected for the coming trial. The findings of this study suggest that the clinical results of lung SBRT trials should be carefully evaluated in comparison with the actual dose given to patients.

Accuracy of single-session extracranial radiotherapy for simple shaped lung tumor or metastasis using fast 3-D CT treatment planning

BACKGROUND

This study is situated in the area of measuring set-up accuracy and time periods of single-session extracranial radiotherapy (SSRT) for simple-shaped targets (e.g., spherical or rotational symmetrical) definitively located in the peripheral lung.

METHODS AND MATERIALS

After adaptation of the stereotactic body frame, the patient has to remain in the vacuum pillow during planning computed tomography (CT), fast three-dimensional (3-D) treatment planning, and direct irradiation after verification. Fast preplanning is performed by using virtual simulation software to accelerate the method.

RESULTS

In our new procedure, SSRT is applied in approximately 1.5 h. The mean setup accuracy vector was 2.4+/-0.7 mm in the range of 1.34 to 4 mm. Mean intrafractional patient movement in the stereotactic body frame before and after radiation was 0.70 mm+/-0.5 mm and 0.76+/-0.76 mm in the range of 0 to 2.8 mm. Mean time period steps were measured at (1) planning CT with 3-D treatment planning: 76+/-12 min; (2) irradiation and verification: 33+/-7 min; and (3) complete procedure duration: 109+/-11 min (range, 89-169).

CONCLUSIONS

The main difference between the positioning technique of SSRT and that of conventional extracranial radiosurgery is the tighter patient fixation, which guarantees minimal patient movement. The main advantages are procedure acceleration and omission of CT simulation. SSRT is a preliminary stage of real-time treatment.

Dosimetric comparison of stereotactic body radiotherapy in different respiration conditions: A modeling study

PURPOSE

To evaluate the dosimetric consequences for irradiated lung tissue for different respiration conditions for hypofractionated stereotactic body radiotherapy (SBRT).

METHODS AND MATERIALS

Thirteen patients with lung lesion undergoing SBRT treatment in shallow breathing with abdominal compression (SB+AP) underwent additional multislice CT studies in free breathing (FB), deep inspiration and expiration breath hold (DIBH, DEBH). For each patient 6 different treatment plans were designed for the various respiration conditions applying standard (7/7/10 mm), reduced (5/5/5 mm) and individual margins. The FB plan with standard margins was used as a reference. The percentage of volume of the ipsilateral lung receiving total doses > or=12, 15> or= and > or=18 Gy, mean lung dose (D(mean)), NTCP corrected for fractionation effects and the total monitor units (MU) were evaluated.

RESULTS

With DIBH it was possible to reduce all lung dose parameters by about 20%. Applying reduced margins in DIBH, this reduction was even increased to about 40%. The standard technique (SB+AP) with individual margins showed similar results as DIBH with standard margins. DEBH showed some improvement over FB only when reduced margins were applied. Only for 5/13 patients NTCP values >1% were obtained. For these patients a significant NTCP reduction was achieved with DIBH techniques.

CONCLUSIONS

In SBRT shallow breathing with abdominal compression produces acceptable results concerning lung DVHs. DIBH, especially with reduced margins, showed the best lung sparing. For the clinical implementation of such a technique some form of gating is advisable. However, there are some practical limitations due to high fractional doses.

Stereotactic body radiation therapy for extracranial oligometastases: does the sword have a double edge?

Understanding the acute and chronic toxicities of stereotactic body radiation therapy (SBRT) for extracranial oligometastases might reveal treatment parameters that can be modulated to enhance the therapeutic ratio. Therefore, we searched PubMed from 1995 to 2005 for reports on stereotactic body radiation therapy, with emphasis on treatment of metastatic lesions of the lung and/or liver. Reports of SBRT for primary tumors of these sites were included to increase the number of evaluable patients. The reports were categorized by organ system and evaluated based on number of patients, number of lesions treated, dose fractionation scheme, and local control. A total of 15 lung studies (including 683 patients) and 7 liver studies (including 156 patients) were identified. Overall grade 3 to 5 toxicity was seen in up to 15% of patients in the lung SBRT studies and up to 18% of patients in the liver SBRT studies. Only 3 deaths were reported after SBRT of the liver and 2 after SBRT of the lung for treatment related mortality rates of 2% and 0.3%, respectively. No definitive relationship was found between radiation dose and toxicity. Conversely, radiation treatment volume may be associated with the infrequent toxicities that occur. The literature supports SBRT as a safe and effective treatment for oligometastases of the liver and lung. Further studies are needed to define the optimal dose and fractionation schedule.

Stereotactic, single-dose irradiation of stage I non-small cell lung cancer and lung metastases

Background

We prospectively reviewed response rates, local control, and side effects after non-fractionated stereotactic high single-dose body radiation therapy for lung tumors.

Methods

Fifty-eight patients underwent radiosurgery involving single-dose irradiation. With 25 patients, 31 metastases in the lungs were irradiated; with each of 33 patients, stage I non-small cell lung cancer (NSCLC) was subject to irradiation. The standard dose prescribed to the isocenter was 30 Gy with an axial safety margin of 10 mm and a longitudinal safety margin of 15 mm. The planning target volume (PTV) was defined using three CT scans with reference to the phases of respiration so that the movement span of the clinical target volume (CTV) was enclosed.

Results

The volume of the metastases (CTV) varied from 2.8 to 55.8 cm³ (median: 6.0 cm³) and the PTV varied from 12.2 to 184.0 cm³ (median: 45.0 cm³). The metastases ranged from 0.7 to 4.5 cm in largest diameter. The volume of the bronchial carcinomas varied from 4.2 to 125.4 cm³(median: 17.5 cm³) and the PTV from 15.6 to 387.3 cm³ (median: 99.8 cm³). The bronchial carcinomas ranged from 1.7 to 10 cm in largest diameter. Follow-up periods varied from 6.8 to 63 months (median: 22 months for metastases and 18 months for NSCLC). Local control was achieved with 94% of NSCLC and 87% of metastases. No serious symptomatic side effects were observed. According to the Kaplan-Meier method the overall survival probability rates of patients with lung metastases were as follows: 1 year: 97%, 2 years: 73%, 3 years: 42%, 4 years: 42%, 5 years: 42% (median survival: 26 months); of those with NSCLC: 1 year: 83%, 2 years: 63%, 3 years: 53%, 4 years: 39%: (median survival: 20.4 months).

Conclusion

Non-fractionated single-dose irradiation of metastases in the lungs or of small, peripheral bronchial carcinomas is an effective and safe form of local treatment and might become a viable alternative to invasive techniques.

Dose as a function of liver volume and planning target volume in helical tomotherapy, intensity-modulated radiation therapy-based stereotactic body radiation therapy for hepatic metastasis

PURPOSE

Stereotactic body radiation therapy (SBRT) has been shown to be an effective, well-tolerated treatment for local control of tumors metastatic to the liver. Multi-institutional Phase II trials are examining 60 Gy in 3 fractions delivered by linac-based, 3D-conformal IMRT. HiArt Helical TomoTherapy is a treatment unit that delivers co-planar helical IMRT that is capable of image-guided SBRT. We hypothesized that the maximum tolerable dose (MTD) delivered to a lesion by Helical TomoTherapy-based SBRT could be predicted based on the planning target volume (PTV) and liver volume.

METHODS AND MATERIALS

To test this, we performed inverse treatment planning and analyzed the dosimetry for multiple hypothetical liver gross tumor volumes (GTV) with conventional PTV expansions. Inverse planning was carried out to find the maximum tolerated SBRT dose up to 60 Gy to be delivered in 3 fractions based on the dose constraint that 700 cc of normal liver would receive less than 15 Gy.

RESULTS

Regression analysis indicated a linear relationship between the MTD, the PTV and the liver volume, supporting our hypothesis. A predictive equation was generated, which was found to have an accuracy of +/-3 Gy. In addition, dose constraints based on proximity to other normal tissues were tested. Inverse planning for PTVs located at varying distances from the heart, small bowel, and spinal cord revealed a predictable decrease in the MTD as the PTV increased in size or approached normal organs.

CONCLUSIONS

These data provide a framework for predicting the likely MTD for patients considered for Helical TomoTherapy liver SBRT.

Optimal number of beams for stereotactic body radiotherapy of lung and liver lesions

PURPOSE

The aim of this study was to determine the optimal number of coplanar and noncoplanar external beams in the setting of stereotactic body radiotherapy (SBRT).

METHODS AND MATERIALS

Spherical targets were delineated within 2 separate extracranial sites, the lung and liver, with diameters varying from 2 cm to 7 cm to cover the range of volumes used in SBRT. Treatment plans were created for all target volumes using 5 to 15 geometrically optimized coplanar and noncoplanar conformal beams. Dose gradient and normal tissue complication probability (NTCP) were evaluated for each set of beam configurations and for each target size.

RESULTS

For all lung and liver target volumes, the dose gradient improved with an increase in beam number from 5 to 15 for both coplanar and noncoplanar beam configurations. NTCP decreased as the beam number increased from 5 to 9 beams for all target sizes for both coplanar and noncoplanar beams. There is no significant improvement in NTCP when more than 9 beams were used for treatment planning regardless of target size.

CONCLUSION

Based on dosimetric criteria, the optimal number of external beams is 13 to 15 for SBRT using either coplanar or noncoplanar beam bouquets. Simple biologic models indicate that the optimal number of beams is 9 for SBRT of lung and liver lesions >2 cm, whereas smaller lesions may benefit from plans using up to 13 beams.

Image-Guided Microtherapy for Tumor Ablation: From Thermal Coagulation to Advanced Irradiation Techniques

Image-guided tumor ablation has been established as a valuable adjunct in oncological treatment concepts. The majority of micro-therapeutic procedures is performed by applying thermal ablation, such as radiofrequency or laser. However, in view of the limitations of thermal ablation regarding tumor size or adjacent risk structures, novel techniques combining brachytherapy with modern interventional techniques have demonstrated favorable outcomes. In addition, advances in non-invasive percutaneous irradiation, such as extracranial stereotaxy, have demonstrated very competitive preliminary results. In this article, state-of-the-art techniques for micro-therapeutic tumor ablation are being described.

Extracranial Radiosurgery (Stereotactic Body Radiation Therapy) for Oligometastases

Extracranial radiosurgery, also known as stereotactic body radiation therapy (SBRT), is an increasingly used method of treatment of limited cancer metastases located in a variety of organs/sites including the spine, lungs, liver, and other areas in the abdomen and pelvis. The techniques used to perform SBRT were initially modeled after intracranial radiosurgery, although considerable evolution in technique and conduct has occurred for extracranial applications. Unlike intracranial radiosurgery, SBRT requires characterization and accounting for inherent organ movement including breathing motion. Potent dose hypofractionation schedules have been used with SBRT such that the treatment is generally both ablative and convenient. Because the treatment is severely damaging to tissues within and about the target, the volume of adjacent normal tissue must be strictly minimized to avoid toxic late effects. Outcomes in various sites show very high rates of local control with toxicity mostly related to tubular tissues like the airways and bowels. With proper conduct though, SBRT can be an extremely effective treatment option for oligometastases.

Radiation therapy in the elderly

The purpose of this review is to highlight aspects of radiation oncology specifically related to aging and caring for the older patient with cancer. Particular emphasis is placed on the preclinical and clinical studies focusing on the efficacy and toxicity of RT in this population. Special techniques are also reviewed that have particular relevance to the treatment of the elderly.

Technical note: gold marker implants and high-frequency jet ventilation for stereotactic, single-dose irradiation of liver tumors

With reference to radiosurgery of the liver, we describe techniques designed to solve the methodological problem of striking targets subject to respiratory motion with the necessary precision. Implanting a gold marker in the vicinity of the liver tumor was the first step in ensuring the reproducibility of the isocenter's position. An 18-karat gold rod measuring 1.9 x 3 mm was implanted approximately 2 cm from the edge of the tumor as this was displayed in the spiral, thin-slice CT with contrast media. Both the implantation of the marker and the required, CT-controlled biopsy of the liver tumor can be achieved simultaneously with the same puncture needle. The efficiency of high-frequency jet ventilation (HFJV) in neutralizing the targeted organ's respiratory motion during stereotactic single-dose irradiation was evaluated. The procedure was carried out on ten patients without any complications. In the time between treatment planning and irradiation (3 days), no significant marker migration was observable. In all cases, the gold marker (volume: 7.5 mm(3)) was readily observable in the treatment beam using portal imaging. HFJV provided reliable immobilization. The liver motion in each anesthetized patient was limited to under 3.0 mm in all directions. Thus, the correct field settings and target reproducibility were able to be analyzed and documented during the irradiation. The combination of marker and HFJV enables the determination of stereotactic coordinates directly related to the liver itself and, in this way, stereotactic radiation treatment of liver tumors is freed from the uncertainties involved in orientation to bony landmarks, in respiratory motion, and in changes of position in the stereotactic body frame. The method is feasible and can improve the accuracy of stereotactic body radiation therapy.

Stereotactic body radiation therapy for nonmetastatic lung cancer: an analysis of 75 patients treated over 5 years

PURPOSE

Non-small-cell lung cancer (NSCLC) may not be medically operable even in patients with surgically resectable disease. For patients who either refuse surgery or are medically inoperable, radiation therapy may be the best therapeutic choice. Stereotactic body radiation therapy (SBRT) employs external fixation and hypofractionation to deliver a high dose per fraction of radiation to a small target volume.

METHODS AND MATERIALS

Retrospective review of 75 patients treated over 5 years at Staten Island University Hospital as definitive treatment for NSCLC or presumed NSCLC. Patients received a median of 5 fractions of 8 Gy per fraction over 27 days.

RESULTS

Overall 1-, 2-, and 5-year actuarial survivals were 63%, 45%, and 17%. Patients with a gross tumor volume (GTV) less than 65 cm3 enjoyed a longer median survival (25.7 vs. 9.9 months, p < 0.003), and at 5 years, the actuarial survival for the patients with GTVs less than 65 cm3 was 24% vs. 0% for those with GTVs larger than 65 cm3.

CONCLUSIONS

Stereotactic body radiation therapy as delivered was ineffective for curing the patients whose GTVs were larger than 65 cm3. SBRT was promising for those with GTVs less than 65 cm3.

Fractionated stereotactic radiotherapy in patients with primary hepatocellular carcinoma

OBJECTIVE

The purpose of our study was to evaluate the feasibility and treatment outcomes of fractionated stereotactic radiotherapy (SRT) for primary hepatocellular carcinoma (HCC).

METHODS

We enrolled 20 patients who had been histologically diagnosed as HCC patients and treated by fractionated SRT. Tumor size was 2-6.5 cm (average: 3.8 cm). We prescribed 50 Gy in 5 or 10 fractions at the 85-90% isodose line of the planning target volume for 2 weeks. The follow-up period was 3-55 months (median: 23 months).

RESULTS

The overall response rate was 80%, with 4 patients showing complete response (20%), 14 patients showing partial response (60%) and 4 patients showing stable disease (20%). The 1-year and 2-year survival rates were 70.0 and 43.1%, respectively (median: 20 months). The 1-year and 2-year disease-free survival rates were 65.0 and 32.5%, respectively (median: 19 months). The fractionated SRT was well tolerated, because grade 3 or grade 4 toxicity was not observed.

CONCLUSION

These results suggest that fractionated SRT is a relatively safe and effective method for treating small primary HCC. Thus, fractionated SRT may be suggested as a local treatment of choice for small HCC when the patients are inoperable or when the patients refuse operation.

Stereotactic hypofractionated radiotherapy for stage I non-small cell lung cancer—Mature results for medically inoperable patients

Medically inoperable patients with stage I NSCLC are mainly offered conventionally fractionated radiotherapy with a limited chance of local control and some toxicity. A technique for stereotactic precision therapy for extracranial tumors using a linear accelerator and a body frame for patient immobilization was applied in an attempt to improve the local control and decrease toxicity for consecutive patients with inoperable stage I NSCLC at Sahlgrenska University hospital since 1998. A hypofractionated schedule with three fractions of 15Gy to a total of 45 Gy during 1 week was used which represents a biological equivalent dose (BED) of 112.5 Gy. Planning target volume (PTV) was a 5mm margin around the tumor in the transversal plane and 10mm in the cranial-caudal direction and the dose was prescribed in the periphery of the PTV. Forty-five patients were treated between September 98 and March 03, 25 men and 20 women, median age 74 years (58-84) and median Karnofsky 80 (100-60). TNM: 18 T1N0, 27 T2N0.

HISTOLOGY

18 squamous cell carcinoma, 15 adenocarcinoma, 3 NSCLC and histology was missing in nine patients. The majority, 51%, did not experience any toxicity at all, four had esophagitis grade I, nine had skin reactions, four had transient chest pain and four had infections. Late toxicity was two rib fractures and three patients with atelectasias. After a median follow-up of 43 months had nine patients developed local recurrence or never achieved local control, two had regional recurrence and nine distant metastases. The 1-, 2-, 3- and 5-year overall survival was 80, 71, 55 and 30%, respectively, with a median survival of 39 months. No prognostic factor for survival could be identified among histology, tumor stage and size, gender and age. We think this hypofractionated stereotactic radiotherapy shows encouraging survival and a relatively low toxicity in this elderly population with substantial comorbidity. A multicenter randomized trial comparing this treatment with conventional fractionated radiotherapy is under way.

Phase-II study on stereotactic radiotherapy of locally advanced pancreatic carcinoma

BACKGROUND AND PURPOSE

The majority of patients with pancreatic cancer have advanced disease at the time of diagnosis and are not amenable for surgery. Stereotactic radiotherapy (SRT) may be an alternative treatment for patients with locally advanced disease. The effect of SRT was investigated in the present phase-II trial.

PATIENTS AND METHODS

Twenty-two patients with locally advanced and surgically non-resectable, histological proven pancreatic carcinoma were included into the trial. The patients were immobilized by the Elekta stereotactic body frame (SBF) or a custom made body frame. SRT was given on standard LINAC with standard multi-leaf collimator. Central dose was 15 Gyx3 within 5-10 days.

RESULTS

Evaluation of response was found to be very difficult due to radiation and tumour related tissue reaction. Only two patients (9%) were found to have a partial response (PR), the remaining had no change (NC) or progression (PD) after treatment. Six patients had local tumour progression, but only one patient had an isolated local failure without simultaneous distant metastasis. Median time to local or distant progression was 4.8 months. Median survival time was 5.7 months and only 5% were alive 1 year after treatment. Acute toxicity reported 14 days after treatment was pronounced. There was a significant deterioration of performance status (P=0.008), more nausea (P=0.001) and more pain (P=0.008) after 14 days compared with base-line. However, 8 of 12 patients (66%) improved in performance status, scored less nausea, pain, or needed less analgesic drugs at 3 months after treatment. Four patients suffered from severe mucositis or ulceration of the stomach or duodenum and one of the patients had a non-fatal ulcer perforation of the stomach.

CONCLUSIONS

SRT was associated with poor outcome, unacceptable toxicity and questionable palliative effect and cannot be recommended for patients with advanced pancreatic carcinoma.

Dose-response in stereotactic irradiation of lung tumors

The dose-response for local tumor control after stereotactic radiotherapy of 92 pulmonary tumors (36 NSCLC and 56 metastases) was evaluated. Short course irradiation of 1-8 fractions with different fraction doses was used. After a median follow-up of 14 months (2-85 months) 11 local recurrences were observed with significant advantage for higher doses. When normalization to a biologically effective dose (BED) is used a dose of 94Gy at the isocenter and 50Gy at the PTV-margin are demonstrated to give 50% probability of tumor control (TCD50). Multivariate analysis revealed the dose at the PTV-margin as the only significant factor for local control.

Accuracy of daily image guidance for hypofractionated liver radiotherapy with active breathing control

PURPOSE

A six-fraction, high-precision radiotherapy protocol for unresectable liver cancer has been developed in which active breathing control (ABC) is used to immobilize the liver and daily megavoltage (MV) imaging and repositioning is used to decrease geometric uncertainties. We report the accuracy of setup in the first 20 patients consecutively treated using this approach.

METHODS AND MATERIALS

After setup using conventional skin marks and lasers, orthogonal MV images were acquired with the liver immobilized using ABC. The images were aligned to reference digitally reconstructed radiographs using the diaphragm for craniocaudal (CC) alignment and the vertebral bodies for anterior-posterior (AP) and mediolateral (ML) alignment. Adjustments were made for positioning errors >3 mm. Verification imaging was repeated after repositioning to assess for residual positioning error. Offline image matching was conducted to determine the setup accuracy using this approach compared with the initial setup error before repositioning. Real-time beam's-eye-view MV movies containing an air-diaphragm interface were also evaluated.

RESULTS

A total of 405 images were evaluated from 20 patients. Repositioning occurred in 109 of 120 fractions because of offsets >3 mm. Three to eight beam angles, with up to four segments per field, were used for each isocenter. Breath holds of up to 27 s were used for imaging and treatment. The average time from the initial verification image to the last treatment beam was 21 min. Image guidance and repositioning reduced the population random setup errors (sigma) from 6.5 mm (CC), 4.2 mm (ML), and 4.7 mm (AP) to 2.5 mm (CC), 2.8 mm (ML), and 2.9 mm (AP). The average individual random setup errors (sigma) were reduced from 4.5 mm (CC), 3.2 mm (AP), and 2.5 mm (ML) to 2.2 mm (CC), 2.0 mm (AP), and 2.0 mm (ML). The standard deviation of the distribution of systematic deviations (Sigma) was also reduced from 5.1 mm (CC), 3.4 mm (ML), and 3.1 mm (AP) to 1.4 mm (CC), 2.0 mm (ML), and 1.9 mm (AP) with image guidance and repositioning. The average absolute systematic errors were reduced from 4.1 mm (CC), 2.4 mm (AP), and 3.1 (ML) to 1.1 mm (CC), 1.3 mm (AP), and 1.6 mm (ML). Analysis of 52 real-time beam's-eye-view MV movies revealed an average absolute CC offset in diaphragm position of 1.9 mm.

CONCLUSION

Image guidance with orthogonal MV imaging and ABC for stereotactic body radiotherapy for liver cancer is feasible, improving setup accuracy compared with ABC without daily imaging and repositioning.

Klatskin tumor treated by inter-disciplinary therapies including stereotactic radiotherapy: A case report

In view of the poor prognosis of patients with cholangiocarcinoma (CCC), there is a need for new therapeutic strategies. Inter-disciplinary therapy seems to be most promising. Radiotherapy is an effective alternative to surgery for hilar CCC (Klatskin tumors) if an adequate radiation dose can be delivered to the liver hilus. Here, we describe a patient for whom we used a stereotactic radiotherapy technique in the context of an inter-disciplinary treatment concept. We report a 45-year-old patient with a locally advanced Klatskin tumor. Explorative laparotomy showed that the tumor was not resectable. A metallic stent was implanted and the patient was treated by stereotactic radiotherapy using a body frame. A total dose of 48 Gy (3×4 Gy/wk) was administered. Therapy was well tolerated. After 32 mo, local tumor recurrence and a chest wall metastasis developed and were controlled by radio-chemotherapy. After more than 56 mo with a good quality of life, the patient died of advanced neoplastic disease. Stereotactic radiotherapy led to a long-term survival of this patient with a locally advanced Klatskin tumor. In the context of inter-disciplinary treatment concepts, this radiotherapy technique is a promising choice of treatment for patients with hilar CCC.

Small lung tumors: long-scan-time CT for planning of hypofractionated stereotactic radiation therapy--initial findings

PURPOSE

To prospectively use long-scan-time computed tomography (CT) to visualize the trajectory of tumor movements or the internal target volume.

MATERIALS AND METHODS

The study was approved by the institutional review board. Written informed consent was obtained from participants after the study and the role of procedures were explained fully. During the planning of stereotactic radiation therapy for 10 patients (nine men, one woman; mean age, 77 years; range, 69-89 years) with small lung tumors (mean volume, 9.0 cm3; range, 3.6-24.9 cm3), fluoroscopic imaging, long-scan-time CT, and thin-section CT were performed. The tumor and the partial-volume-averaging effects that resulted from tumor movement were delineated on each section at long-scan-time CT performed during the patient's steady breathing with scan time of 8 seconds per image. Visualized internal target volume was defined by integrating the sections. A simple model was examined for estimating internal target volume on the basis of respiratory motion and gross target volume delineated on thin-section CT images. Visualized internal target volume and estimated internal target volume were compared quantitatively and graphically. The Mann-Whitney test was used to analyze the relation between gross target volume delineated on thin-section CT images and the ratio of visualized internal target volume to the defined gross target volume.

RESULTS

The correlation coefficient between visualized internal target volume and estimated internal target volume was r = 0.98 (P < .001). The mean relative error +/- standard deviation was 1.9% +/- 19.0 (range, -11.0% to 56.4%). Excluding one case with an irregularly shaped tumor (56.4%), the mean relative error was -4.1% +/- 4.1. In patients with small tumors (defined gross target volume, < or = 10 cm3), the ratio of the visualized internal target volume to the defined gross tumor volume was significantly larger than that in patients with larger tumors (1.2-2.0 vs 1.0-1.2; P < .05). In some cases in which marginal spiculation depicted on thin-section CT images was blurred on long-scan-time CT images, the blurred area was erroneously excluded from the target volume.

CONCLUSION

In most cases, values for visualized internal target volume and estimated internal target volume were similar and long-scan-time CT depicted virtually the entire tumor trajectory.

Extracranial Stereotactic Radiation Delivery

Extracranial stereotactic radiation delivery, also known as stereotactic body radiation therapy (SBRT), involves delivering very potent doses of radiation to well-demarcated tumors in the neck, spine, chest, abdomen, and pelvis. Beyond just stereotactic targeting, it represents a formalism of treatment planning and conduct that facilitates the delivery of the most potent dose fractionation schedules ever considered in the field of radiation oncology. In doing so, it uses the most modern technologies to simultaneously hit the target and avoid normal innocent tissues. Clinical results already show that SBRT constitutes a new paradigm in cancer treatment that deserves careful implementation and assessment for the improvement in patient outcomes.