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

Oligometastatic Disease Management: Finding the Sweet Spot

Hematogenous dissemination represents a common manifestation of squamous cell carcinoma of the head and neck, and the recommended therapeutic options usually consist of systemically administered drugs with palliative intent. However, mounting evidence suggests that patients with few and slowly progressive distant lesions of small size may benefit from various local ablation techniques, which have already been established as standard-of-care modalities for example in colorectal and renal cell carcinomas and in sarcomas. In principle, serving as radical approaches to eradicate cancer, these interventions can be curative. Their impact on local control and overall survival has been shown in numerous retrospective and prospective studies. The term oligometastatic refers to the number of distant lesions which should generally not surpass five in total, ideally in one organ. Currently, surgical resection remains the method of choice supported by the majority of published data. More recently, stereotactic (ablative) body radiotherapy (SABR/SBRT) has emerged as a viable alternative. In cases technically amenable to such local interventions, several other clinical variables need to be taken into account also, including patient-related factors (general health status, patient preferences, socioeconomic background) and disease-related factors (primary tumor site, growth kinetics, synchronous or metachronous metastases). In head and neck cancer, patients presenting with late development of slowly progressive oligometastatic lesions in the lungs secondary to human papillomavirus (HPV)-positive oropharyngeal cancer are the ideal candidates for metastasectomy or other local therapies. However, literature data are still limited to say whether there are other subgroups benefiting from this approach. One of the plausible explanations is that radiological follow-up after primary curative therapy is usually not recommended because its impact on survival has not been unequivocal, which is also due to the rarity of oligometastatic manifestations in this disease. At the same time, aggressive treatment of synchronous metastases early in the disease course should be weighed against the risk of futile interventions in a disease with already multimetastatic microscopic dissemination. Therefore, attentive treatment sequencing, meticulous appraisal of cancer extension, refinement of post-treatment surveillance, and understanding of tumor biology and kinetics are crucial in the management of oligometastases.

Long-Term Results of a Phase 1 Dose-Escalation Trial and Subsequent Institutional Experience of Single-Fraction Stereotactic Ablative Radiation Therapy for Liver Metastases

PURPOSE

We report long-term outcomes from our phase 1 dose-escalation study to determine the maximum tolerated dose of single-fraction liver SABR pooled with our subsequent single institutional experience with patients treated postprotocol at the highest dose level (40 Gy) established from the phase 1 study.

METHODS AND MATERIALS

Patients with liver metastases from solid tumors located outside of the central liver zone were treated with single-fraction SABR on a phase 1 dose escalation trial. At least 700 cc of normal liver had to receive <9.1 Gy. Seven patients with 10 liver metastases received the initial prescription dose of 35 Gy, and dose was then escalated to 40 Gy for 7 more patients with 7 liver metastases. An additional 19 postprotocol patients with 22 liver metastases were treated to 40 Gy in a single fraction. Patients were followed for toxicity and underwent serial imaging to assess local control.

RESULTS

Median imaging follow-up for the combined cohort (n = 33, 39 lesions) was 25.9 months; 38.9 months for protocol patients and 20.2 months for postprotocol patients. Median lesion size was 2.0 cm (range, 0.5-5.0 cm). There were no dose-limiting toxicities observed for protocol patients, and only 3 grade 2 toxicities were observed in the entire cohort, with no grade ≥3 toxicities attributable to treatment. Four-year actuarial local control of irradiated lesions in the entire cohort was 96.6%, 100% in the protocol group and 92.9% in the subsequent patients. Two-year overall survival for all treated patients was 82.0%.

CONCLUSIONS

For selected patients with liver metastases, single-fraction SABR at doses of 35 and 40 Gy was safe and well-tolerated, and shows excellent local control with long-term follow-up; results in subsequent patients treated with single-fraction SABR doses of 40 Gy confirmed our earlier results.

A single-institutional experience with low dose stereotactic body radiation therapy for liver metastases

AIM

This study reports a single-institutional experience treating liver metastases with stereotactic body radiation therapy (SBRT).

MATERIALS AND METHODS

107 patients with 169 lesions were assessed to determine factors predictive for local control, radiographic response, and overall survival (OS). Machine learning techniques, univariate analysis, and the Kaplan-Meier method were utilized.

RESULTS

Patients were treated with a relatively low median dose of 30 Gy in 3 fractions. Fractions were generally delivered once weekly. Median biologically effective dose (BED) was 60 Gy, and the median gross tumor volume (GTV) was 12.16 cc. Median follow-up was 7.36 months. 1-year local control was 75% via the Kaplan-Meier method. On follow-up imaging, 43%, 40%, and 17% of lesions were decreased, stable, and increased in size, respectively. 1-year OS was 46% and varied by primary tumor, with median OS of 34.3, 25.1, 12.5, and 4.6 months for ovarian, breast, colorectal, and lung primary tumors, respectively. Breast and ovarian primary patients had better OS (p < 0.0001), and lung primary patients had worse OS (p = 0.032). Higher BED values, the number of hepatic lesions, and larger GTV were not predictive of local control, radiographic response, or OS. 21% of patients suffered from treatment toxicity, but no grade ≥3 toxicity was reported.

CONCLUSION

Relatively low-dose SBRT for liver metastases demonstrated efficacy and minimal toxicity, even for patients with large tumors or multiple lesions. This approach may be useful for patients in whom higher-dose therapy is contraindicated or associated with high risk for toxicity. OS depends largely on the primary tumor.

External Beam Radiation Therapy for Liver Metastases

Stereotactic ablative radiotherapy (SABR) commonly is used for small liver metastases. Modern conformal radiotherapy techniques, including 3-dimensional conformal radiotherapy and intensity-modulated radiation therapy, enable the safe delivery of SABR to small liver volumes. For larger tumors, the safe delivery of SABR can be challenging due to a more limited volume of healthy normal liver parenchyma and the proximity of the tumor to radiosensitive organs, such as the stomach, duodenum, and large intestine. Controlling respiratory motion, the use of image guidance, and increasing the number of radiation fractions sometimes are necessary for the safe delivery of SABR in these situations.

Image-guided Radiotherapy to Manage Respiratory Motion: Lung and Liver

Organ motion as a result of respiratory and cardiac motion poses significant challenges for the accurate delivery of radiotherapy to both the thorax and the upper abdomen. Modern imaging techniques during radiotherapy simulation and delivery now permit better quantification of organ motion, which in turn reduces tumour and organ at risk position uncertainty. These imaging advances, coupled with respiratory correlated radiotherapy delivery techniques, have led to the development of a range of approaches to manage respiratory motion. This review summarises the key strategies of image-guided respiratory motion management with a focus on lung and liver radiotherapy.

Using deep learning to model the biological dose prediction on bulky lung cancer patients of partial stereotactic ablation radiotherapy

PURPOSE

To develop a biological dose prediction model considering tissue bio-reactions in addition to patient anatomy for achieving a more comprehensive evaluation of tumor control and promoting the automatic planning of bulky lung cancer.

METHODS

A database containing images and partial stereotactic ablation boost radiotherapy (P-SABR) plans of 94 bulky lung cancer patients was studied. Patient-specific parameters of gross tumor boost volume (GTVb), planning gross target volume (PGTV), and identified organs at risk (OARs) were extracted via Numpy and simple ITK. The original dose and structure maps for P-SABR patients were resampled to have a voxel resolution of 3.9 × 3.9 × 3 mm³ . Biological equivalent dose (BED) distributions were reprogrammed based on physical dose volumes. A developed deep learning architecture, Nestnet, was adopted as the training framework. We utilized two approaches for data organization to correlate the structures and BED: (a) BED programming before training model (B-Nestnet); (b) BED programming after the training process (D-B Nestnet). The early-stop mechanism was adopted on the validation set to avoid overfitting. The evaluation criteria of predictive accuracy contain the minimum BED of GTVb and PGTV, the maximum and the mean BED of all targets, BED-volume metrics. For comparison, we also used the original Unet for BED prediction. The absolute differences were statistically analyzed with the paired-samples t test.

RESULTS

The statistical outcomes demonstrate that D-B Nestnet model predicts biological dose distributions accurately. The average absolute biases of [max, mean] BED for GTVb, PGTV are [2.1%, 3.3%] and [2.1%, 4.7%], respectively. Averaging across most of OARs, the D-B Nestnet model is capable of predicting the errors of the max and mean BED within 6.3% and 6.1%, respectively. While the compared models performed worse with averaged max and mean BED prediction errors surpassing 10% on some specific OARs.

CONCLUSIONS

The study developed a D-B Nestnet model capable of predicting BED distribution accurately for bulky lung cancer patients in P-SABR. The predicted BED map enables a quick intuitive evaluation of tumor ablation, modification of the ablation range to improve BED of tumor targets, and quality assessment. It represents a major step forward toward automated P-SABR planning on bulky lung cancer in real clinical practice.

Stereotactic Body Radiation Therapy (SBRT) in Pelvic Lymph Node Oligometastases

The role of stereotactic body radiation therapy (SBRT) in achieving durable local control and palliation of pain in pelvic lymph node oligometastatic disease is not well-studied. We performed a retrospective analysis of 30 patients with 43 pelvic lymph node oligometastases from various primary cancers all but one with non-prostate primaries treated at our institution with SBRT. The median follow-up time was 21 months. The median SBRT dose was 24 Gy in four fractions. The one-, two-, and five-year local control was 74%, 71%, and 70% and one-, two-, and five-year overall survival was 70%, 47%, and 31%. Toxicities were mild with no grade 3 or higher.

The Promise of Combining Radiation Therapy With Immunotherapy

The development of immunotherapy in oncology builds upon many years of scientific investigation into the cellular mechanics underlying interactions between tumor cells and immune cell populations. The past decade has brought an accelerating pace to the clinical investigation of new immunotherapy agents, particularly in the setting of metastatic disease. The integration of immunotherapy into phase 3 clinical trial design has lagged in settings of advanced locoregional disease, where combination with radiation therapy may be critical. Yet, such may be the settings where immunotherapies have their greatest potential to affect patient survival and achieve curative outcomes. In this review, we discuss the interaction of radiation with the immune system and the potential to augment antitumor immunity through combined-modality approaches that integrate radiation and immunotherapies. The dynamics of cellular and tumor response to radiation offer unique opportunities for beneficial interplay with immunotherapy that may go unrecognized with conventional screening and monotherapy clinical testing of novel pharmaceutical agents. Using immune checkpoint blockade as a primary example, we discuss recent preclinical and clinical studies that illustrate the potential synergy of such therapies in combination with radiation, and we highlight the potential clinical value of such interactions. For various immunotherapy agents, their greatest clinical effect may rest in combination with radiation, and efforts to facilitate systematic investigation of this approach are highly warranted.

Modern evidence and future prospects of external body radiation therapy for lung oligometastases of breast cancer

After Hellman and Weichselbaum defined "Oligometastasis" in 1995, several local therapies for lung oligometastases including surgical resection and external body radiation therapy were reported that improved local control (LC) and progression-free survival, overall survival, and quality of life. This suggests that oligometastases is a potentially curable state. Modern advances in radiation therapy such as stereotactic body radiation therapy (SBRT) in which high dose coverage of target lesion without exposure of normal organ is possible, and are widely used to treat solitary or a limited number of primary lung cancer and metastases. Several reports showed that SBRT was a useful treatment method for lung oligometastases, and the LC rate of SBRT was 80-90% in 2 years and less invasive than surgical resection. SBRT is a safe and effective especially for small and peripheral lung metastases. However, if the metastatic lesion is big or centrally located, careful treatment is necessary to prevent radiation pneumonitis. After SBRT, it is sometimes difficult to differentiate local recurrence and pulmonary injury, especially in the early phase. However, it is important to detect local recurrence especially in patients who require further local therapy such as surgical resection and re-irradiation or systemic therapy. The diagnosis can be improved by determining the natural course after SBRT and local recurrence with computed tomography imaging and ¹⁸F-fluorodeoxyglucose positron emission tomography, respectively. Moreover, radiation therapy may have both local and systemic effects that are related to the enhancement of immune-response after radiation. Currently, several trials evaluating the benefits of SBRT for oligometastatic breast cancer are underway. However, the adaption of SBRT for lung metastases including other treatment strategies should be carefully discussed by the radiation oncologist and a multi-disciplinary team comprising a breast surgeon, medical oncologist, diagnostic radiologist, and radiation oncologist, among others.

Retrospective dose reconstruction of prostate stereotactic body radiotherapy using cone-beam CT and a log file during VMAT delivery with flattening-filter-free mode

This study aimed to reconstruct the dose distribution of single fraction of stereotactic body radiotherapy for patients with prostate cancer using cone-beam computed tomography (CBCT) and a log file during volumetric-modulated arc therapy (VMAT) delivery with flattening-filter-free (FFF) mode. Twenty patients with clinically localized prostate cancer were treated with FFF-VMAT, and projection images for in-treatment CBCT (iCBCT) imaging were concomitantly acquired with a log file. A D₉₅ dose of 36.25 Gy in five fractions was prescribed to each planning target volume (PTV) on each treatment planning CT (pCT). Deformed pCT (dCT) was obtained from the iCBCT using a hybrid deformable image registration algorithm. Dose distributions on the dCT were calculated using Pinnacle³ v9.10 by converting the log file data to Pinnacle³ data format using an in-house software. Dose warping was performed by referring to deformation vector fields calculated from pCT and dCT. Reconstructed dose distribution was compared with that of the original plan. Dose differences between the original and reconstructed dose distributions were within 3% at the isocenter and observed in PTV and organ-at-risk (OAR) regions. Differences in OAR regions were relatively larger than those in the PTV, presumably because OARs were more deformed than the PTV. Therefore, our method can be used successfully to reconstruct the dose distributions of one fraction using iCBCT and a log file during FFF-VMAT delivery.

Bronchoscopic treatments for early-stage peripheral lung cancer: Are we ready for prime time?

Lung cancer is the leading cause of cancer-related death worldwide and surgical lobectomy remains the preferred therapy for patients with early-stage NSCLC. Medical comorbidities and advanced age preclude resection in many patients and minimally invasive ablative therapies are needed for treatment. Stereotactic ablative radiation is established as an effective modality in this patient group, although may be contraindicated in some patients with prior radiation exposure, comorbidities or centrally positioned tumours. Percutaneous ablative methods are available, although are frequently associated with significant complications. Numerous endoscopic ablative techniques are under evaluation. With a more favourable safety profile and the ability to provide diagnosis and staging information potentially within a single procedure, there is a strong rationale for development of bronchoscopic ablative modalities. In the following article, the authors aim to explore the role bronchoscopic ablation may play in treatment of peripheral lung tumours, and to describe a pathway to establishing these modalities as part of routine care. The current status of several bronchoscopic ablative options is discussed in detail.

Stereotactic body radiotherapy in patients with lung tumors composed of mainly ground-glass opacity

We retrospectively reviewed the effect of stereotactic body radiation therapy (SBRT) in patients with stage I lung cancer whose lung tumor showed a nodular appearance of ground glass opacity, so-called ground glass nodule (GGN). A total of 84 patients (42 men, 42 women; mean age, 75 years) with stage I lung cancer with GGN accompanying a solid component <50% in diameter of the tumor and no metastases were studied. Concerning histology, 32 tumors were adenocarcinoma, 1 was squamous cell carcinoma, 2 were unclassified carcinoma and 49 cases were histology-unproven but increased in size or had a positive finding in 18F-FDG positron emission tomography (PET) examination. The median tumor size was 20 mm (range, 10-41 mm). All of the patients were treated with SBRT, and the total prescribed dose at the isocenter ranged between 48 Gy in four fractions and 84 Gy in ten fractions. Median follow-up duration was 33 months. No patient had local failure nor regional lymph node failure. The 3-year rate of distant failure was 2.6%. Two patients who experienced distant metastases had a past surgical history of initial lung cancer before SBRT. The rates of cause-specific and overall survival at 3 years were 98.2 and 94.6%, respectively. Treatment-related adverse events of ≥grade 4 were not reported. Although more cases and longer follow-ups are mandatory, SBRT may be one of the radical treatment options for patients with GGN.

Isotoxic dose prescription level strategies for stereotactic liver radiotherapy: the price of dose uniformity

Introduction: To find the optimal dose prescription strategy for liver SBRT, this study investigated the tradeoffs between achievable target dose and healthy liver dose for a range of isotoxic uniform and non-uniform prescription level strategies.Material and methods: Nine patients received ten liver SBRT courses with intrafraction motion monitoring during treatment. After treatment, five VMAT treatment plans were made for each treatment course. The PTV margin was 5 mm (left-right, anterior-posterior) and 10 mm (cranio-caudal). All plans had a mean CTV dose of 56.25 Gy in three fractions, while the PTV was covered by 50%, 67%, 67 s% (steep dose gradient outside CTV), 80%, and 95% of this dose, respectively. The 50%, 67 s%, 80%, and 95% plans were then renormalized to be isotoxic with the standard 67% plan according to a Lyman-Kutcher-Burman normal tissue complication probability model for radiation induced liver disease. The CTV D98 and mean dose of the iso-toxic plans were calculated both without and with the observed intrafraction motion, using a validated method for motion-including dose reconstruction.Results: Under isotoxic conditions, the average [range] mean CTV dose per fraction decreased gradually from 21.2 [20.5-22.7] Gy to 15.5 [15.0-16.6] Gy and the D98 dose per fraction decreased from 20.4 [19.7-21.7] Gy to 15.0 [14.5-15.5] Gy, as the prescription level to the PTV rim was increased from 50% to 95%. With inclusion of target motion the mean CTV dose was 20.5 [16.5-22.5] Gy (50% PTV rim dose) and 15.4 [13.9-16.7] Gy (95% rim dose) while D98 was 17.8 [7.4-20.6] Gy (50% rim dose) and 14.6 [8.8-15.7] Gy (95% rim dose).Conclusion: Requirements of a uniform PTV dose come at the price of excess normal tissue dose. A non-uniform PTV dose allows increased CTV mean dose at the cost of robustness toward intrafraction motion. The increase in planned CTV dose by non-uniform prescription outbalanced the dose deterioration caused by motion.

Alternatives to Surgery for Early-Stage Non-Small Cell Lung Cancer: Stereotactic Radiotherapy

Lung cancer is the leading cause of cancer death worldwide. Diagnosis of early-stage disease is becoming more common. In an aging population, more and more patients have substantial comorbidities that might limit feasibility of surgical management of early-stage disease. Stereotactic body radiotherapy (SBRT) enables delivery of high-dose, precisely delivered radiation to early-stage lung cancers without surgical risk. This technique has rates of local control similar to surgery and can be considered in medically operable patients who refuse surgery. This article details the technique of SBRT, the data for its efficacy, as well as the potential toxicities of treatment.

Stereotactic body radiotherapy feasibility for patients with peripheral stage I lung cancer and poor pulmonary function

The aim of the present study was to evaluate the toxicity and investigate the prognostic factors of stereotactic body radiotherapy (SBRT) for peripheral stage I lung cancer in patients with poor pulmonary function. Data from 95 patients with stage I lung cancer with poor pulmonary function treated using SBRT at Osaka Rosai Hospital were retrospectively analyzed. Poor pulmonary function was defined as the forced expiratory volume %/sec (FEV1/FVC) <70% or percentage of vital capacity (%VC) <80% during pretreatment spirometry testing. The median FEV1/FVC and %VC of the patients were 59.1 and 78.8%, respectively. The most commonly prescribed dose of SBRT was 50 Gy in four fractions (68 patients, 72%). The median follow-up period was 34 months. Four patients developed adverse effects of grade ≥3, one patient developed grade 5 radiation pneumonitis, one grade 5 hemoptysis, one grade 3 radiation pneumonitis and one grade 3 chest wall pain. The 3-year local control and overall survival (OS) rates were 78.8 and 59.9%, respectively. Univariate analysis revealed that Karnofsky performance status (KPS) significantly predicted OS (P=0.037). Thus, SBRT in patients with stage I lung cancer with poor pulmonary function may be effective with acceptable toxicity. A KPS score ≥80 indicated good prognosis.

CyberKnife Stereotactic Body Radiation Therapy as an Effective Treatment for Hepatocellular Carcinoma Patients With Decompensated Cirrhosis

Purpose: The aim of our study was to evaluate the curative effect and safety of CyberKnife stereotactic body radiation therapy in treating decompensated cirrhosis hepatocellular carcinoma (HCC) patients. Methods: From March 2011 to December 2015, 32 HCC patients who refused or were ineligible for other treatments were treated with CyberKnife stereotactic body radiation therapy. Among these patients, 17 were Child-Pugh score 7 (53.13%), 7 were Child-Pugh score 8 (21.87%), 4 were Child-Pugh score 9 (12.50%), and 4 were Child-Pugh score 10 (12.50%). A total dose of 45-54 Gy in 5-10 fractions was given according to the location of lesions. Results: The median follow-up period was 30 months (8-46 months). By July 2019, the tumors were recurrent or metastasized in 17 patients. The overall survival rates of 1, 2, and 3 years were 84.4, 61.8, and 46.0%, respectively. After 1, 2, and 3 years, the local control rates were 92.9%. The progression-free survival rates of the 1, 2, and 3-year treatments were 73.8, 44.6, and 33.4%, respectively. Conclusions: CyberKnife stereotactic body radiation therapy was an effective option for HCC patients with decompensated cirrhosis. The liver injury occurrence rate was acceptable in our study.

Image guidance: past and future of radiotherapy

Image guidance has been playing a decisive role throughout the history of radiotherapy, but developments in 3D-and 4D imaging data acquisition using computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET) have significantly boosted the precision of conformal radiotherapy. An overarching aim of radiotherapy is conforming the treatment dose to the tumor in order to optimally limit a high radiation dose outside the target. Stereotactic, intensity modulated, and adaptive radiotherapy are all largely based on appropriately using imaging information both before and during treatment delivery using on-board imaging devices. While pretreatment imaging for planning has reached a very high level in the past two decades, the next step will be to further refine and accelerate imaging during treatment delivery, resulting in adaptation of the dose fluence during a patient’s treatment in various scenarios, some of which are discussed in this article.

Assessing the Variability and Quality of Lung Stereotactic Radiation Therapy Treatment Plans Using a Web-Based Crowdsourcing Platform

PURPOSE

The quality of stereotactic body radiation therapy (SBRT) treatment plans for early stage lung cancer are unknown outside of peer-reviewed publications. Thus, a study was conducted to crowdsource and analyze a variety of lung SBRT treatment plans from around the world.

METHODS AND MATERIALS

This study had 2 parts, planning and contouring, and each was facilitated by a web-based technology platform. For planning, lung SBRT planners were invited to design, score, and submit their treatment plans (prescription of 11 Gy × 5) for a centralized stage I lung cancer case using standardized images and predefined contours. Each plan was scored with 20 weighted metrics adapted from currently recruiting phase 3 lung SBRT trials. For contouring, a separate image set was used to evaluate organ-at-risk contour accuracy using Dice coefficients and a StructSure score.

RESULTS

For planning 227 plans were submitted in total with 7 different treatment planning systems and 7 different delivery methods represented. Variability was primarily user driven and not associated with the treatment planning system, delivery modality, total monitor units, or estimated beam-on time. Many of the highest-quality plans required the shortest amount of time to deliver, independent of the delivery technique. For contouring, organ-at-risk contours were frequently over- or undercontoured and often included only the luminal air of the trachea, proximal bronchial tree, and esophagus, even when the mucosal linings were within a few centimeters of the target tumor.

CONCLUSIONS

These findings demonstrate the importance of quality assurance to help improve planning and contouring and the value of peer review and comparison. More readily accessible quality evaluation software solutions, such as the one used herein, may help meet this growing need.

Selection of prescription isodose line for brain metastases treated with volumetric modulated arc radiotherapy

Purpose

To exploit the optimal prescription isodose line (IDL) for brain metastases treated with volumetric modulated arc radiotherapy (VMAT) as there is no consensus on the selection of IDL with VMAT.

Methods and materials

Eighteen patients with 20 brain tumors, who were treated with VMAT, were enrolled in this study. For each tumor of every patient, five plans were designed with IDL ranging from 50% to 90% in 10% increments. Different IDLs were obtained through adjusting the constraint parameters during planning optimization. Prescription dose (10 × 5 Gy) were identical for all plans, and the plans were compared in terms of gradient index (GI), conformity Index (CI), V26 Gy/V_PTV, and V32 Gy/V_PTV in normal brain tissue, which correlate to radiation necrosis.

Results

IDL with lowest GI has a median value of 60.0% (ranging from 50% to 80%). Except for one tumor with volume larger than 10 cc, the IDL with lowest GI varies from 50% to 70%, which depends on the shape of PTV, location, and whether the target volume is adjacent to crucial OAR. Moreover, there is no significant difference for CI with varying IDL plans. The average V26 Gy/V_PTV and V32 Gy/V_PTV in normal brain tissue 60% IDL plans are 27.3%, 31.7% lower than 90% IDL plans separately (P < 0.05). However, by further decreasing IDL from 60% to 50%, the average V26 Gy/V_PTV and V32 Gy/V_PTV may increase comparing with 60% IDL plans (P > 0.05). Furthermore, a lower IDL is found to result in higher mean dose to the target volume (P < 0.05).

Conclusions

Plans using VMAT with PTV smaller than 10 cc tend to be optimal with IDL around 60–70% for lower GI, smaller V26 Gy/V_PTV, V32 Gy/V_PTV in normal brain tissue, and higher mean dose in tumor comparing with high IDL plans which have potential benefit in reducing risk of radiation necrosis and increasing the local control. However, IDL lower than 60% is not recommended for the disadvantage of increasing V26 Gy/V_PTV and V32 Gy/V_PTV in normal brain tissue.

Establishing the Impact of Vascular Damage on Tumor Response to High-Dose Radiation Therapy

Approximately half of all patients with cancer receive radiotherapy, which is conventionally delivered in relatively small doses (1.8-2 Gy) per daily fraction over one to two months. Stereotactic body radiation therapy (SBRT), in which a high daily radiation dose is delivered in 1 to 5 fractions, has improved local control rates for several cancers. However, despite the widespread adoption of SBRT in the clinic, controversy surrounds the mechanism by which SBRT enhances local control. Some studies suggest that high doses of radiation (≥10 Gy) trigger tumor endothelial cell death, resulting in indirect killing of tumor cells through nutrient depletion. On the other hand, mathematical models predict that the high radiation dose per fraction used in SBRT increases direct tumor cell killing, suggesting that disruption of the tumor vasculature is not a critical mediator of tumor cure. Here, we review the application of genetically engineered mouse models to radiosensitize tumor cells or endothelial cells to dissect the role of these cellular targets in mediating the response of primary tumors to high-dose radiotherapy in vivo These studies demonstrate a role for endothelial cell death in mediating tumor growth delay, but not local control following SBRT.

Pain REduction with bone metastases STereotactic radiotherapy (PREST): A phase III randomized multicentric trial

Background

Palliative antalgic treatments represent an issue for clinical management and a challenge for scientific research. Radiotherapy (RT) plays a central role. Techniques such as stereotactic body radiotherapy (SBRT) were largely investigated in several phase 2 studies with good symptom response, becoming widely adopted. However, evidence from randomized, direct comparison of RT and SBRT is still lacking.

Methods/design

The PREST trial was designed as an interventional study without medicinal treatment. It is a phase 3, open-label, multicentric trial randomized 1:1. Inclusion criteria include painful spinal bone metastases presenting with a pain level > 4 (or > 1 if being treated with an analgesic) on the Numeric Rating Scale (NRS); expected intermediate/high prognosis (greater than 6 months) according to the Mizumoto prognostic score; low spine instability neoplastic score (SINS) sores (< 7); magnetic resonance imaging (MRI) assessment of the bulky lesion. Patients will be assigned to either standard conventional radiotherapy involving 4 Gy × 5 fractions (fx) to the whole involved vertebra or SBRT by intensity modulated radiotherapy with simultaneous integrated boost (IMRT-SIB) involving 7 Gy × 3 fx to the whole involved vertebra + 10 Gy × 3 fx on the macroscopic lesion (gross tumor volume (GTV)). In the experimental arm, the GTV will be contoured by registration with baseline MRI.

Discussion

The primary endpoint is overall pain reduction, defined in terms of variation between baseline and 3-month evaluation; pain will be measured using the NRS. Secondary endpoints include pain control duration; retreatment rates (after a minimum interval of 1 month); local control assessed with RECIST criteria; symptom progression free survival; progression-free survival; overall survival; and quality of life (at 0, 30, and 90 days). Accrual of 330 lesions is planned. The experimental arm is expected to have an improvement in overall pain response rates of 15% with respect to the standard arm (60% according to Chow et al. (Int J Radiat Oncol Biol Phys. 82(5):1730–7, 2012)).

Trial registration

ClinicalTrials.gov, NCT03597984. Registered on July 2018.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3676-x) contains supplementary material, which is available to authorized users.

Management of oligometastatic non-small cell lung cancer patients: Current controversies and future directions

Oligometastatic non-small cell lung cancer (NSCLC) describes an intermediate stage of NSCLC between localized and widely-disseminated disease. This stage of NSCLC is characterized by a limited number of metastases and a more indolent tumor biology. Currently, the management of oligometastatic NSCLC involves radical treatment (radiotherapy or surgery) that targets the metastatic lesions and the primary tumor to achieve disease control. This approach offers the potential to achieve prolonged survival in patients who, in the past, would have only received palliative measures. The optimal therapeutic strategies for the different scenarios of oligometastatic disease (intracranial vs extracranial disease, synchronous vs metachronous) remain undefined. Given the lack of head-to-head studies comparing radiotherapy to surgery in these patients, the decision to apply surgery or radiotherapy (with or without systemic treatment) must be based on prognostic factors that allow us to classify patients. This classification will allow us to select the most appropriate therapeutic strategy on an individualized basis. In the future, the molecular or microRNA profiles will likely improve the treatment selection process. The objective of the present article is to review the most relevant scientific evidence on the management of patients with oligometastatic NSCLC, focusing on the role of radiotherapy and surgery. We also discuss areas of controversy and future directions.

Current status of stereotactic body radiotherapy for the treatment of hepatocellular carcinoma

Stereotactic body radiotherapy (SBRT) is an advanced form of radiotherapy (RT) with a growing interest on its application in the treatment of hepatocellular carcinoma (HCC). It can deliver ablative radiation doses to tumors in a few fractions without excessive doses to normal tissues, with the help of advanced modern RT and imaging technologies. Currently, SBRT is recommended as an alternative to curative treatments, such as surgery and radiofrequency ablation. This review discusses the current status of SBRT to aid in the decision making on how it is incorporated into the HCC management.

Stereotactic body radiotherapy in patients with chronic obstructive pulmonary disease and interstitial pneumonia: a review

Stereotactic body radiation therapy (SBRT) can yield excellent local tumor control, as well as survival benefit comparable to that of surgery for early-stage lung cancer. However, in terms of toxicity, SBRT might lead to fatal radiation pneumonitis. Lung diseases, such as chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD), are major risk factors for lung cancer. However, these patients are typically not candidates for the gold-standard treatment option, lobectomy, because of the perioperative risks. In addition, patients with poor respiratory function can be excluded in prospective clinical trials. Thus, SBRT for patients with pulmonary diseases is still challenging, but there appears to be a clinical role for this modality as an alternative treatment. However, there are few well-documented review articles on SBRT for patients with pulmonary diseases. Therefore, we aimed to review SBRT in the context of important patient-related factors, including COPD and ILD. SBRT is an acceptable alternative treatment option for patients with lung cancer who also have COPD with an equivalent risk of radiation pneumonitis to normal lung. However, latent ILD should be detected prior to treatment. The indication for SBRT should be decided by carefully considering the risks and benefit for patients with ILD.

Technological evolution of radiation treatment: Implications for clinical applications

The contemporary approach to the management of a cancer patient requires an "ab initio" involvement of different medical domains in order to correctly design an individual patient's pathway toward cure. With new therapeutic tools in every medical field developing faster than ever before the patient care outcomes can be achieved if all surgical, drug, and radiation options are considered in the design of the appropriate therapeutic strategy for a given patient. Radiation therapy (RT) is a clinical discipline in which experts from different fields continuously interact in order to manage the multistep process of the radiation treatment. RT is found to be an appropriate intervention for diverse indications in about 50% of cancer patients during the course of their disease. Technologies are essential in dealing with the complexity of RT treatments and for driving the increasingly sophisticated RT approaches becoming available for the treatment of Cancer. High conformal techniques, namely intensity modulated or volumetric modulated arc techniques, ablative techniques (Stereotactic Radiotherapy and Stereotactic Radiosurgery), particle therapy (proton or carbon ion therapy) allow for success in treating irregularly shaped or critically located targets and for the sharpness of the dose fall-off outside the target. The advanced on-board imaging, including real-time position management systems, makes possible image-guided radiation treatment that results in substantial margin reduction and, in select cases, implementation of an adaptive approach. The therapeutic gains of modern RT are also due in part to the enhanced anticancer activity obtained by coadministering RT with chemotherapy, targeted molecules, and currently immune checkpoints inhibitors. These main clinically relevant steps forward in Radiation Oncology represent a change of gear in the field that may have a profound impact on the management of cancer patients.

Multidisciplinary management of liver metastases in patients with colorectal cancer: a consensus of SEOM, AEC, SEOR, SERVEI, and SEMNIM

Colorectal cancer (CRC) has the second-highest tumor incidence and is a leading cause of death by cancer. Nearly 20% of patients with CRC will have metastases at the time of diagnosis, and more than 50% of patients with CRC develop metastatic disease during the course of their disease. A group of experts from the Spanish Society of Medical Oncology, the Spanish Association of Surgeons, the Spanish Society of Radiation Oncology, the Spanish Society of Vascular and Interventional Radiology, and the Spanish Society of Nuclear Medicine and Molecular Imaging met to discuss and provide a multidisciplinary consensus on the management of liver metastases in patients with CRC. The group defined the different scenarios in which the disease can present: fit or unfit patients with resectable liver metastases, patients with potential resectable liver metastases, and patients with unresectable liver metastases. Within each scenario, the different strategies and therapeutic approaches are discussed.

Rethinking the Role of Radiation Therapy in the Treatment of Unresectable Hepatocellular Carcinoma: A Data Driven Treatment Algorithm for Optimizing Outcomes

Hepatocellular carcinoma (HCC) is the second most common cause of cancer death worldwide, with a majority of HCC patients not suitable for curative therapies. Approximately 70% of initially diagnosed patients cannot undergo surgical resection or transplantation due to locally advanced disease, poor liver function/underlying cirrhosis, or additional comorbidities. Local therapeutic options for patients with unresectable HCC, who are not suitable for thermal ablation, include transarterial embolization (bland, chemoembolization, radioembolization) and/or external beam radiation therapy (EBRT). Regarding EBRT specifically, technological advancements provide a means for safe and effective radiotherapy delivery in a wide spectrum of HCC patients. In multiple prospective studies, EBRT delivery in a variety of different fractionation schemes or in combination with transcatheter arterial chemoembolization (TACE) demonstrate improved outcomes, particularly with combination therapy. The Barcelona Clinic Liver Cancer classification provides a framework for treatment selection; however, given the growing complexity of treatment strategies, this classification system tends to simplify decision-making. In this review, we discuss the current literature regarding unresectable HCC and propose a modified treatment algorithm that emphasizes the role of radiation therapy for Child-Pugh score A or B patients with ≤3 nodules measuring >3 cm, multinodular disease or portal venous thrombosis.

The Combination of Stereotactic Body Radiation Therapy and Immunotherapy in Primary Liver Tumors

Treatment recommendations for primary liver malignancies, including hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), are complex and require a multidisciplinary approach. Despite surgical options that are potentially curative, options for nonsurgical candidates include systemic therapy, radiotherapy (RT), transarterial chemoembolization (TACE), and radiofrequency ablation (RFA). Stereotactic Body Radiation Therapy (SBRT) is now in routine use for the treatment of lung cancer, and there is growing evidence supporting its use in liver tumors. SBRT has the advantage of delivering ablative radiation doses in a limited number of fractions while minimizing the risk of radiation-induced liver disease (RILD) through highly conformal treatment plans. It should be considered in a multidisciplinary setting for the management of patients with unresectable, locally advanced primary liver malignancies and limited treatment options. Recently, the combination of immunotherapy with SBRT has been proposed to improve antitumor effects through engaging the immune system. This review aims at shedding light on the novel concept of the combination strategy of immune-radiotherapy in liver tumors by exploring the evidence surrounding the use of SBRT and immunotherapy for the treatment of HCC and CCA.

Stereotactic body radiation therapy for early hepatocellular carcinoma: a retrospective analysis of the South Australian experience

BACKGROUND

Stereotactic body radiation therapy (SBRT) is an emerging treatment option for liver tumours unsuitable for established curative treatment such as ablation or surgery. The aim of the study is to evaluate the efficacy and safety of SBRT in the treatment of small hepatocellular carcinoma (HCC) in South Australia.

METHODS

From 2014 to 2018, 13 HCC patients were treated with SBRT. Eligibility criteria for SBRT included: unsuitable for standard curative therapies (resection or percutaneous ablation), lack of complete response to prior transarterial chemoembolization, Child-Pugh classification ≤B7, tumours ≤5 cm and minimum of up to 6 months follow-up post-SBRT. The prescribed radiation dose was determined by liver function with doses ranging from 40 to 45 Gy in three or five fractions. Records for all patients were reviewed, and treatment response was scored according to the modified response evaluation criteria in solid tumours. Toxicity was graded according to the Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

The median follow-up time was 22.7 months, and the median tumour size was 40 mm. The 1 year local control was 92.3%, recurrence-free survival was 67.7% and overall survival was 86.4% at end of study. Three patients underwent liver transplant. No grade ≥3 non-haematological toxicities were observed. One patient experienced acute grade ≥3 haematological toxicity.

CONCLUSION

SBRT is a safe, effective and non-invasive alternative treatment option for patients with small HCCs, unsuitable for standard, evidence-based therapies and lacking complete response to transarterial chemoembolization. Randomized controlled trials are required to further investigate the role of SBRT in HCC.

[Stereotactic body radiation therapy for hepatocellular carcinoma: Results from a retrospective multicentre study]

PURPOSE

The purpose of this paper was to describe local control, overall survival, progression-free survival and toxicity of CyberKnife^®-based stereotactic body radiation therapy of hepatocellular carcinoma.

MATERIAL AND METHODS

Records of all the patients treated for hepatocellular carcinoma at the Eugene-Marquis cancer centre, Rennes and the Bretonneau hospital, Tours (France), between November 2010 and December 2016, were reviewed. Radiation therapy was performed as a salvage treatment, while awaiting liver transplantation or if no other treatment was possible.

RESULTS

One hundred and thirty-six patients were consecutively included in the study. The median follow-up was 13months. Median total dose prescribed, fractionation and overall treatment time were respectively 45Gy, three fractions and 5 days. Overall survival, progression-free survival and local control rates at 1year and 2years were 79.8 % and 63.5 %, 61.3 % and 39.4 %; 94.5 % and 91 %. Two grade 3 acute toxicity events and two grade 4 late toxicity events corresponding to a duodenal ulcer have been reported. Seven patients underwent classic radiation-induced hepatitis and 13 patients showed non-classical radiation-induced hepatitis. Barcelona Clinic Liver Cancer stage, World Health Organisation grade and planning target volume were correlated with overall survival in univariate Cox analysis.

CONCLUSION

Stereotactic body radiation therapy is effective and well-tolerated for inoperable hepatocellular carcinoma or as a bridge to liver transplantation. Toxicity is mainly related to cirrhotic background and requires a selection of patients and strict dose constraints.

Evidence for surgical resections in oligometastatic lung cancer

With the advent of advanced technology in performing diagnostics for lung cancer, an incremental increase in the number of patients with oligometastatic disease is currently being managed with intent to cure. As treatment of selected types of patients with oligometastasis show favourable outcomes, the past notion of managing these patients palliatively is fast becoming extinct. Selection of patients based on established criterion together with surgical metastasectomy combined with multiple ablative techniques with or without systemic chemotherapy offers a reasonable rate of treatment success which provides basis for treating such patient population. As more evidence becomes available to suggest that the oligometastatic state of lung cancer does exist, and are potentially curable, a better understanding of the condition is necessary for clinicians, and surgeons to provide optimal care. In this review we present some of the clinical basis which may cause a paradigm shift in management of patients with oligometastatic lung disease.

Stereotactic body radiation therapy in early-stage NSCLC: historical review, contemporary evidence and future implications

Clinical use of stereotactic body radiation therapy (SBRT) has increased dramatically over the last 2 decades and is the current standard-of-care in cases of inoperable early stage non-small-cell lung cancer. While surgical resection remains the standard-of-care for operable patients, several ongoing clinical trials are investigating the role of SBRT in these operative candidates as well. Taking into consideration the expanding role and utility of SBRT, this paper will: review the historical basis of SBRT; examine landmark trials establishing the framework for the current body of evidence; discuss areas of active and future research; and identify epidemiological trends that are likely to further increase the use of SBRT.

Stereotactic body radiation therapy for hepatocellular carcinoma: Practice patterns, dose selection and factors impacting survival

Background

Stereotactic body radiation therapy (SBRT) is an emerging option for unresectable hepatocellular carcinoma (HCC) without consensus regarding optimal dose schemas. This analysis identifies practice patterns and factors that influence dose selection and overall survival, with particular emphasis on dose and tumor size.

Materials/Methods

Query of the National Cancer Database (NCDB) identified patients with unresectable, nonmetastatic HCC who received SBRT from 2004 to 2013. Biological Effective Dose (BED) was calculated for each patient in order to uniformly analyze different fractionation regimens.

Results

A total of 456 patients met the inclusion criteria. The median BED was 100 Gy (22.5‐208.0), which corresponded to the most common dose fractionation (50 Gy in five fractions). Various factors influenced dose selection including tumor size (P < 0.001), tumor stage (P = 0.002), and facility case volume (<0.001). On multivariate analysis, low BED (<75 Gy, HR 2.537, P < 0.001; 75‐100 Gy, HR 1.986, P = 0.007), increasing tumor size (HR 1.067, P = 0.032), elevated AFP (HR 1.585, P = 0.019), stage 3 (HR 1.962, P < 0.001), low‐volume facilities (1‐5 cases HR 1.687, P = 0.006), and a longer time interval from diagnosis to SBRT (>2 to ≤4 months, HR 1.456, P = 0.048; >4 months, HR 2.192, P < 0.001) were associated with worse survival.

Conclusion

SBRT use is increasing for HCC, and multiple regimens are clinically employed. Although high BED was associated with improved outcomes, multiple factors contributed to the dose selection with favorable patients receiving higher doses. Continued efforts to enhance radiation planning and delivery may help improve utilization, safety, and efficacy.

Stereotactic Radiotherapy for Oligometastasis

Oligometastatic disease is defined as “a condition with a few metastases arising from tumors that have not acquired a potential for widespread metastases.” Its behavior suggests a transitional malignant state somewhere between localized and metastatic cancer. Treatment of oligometastatic disease is expected to achieve long-term local control and to improve survival. Historically, patients with oligometastases have often undergone surgical resection since it was anecdotally believed that surgical resection could result in progression-free or overall survival benefits. To date, no prospective randomized trials have demonstrated surgery-related survival benefits. Short courses of highly focused, extremely high-dose radiotherapies (e.g., stereotactic radiosurgery and stereotactic ablative body radiotherapy (SABR)) have frequently been used as alternatives to surgery for treatment of oligometastasis. A randomized study has demonstrated the overall survival benefits of stereotactic radiosurgery for solitary brain metastasis. Following the success of stereotactic radiosurgery, SABR has been widely accepted for treating extracranial metastases, considering its efficacy and minimum invasiveness. In this review, we discuss the history of and rationale for the local treatment of oligometastases and probe into the implementation of SABR for oligometastatic disease.

Local control rates in stereotactic body radiotherapy (SBRT) of lung metastases associated with the biologically effective dose

Aim

To evaluate dose differences in lung metastases treated with stereotactic body radiotherapy (SBRT), and the correlation with local control, regarding the dose algorithm, target volume and tissue density.

Background

Several studies showed excellent local control rates in SBRT for lung metastases, with different fractionation schemes depending on the tumour location or size. These results depend on the dose distributions received by the lesions in terms of the tissue heterogeneity corrections performed by the dose algorithms.

Materials and methods

Forty-seven lung metastases treated with SBRT, using intrafraction control and respiratory gating with internal fiducial markers as surrogates (ExacTrac, BrainLAB AG), were calculated using Pencil Beam (PB) and Monte Carlo (MC) (iPlan, BrainLAB AG).Dose differences between both algorithms were obtained for the dose received by 99% (D _99%) and 50% (D _50%) of the planning treatment volume (PTV). The biologically effective dose delivered to 99% (BED_99%) and 50% (BED_50%) of the PTV were estimated from the MC results. Local control was evaluated after 24 months of median follow-up (range: 3-52 months).

Results

The greatest variations (40.0% in ΔD _99% and 38.4% in ΔD _50%) were found for the lower volume and density cases. The BED_99% and BED_50% were strongly correlated with observed local control rates: 100% and 61.5% for BED_99% > 85 Gy and <85 Gy (p < 0.0001), respectively, and 100% and 58.3% for BED_50% > 100 Gy and <100 Gy (p < 0.0001), respectively.

Conclusions

Lung metastases treated with SBRT, with delivered BED_99% > 85 Gy and BED_50% > 100 Gy, present better local control rates than those treated with lower BED values (p = 0.001).

Stereotactic Body Radiation Therapy for Spinal Malignancies

Stereotactic body radiation therapy and stereotactic radiosurgery have become important treatment options for the treatment of spinal malignancies. A better understanding of dose tolerances with more conformal technology have allowed administration of higher and more ablative doses. In this review, the framework for approaching a patient with spinal metastases and primary tumors will be discussed as well as details on the delivery of this treatment.

Simulation of dosimetry impact of 4DCT uncertainty in 4D dose calculation for lung SBRT

Background

Due to the heterogeneity of patient’s individual respiratory motion pattern in lung stereotactic body radiotherapy (SBRT), treatment planning dose assessment using a traditional four-dimensional computed tomography (4DCT_traditional) images based on a uniform breathing curve may not represent the true treatment dose delivered to the patient. The purpose of this study was to evaluate the accumulated dose discrepancy between based on the 4DCT_traditional and true 4DCT (4DCT_true) that incorporated with the patient’s real entire breathing motion. The study also explored a novel 4D robust planning strategy to compensate for such heterogeneity respiratory motion uncertainties.

Methods

Simulated and measured patient specific breathing curves were used to generate 4D targets motion CT images. Volumetric-modulated arc therapy (VMAT) was planned using two arcs. Accumulated dose was obtained by recalculating the plan dose on each individual phase image and then deformed the dose from each phase image to the reference image. The “4 D dose” (D^4D) and “true dose” (D^true) were the accumulated dose based on the 4DCT_traditional and 4DCT_true respectively. The average worse case dose discrepancy (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{\Delta D} $$\end{document}ΔD¯) between D^4D and D^true in all treatment fraction was calculated to evaluate dosimetric /planning parameters and correlate them with the heterogeneity of respiratory-induced motion patterns. A novel 4D robust optimization strategy for VMAT (4D Ro-VMAT) based on the probability density function(pdf) of breathing curve was proposed to improve the target coverage in the presence of heterogeneity respiratory motion. The data were assessed with a paired t-tests.

Results

With increasing breathing amplitude from 5 to 20 mm, target \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{\Delta {D}_{99}} $$\end{document}ΔD99¯, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{\Delta {D}_{95}} $$\end{document}ΔD95¯ increased from 1.59,1.39 to 10.15%,8.66% respectively. When the standard deviation of breathing amplitude increased from 15 to 35% of the mean amplitude, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{\Delta {D}_{99}} $$\end{document}ΔD99¯, \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \overline{\Delta {D}_{95}} $$\end{document}ΔD95¯ increased from 4.06,3.48 to 10.25%,6.63% respectively. The 4D Ro-VMAT plan significantly improve the target dose compared to VMAT plan.

Conclusion

When the breathing curve amplitude is more than 10 mm and standard deviation of amplitude is higher than 25% of mean amplitude, special care is needed to choose an appropriated dose accumulation approach to evaluate lung SBRT plan target coverage robustness. The proposed 4D Ro_VMAT strategy based on the pdf of patient specific breathing curve could effectively compensate such uncertainties.

Clinical feasibility and efficacy of stereotactic body radiotherapy for hepatocellular carcinoma: A systematic review and meta-analysis of observational studies

BACKGROUND AND PURPOSE

Stereotactic body radiotherapy (SBRT) is an emerging ablative modality for hepatocellular carcinoma (HCC). This study aimed to synthesize available evidence to evaluate the clinical feasibility and efficacy of SBRT for HCC.

MATERIALS AND METHODS

A systematic search was performed of the PubMed, Medline, Embase, and Cochrane Library databases. Primary endpoints were overall survival (OS) and local control (LC), and the secondary endpoint was grade ≥3 complications.

RESULTS

Thirty-two studies involving 1950 HCC patients who underwent SBRT were included. Pooled 1-, 2-, and 3-year OS rates were 72.6% (95% confidence interval [CI]: 65.7-78.6), 57.8% (50.9-64.4), and 48.3% (40.3-56.5), respectively. Pooled 1-, 2-, and 3-year LC rates were 85.7% (95% CI: 80.1-90.0), 83.6% (77.4-88.3), and 83.9% (77.6-88.6), respectively. The median value of median tumor sizes among studies was 3.3 cm (range: 1.6-8.6). Median radiation doses, calculated in dose equivalent with 2 Gy per fraction, ranged from 48 to 114.8 Gy₁₀ (median 83.3 Gy₁₀). Subgroup comparison regarding tumor size showed significant differences for 1- and 2-year OS rates and 1-, 2-, and 3-year LC rates, and that regarding radiation dose showed no difference for OS and a marginal difference for 1-year LC rate. Pooled rates of hepatic and gastrointestinal grade ≥3 complications were 4.7% (95% CI: 3.4-6.5) and 3.9% (2.6-5.6), respectively. Child-Pugh class was significantly correlated with hepatic complication of grade ≥3 in meta-regression analysis (p = 0.013).

CONCLUSION

SBRT for HCC was a feasible option conferring excellent LC persisting up to 3 years. Both OS and LC were affected by tumor size, and radiation dose marginally affected LC. Severe complications rarely occurred, but liver function should be considered to avoid serious hepatic toxicity.

Developments in Stereotactic Body Radiotherapy

Stereotactic body radiotherapy is the technique of accurately delivering high doses of radiotherapy to small volume targets in a single or small number of sessions. The high biological effective dose of this treatment is reflected in the high rates of local control achieved across multiple tumour sites. Toxicity of the treatment can be significant and ongoing prospective trials will help define the utility of this treatment as an alternative to surgery in treating primary tumours and oligometastatic disease. Longer follow-up and survival data from prospective trials will be essential in determining the value of this resource-intensive treatment. The opportunity to combine this treatment with systemic therapies and its potential synergy with immunotherapy opens up interesting avenues for research in the future.