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

Stereotactic radiotherapy for early stage non-small cell lung cancer

Stereotactic body radiotherapy (SBRT) represents a consolidated treatment option for patients with medically inoperable early stage non-small cell lung cancer (NSCLC). The clinical evidence accumulated in the past decade supports its use as an alternative to surgery with comparable survival outcomes. Due to its limited toxicity, SBRT is also applicable to elderly patients with very poor baseline pulmonary function or other severe comorbidities. Recent comparative studies in operable patients raised the issue of the possible use of SBRT also for this subgroup, with quite promising results that still should be fully confirmed by prospective trials with long-term follow-up. Aim of this review is to summarize and discuss the major studies conducted over the years on SBRT and to provide data on the efficacy and toxicity of this radiotherapy technique for stage I NSCLC. Technical aspects and quality of life related issues are also discussed, with the goal to provide information on the current role and limitations of SBRT in clinical practice.

Stereotactic body radiation therapy as an ablative treatment for inoperable hepatocellular carcinoma

PURPOSE

To describe efficacy and safety of stereotactic body radiation therapy (SBRT) for the treatment of inoperable hepatocellular carcinoma.

METHODS

The records of 77 consecutive patients treated with SBRT for 97 liver-confined HCC were reviewed. A total dose of 45Gy in 3 fractions was prescribed to the 80% isodose line. Local control (LC), overall survival (OS), progression-free survival (PFS) and toxicity were studied.

RESULTS

The median follow-up was 12months. The median tumor diameter was 2.4cm. The LC rate was 99% at 1 and 2years. The 1 and 2-year OS were 81.8% and 56.6% respectively. The median time to progression was 9months (0-38). The rate of hepatic toxicity was 7.7% [1.6-13.7], 14.9% [5.7-23.2] and 23.1% [9.9-34.3] at 6months, 1year and 2years respectively. In multivariate analysis, female gender (HR 7.87 [3.14-19.69]), a BCLC B-C stage (HR 3.71 [1.41-9.76]), a sum of all lesion diameters ⩾2cm (HR 7.48 [2.09-26.83]) and a previous treatment (HR 0.10 [0.01-0.79]) were independent prognostic factors of overall survival.

CONCLUSION

SBRT allows high local control for inoperable hepatocellular carcinomas. It should be considered when an ablative treatment is indicated in Child A patients.

A Phase I Dose-Escalation Trial of Single-Fraction Stereotactic Radiation Therapy for Liver Metastases

Background

There is significant interest in the use of stereotactic ablative radiotherapy (SABR) as a treatment modality for liver metastases. A variety of SABR fractionation schemes are in clinical use. We conducted a phase I dose-escalation study to determine the maximum tolerated dose of single-fraction liver SABR.

Methods

Patients with liver metastases from solid tumors, for whom a critical volume dose constraint could be met, were treated with single-fraction SABR. Seven patients were enrolled to the first group, with a prescription dose of 35 Gy. Dose was then escalated to 40 Gy in a single fraction, and seven more patients were treated at this dose level. Patients were followed for toxicity and underwent serial imaging to assess lesion response and local control.

Results

Fourteen patients with 17 liver metastases were treated. There were no dose-limiting toxicities observed at either dose level. Nine of the 13 lesions assessable for treatment response showed a complete radiographic response to treatment; the remainder showed partial response. Local control of irradiated lesions was 100 % at a median imaging follow-up of 2.5 years. Two-year overall survival for all patients was 78 %.

Conclusions

For selected patients with liver metastases, single-fraction SABR at doses of 35 and 40 Gy is tolerable and shows promising signs of efficacy at intermediate follow-up.

Primary Treatment Options for High-Risk/Medically Inoperable Early Stage NSCLC Patients

Lung cancer is among the most common cancers worldwide and is the leading cause of cancer death in both men and women. For patients with early stage (American Joint Committee on Cancer T1-2, N0) non-small-cell lung cancer, the current standard of care is lobectomy with systematic lymph node evaluation. Unfortunately, patients with lung cancer often have medical comorbities, which may preclude the option of surgical resection. In such cases, a number of minimally invasive to noninvasive treatment options have gained popularity in the treatment of these high-risk patients. These modalities provide significant advantages, including patient convenience, treatment in an outpatient setting, and acceptable toxicities, including reduced impact on lung function and a modest risk of postprocedure chest wall pain. We provide a comprehensive review of the literature, including reported outcomes, complications, and limitations of sublobar resection with or without intraoperative brachytherapy, radiofrequency ablation, microwave ablation, percutaneous cryoablation, photodynamic therapy, and stereotactic body radiotherapy.

Available evidence on re-irradiation with stereotactic ablative radiotherapy following high-dose previous thoracic radiotherapy for lung malignancies

Patients affected with intra-thoracic recurrences of primary or secondary lung malignancies after a first course of definitive radiotherapy have limited therapeutic options, and they are often treated with a palliative intent. Re-irradiation with stereotactic ablative radiotherapy (SABR) represents an appealing approach, due to the optimized dose distribution that allows for high-dose delivery with better sparing of organs at risk. This strategy has the goal of long-term control and even cure. Aim of this review is to report and discuss published data on re-irradiation with SABR in terms of efficacy and toxicity. Results indicate that thoracic re-irradiation may offer satisfactory disease control, however the data on outcome and toxicity are derived from low quality retrospective studies, and results should be cautiously interpreted. As SABR may be associated with serious toxicity, attention should be paid for an accurate patients' selection.

Recent advances in multidisciplinary management of hepatocellular carcinoma

The incidence of hepatocellular carcinoma (HCC) is increasing, and it is currently the second leading cause of cancer-related death worldwide. Potentially curative treatment options for HCC include resection, transplantation, and percutaneous ablation, whereas palliative treatments include trans-arterial chemoembolization (TACE), radioembolization, and systemic treatments. Due to the diversity of available treatment options and patients' presentations, a multidisciplinary team should decide clinical management of HCC, according to tumor characteristics and stage of liver disease. Potentially curative treatments are suitable for very-early- and early-stage HCC. However, the vast majority of HCC patients are diagnosed in later stages, where the tumor characteristics or progress of liver disease prevent curative interventions. For patients with intermediate-stage HCC, TACE and radioembolization improve survival and are being evaluated in addition to potentially curative therapies or with systemic targeted therapy. There is currently no effective systemic chemotherapy, immunologic, or hormonal therapy for HCC, and sorafenib is the only approved molecular-targeted treatment for advanced HCC. Other targeted agents are under investigation; trials comparing new agents in combination with sorafenib are ongoing. Combinations of systemic targeted therapies with local treatments are being evaluated for further improvements in HCC patient outcomes. This article provides an updated and comprehensive overview of the current standards and trends in the treatment of HCC.

Liver cancer: Approaching a personalized care

The knowledge and understanding of all aspects of liver cancer [this including hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA)] have experienced a major improvement in the last decades. New laboratory technologies have identified several molecular abnormalities that, at the very end, should provide an accurate stratification and optimal treatment of patients diagnosed with liver cancer. The seminal discovery of the TP53 hotspot mutation [1 ,2 ] was an initial landmark step for the future classification and treatment decision using conventional clinical criteria blended with molecular data. At the same time, the development of ultrasound, computed tomography (CT) and magnetic resonance (MR) has been instrumental for earlier diagnosis, accurate staging and treatment advances. Several treatment options with proven survival benefit if properly applied are now available. Major highlights include: i) acceptance of liver transplantation for HCC if within the Milan criteria [3 ], ii) recognition of ablation as a potentially curative option [4 ,5 ], iii) proof of benefit of chemoembolization (TACE), [6 ] and iv) incorporation of sorafenib as an effective systemic therapy [7 ]. These options are part of the widely endorsed BCLC staging and treatment model (Fig. 1 ) [8 ,9 ]. This is clinically useful and it will certainly keep evolving to accommodate new scientific evidence.

This review summarises the data which are the basis for the current recommendations for clinical practice, while simultaneously exposes the areas where more research is needed to fulfil the still unmet needs (Table 1 ).

Radiotherapy for liver tumors

Many patients with primary hepatic malignancies present with advanced disease that is not suitable for surgical resection, orthotopic liver transplantation, or radiofrequency ablation. Outcomes are particularly dismal in patients with large, unresectable tumors and/or tumor venous thrombosis. Liver-directed radiotherapy, including stereotactic body radiotherapy (SBRT), is able to treat a variety of tumor sizes and tumors with venous involvement and has demonstrated excellent safety and control outcomes. SBRT should be considered a standard option in patients with early-stage hepatocellular carcinoma who are not candidates for surgical resection, orthotopic liver transplantation or radiofrequency ablation. SBRT should be strongly considered in patients with larger tumors and/or tumors with tumor venous thrombosis who have adequate liver function. Radiotherapy should remain a focus of hepatocellular carcinoma research.

Chemoradiation for gastric cancer: controversies, updates and novel techniques

The INT0116 trial established the role of adjuvant chemoradiation (CRT) in the multidisciplinary approach to the management of locally advanced gastric cancer. However, whether adjuvant CRT is indispensable for patients undergoing D2 dissection remains undefined. The adjuvant chemoradiation therapy in stomach cancer (ARTIST) trial, which was designed to compare adjuvant chemotherapy to CRT, failed to demonstrate differences in disease-free and overall survival in the whole study group; however, subgroup analysis indicated that patients with lymph node metastasis may benefit from additional radiation. A follow-up ARTIST II trial is currently under way. The efficacy of adjuvant CRT remains controversial because of variation among studies in the inclusion criteria and treatment delivery methods; however, the identification of patients who would benefit from CRT is critical. Advanced radiotherapy techniques such as intensity-modulated radiotherapy protect normal tissues via motion management and decreased radiation-induced toxicity and contribute to plan optimization. Further studies integrating clinical and molecular factors as well as neoadjuvant CRT are warranted.

Non-operative therapies for colorectal liver metastases

Locoregional therapies for colorectal liver metastases complement systemic therapy by providing an opportunity for local control of hepatic spread. The armamentarium for liver-directed therapy includes ablative therapies, embolization, and stereotactic body radiation therapy. At this time, prospective studies comparing these modalities are limited and decision-making relies on a multidisciplinary approach for optimal patient management. Herein, we describe multiple therapeutic non-surgical procedures and an overview of the results of these treatments.

Challenges in the treatment of early non-small cell lung cancer: what is the standard, what are the challenges and what is the future for radiotherapy?

In the last 15 years, the use of Stereotactic Ablative Radiation Therapy (SABRT) in the management of small peripheral lung tumours has developed considerably, so that it currently represents a standard of care for inoperable stage I non-small cell lung cancer (NSCLC), offering a survival advantage over traditional radiotherapy, local control rates at 3 years around 90%, with a low risk of toxicity. Indications have extended to larger tumours up to 5 cm and centrally located tumours. In this review we will explore the role of SABRT in early stage NSCLC, the state of the art, the challenges and the future for this technique. There are ongoing studies to optimize such approaches within a multicentric setting. Trials comparing surgery to SABRT in operable or marginally operable have failed because of poor accrual. Several questions remain that need to be addressed in prospective studies.

Are three doses of stereotactic ablative radiotherapy (SABR) more effective than 30 doses of conventional radiotherapy?

In early stage non-small cell lung cancer (NSCLC) definitive radiation therapy is an appropriate alternative to surgery. Recent studies show, that in such patients hypofractionation schedules (for example 3 times 18 Gy or 5 times 12 Gy), can be safely applied, without causing severe toxicities and achieving high local control rates of up to 90% and more. In the last couple of years a lot of knowledge about the cancer biology, technical aspects, clinical outcomes and toxicities has been accumulated from different clinical trials. The purpose of this review is to summarize recent outcomes and developments in stereotactic radiation therapy for patients with early stage NSCLC.

The radiobiology of hypofractionation

If the α/β ratio is high (e.g. 10 Gy) for tumour clonogen killing, but low (e.g. 3 Gy) for late normal tissue complications, then delivering external beam radiotherapy in a large number (20-30) of small (≈2 Gy) dose fractions should yield the highest 'therapeutic ratio'; this is demonstrated via the linear-quadratic model of cell killing. However, this 'conventional wisdom' is increasingly being challenged, partly by the success of stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR) extreme hypofractionation regimens of three to five large fractions for early stage non-small cell lung cancer and partly by indications that for certain tumours (prostate, breast) the α/β ratio may be of the same order or even lower than that characterising late complications. It is shown how highly conformal dose delivery combined with quasi-parallel normal tissue behaviour (n close to 1) enables 'safe' hypofractionation; this can be predicted by the (α/β)eff concept for normal tissues. Recent analyses of the clinical outcomes of non-small cell lung cancer radiotherapy covering 'conventional' hyper- to extreme hypofractionation (stereotactic ablative radiotherapy) regimens are consistent with linear-quadratic radiobiology, even at the largest fraction sizes, despite there being theoretical reasons to expect 'LQ violation' above a certain dose. Impairment of re-oxygenation between fractions and the very high (α/β) for hypoxic cells can complicate the picture regarding the analysis of clinical outcomes; it has also been suggested that vascular damage may play a role for very large dose fractions. Finally, the link between high values of (α/β)eff and normal-tissue sparing for quasi-parallel normal tissues, thereby favouring hypofractionation, may be particularly important for proton therapy, but more generally, improved conformality, achieved by whatever technique, can be translated into individualisation of both prescription dose and fraction number via the 'isotoxic' (iso-normal tissue complication probability) concept.

Quantifying isocenter measurements to establish clinically meaningful thresholds

A dataset range of isocenter congruency verification tests have been examined from a statistical perspective for the purpose of establishing tolerance levels that are meaningful, based on the fundamental limitation of linear accelerator isocentricity and the demands of a high-precision stereotactic radiosurgery program. Using a laser-defined isocenter, a total of 149 individual isocenter congruency tests were examined with recorded values for ideal spatial corrections to the isocenter test tool. These spatial corrections were determined from radiation exposures recorded on an electronic portal imaging device (EPID) at various gantry, collimator, and treatment couch combinations. The limitations of establishing an ideal isocenter were quantified from each variable which contributed to uncertainty in isocenter definition. Individual contributors to uncertainty, specifically, daily positioning setup errors, gantry sag, multileaf collimator (MLC) offset, and couch walkout, were isolated from isocenter congruency measurements to determine a clinically meaningful isocenter measurement. Variations in positioning of the test tool constituted, on average, 0.38 mm magnitude of correction. Gantry sag and MLC offset contributed 0.4 and 0.16 mm, respectively. Couch walkout had an average degrading effect to isocenter of 0.72 mm. Considering the magnitude of uncertainty contributed by each uncertainty variable and the nature of their combination, an appropriate schedule action and immediate action level were determined for use in analyzing daily isocenter congruency test results in a stereotactic radiosurgery (SRS) program. The recommendations of this study for this linear accelerator include a schedule action level of 1.25 mm and an immediate action level of 1.50mm, requiring prompt correction response from clinical medical physicists before SRS or stereotactic body radiosurgery (SBRT) is administered. These absolute values were derived from considering relative data from a specific linear accelerator and, therefore, represent a means by which a numerical quantity can be used as a test threshold with relative specificity to a particular linear accelerator.

Surgery or stereotactic ablative radiation therapy: how will be treated operable patients with early stage not small cell lung cancer in the next future?

Lung neoplasm is the most influent cause of death for cancer. With the increasing of life expectancy in elderly patients and with the intensification of lung cancer screening by low-dose computed tomography, a further rise of the number of new non-small cell lung cancer (NSCLC) cases has been shown. Standard of care of early stage NSCLC patients is lobectomy but approximately 20% of them are not fit for surgery for comorbidities. Due to the high local control rates and the little adverse effects, stereotactic body radiation therapy (SBRT) also called stereotactic ablative radiation therapy (SABR), has rapidly replaced the conventional radiotherapy in not operable patients with stage I NSCLC. We review the evidence for use of SABR in medically inoperable patients with stage I NSCLC, and its possible extension of use to operable patients, from the perspectives of radiation oncologists and thoracic surgeons. Until the results of large randomized trials will be available, the multidisciplinary management, balancing during discussion the advantages/disadvantages of each treatment modality, could be the coming soon best approach for medically operable early-stage NSCLC. As a result, the minimally invasive thoracic surgery advantages and the SABR innovations will be translated into real clinical benefits.

Stereotactic body radiotherapy for liver metastases

The role for local ablative therapies in the management paradigm of oligometastatic liver disease is increasing. The evidence base supporting the use of stereotactic body radiotherapy for liver metastases has expanded rapidly over the past decade, showing high rates of local control with low associated toxicity. This review summarises the evidence base to date, discussing optimal patient selection, challenges involved with treatment delivery and optimal dose and fractionation. The reported toxicity associated with liver stereotactic body radiotherapy is presented, together with possible pitfalls in interpreting the response to treatment using standard imaging modalities. Finally, potential avenues for future research in this area are highlighted.

The role of stereotactic radiotherapy in the treatment of oligometastases

"Oligometastasis" describes a limited number of metastases arising typically from solid tumors whose behavior suggests an "intermediate" malignant state since it may potentially have a more favorable prognosis. Historically, selected patients with oligometastases often underwent surgical resection since anecdotal evidence suggested it could improve progression-free or overall survival. No prospective randomized trial evidence to date supports survival benefits from surgery. Short courses of highly focused, very high dose radiotherapy (stereotactic radiosurgery; stereotactic body radiotherapy) have emerged as a surgical surrogate to manage oligometastates. For solitary brain metastases, randomized study evidence supports stereotactic radiosurgery as part of their management because of overall survival benefits. Modeled after stereotactic radiosurgery, stereotactic body radiotherapy for extracranial metastases is becoming increasingly common given its efficacy and low toxicity, is an active area of clinical research, and is the subject of this review.

Minimally invasive local therapies for liver cancer

Primary and metastatic liver tumors are an increasing global health problem, with hepatocellular carcinoma (HCC) now being the third leading cause of cancer-related mortality worldwide. Systemic treatment options for HCC remain limited, with Sorafenib as the only prospectively validated agent shown to increase overall survival. Surgical resection and/or transplantation, locally ablative therapies and regional or locoregional therapies have filled the gap in liver tumor treatments, providing improved survival outcomes for both primary and metastatic tumors. Minimally invasive local therapies have an increasing role in the treatment of both primary and metastatic liver tumors. For patients with low volume disease, these therapies have now been established into consensus practice guidelines. This review highlights technical aspects and outcomes of commonly utilized, minimally invasive local therapies including laparoscopic liver resection (LLR), radiofrequency ablation (RFA), microwave ablation (MWA), high-intensity focused ultrasound (HIFU), irreversible electroporation (IRE), and stereotactic body radiation therapy (SBRT). In addition, the role of combination treatment strategies utilizing these minimally invasive techniques is reviewed.

Survival and prognostic factors in 321 patients treated with stereotactic body radiotherapy for oligo-metastases

BACKGROUND AND PURPOSE

To establish a model to predict survival after SBRT for oligo-metastases in patients considered ineligible for surgical resection (SR) and radiofrequency ablation (RFA).

MATERIAL AND METHODS

Overall survival (OS) rates were estimated in 321 patients treated for 587 metastases with SBRT over 13years. Patients were treated for a variety of metastasis types with colorectal cancer (CRC) being the most frequent (n=201).

RESULTS

With a median follow-up time of 5.0years, the median OS was 2.4years (95% CI 2.3-2.7) and the survival rates were 80%, 39%, 23% and 12% at 1, 3, 5 and 7.5years after SBRT, respectively. WHO performance status (PS) (0-1) (HR 0.49; p<0.001), solitary metastasis (HR 0.75; p=0.049), metastasis ⩽30mm (HR 0.53; p<0.001), metachronous metastases (HR 0.71; p=0.02) and pre-SBRT chemotherapy (HR 0.59; p<0.001) were independently related to favorable OS. Median OS rates were 7.5, 2.8, 2.5, 1.7 and 0.8years with 0, 1, 2, 3, ⩾4 unfavorable prognostic factors, respectively. The treatment-related morbidity was moderate. However, three deaths were possibly treatment-related.

CONCLUSION

Prognostic factors may predict long-term survival in patients with oligo-metastases treated with SBRT.

To SABR or not to SABR? Indications and contraindications for stereotactic ablative radiotherapy in the treatment of early-stage, oligometastatic, or oligoprogressive non-small cell lung cancer

Stereotactic ablative radiotherapy (SABR) is a highly effective treatment for early-stage non-small cell lung cancer. Although direct comparisons from randomized trials are not available, rates of both primary tumor control and distant metastasis are similar between SABR and surgery. Overall survival is lower after SABR compared with surgery, largely reflecting that a primary selection criterion for SABR has been medical inoperability because of decreased cardiopulmonary function and other comorbidities that lead to decreased survival independent of non-small cell lung cancer. Survival outcomes between SABR and surgery are much more similar in propensity-matched cohorts. Newer potential indications for SABR include treatment of operable patients; of oligometastatic lung cancer, in which SABR has emerged as an alternative to metastasectomy; and of oligoprogressive lung cancer, an attractive concept especially as improved personalized systemic therapies emerge, and prospective trials are currently being conducted in these settings. Although toxicity in modern series is low, SABR is clearly capable of producing fatal complications, and understanding the risk factors and approaches for mitigating them has been emerging in recent years. Thus, appropriate patient selection is a vital, evolving, and controversial topic.

[Dose reconstruction using respiratory signals and machine parameters during treatment in stereotactic body radiotherapy]

PURPOSE

Volumetric modulated arc therapy (VMAT) is a rotational intensity-modulated radiotherapy (IMRT) technique capable of acquiring projection images during treatment. The purpose of this study was to reconstruct the dose distribution from respiratory signals and machine parameters acquired during stereotactic body radiotherapy (SBRT).

METHODS

The treatment plans created for VMAT-SBRT included the constraint of 1 mm/degree in multileaf collimator (MLC) for a moving phantom and three patients with lung tumors. The respiratory signals were derived from projection images acquired during VMAT delivery, while the machine parameters were derived from machine logs. The respiratory signals and machine parameters were then linked along with the gantry angle. With this data, the dose distribution of each respiratory phase was calculated on the planned four-dimensional CT (4D CT). The doses at the isocenter, the point of max dose and the centroid of the target were compared with those of the corresponding plans.

RESULTS AND DISCUSSION

In the phantom study, the maximum dose difference between the plan and "in-treatment" results was -0.4% at the centroid of the target. In the patient study, the difference was -1.8 ± 0.4% at the centroid of the target. Dose differences of the evaluated points between 4 and 10 phases were not significant.

CONCLUSION

The present method successfully reconstructed the dose distribution using the respiratory signals and machine parameters acquired during treatment. This is a feasible method for verifying the actual dose for a moving target.

Stereotactic body radiotherapy

Extracranial stereotactic body radiotherapy (SBRT) has been developed and refined over the last 25 years as a means to precisely deliver ablative doses of hypofractionated radiotherapy to small targets located outside of the cranial vault. SBRT has armed the radiation oncologist with a therapeutic approach that allows for intensification of both dose delivered and fractionation regimen employed. As a consequence, tumor control rates have improved to levels that previously have been associated only with surgical resection. Several prospective phase I and II studies have evaluated the use of SBRT for non-small cell lung cancer (NSCLC), liver tumors, and spinal metastases. This article will give an overview of SBRT and evidence for its use in the most common sites of disease for which it is employed today.

Stereotactic body radiation therapy for post-pulmonary lobectomy isolated lung metastasis of thoracic tumor: survival and side effects

BACKGROUND

Stereotactic body radiation therapy (SBRT) has emerged as an alternative treatment for patients with early stage non-small cell lung cancer (NSCLC) or metastatic pulmonary tumors. However, for isolated lung metastasis (ILM) of thoracic malignances after pulmonary lobectomy, reported outcomes of SBRT have been limited. This study evaluates the role of SBRT in the treatment of such patients.

METHODS

A retrospective search of the SBRT database was conducted in three hospitals. The parameters analyzed in the treated patients were local control, progression-free survival (PFS), overall survival (OS), and the treatment-related side-effects.

RESULTS

In total, 23 patients with single ILM after pulmonary lobectomy treated with SBRT were identified and the median follow-up time was 14 months (range: 6.0-47.0 months). Local recurrences were observed in two patients during follow-up and the 1-year local control rate was 91.3%. Median PFS and OS for the studied cohort were 10.0 months [95% confidence interval (CI) 5.1-14.9 months] and 21.0 months (95% CI 11.4-30.6 months), respectively. Acute radiation pneumonitis (RP) of grade 2 or worse was observed in five (21.7%) and three (13.0%) patients, respectively. Other treatment-related toxicities included chest wall pain in one patient (4.3%) and acute esophagitis in two patients (8.7%). By Pearson correlation analysis, the planning target volume (PTV) volume and the volume of the ipsilateral lung exposed to a minimum dose of 5 Gy (IpV5) were significantly related to the acute RP of grade 2 or worse in present study (p < 0.05). The optimal thresholds of the PTV and IpV5 to predict RP of acute grade 2 or worse RP were 59 cm3 and 51% respectively, according to the receiver-operating characteristics curve analysis, with sensitivity/specificity of 75.0%/80.0% and 62.5%/80.0%.

CONCLUSIONS

SBRT for post-lobectomy ILM was effective and well tolerated. The major reason for disease progression was distant failure but not local recurrence. The PTV and IpV5 are potential predictors of acute RP of grade 2 or higher and should be considered in treatment planning for such patients.

[Stereotactic body radiation therapy in the management of liver tumours]

Stereotactic radiotherapy is a high-precision technique based on the administration of high doses to a limited target volume. This treatment constitutes a therapeutic progress in the management of many tumours, especially hepatic ones. If surgery remains the standard local therapy, stereotactic radiotherapy is first dedicated to inoperable patients or unresectable tumours. Patients with moderately altered general status, preserved liver function and tumour lesions limited in number as in size are eligible to this technique. Results in terms of local control are satisfying, regarding primary tumours (notably hepatocellular carcinomas) as metastases stemming from various origins. If treatment protocols and follow-up modalities are not standardized to this day, iconographic acquisition using four-dimensional computed tomography, target volumes delineation based on morphological and/or metabolic data, and image-guided radiotherapy contribute to an oncologic efficacy and an improved sparing of the functional liver. The purpose of this literature review is to report the results of the main works having assessed stereotactic radiotherapy in the management of primary and secondary liver tumours. Technical particularities of this radiation modality will also be described.

Stereotactic radiosurgery (SRS) with volumetric modulated arc therapy (VMAT): interim results of a multi-arm phase I trial (DESTROY-2)

AIMS

To present the interim results of a phase I trial on stereotactic radiosurgery (SRS) delivered using volumetric modulated arc therapy (VMAT) in patients with primary or metastatic tumours in different extracranial sites.

MATERIALS AND METHODS

Patients were enrolled in different arms according to tumour site and clinical stage, and sequentially assigned to a given dose level. Acute toxicity, tumour response and early local control were investigated and reported.

RESULTS

One hundred lesions in 65 consecutive patients (male/female: 30/35, median age: 66 years; range: 40-89) were treated. Of these 100 lesions, 21 were primary or metastatic lung tumours, 24 were liver metastases, 30 were bone metastases, 24 were nodal metastases and one was a primary vulvar melanoma. The prescribed dose ranged from 12 (BED(2Gy,α/β:10) = 26.4 Gy) to 28 Gy (BED(2Gy,α/β:10) = 106.4 Gy) to the planning target volume. Twenty-one patients (32.3%) experienced grade 1-2 acute toxicity, which was grade 2 in only two cases. The overall response rate based on computed tomography/magnetic resonance imaging was 52% (95% confidence interval 40.1-63.2%) and based on positron emission tomography scan was 90% (95% confidence interval 76.2-96.4%). As of November 2013, the median duration of follow-up was 11 months (range = 1-38). Recurrence/progression within the SRS-VMAT treated field was observed in nine patients (total lesions = 18): the inside SRS-VMAT field local control expressed on a per lesion basis was 87.8% at 12 months and 71.9% at 24 months.

CONCLUSIONS

The maximum tolerable dose has not yet been reached in any study arm. SRS-VMAT resulted in positive early clinical results in terms of tumour response, local control rate and acute toxicity.

Radical irradiation of extracranial oligometastases

Advances in radiotherapy planning and delivery have been used to treat patients with limited metastatic disease. With these techniques, high rates of treated metastasis control and low toxicity have been reported. Some patients have long disease-free intervals after radiotherapy similar to those seen after surgical resection. Ongoing studies will determine the benefit of these irradiation techniques to treat limited metastases, identify appropriate candidates, and assist in integrating these treatments into management strategies for specific diseases.

Emergence of stereotactic body radiation therapy and its impact on current and future clinical practice

Stereotactic body radiation therapy (SBRT) is generally a tumor-ablative radiation modality using essential technologies capable of accurately and precisely damaging the target with a high dose while geometrically sparing innocent normal tissues. The intent, conduct, and tissue biology are all dramatically distinct from conventionally fractionated radiotherapy such that new understanding is required for its optimization. It is most practical, tolerable, and tumoricidal in its most potent form treating tumors in the lung and liver. However, it is increasingly being used for tumors adjacent to bowels and nervous tissue, albeit with somewhat less ablative potency. Its strengths include high rates of tumor eradication via a noninvasive, convenient outpatient treatment. Its weakness relates to the possibility of causing difficult-to-manage toxicity (eg, ulceration, stenosis, fibrosis, and even necrosis) that may occur considerably later after treatment, particularly in the vicinity of the body's many tubular structures (eg, organ hila, bowel). However, clinical trials in a variety of organs and sites have shown SBRT to result in good outcomes in properly selected patients. Given its short course, lack of need for recovery, and favorable overall toxicity profile, there is great hope that SBRT will find a prominent place in the treatment of metastatic cancer as a consolidative partner with systemic therapy. With considerable published experience, available required technologies and training, and many patients in need of local therapy, SBRT has found a place in the routine cancer-fighting arsenal.

Survival and tumour control probability in tumours with heterogeneous oxygenation: a comparison between the linear-quadratic and the universal survival curve models for high doses

BACKGROUND

The validity of the linear-quadratic (LQ) model at high doses has been questioned due to a decreasing agreement between predicted survival and experimental cell survival data. A frequently proposed alternative is the universal survival curve (USC) model, thought to provide a better fit in the high-dose region. The comparison between the predictions of the models has mostly been performed for uniform populations of cells with respect to sensitivity to radiation. This study aimed to compare the two models in terms of cell survival and tumour control probability (TCP) for cell populations with mixed sensitivities related to their oxygenation.

METHODS

The study was performed in two parts. For the first part, cell survival curves were calculated with both models assuming various homogeneous populations of cells irradiated with uniform doses. For the second part, a realistic three-dimensional (3D) model of complex tumour oxygenation was used to study the impact of the differences in cell survival on the modelled TCP. Cellular response was assessed with the LQ and USC models at voxel level and a Poisson TCP model at tumour level.

RESULTS

For hypoxic tumours, the disputed continuous bend of the LQ survival curve was counteracted by the increased radioresistance of the hypoxic cells and the survival curves started to diverge only at much higher doses than for oxic tumours. This was also reflected by the TCP curves for hypoxic tumours for which the difference in D50 values for the LQ and USC models was reduced from 5.4 to 0.2 Gy for 1 and 3 fractions, respectively, in a tumour with only 1.1% hypoxia and from 9.5 to 0.4 Gy in a tumour with 11.1% hypoxia.

CONCLUSIONS

For a large range of fractional doses including hypofractionated schemes, the difference in predicted survival and TCP between the LQ and USC models for tumours with heterogeneous oxygenation was found to be negligible.

Radiation therapy for liver tumors: ready for inclusion in guidelines?

Despite the historically limited role of radiotherapy in the management of primary hepatic malignancies, modern advances in treatment design and delivery have renewed enthusiasm for radiation as a potentially curative treatment modality. Surgical resection and/or liver transplantation are traditionally regarded as the most effective forms of therapy, although the majority of patients with hepatocellular carcinoma and intrahepatic cholangiocarcinoma present with locally advanced or unresectable disease on the basis of local vascular invasion or inadequate baseline hepatobiliary function. In this context, many efforts have focused on nonoperative treatment approaches including novel systemic therapies, transarterial chemoembolization, ethanol ablation, radiofrequency ablation, and stereotactic body radiation therapy (SBRT). This review aims to summarize modern advances in radiotherapy, particularly SBRT, in the treatment of primary hepatic malignancies.

Stereotactic body radiation therapy for liver metastases

Over the years, early diagnosis of metastatic disease has improved and the prevalence of oligometastatic patients is increasing. Liver is a most common site of progression from gastrointestinal, lung and breast cancer and in the setting of oligometastatic patients, surgical resection is associated with increased survival. Approximately 70-90% of liver metastases, however, are unresectable and an effective and safe alternative therapeutic option is necessary for these patients. The role of stereotactic body radiation therapy (SBRT) was investigated in the treatment of oligometastatic patients with promising results, thanks to the ability of this procedure to deliver a conformal high dose of radiation to the target lesion and a minimal dose to surrounding critical tissues. This paper was performed to review the current literature and to provide the practice guidelines on the use of stereotactic body radiotherapy in the treatment of liver metastases. We performed a literature search using Medical Subject Heading terms "SBRT" and "liver metastases", considering a period of ten years.

Treatment fractionation for stereotactic radiotherapy of lung tumours: a modelling study of the influence of chronic and acute hypoxia on tumour control probability

Background

Stereotactic body radiotherapy (SBRT) for non-small-cell lung cancer (NSCLC) has led to promising local control and overall survival for fractionation schemes with increasingly high fractional doses. A point has however been reached where the number of fractions used might be too low to allow efficient local inter-fraction reoxygenation of the hypoxic cells residing in the tumour. It was therefore the purpose of this study to investigate the impact of hypoxia and extreme hypofractionation on the tumour control probability (TCP) from SBRT.

Methods

A three-dimensional model of tumour oxygenation able to simulate oxygenation changes on the microscale was used. The TCP was determined for clinically relevant SBRT fractionation schedules of 1, 3 and 5 fractions assuming either static tumour oxygenation or that the oxygenation changes locally between fractions due to fast reoxygenation of acute hypoxia without an overall reduction in chronic hypoxia.

Results

For the schedules applying three or five fractions the doses required to achieve satisfying levels of TCP were considerably lower when local oxygenation changes were assumed compared to the case of static oxygenation; a decrease in D₅₀ of 17.7 Gy was observed for a five-fractions schedule applied to a 20% hypoxic tumour when fast reoxygenation was modelled. Assuming local oxygenation changes, the total doses required for a tumor control probability of 50% were of similar size for one, three and five fractions.

Conclusions

Although attractive from a practical point of view, extreme hypofractionation using just one single fraction may result in impaired local control of hypoxic tumours, as it eliminates the possibility for any kind of reoxygenation.

Safety and efficacy of intensity-modulated stereotactic body radiotherapy using helical tomotherapy for lung cancer and lung metastasis

Stereotactic body radiotherapy (SBRT) proved to be an effective treatment with acceptable toxicity for lung tumors. However, the use of helical intensity-modulated (IM) SBRT is controversial. We investigated the outcome of lung tumor patients treated by IMSBRT using helical tomotherapy with a Japanese standard fractionation schedule of 48 Gy in 4 fractions (n = 37) or modified protocols of 50-60 Gy in 5-8 fractions (n = 35). Median patient's age was 76 years and median follow-up period for living patients was 20 months (range, 6-46). The median PTV was 6.9 cc in the 4-fraction group and 14 cc in the 5- to 8-fraction group (P = 0.001). Grade 2 radiation pneumonitis was seen in 2 of 37 patients in the 4-fraction group and in 2 of 35 patients in the 5- to 8-fraction group (log-rank P = 0.92). Other major complications were not observed. The LC rates at 2 years were 87% in the 4-fraction group and 83% in the 5- to 8-fraction group. Helical IMSBRT for lung tumors is safe and effective. Patients with a high risk of developing severe complications may also be safely treated using 5-8 fractions. The results of the current study warrant further studies of helical IMSBRT.

Local effect of stereotactic body radiotherapy for primary and metastatic liver tumors in 130 Japanese patients

BACKGROUND AND AIMS

Stereotactic body radiotherapy (SBRT) is a relatively new treatment for liver tumor. The outcomes of SBRT for liver tumor unfit for ablation and surgical resection were evaluated.

METHODS

Liver tumor patients treated with SBRT in seven Japanese institutions were studied retrospectively. Patients given SBRT for liver tumor between 2004 and 2012 were collected. Patients treated with SBRT preceded by trans-arterial chemoembolization (TACE) were eligible. Seventy-nine patients with hepatocellular carcinoma (HCC) and 51 patients with metastatic liver tumor were collected. The median biologically effective dose (BED) (α/β = 10 Gy) was 96.3 Gy for patients with HCC and 105.6 Gy with metastatic liver tumor.

RESULTS

The median follow-up time was 475.5 days in patients with HCC and 212.5 days with metastatic liver tumor. The 2-year local control rate (LCR) for HCC and metastatic liver tumor was 74.8% ± 6.3% and 64.2 ± 9.5% (p = 0.44). The LCR was not different between BED10 ≥ 100 Gy and < 100 Gy (p = 0.61). The LCR was significantly different between maximum tumor diameter > 30 mm vs. ≤ 30 mm (64% vs. 85%, p = 0.040) in all 130 patients. No grade 3 laboratory toxicities in the acute, sub-acute and chronic phases were observed.

CONCLUSIONS

There was no difference in local control after SBRT in the range of median BED10 around 100 Gy for between HCC and metastatic liver tumor. SBRT is safe and might be an alternative method to resection and ablation.

SUMMARY

There was no difference in local control after SBRT in the range of median BED10 around 100 Gy for between HCC and metastatic liver tumor and SBRT is safe and might be an alternative method to resection and ablation.

Novel application of stereotactic ablative radiotherapy using CyberKnife® for early-stage renal cell carcinoma in patients with pre-existing chronic kidney disease: Initial clinical experiences

The treatment of renal cell carcinoma (RCC) in patients diagnosed with chronic kidney disease (CKD) requires particular care in order to preserve the remaining renal function. The present study aimed to investigate the potential of a novel nephron-sparing treatment, which is capable of targeting tumors embedded deep within tissues. The present study analyzed three patients, with pre-existing CKD and multiple comorbidities, who were successfully treated for stage I RCC using the CyberKnife^® stereotactic ablative radiotherapy (SABR) system. The total prescribed dose was 40 Gy in five fractions administered over five consecutive days. Treatment efficiency was determined using computed tomography scans of the tumors and periodic measurements of the glomerular filtration rate over a period of 12–40 months. Local control, defined as a radiologically stable condition, was achieved in all patients. Lung metastasis was observed in one patient nine months after SABR; however, the side-effects were generally mild and self-limiting. One patient developed renal failure 26 months after SABR, while the severity of CKD was only marginally altered in the other two patients and renal failure did not occur. In conclusion, in the present study, SABR with CyberKnife^® was observed to be well tolerated in the patients, with an acceptable acute toxicity effect. Therefore, it may represent a potential therapeutic option for patients with early-stage RCC who have previously been diagnosed with CKD, but for whom other nephron-sparing treatments are contraindicated.

Design, development of water tank-type lung phantom and dosimetric verification in institutions participating in a phase I study of stereotactic body radiation therapy in patients with T2N0M0 non-small cell lung cancer: Japan Clinical Oncology Group trial (JCOG0702)

A domestic multicenter phase I study of stereotactic body radiotherapy (SBRT) for T2N0M0 non-small cell lung cancer in inoperable patients or elderly patients who refused surgery was initiated as the Japan Clinical Oncology Group trial (JCOG0702) in Japan. Prior to the clinical study, the accuracy of dose calculation in radiation treatment-planning systems was surveyed in participating institutions, and differences in the irradiating dose between the institutions were investigated. We developed a water tank-type lung phantom appropriate for verification of the exposure dose in lung SBRT. Using this water tank-type lung phantom, the dose calculated in the radiation treatment-planning system and the measured dose using a free air ionization chamber and dosimetric film were compared in a visiting survey of the seven institutions participating in the clinical study. In all participating institutions, differences between the calculated and the measured dose in the irradiation plan were as follows: the accuracy of the absolute dose in the center of the simulated tumor measured using a free air ionization chamber was within 2%, the mean gamma value was ≤ 0.47 on gamma analysis following the local dose criteria, and the pass rate was >87% for 3%/3 mm from measurement of dose distribution with dosimetric film. These findings confirmed the accuracy of delivery doses in the institutions participating in the clinical study, so that a study with integration of the institutions could be initiated.

Stereotactic ablative radiotherapy for oligometastatic disease in liver

Liver metastasis in solid tumors, including colorectal cancer, is the most frequent and lethal complication. The development of systemic therapy has led to prolonged survival. However, in selected patients with a finite number of discrete lesions in liver, defined as oligometastatic state, additional local therapies such as surgical resection, radiofrequency ablation, cryotherapy, and radiotherapy can lead to permanent local disease control and improve survival. Among these, an advance in radiation therapy made it possible to deliver high dose radiation to the tumor more accurately, without impairing the liver function. In recent years, the introduction of stereotactic ablative radiotherapy (SABR) has offered even more intensive tumor dose escalation in a few fractions with reduced dose to the adjacent normal liver. Many studies have shown that SABR for oligometastases is effective and safe, with local control rates widely ranging from 50% to 100% at one or two years. And actuarial survival at one and two years has been reported ranging from 72% to 94% and from 30% to 62%, respectively, without severe toxicities. In this paper, we described the definition and technical aspects of SABR, clinical outcomes including efficacy and toxicity, and related parameters after SABR in liver oligometastases from colorectal cancer.

[Winston-lutz test and acquisition of flexmap using rotational irradiation]

PURPOSE

IGRT (image guided radiation therapy) is a useful technique for implementing precisely targeted radiation therapy. Quality assurance and quality control (QA/QC) medical linear accelerators with a portal imaging system (electronic portal imaging device: EPID) are the key to ensuring safe IGRT. The Winston-Lutz test (WLT) provides an evaluation of the MV isocenter, which is the intersection of radiation, collimator, and couch isocenters. A flexmap can indicate a displacement of EPID from the beam center axis as a function of gantry angles which can be removed from the images. The purpose of this study was to establish a novel method for simultaneously carrying out WLT and acquiring a flexmap using rotational irradiation. We also observed long-term changes in flexmaps over a period of five months.

METHOD

We employed rotational irradiation with a rectangular field (30×30 mm). First, the displacement of EPID from the beam center axis, indicated by the ball bearing (BB) center, was evaluated using an in-house program. The location of the BB center was then modified according to WLT. Second, a second irradiation was used to acquire a flexmap. We performed this examination regularly and evaluated long-term changes in the flexmap.

RESULTS AND DISCUSSION

It proved feasible to perform WLT and flexmap measurements using our proposed methods. The precision of WLT using rotational irradiation was 0.1 mm. In flexmap analysis, the maximum displacement from the mean value for each angle was 0.4 mm over five months.

CONCLUSION

We have successfully established a novel method of simultaneously carrying out WLT and flexmap acquisition using rotational irradiation. Maximum displacement from the mean in each angle was 0.4 mm over five months.

Locally ablative therapies for primary and metastatic liver cancer

Locally ablative therapies have an increasing role in the effective multidisciplinary approach towards the treatment of both primary and metastatic liver tumors. In patients who are not considered surgical candidates and have low volume disease, these therapies have now become established into consensus practice guidelines. A large range of therapeutic options exist including percutaneous ethanol injection (PEI), radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation, percutaneous laser ablation (PLA), irreversible electroporation (IRE), stereotactic body radiation therapy (SBRT) and high intensity focused ultrasound (HIFU); each having benefits and drawbacks. The greatest body of evidence supporting clinical utility in the liver currently exists for RFA, with PEI having fallen out of favor. MWA, IRE, SBRT and HIFU are relatively nascent technologies, and outcomes data supporting their use is promising. Future directions of ablative therapies include tandem approaches to improve efficacy in the treatment of liver tumors.

[Radiation pneumonitis after stereotactic body radiation therapy for early stage non-small cell lung cancer]

With the development of radiation technology, stereotactic body radiation therapy (SBRT) has been widely used in early stage non-small cell lung cancer (NSCLC). It is not only the standard therapy for medically inoperable early-stage NSCLC, but also one of the therapies for operable early-stage NSCLC. Radiation pneumonitis (RP) is one of the most common adverse effects after SBRT, it may reduce the patients' quality of life, even cause treatment failure. Therefore, in order to improve the patients' quality of life and enhance local control rate of tumor, it is important to reduce the risk of RP. The unique fractionation schemes and the dose distribution of SBRT make it not only different from conventional fraction radiation therapy in treatment outcomes, but also in the incidence of radiation pneumonitis. This article reviews the applying of SBRT for early stage NSCLC, the incidence of radiation pneumonitis, radiological appearance after SBRT and predictive factors.

Survey of stereotactic ablative body radiotherapy in the UK by the QA group on behalf of the UK SABR Consortium

OBJECTIVE

To ascertain the progress being made towards the implementation of stereotactic ablative body radiotherapy (SABR) treatment in the UK, to obtain details of current practice in centres with an active treatment programme and to assess the projected future provision.

METHODS

In August 2012, an online questionnaire was sent to all 65 UK radiotherapy institutions. The included questions covered the current number of patients being treated and the intended number of patients for each clinical site; immobilization and motion management methods; CT scanning protocols; target and organ-at-risk delineation; treatment planning; image-guidance and treatment protocols; and quality assurance methods.

RESULTS

48/65 (74%) institutions responded by the end of November 2012, with 15 indicating an active SABR programme. A further four centres indicated that a SABR protocol had been established but was not yet in clinical use. 14 of the 29 remaining responses stated an intention to develop a SABR programme in the next 2 years.

CONCLUSION

The survey responses confirm that SABR provision in the UK is increasing and that this should be expected to continue in the next 2 years. A projection of the future uptake would suggest that by the end of 2014, UK SABR provision will be broadly in line with international practice.

A radiation oncologist's and thoracic surgeon's view on the role of stereotactic ablative radiotherapy for operable lung cancer

Stereotactic ablative radiotherapy, also known as stereotactic body radiation therapy, has been developed as an innovative therapy for stage I non-small cell lung cancer and has now emerged as a standard treatment option for medically inoperable patients through careful analysis using prospective multi-institutional trials. We review and update the evidence for use of stereotactic ablative radiotherapy in medically inoperable patients with stage I lung cancer, and its possible extension of use to operable patients, from the perspectives of an experienced radiation oncologist and a thoracic surgeon.