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

Treatment of metastatic liver tumors using stereotactic ablative radiotherapy

The prognosis of patients with metastatic liver disease remains dismal with a median survival of only 6-12 mo. As 80%-90% of patients are not candidates for surgical therapy, there is a need for effective non-surgical therapies that would improve outcomes in these patients. The body of evidence related to the use of stereotactic ablative radiotherapy (SABR) in metastatic liver disease has substantially grown and evolved over the past decade. This review summarizes the current evidence supporting liver SABR with particular attention given to patient selection, target delineation, organ at risk dose volume constraints, response evaluation imaging and the various SABR techniques for delivering ablative radiotherapy to the liver. Even though it is unclear what dose-fractionation scheme, delivery system, concomitant therapy or patient selection strategy yields the optimum liver SABR outcomes, clear and growing evidence is available that SABR is a safe and effective therapy for the treatment of oligometastatic liver disease.

Radiotherapy and the tumor stroma: the importance of dose and fractionation

Ionizing radiation is a non-specific but highly effective way to kill malignant cells. However, tumor recurrence sustained by a minor fraction of surviving tumor cells is a commonplace phenomenon caused by the activation of both cancer cell intrinsic resistance mechanisms, and also extrinsic intermediaries of therapy resistance, represented by non-malignant cells and structural components of the tumor stroma. The improved accuracy offered by advanced radiotherapy (RT)-technology permits reduced volume of healthy tissue in the irradiated field, and has been triggering an increase in the prescription of high-dose oligo-fractionated regimens in the clinics. Given the remarkable clinical success of high-dose RT and the current therapeutic shift occurring in the field, in this review we revise the existing knowledge on the effects that different radiation regimens exert on the different compartments of the tumor microenvironment, and highlight the importance of anti-tumor immunity and other tumor cell extrinsic mechanisms influencing therapeutic responses to high-dose radiation.

Rationale for ablation of oligometastatic disease and the role of stereotactic body radiation therapy for hepatic metastases

Management paradigms for metastatic solid tumors are evolving. Once regarded as uniformly incurable, today there is recognition of an intermediate oligometastatic state, where ablation of metastatic foci may improve disease control and prolong survival. In the setting of limited colorectal liver metastases, hepatic resection has resulted in favorable long-term outcomes, but is technically unsuitable for most patients. Stereotactic body radiation therapy represents an effective, noninvasive means of tumor ablation, supported by a large body of prospective evidence specific to hepatic metastases. This review examines the current rationale for ablation of oligometastatic disease, including various objectives beyond indefinite disease-free survival. The role of stereotactic body radiation therapy for ablation of hepatic metastases is then comprehensively reviewed.

Stereotactic body radiotherapy: a critical review for nonradiation oncologists

Stereotactic body radiotherapy (SBRT) involves the treatment of extracranial primary tumors or metastases with a few, high doses of ionizing radiation. In SBRT, tumor kill is maximized and dose to surrounding tissue is minimized, by precise and accurate delivery of multiple radiation beams to the target. This is particularly challenging, because extracranial lesions often move with respiration and are irregular in shape, requiring careful treatment planning and continual management of this motion and patient position during irradiation. This review presents the rationale, process workflow, and technology for the safe and effective administration of SBRT, as well as the indications, outcome, and limitations for this technique in the treatment of lung cancer, liver cancer, and metastatic disease.

An emerging role for radiation therapy in the treatment of hepatocellular carcinoma and intrahepatic cholangiocarcinoma

Radiation therapy is emerging as a potentially effective treatment of locally advanced, unresectable hepatocellular carcinoma (HCC). Outcomes from early prospective studies seem promising, with improved survival compared with historical controls. Cure of early stage and unresectable HCC may be possible with high-quality radiation therapy. Many questions remain, including determination of the ideal radiation dose and fractionation schema, optimal patient selection criteria based on tumor size, tumor location, extent of vascular invasion, and baseline liver function, and the role of radiation therapy compared with other localized standard treatments including radiofrequency ablation or transarterial chemoembolization.

Toward correcting drift in target position during radiotherapy via computer-controlled couch adjustments on a programmable Linac

PURPOSE

Real-time tracking of respiratory target motion during radiation therapy is technically challenging, owing to rapid and possibly irregular breathing variations. The authors report on a method to predict and correct respiration-averaged drift in target position by means of couch adjustments on an accelerator equipped with such capability.

METHODS

Dose delivery is broken up into a sequence of 10 s field segments, each followed by a couch adjustment based on analysis of breathing motion from an external monitor as a surrogate of internal target motion. Signal averaging over three respiratory cycles yields a baseline representing target drift. A Kalman filter predicts the baseline position 5 s in advance, for determination of the couch correction. The method's feasibility is tested with a motion phantom programmed according to previously recorded patient signals. Computed couch corrections are preprogrammed into a research mode of an accelerator capable of computer-controlled couch translations synchronized with the motion phantom. The method's performance is evaluated with five cases recorded during hypofractionated treatment and five from respiration-correlated CT simulation, using a root-mean-squared deviation (RMSD) of the baseline from the treatment planned position.

RESULTS

RMSD is reduced in all 10 cases, from a mean of 4.9 mm (range 2.7-9.4 mm) before correction to 1.7 mm (range 0.7-2.3 mm) after correction. Treatment time is increased ∼5% relative to that for no corrections.

CONCLUSIONS

This work illustrates the potential for reduction in baseline respiratory drift with periodic adjustments in couch position during treatment. Future treatment machine capabilities will enable the use of "on-the-fly" couch adjustments during treatment.

Impact of stereotactic body radiotherapy on colorectal cancer with distant metastases

Stereotactic radiotherapy is a minimally invasive technique for delivering highly focused ionizing radiation with extreme precision. This technique was initially developed in neurosurgical practice and applied to extracranial lesions in the 1990s, and was termed stereotactic body radiotherapy (SBRT). Studies have reported that the resection of distant metastases from colorectal cancer (CRC) contributes to relatively long-term survival. However, the resection of pulmonary and liver metastases is not possible for various reasons. SBRT offers a therapeutic alternative to unresectable metastatic lesions. The present study describes three cases of distant metastasis from CRC that exhibited a complete response (CR) to SBRT. Case 1 is a 70-year-old man with recurrent liver metastases after surgery for rectal cancer with liver metastasis (S3: diameter 1.8 cm and volume 3.0 ml; S6: diameter 1.3 cm and volume 1.2 ml). Cases 2 and 3 were 65-year-old and 70-year-old men, respectively. Both patients had pulmonary metastasis after surgery for rectal and cecum cancer (Case 2: diameter 1.2 cm and volume 0.9 ml; Case 3: diameter 0.8 cm and volume 0.27 ml). All cases were moderately differentiated adenocarcinomas. No serious adverse side-effects were observed during the therapy. CR was obtained in all patients on the basis of computed tomography 15-33 months after radiotherapy. Our experience supports that SBRT is a safe and alternative technique for resection in patients with distant metastasis from CRC who have small metastatic tumor volume.

The RSSearch™ Registry: patterns of care and outcomes research on patients treated with stereotactic radiosurgery and stereotactic body radiotherapy

BACKGROUND

The RSSearch™ Registry is a multi-institutional, observational, ongoing registry established to standardize data collection from patients treated with stereotactic radiosurgery (SRS) and/or stereotactic body radiotherapy (SBRT). This report describes the design, patient demographics, lesion characteristics, and SRS/SBRT treatment patterns in RSSearch™. Illustrative patient-related outcomes are also presented for two common treatment sites--brain metastases and liver metastases.

MATERIALS AND METHODS

Thirty-nine US centers participated in RSSearch™. Patients screened for SRS/SBRT were eligible to be enrolled. Descriptive analyses were performed to assess patient characteristics, physician treatment practices, and clinical outcomes. Kaplan-Meier analysis was used to determine overall survival (OS), local progression-free (LPFS), and distant disease-free survival (DDFS).

RESULTS

From January, 2008-January, 2013, 11,457 patients were enrolled. The median age was 67 years (range 7-100 years); 51% male and 49% female. Forty-six percent had no prior treatment, 22% had received chemotherapy, 19% radiation therapy and 17% surgery. There were 11,820 lesions from 65 treatment locations; 54% extracranial and 46% intracranial. The most common treatment locations were brain/cranial nerve/spinal cord, lung, prostate and liver. Metastatic lesions accounted for the majority of cases (41.6%), followed by primary malignant (32.9%), benign (10.9%), recurrent (9.4%), and functional diseases (4.3%). SRS/SBRT was used with a curative intent in 39.8% and palliative care in 44.8% of cases. The median dose for all lesions was 30 Gy (range < 1-96.7 Gy) delivered in a median number of 3 fractions. The median dose for lesions in the brain/cranial nerve/spinal cord, lung, liver, pancreas and prostate was 24, 54, 45, 29 and 36.25 Gy, respectively. In a subset analysis of 799 patients with 952 brain metastases, median OS was 8 months. For patients with a Karnofsky performance score (KPS) > 70, OS was 11 months vs. 4 months for KPS ≤ 70. Six-month and 12-month local control was 79% and 61%, respectively for patients with KPS ≤ 70, and 85% and 74%, respectively for patients with KPS > 70. In a second subset analysis including 174 patients with 204 liver metastases, median OS was 22 months. At 1-year, LPFS and DDFS rates were 74% and 53%, respectively.

LPFS CONCLUSION

This study demonstrates that collective patterns of care and outcomes research for SRS/SBRT can be performed and reported from data entered by users in a common database. The RSSearch™ dataset represents SRS/SBRT practices in a real world setting, providing a useful resource for expanding knowledge of SRS/SBRT treatment patterns and outcomes and generating robust hypotheses for randomized clinical studies.

High-dose stereotactic body radiotherapy correlates increased local control and overall survival in patients with inoperable hepatocellular carcinoma

BACKGROUND

Recent studies using stereotactic body radiotherapy (SBRT) for hepatocellular carcinoma (HCC) have reported high tumor response and local control. However, the optimal SBRT dose remains unknown, and it is still not clear whether a dose response relationship for local control (LC) and overall survival (OS) exist or not. We performed this study to determine whether a dose response relationship for LC and OS is observed in SBRT for inoperable HCC.

METHODS

Between 2003 and 2011, 108 patients with HCC were treated with SBRT. All patients were unsuitable for surgery or local ablation and had incomplete response to transarterial chemoembolization. Eighty-two patients with a longest tumor diameter (LD) less than or equal to 7.0 cm who were treated with 3-fraction SBRT and were analyzed. This cohort comprised 74 Child-Turcotte-Pugh (CTP) class A patients and 8 CTP class B7 patients. The median LD was 3.0 cm (range, 1.0-7.0 cm), and the median dose was 51 Gy (range, 33-60 Gy).

RESULTS

LC and OS rates at 2 years after SBRT were 87% and 63%, respectively, with a median follow-up duration of 30 months for all patients. The 2-year LC/OS rates for patients treated with doses of > 54, 45-54, and < 45 Gy were 100/71, 78/64, and 64%/30%, respectively (p = .009/p < .001). Multivariate analysis revealed that the SBRT dose (p = .005) and Barcelona Clinic Liver Cancer stage (p = .015) were significant prognostic factors for OS. Correlation analysis revealed a positive linear relationship between the SBRT dose and LC (p = .006, R = .899)/OS (p = .002, R = .940) at 2 years. Based on the tumor-control probability model, a dose of 54.8 Gy provides 2-year LC with a 90% probability. Five patients experienced grade 3 or higher gastrointestinal toxicity, and 6 had deteriorating of CTP score by greater than or equal to 2 within 3 months of SBRT.

CONCLUSIONS

This study demonstrated a dose response relationship for LC and OS with SBRT for HCC. Higher LC rates resulting from an increased dose may translate into survival benefits for patients with HCC.

Stereotactic body radiation therapy for hepatocellular carcinoma: prognostic factors of local control, overall survival, and toxicity

Purpose

Stereotactic body radiation therapy (SBRT) for hepatocellular carcinoma (HCC) has been evaluated in several recent studies. The CyberKnife^® is an SBRT system that allows for real-time tracking of the tumor. The purpose of this study was to evaluate the prognostic factors for local control and overall survival following this treatment.

Patients and Methods

75 patients with 96 liver-confined HCC were treated with SBRT at the Oscar Lambret Comprehensive Cancer Center. Fiducials were implanted in the liver before treatment and were used as markers to track the lesion’s movement. Treatment response was scored according to RECIST v1.1. Local control and overall survival were calculated using the Kaplan and Meier method. A stepwise multivariate analysis (Cox regression) of prognostic factors was performed for local control and overall survival.

Results

There were 67 patients with Child-Turcotte-Pugh (CTP) Class A and eight patients with CTP Class B. Treatment was administered in three sessions. A total dose of 40–45 Gy to the 80% isodose line was delivered. The median follow-up was 10 months (range, 3–49 months). The local control rate was 89.8% at 1 and 2 years. Overall survival was 78.5% and 50.4% at 1 and 2 years, respectively. Toxicity mainly consisted of grade 1 and grade 2 events. Higher alpha-fetoprotein (aFP) levels were associated with less favorable local control (HR=1.001; 95% CI [1.000, 1.002]; p=0.0063). A higher dose was associated with better local control (HR=0.866; 95% CI [0.753, 0.996]; p=0.0441). A Child-Pugh score higher than 5 was associated with worse overall survival (HR= 3.413; 95% CI [1.235, 9.435]; p=0.018).

Conclusion

SBRT affords good local tumor control and higher overall survival rates than other historical controls (best supportive care or sorafenib). High aFP levels were associated with lesser local control, but a higher treatment dose improved local control.

Alternatives to surgery in early stage disease-stereotactic body radiotherapy

The management of early stage non-small cell lung carcinoma (NSCLC) has been revolutionized by the introduction of stereotactic body radiotherapy (SBRT). SBRT is now the standard of care for medically inoperable patients with early stage NSCLC. However, the role of SBRT in medically operable patients remains controversial. This article will review the indications, the technical considerations, image guidance principles, potential toxicities and special circumstances in lung SBRT.

Multidisciplinary approaches to intrahepatic cholangiocarcinoma

After hepatocellular carcinoma, intrahepatic cholangiocarcinoma (ICC) is the second most common primary hepatic malignancy. The etiology of ICC in most patients is not known, but its incidence is on the rise worldwide. There are 3 morphologic subtypes of ICC that can be characterized on cross-sectional imaging, mass forming, periductal infiltrating, and intraductal growth; and the radiographic characteristics of ICC may vary based on the subtype. Complete surgical resection remains the only potentially curative option for patients with ICC. Routine lymphadenectomy at the time of surgical resection should be strongly considered, because lymph node status provides important prognostic information. After surgery, the 5-year survival rate for ICC remains poor at only 25% to 35% in most series. Although numerous clinical trials have been conducted using a variety of chemotherapy regimens to treat ICC, systemic options for ICC remain limited. Doublet gemcitabine and cisplatin therapy is currently considered the standard-of-care first-line therapy for patients with advanced disease. Because ICC is typically confined to the liver and systemic chemotherapy traditionally has had only limited efficacy, there has been increasing interest in locoregional therapy. Although locoregional therapy may include intra-arterial therapies, stereotactic radiotherapy, hepatic artery pump therapy, or ablation, most data are limited. The purpose of this article was to provide a multidisciplinary appraisal of the current therapeutic approaches to ICC.

Patterns-of-care for thoracic stereotactic body radiotherapy among practicing radiation oncologists in the United States

INTRODUCTION

Radiation oncologists were surveyed to assess practice patterns in the use of stereotactic body radiotherapy (SBRT) for lung cancer.

METHODS

A customized patterns-of-care survey, consisting of 18 questions and two clinical scenarios, was e-mailed to 136 academic radiation oncologists and 768 community practitioners to evaluate the technical basis and delivery parameters associated with SBRT.

RESULTS

A total of 117 surveys were evaluable. The cited delivery techniques included: static noncoplanar beams (48%), intensity-modulated radiotherapy (41%), rotational intensity-modulated radiotherapy (47%), dynamic conformal arcs (7%), and small-beam delivery with fiducial tracking (24%), with 46% using multiple techniques. The immobilization methods included: stereotactic frame (10%), alpha cradle or vacuum-lock system (52%), wingboard (3%), stereotactic frame with an alpha cradle or vacuum-lock system (11%); combination of devices (14%), or no immobilization (9%). Abdominal compression was used by 51% and respiratory gating by 31%. For a peripheral T1N0 tumor, the preferred doses included: 25 to 34 Gy in one fraction (1%); 54 to 60 Gy in three fractions (56%), 48 to 50 Gy in four fractions (18%), and 50 to 60 Gy in five fractions (25%). For a centrally located T1N0 tumor, 58% recommended SBRT outside a clinical protocol, with recommended doses ranging from 40 to 60 Gy in three to 10 fractions. The recommended interval to first surveillance imaging ranged from 6 weeks or lesser (32%) to 25 weeks or more (2%).

CONCLUSIONS

Considerable variation exists for thoracic SBRT with regard to dose selection, fractionation, immobilization, planning, management of central lesions, and surveillance. Ongoing prospective evaluation is recommended to identify best practices and provide continual process improvement.

Extracranial radiosurgery with volumetric modulated arc therapy: Feasibility evaluation of a phase I trial

The aim of this study was to report early clinical experience in stereotactic body radiosurgery (SBRS) delivered using volumetric intensity modulated arc therapy (VMAT) in patients with primary or metastatic tumors in various extra-cranial body sites. Each enrolled subject was included in a different phase I study arm, depending on the tumor site and the disease stage (lung, liver, bone, metastatic), and sequentially assigned to a particular dose level. Technical feasibility and dosimetric results were investigated. The acute toxicity, tumor response and early local control were also studied. In total, 25 lesions in 20 consecutive patients (male/female, 11/9; median age, 67 years; age range, 47-86 years) were treated. Of these 25 lesions, 4 were primary or metastatic lung tumors, 6 were liver metastases, 8 were bone metastases and 7 were nodal metastases. The dose-volume constraints for organs at risk (OARs) were observed in 19 patients using a single-arc technique. Only in one patient were two arcs required. The treatment was performed without interruption or any other technical issues. The prescribed dose ranged from 12-26 Gy to the planning target volume (PTV). Delivery time ranged from 4 min to 9 min and 13 sec (median, 6 min and 6 sec). No incidence of grade 2-4 acute toxicity was recorded. The overall response rate was 48% (95% confidence interval (CI), 24.2-70.2) based on computed tomography (CT)/magnetic resonance imaging (MRI) and 89% (95% CI, 58.6-98.7) based on the positron emission tomography (PET) scan. SBRS delivered by means of VMAT allowed the required target coverage to be achieved while remaining within the normal tissue dose-volume constraints in the 20 consecutive patients. VMAT-SBRS resulted in adequate technical feasibility; the maximum tolerable dose has not yet been reached in any study arm.

Stereotactic radiosurgery and stereotactic body radiation therapy cost-effectiveness results

Objective: To describe and synthesize the current stereotactic radiosurgery (SRS) and stereotactic body radiation therapy (SBRT) cost-effectiveness research to date across several common SRS and SBRT applications.

Methods: This review was limited to comparative economic evaluations of SRS, SBRT, and alternative treatments (e.g., other radiotherapy techniques or surgery). Based on PubMed searches using the terms, “stereotactic,” “SRS,” “stereotactic radiotherapy,” “stereotactic body radiotherapy,” “SBRT,” “stereotactic ablative radiotherapy,” “economic evaluation,” “quality adjusted life year (QALY),” “cost,” “cost-effectiveness,” “cost-utility,” and “cost analysis,” published studies of cost-effectiveness and health economics were obtained. Included were articles in peer-reviewed journals that presented a comparison of costs between treatment alternatives from January 1997 to November 2012. Papers were excluded if they did not present cost calculations, therapeutic cost comparisons, or health economic endpoints.

Results: Clinical outcomes and costs of SRS and SBRT were compared to other therapies for treatment of cancer in the brain, spine, lung, prostate, and pancreas. Treatment outcomes for SRS and SBRT are usually superior or comparable, and cost-effective, relative to alternative techniques.

Conclusion: Based on the review of current SRS and SBRT clinical and health economic literature, from a patient perspective, SRS and SBRT provide patients a clinically effective treatment option, while from the payer and provider perspective, SRS and SBRT demonstrate cost savings.

Respiratory Gating for Radiotherapy: Main Technical Aspects and Clinical Benefits

Respiratory-gated radiotherapy offers a significant potential for improvement in the irradiation of tumor sites affected by respiratory motion such as lung, breast, and liver tumors. An increased conformality of irradiation fields leading to decreased complication rates of organs at risk is expected. Five main strategies are used to reduce respiratory motion effects: integration of respiratory movements into treatment planning, forced shallow breathing with abdominal compression, breath-hold techniques, respiratory gating techniques, and tracking techniques. Measurements of respiratory movements can be performed either in a representative sample of the general population, or directly on the patient before irradiation. Reduction of breathing motion can be achieved by using either abdominal compression, breath-hold techniques, or respiratory gating techniques. Abdominal compression can be used to reduce diaphragmatic excursions. Breath-hold can be achieved with active techniques, in which airflow of the patient is temporarily blocked by a valve, or passive techniques, in which the patient voluntarily breath-holds. Respiratory gating techniques use external devices to predict the phase of the breathing cycle while the patient breathes freely. Another approach is tumor-tracking technique, which consists of a real-time localization of a constantly moving tumor. This work describes these different strategies and gives an overview of the literature.

Differences in the dose-volume metrics with heterogeneity correction status and its influence on local control in stereotactic body radiation therapy for lung cancer

The purpose of this study is to evaluate the dose-volume metrics under different heterogeneity corrections and the factors associated with local recurrence (LR) after stereotactic body radiation therapy (SBRT) for non-small-cell lung cancer (NSCLC). Eighty-three patients who underwent SBRT for pathologically proven stage I NSCLC were reviewed retrospectively. The prescribed dose was 48 Gy in four fractions at the isocenter (IC) under heterogeneity correction with the Batho power law (BPL). The clinical plans were recalculated with Eclipse (Varian) for the same monitor units under the BPL and anisotropic analytical algorithm (AAA) and with no heterogeneity correction (NC). The dose at the IC, dose that covers 95% of the volume (D95), minimum dose (Min), and mean dose (Mean) of the planning target volume (PTV) were compared under each algorithm and between patients with local lesion control (LC) and LR. The IC doses under NC were significantly lower than those under the BPL and AAA. Under the BPL, the mean PTV D95, Min and Mean were 8.0, 9.4 and 7.4% higher than those under the AAA, and 9.6, 9.2 and 4.6% higher than those under NC, respectively. Under the AAA, all dose-volumetric parameters were significantly lower in T1a patients than in those with T1b and T2a. With a median follow-up of 35.9 months, LR occurred in 18 patients. Between the LC and LR groups, no significant differences were observed for any of the metrics. Even after stratification according to T-stage, no significant difference was observed between LC and LR.

Locally ablative non-surgical management of colo-rectal liver metastasis

BACKGROUND

Liver is one of the commonest sites of metastasis in colorectal cancer patients. Solitary liver metastasis or oligometastasis are traditionally treated by surgical resection or chemotherapy.

DISCUSSION

There may be a subgroup of these patients who are not suitable for surgery or chemotherapy due to various co-morbid factors. These patients can be treated by novel minimally invasive or noninvasive ablative techniques like interstitial brachytherapy, extracranial stereotactic radiotherapy, and radiofrequency ablation.

Stereotactic body radiation therapy for stage I non-small-cell lung cancer: a historical overview of clinical studies

Because of difficulties with stabilization, breathing motion and dosimetry, stereotactic body radiotherapy for lung cancer has only been practiced for the past 15 years. However, a large amount of case data has rapidly been accumulated in recent years. Stereotactic body radiotherapy for Stage I non-small-cell lung cancer has been actively investigated in inoperable patients since around 1995, and a number of clinical trials have been undertaken. Early studies from 2001 presented a 3-year local control rate of 94% and a 3-year overall survival rate of 66% for patients receiving 50-60 Gy in 10 fractions. Another study in 2005, using 48 Gy in four fractions, presented a 3-year local control rate of 98% and 3-year overall survival rates of 83% for Stage IA patients and 72% for Stage IB patients. A multi-institutional study showed favorable local control and survival rates in a group receiving a biologically effective dose of 100 Gy. A dose-escalation study in the USA suggested a maximum tolerated dose of 60 Gy in three fractions. A Phase II clinical trial (RTOG0236) followed, with a reported 3-year local control rate of 98% and a 3-year overall survival rate of 56% for patients who received 60 Gy in three fractions. A Japanese Phase II clinical trial (JCOG0403) investigated a dose of 48 Gy in four fractions among 165 Stage IA patients, showing a 3-year survival rate of 76% and a 3-year locally progression-free survival rate of 69% for the operable group. An overview of past clinical trials in stereotactic body radiotherapy for Stage I non-small-cell lung cancer and current issues is presented and discussed.

Hepatocellular carcinoma radiation therapy: review of evidence and future opportunities

Hepatocellular carcinoma (HCC) is a leading cause of global cancer death. Curative therapy is not an option for most patients, often because of underlying liver disease. Experience in radiation therapy (RT) for HCC is rapidly increasing. Conformal RT can deliver tumoricidal doses to focal HCC with low rates of toxicity and sustained local control in HCC unsuitable for other locoregional treatments. Stereotactic body RT and particle therapy have been used with long-term control in early HCC or as a bridge to liver transplant. RT has also been effective in treating HCC with portal venous thrombosis. Patients with impaired liver function and extensive disease are at increased risk of toxicity and recurrence. More research on how to combine RT with other standard and novel therapies is warranted. Randomized trials are also needed before RT will be generally accepted as a treatment option for HCC. This review discusses the current state of the literature and opportunities for future research.

Management of single malignant lung nodules in elderly patients (70 years or older) who are not candidates for lobectomy

PURPOSE

The aim of this study was to evaluate and compare sublobar resection plus intraoperative seed implant (IOS) versus stereotactic body radiation therapy (SBRT) in patients with single malignant lung nodules in patients 70 years of age or older.

MATERIALS AND METHODS

A retrospective chart review was performed and 47 patients with adequate information were selected for analysis. Thirty patients with single malignant lung nodules received SBRT. Seventeen patients received limited surgical resection plus radioactive seed implantation for solitary malignant lung nodules. Univariate statistical analysis showed a significant difference only for the age in the 2 groups: the mean age in the radioactive seed group, 78.8 years versus 76.1 years in the SBRT group (2-sided, P=0.05).

RESULTS

There was high local control and minimal toxicity with either treatment modality and no significant difference among the 2 groups in terms of local control, survival, and toxicity. However, the distant failure was higher but not statistically significant in the SBRT group (9 of 30 patients in SBRT vs. 0 of 17 in IOS, P=0.1).

CONCLUSIONS

Our study has shown excellent outcomes and limited toxicity in both IOS and SBRT for treatment of single malignant lung nodules in patients who are not candidates for lobectomy. However, a randomized trial is needed in this group of elderly patients to determine the most appropriate treatment.

Stereotactic body radiotherapy for metachronous multisite oligo-recurrence: a long-surviving case with sequential oligo-recurrence in four different organs treated using locally radical radiotherapy and a review of the literature

Stereotactic body radiotherapy (SBRT) for oligometastases represents a recent trend in radiation oncology. While abundant data are available regarding the use of SBRT for the treatment of lung or liver oligometastases from various retrospective series and prospective trials, relatively little information has been accumulated for the treatment of oligometastases at sites other than the lungs and liver, particularly for sequential oligometastases in multiple organs. Oligometastases with primary lesions controlled is called “oligo-recurrence.” We describe herein the case of a lung cancer patient who developed repeated oligo-recurrence at multiple sites that were each controlled by radical radiotherapy and achieved long-term survival and discuss the merits of locally aggressive radiotherapy for this type of disease condition with reviewing the literature. Although further investigation should be undertaken to clarify the benefits, objectives, and methods of SBRT for the treatment of oligometastases, we believe utilization of SBRT may be worthwhile for patients with remote metastases who hope for treatment to acquire better local control and possible longer survival.

Prognostic factors affecting local control of hepatic tumors treated by Stereotactic Body Radiation Therapy

Purpose

Robotic Stereotactic Body Radiation Therapy with real-time tumor tracking has shown encouraging results for hepatic tumors with good efficacy and low toxicity. We studied the factors associated with local control of primary or secondary hepatic lesions post-SBRT.

Methods and materials

Since 2007, 153 stereotactic liver treatments were administered to 120 patients using the CyberKnife® System. Ninety-nine liver metastases (72 patients), 48 hepatocellular carcinomas (42 patients), and six cholangiocarcinomas were treated. On average, three to four sessions were delivered over 12 days. Twenty-seven to 45 Gy was prescribed to the 80% isodose line. Margins consisted of 5 to 10 mm for clinical target volume (CTV) and 3 mm for planning target volume (PTV).

Results

Median size was 33 mm (range, 5–112 mm). Median gross tumor volume (GTV) was 32.38 cm³ (range, 0.2–499.5 cm³). Median total dose was 45 Gy in three fractions. Median minimum dose was 27 Gy in three fractions. With a median follow-up of 15.0 months, local control rates at one and two years were 84% and 74.6%, respectively. The factors associated with better local control were lesion size < 50 mm (p = 0.019), GTV volume (p < 0.05), PTV volume (p < 0.01) and two treatment factors: a total dose of 45 Gy and a dose–per-fraction of 15 Gy (p = 0.019).

Conclusions

Dose, tumor diameter and volume are prognostic factors for local control when a stereotactic radiation therapy for hepatic lesions is considered. These results should be considered in order to obtain a maximum therapeutic efficacy.

Results of stereotactic radiotherapy for stage I non-small-cell lung cancer: is there a need for image guidance and highly sophisticated devices?

SUMMARY In stage I non-small-cell lung cancer, stereotactic body radiation therapy achieves a local control of 90%, by accurate dose delivery with stereotactic beam navigation and/or image-guided techniques, and extremely dose-escalated hypofractionated radiotherapy. Three-to-ten fractions over 1–2 weeks or one single fraction as radiosurgery are used. A broad spectrum of different techniques have also been introduced, some encouraged by electric companies, and heavily commercialized by institutions and physicians. Although a direct comparison of these techniques has been carried out only in technical and not within clinical trials; clinical data from the few prospective Phase I and II trials and the majority of retrospective evaluations have not shown superiority of either technique. Based on personal experiences, there are nearly no limitations for the use of very simple and cheap techniques, and the broad and increasing disposition of dedicated systems is questionable.

Stereotactic body radiotherapy treatment of extracranial metastases

Radiotherapy is an integral treatment for patients with metastatic cancer, although it is usually reserved for palliation of pain, dyspnoea, oedema, bleeding and neurological symptoms. However, the administration of high-precision radiotherapy, termed stereotactic body radiotherapy (SBRT), has the potential to significantly affect the disease course for some patients with metastatic cancer by delivering high doses of radiation to the secondary tumours with limited high-dose delivery to adjacent healthy tissues. Indeed, such accurate delivery has been firmly established as a therapy for medically inoperable early-stage non-small-cell lung cancer. To date, the technique has demonstrated improvements in controlling metastasis and, in some cases, improved palliation compared with conventionally fractionated radiotherapy. Active areas of research in SBRT include patient selection for curative intent, optimization of SBRT planning techniques, dosing schema and integration of SBRT into systemic therapies. Given the improvements in cytotoxic and targeted therapies over the past decade, studies testing the careful integration of SBRT into standard systemic therapy regimens are needed. Further investigations are also needed to understand the basic biological mechanisms underlying SBRT because they are likely to be different to those mechanisms in conventional radiotherapy.

[Oligometastatic disease, a new concept: stereotactic irradiation for lung metastases. Literature review]

Metastatic lung disease has long been the preserve of systemic treatments, local treatments being considered in a purely palliative intention. Several studies have objectified benefit to the local treatment of metastases, especially oligometastases. Surgery then took an important place in this setting, but the development of techniques for stereotactic radiotherapy on the one hand and the refusal or contraindication for surgery on the other hand led authors to conduct studies in this direction. This literature review describes the realization of stereotactic radiotherapy in treating pulmonary oligometastases and evaluates criteria for the selection of patients who would benefit. A comparison between the results of different studies on this technique allowed to show its effectiveness for local control, overall survival and tolerance. Stereotactic radiotherapy has emerged as a viable alternative, effective and well tolerated with local control rates comparable to that obtained by surgery (74 to 100%). Quality of life after stereotactic radiotherapy should be in a near future an important parameter to support this therapeutic choice, and needs to be precisely assessed.

On the beam direction search space in computerized non-coplanar beam angle optimization for IMRT-prostate SBRT

In a recent paper, we have published a new algorithm, designated 'iCycle', for fully automated multi-criterial optimization of beam angles and intensity profiles. In this study, we have used this algorithm to investigate the relationship between plan quality and the extent of the beam direction search space, i.e. the set of candidate beam directions that may be selected for generating an optimal plan. For a group of ten prostate cancer patients, optimal IMRT plans were made for stereotactic body radiation therapy (SBRT), mimicking high dose rate brachytherapy dosimetry. Plans were generated for five different beam direction input sets: a coplanar (CP) set and four non-coplanar (NCP) sets. For CP treatments, the search space consisted of 72 orientations (5° separations). The NCP CyberKnife (CK) space contained all directions available in the robotic CK treatment unit. The fully non-coplanar (F-NCP) set facilitated the highest possible degree of freedom in selecting optimal directions. CK(+) and CK(++) were subsets of F-NCP to investigate some aspects of the CK space. For each input set, plans were generated with up to 30 selected beam directions. Generated plans were clinically acceptable, according to an assessment of our clinicians. Convergence in plan quality occurred only after around 20 included beams. For individual patients, variations in PTV dose delivery between the five generated plans were minimal, as aimed for (average spread in V(95): 0.4%). This allowed plan comparisons based on organ at risk (OAR) doses, with the rectum considered most important. Plans generated with the NCP search spaces had improved OAR sparing compared to the CP search space, especially for the rectum. OAR sparing was best with the F-NCP, with reductions in rectum D(Mean), V(40Gy), V(60Gy) and D(2%) compared to CP of 25%, 35%, 37% and 8%, respectively. Reduced rectum sparing with the CK search space compared to F-NCP could be largely compensated by expanding CK with beams with relatively large direction components along the superior-inferior axis (CK(++)). Addition of posterior beams (CK(++) → F-NCP) did not lead to further improvements in OAR sparing. Plans with 25 beams clearly performed better than 11-beam plans. For CP plans, an increase from 11 to 25 involved beams resulted in reductions in rectum D(Mean), V(40Gy), V(60Gy) and D(2%) of 39%, 57%, 64% and 13%, respectively.

Stereotactic body radiation therapy for abdominal oligometastases: a biological and clinical review

Advances in imaging and biological targeting have led to the development of stereotactic body radiation therapy (SBRT) as an alternative treatment of extracranial oligometastases. New radiobiological concepts, such as ceramide-induced endothelial apoptosis after hypofractionated high-dose SBRT, and the identification of patients with oligometastatic disease by microRNA expression may yet lead to further developments. Key factors in SBRT are delivery of a high dose per fraction, proper patient positioning, target localisation, and management of breathing-related motion. Our review addresses the radiation doses and schedules used to treat liver, abdominal lymph node (LN) and adrenal gland oligometastases and treatment outcomes. Reported local control (LC) rates for liver and abdominal LN oligometastases are high (median 2-year actuarial LC: 61 -100% for liver oligometastases; 4-year actuarial LC: 68% in a study of abdominal LN oligometastases). Early toxicity is low-to-moderate; late adverse effects are rare. SBRT of adrenal gland oligometastases shows promising results in the case of isolated lesions. In conclusion, properly conducted SBRT procedures are a safe and effective treatment option for abdominal oligometastases.

A retrospective study of SBRT of metastases in patients with primary sarcoma

We retrospectively reviewed the results of stereotactic body radiotherapy (SBRT) in 46 patients with a total of 136 metastases from primary sarcoma. The purpose of this study was to evaluate the overall response rate and side effects of SBRT in metastatic sarcoma. The patients were treated at Karolinska University Hospital between 1994 and 2005, using 3D conformal multifield technique and a stereotactic body-frame. Prescribed doses ranged from 4 to 20 Gy per fraction in 1–5 fractions, with total doses of 10–48 Gy. All 46 patients were diagnosed with a primary sarcoma. The treated metastases were localized mainly in the lungs. A total number of 136 metastases were treated (1–14 per patient). Overall response rate (local control = CR, PR and SD) for each tumour was 88 % (119/135). Median follow-up was 21.8 months (range 2.7–112.8 months). Thirteen patients (31 %) were long-term survivors (>36 months), and 5 patients are still alive after last follow-up. Two cases of serious non-lethal side effects were seen, one patient had a colon perforation and another patient had contracture of the hip region. SBRT is a safe, convenient and effective non-invasive treatment with high local control for patients with metastatic sarcoma.

4D digitally reconstructed radiography for verifying a lung tumor position during volumetric modulated arc therapy

We have proposed four dimensional (4D) digitally reconstructed radiography (DRR) for verifying a lung tumor position during volumetric modulated arc therapy (VMAT). An internal target volume (ITV) was defined based on two clinical target volumes (CTVs) delineated on maximum exhalation and maximum inhalation images acquired by 4D planning computed tomography (CT). A planning target volume (PTV) was defined by adding a margin of 5 mm to the ITV on the maximum exhalation 3D CT images. A single-arc VMAT plan was created on the same CT data using Pinnacle SmartArc with a maximum multi-leaf collimator leaf speed of 1 mm/degree, thereby resulting in quasi-conformal field shapes while optimizing each beam intensity for each gantry angle. During VMAT delivery, cone-beam CT (CBCT) projection data were acquired by an on-board kilovoltage X-ray unit and a flat panel 2D detector. Four CBCT image sets with different respiratory phases were reconstructed using in-house software, where respiratory phases were extracted from the projection data. Subsequently a CTV was delineated on each of the 4D CBCT images by an oncologist. Using the resulting 4D CBCT data including the CTV contours, 4D DRRs during the VMAT delivery were calculated as a function of gantry angle. It was confirmed that the contoured CTV was within the radiation field during the four-fraction lung VMAT delivery. The proposed 4D DRR may facilitate the verification of the position of a respiratory moving lung tumor during VMAT delivery on each treatment day.

Review and uses of stereotactic body radiation therapy for oligometastases

In patients with proven distant metastases from solid tumors, it has been a notion that the condition is incurable, warranting palliative care only. The term "oligometastases" was coined to refer to isolated sites of metastasis, whereby the entire burden of disease can be recognized as a finite number of discrete lesions that can be potentially cured with local therapies. Stereotactic body radiation therapy (SBRT) is a novel treatment modality in radiation oncology that delivers a very high dose of radiation to the tumor target with high precision using single or a small number of fractions. SBRT is the result of technological advances in patient and tumor immobilization, image guidance, and treatment planning and delivery. A number of studies, both retrospective and prospective, showed promising results in terms of local tumor control and, in a limited subset of patients, of survival. This article reviews the radiobiologic, technical, and clinical aspects of SBRT for various anatomical sites.

Hypofractionated image-guided breath-hold SABR (stereotactic ablative body radiotherapy) of liver metastases--clinical results

Purpose

Stereotactic Ablative Body Radiotherapy (SABR) is a non-invasive therapy option for inoperable liver oligometastases. Outcome and toxicity were retrospectively evaluated in a single-institution patient cohort who had undergone ultrasound-guided breath-hold SABR.

Patients and methods

19 patients with liver metastases of various primary tumors consecutively treated with SABR (image-guidance with stereotactic ultrasound in combination with computer-controlled breath-hold) were analysed regarding overall-survival (OS), progression-free-survival (PFS), progression pattern, local control (LC), acute and late toxicity.

Results

PTV (planning target volume)-size was 108 ± 109cm³ (median 67.4 cm³). BED2 (Biologically effective dose in 2 Gy fraction) was 83.3 ± 26.2 Gy (median 78 Gy). Median follow-up and median OS were 12 months. Actuarial 2-year-OS-rate was 31%. Median PFS was 4 months, actuarial 1-year-PFS-rate was 20%. Site of first progression was predominantly distant. Regression of irradiated lesions was observed in 84% (median time to detection of regression was 2 months). Actuarial 6-month-LC-rate was 92%, 1- and 2-years-LC-rate 57%, respectively. BED2 influenced LC. When a cut-off of BED2 = 78 Gy was used, the higher BED2 values resulted in improved local control with a statistical trend to significance (p = 0.0999). Larger PTV-sizes, inversely correlated with applied dose, resulted in lower local control, also with a trend to significance (p-value = 0.08) when a volume cut-off of 67 cm³ was used.

No local relapse was observed at PTV-sizes < 67 cm³ and BED2 > 78 Gy. No acute clinical toxicity > °2 was observed. Late toxicity was also ≤ °2 with the exception of one gastrointestinal bleeding-episode 1 year post-SABR. A statistically significant elevation in the acute phase was observed for alkaline-phosphatase; in the chronic phase for alkaline-phosphatase, bilirubine, cholinesterase and C-reactive protein.

Conclusions

A trend to statistically significant correlation of local progression was observed for BED2 and PTV-size. Dose-levels BED2 > 78 Gy cannot be reached in large lesions constituting a significant fraction of this series. Image-guided SABR (igSABR) is therefore an effective non-invasive treatment modality with low toxicity in patients with small inoperable liver metastases.

Dosimetric impact of a frame-based strategy in stereotactic radiotherapy of lung tumors

INTRODUCTION

Technological innovations have taken stereotactic body radiotherapy (SBRT) from frame-based strategies to image-guided strategies. In this study, cone beam computed tomography (CBCT) images acquired prior to SBRT of patients with lung tumors was used to study the dosimetric impact of a pure frame-based strategy.

MATERIAL AND METHODS

Thirty patients with inoperable lung tumors were retrospectively analyzed. All patients had received CBCT-guided SBRT with 3 fractions of 15 Gy to the planning target volume (PTV) margin including immobilization in a stereotactic body frame (SBF). Using the set-up corrections from the co-registration of the CBCT with the planning CT, all individual dose plans were recalculated with an isocenter position equal to the initial set-up position. Dose Volume Histogram (DVH) parameters of the recalculated dose plans were then analyzed.

RESULTS

The simulated plans showed that 88% of all fractions resulted in minimum 14.5 Gy to the internal target volume (ITV). For the simulated summed treatment (3 fractions per patient), 83% of the patients would minimum receive the prescription dose (45 Gy) to 100% of the ITV and all except one would receive the prescription dose to more than 90% of the ITV.

CONCLUSIONS

SBRT including SBF, but without image guidance, results in appropriate dose coverage in most cases, using the current margins. With image guidance, margins for SBRT of lung tumors could possibly be reduced.