MR-guided stereotactic radiation therapy for head and neck cancers

Purpose

MR-guided radiotherapy (MRgRT) has the advantage of utilizing high soft tissue contrast imaging to track daily changes in target and critical organs throughout the entire radiation treatment course. Head and neck (HN) stereotactic body radiation therapy (SBRT) has been increasingly used to treat localized lesions within a shorter timeframe. The purpose of this study is to examine the dosimetric difference between the step-and-shot intensity modulated radiation therapy (IMRT) plans on Elekta Unity and our clinical volumetric modulated arc therapy (VMAT) plans on Varian TrueBeam for HN SBRT.

Method

Fourteen patients treated on TrueBeam sTx with VMAT treatment plans were re-planned in the Monaco treatment planning system for Elekta Unity MR-Linac (MRL). The plan qualities, including target coverage, conformity, homogeneity, nearby critical organ doses, gradient index and low dose bath volume, were compared between VMAT and Monaco IMRT plans. Additionally, we evaluated the Unity adaptive plans of adapt-to-position (ATP) and adapt-to-shape (ATS) workflows using simulated setup errors for five patients and assessed the outcomes of our treated patients.

Results

Monaco IMRT plans achieved comparable results to VMAT plans in terms of target coverage, uniformity and homogeneity, with slightly higher target maximum and mean doses. The critical organ doses in Monaco IMRT plans all met clinical goals; however, the mean doses and low dose bath volumes were higher than in VMAT plans. The adaptive plans demonstrated that the ATP workflow may result in degraded target coverage and OAR doses for HN SBRT, while the ATS workflow can maintain the plan quality.

Conclusion

The use of Monaco treatment planning and online adaptation can achieve dosimetric results comparable to VMAT plans, with the additional benefits of real-time tracking of target volume and nearby critical structures. This offers the potential to treat aggressive and variable tumors in HN SBRT and improve local control and treatment toxicity.

Role of Metastasis-Directed Therapy in Genitourinary Cancers

OPINION STATEMENT

The treatment of oligometastatic genitourinary cancers is a rapidly advancing field with ablative radiotherapy as one of the critical treatment components. The oligometastatic disease state, which can be defined as 1-5 metastatic sites with a controlled primary, represents a distinct clinical state where comprehensive ablative local therapies may provide improved outcomes. Enhanced imaging has increased the number of patients identified with oligometastatic disease. Evidence for improved outcomes with metastasis-directed therapy (MDT) in oligometastatic genitourinary cancers is increasing, and previously published outcome data continues to mature with an increasing body of prospective data to inform the role of MDT in histology-specific settings or in the context of systemic therapy. In select patients, MDT can offer benefits beyond improved local control and allow for time off of systemic therapy, prolonged time until next therapy, or even the hope of cure. However, treatment decisions for locally ablative therapy must be balanced with consideration towards safety. There are exciting advances in technologies to target and adapt treatment in real-time which have expanded options for safer delivery and dose escalation to metastatic targets near critical organs at risk. The role of systemic therapies in conjunction with MDT and incorporation of tumor genetic information to further refine prognostication and treatment decision-making in the oligometastatic setting is actively being investigated. These developments highlight the evolving field of treatment of oligometastatic disease. Future prospective studies combining MDT with enhanced imaging and integrating MDT with evolving systemic therapies will enable the optimal selection of patients most likely to benefit from this "all-or-none" approach and reveal settings in which a combination of therapies could result in synergistic outcomes.

Role of Stereotactic Body Radiation Therapy in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC)is a common type of liver cancer with a poor prognosis, especially in patients with advanced stages or underlying liver disease. While surgical resection, liver transplantation, and ablation therapies have traditionally been the mainstay of treatment for HCC, radiation therapy has become increasingly recognized as an effective alternative, particularly for those who are not surgical candidates. Stereotactic Body Radiation Therapy (SBRT) is a highly precise form of radiation therapy that delivers very high doses of radiation to the tumor while sparing surrounding healthy tissue. Several studies have reported favorable outcomes with SBRT in HCC treatment. Moreover, SBRT can be used to treat recurrent HCC after prior treatment, offering a potentially curative approach in select cases. While SBRT has demonstrated its efficacy and safety in treating HCC, future studies are needed to further investigate the potential role of SBRT in combination with other treatments for HCC.

MR-guided prostate SBRT in prostate cancer patients with low-volume metastatic disease

BACKGROUND

Recent data have found an overall survival benefit from prostate-directed radiotherapy in patients with low-volume metastatic prostate cancer. Prostate SBRT is an attractive treatment in this setting and may be optimised with MR-guided adaptive treatment. Here, we share our institutional experience delivering stereotactic MR-guided adaptive prostate SBRT (SMART) for patients with low-volume metastatic disease.

METHODS

We reviewed patients with low-volume metastatic disease who received prostate SMART from October 2019 to December 2021 on a 0.35T MR-Linac. The cohort included 14 patients. Genitourinary (GU) and gastrointestinal (GI) toxicities were assessed using CTCAE v 5.0. Progression was defined as a change in systemic or hormonal therapy regimen as a result of PSA rise or disease progression.

RESULTS

The median follow-up time was 29 months. Seven patients had hormone sensitive prostate cancer and 7 had castrate resistant prostate cancer (CRPC). 13 patients received 36.25 Gy in 5 fractions and one patient received 33 Gy in 5 fractions. At the time of last follow-up, 11 patients had not experienced progression and three patients, all with CRPC, had experienced progression. No patients developed local progression in the prostate after SMART. One patient experienced acute grade 2 urinary toxicity (7%) and no patients experienced acute grade 2 GI toxicity (0%). No grade 3 + acute toxicities were observed.

CONCLUSIONS

Prostate SMART was found to be well tolerated and all patients had local control of disease within the prostate at the time of last follow-up. Prostate SMART may represent a low-risk and well-tolerated approach for delivering prostate-directed radiotherapy for patients with limited metastatic disease.

Definitive ablative stereotactic partial breast irradiation in early stage inoperable breast cancer

PURPOSE

This case series and literature review aims to investigate the efficacy and safety of definitive ablative radiation therapy as a treatment modality for non-operable patients with early stage breast cancer. We present two cases demonstrating the potential of this approach to achieve durable responses.

METHODS

We assessed the long-term response of two non-operable patients diagnosed with Stage II (cT2N0M) and Stage IA (T1bN0M0) invasive ductal carcinoma (IDC), who were deemed unfit for surgery due to significant co-morbid conditions. Definitive ablative radiation therapy was administered using stereotactic partial breast irradiation with ablative doses delivered in either a single fraction or two fractions. Serial imaging was conducted to assess treatment response and monitor adverse events.

RESULTS

Both patients exhibited notable treatment responses following definitive ablative radiation therapy. The first patient, an 84-year-old woman, experienced a 69% reduction in tumor size over a follow-up period exceeding 2 years. The second patient, an 87-year-old woman, achieved complete resolution of disease on imaging, with no signs of progression even 26 month post-treatment. Both patients tolerated the treatment well, without significant treatment-related adverse events.

CONCLUSIONS

Our case series suggests that definitive ablative radiation therapy may serve as a safe and effective treatment option for non-operable patients with early stage breast cancer. The observed durable treatment responses and minimal toxicity support the potential of this approach. Furthermore, a longer interval between ablative radiation therapy and surgery may enhance treatment response, potentially leading to increased complete pathologic response rates.

Target volume size effect on comparison of dynamic arc treatment plans computed using flattened and unflattened 6MV beams

INTRODUCTION/BACKGROUND

In conventional linear accelerators, to obtain flat profiles leading to uniform dose distribution in homogeneous medium, the flattening filter is usually applied on the beam path. In recent years, to obtain higher dose rates, there have been the options of flattening filter free (FFF) beams and it has been noticed that these have many advantages. The aim of this study was to clearly underline the advantages and the drawbacks of flattened filter free (FFF) beams in comparison with the flattening filter (FF) beams for different clinical contexts (planning target volumes locations).

METHODS

Two groups (planned with auto-planning VMAT, full and partial arcs) of eight patients each were analyzed: Group I (small planning target volume PTV, with average volume 48.9 ±44.4 cm³), Group II (large PTV, with average volume 532.4 ±368.8 cm³). Both beam modalities 6MV and 6MVFFF were compared in terms of Dmax, D95%, D1cc, D2cc, homogeneity index (HI), number of monitor units (MU), treatment delivery time.

RESULTS

Using the 6MVFFF, the treatment delivery time was significantly reduced (p<0.05). For larger PTVs, the number of MU increased by more than twice, and the p-value shown a significant difference (p= 0.008). The value of Dmax increased by 4%. On the contrary, for small volumes, the results were quite similar from 6MVFFF to 6MV except some differences in terms of MU.

CONCLUSION

It is recommended to use 6MVFFF beam with small PTV volumes. Dose distributions are almost the same as with 6MV and there is a significant reduction of the treatment delivery time up to 57%. Due to the dose profile shape in FFF mode, the dose is lowered beyond the central axis for the FFF beams, and the additional MU allows the dose to be delivered away from the beam axis.

Recall of reactive cutaneous capillary endothelial proliferation (RCCEP) induced by stereotactic body radiation therapy (SBRT) in a patient with lung squamous cell carcinoma

Camrelizumab (SHR-1210) is a humanized IgG4 monoclonal anti-programmed cell death protein 1 (PD-1) antibody that has been shown to inhibit the binding of PD-1 to PD-L1, thereby blocking the immune escape of various types of cancer, including lung squamous cell carcinoma (LSCC). Reactive cutaneous capillary endothelial proliferation (RCCEP) is the most common adverse event in camrelizumab-treated patients. Here, we introduce a case of LSCC with recall RCCEP induced by stereotactic body radiation therapy (SBRT). A 76-year-old LSCC patient developed RCCEP when he received camrelizumab and chemotherapy. After discontinuing camrelizumab treatment, the RCCEP lesions spontaneously regressed and fell off. However, when the patient received subsequent SBRT, the RCCEP occurred again at the same sites. This case may provide clues for additional study of the immune reactivation effect of SBRT or the underlying mechanism of RCCEP.

Stereotactic body radiation therapy for metastatic lung metastases

Although systemic therapy is standard management for patients with metastatic disease, several recent reports have indicated that an addition of local therapies including stereotactic body radiation therapy (SBRT) for patients with oligometastatic disease (OMD) could improve survival. The lung is the most common site of distant metastasis from many solid tumors, and the strategy of SBRT, such as dose-fraction schedules, timing, etc., would be different depending on the type of primary tumor, location, and patterns of OMD. This review describes the role of SBRT with curative-intent for patients with pulmonary OMD for each of these variables. First, differences according to the type of primary tumor, for which many studies suggest that SBRT-mediated local control (LC) for patients with pulmonary OMD from colorectal cancer (CRC) is less successful than for those from non-CRC tumors. In addition, higher dose-fraction schedules seemed to correlate with higher LC; hence, different SBRT treatment strategies may be needed for patients with pulmonary OMD from CRC relative to other tumors. Second, differences according to location, where the safety of SBRT for peripheral pulmonary tumors has been relatively well established, but safety for central pulmonary tumors including pulmonary OMD is still considered controversial. To determine the optimal dose-fraction schedules, further data from prospective studies are still needed. Third, differences according to the patterns of OMD, the number of metastases and the timing of SBRT whereby 1–5 lesions in most patients and patients with synchronous or metachronous OMD are considered good candidates for SBRT. We conclude that there are still several problems in defining suitable indications for local therapy including SBRT, and that further prospective studies are required to resolve these issues.

Stereotactic body radiation therapy (SBRT) for lung metastases from sarcoma in oligometastatic patients: a phase 2 study

PURPOSE

Lung is the most frequent site of metastasis in sarcoma patients. Pulmonary metastasectomy is the most common treatment performed. Stereotactic body radiation therapy(SBRT) has proven to be a potential alternative to resection. We aimed to assess role of SBRT for lung metastatic patients in a prospective phase 2 study.

METHODS AND MATERIALS

Adults patients with lung metastasis(LMs) up to 4, ≤5cm, unsuitable for surgery were included. Dose prescription was based on site and size: 30Gy/1fraction for peripheral lesions ≤10mm, 60 Gy/3fractions for peripheral lesions 11-20mm, 48 Gy/4fractions for peripheral lesions >20mm, and 60 Gy/8fractions for central lesions. Primary endpoint was proportion of treated lesions free from progression at 12 months. Secondary endpoints were disease free survival(DFS), overall survival(OS), and toxicity.

RESULTS

Between March 2015, and December 2020, 44 patients for 71 LMs were enrolled. Twelve-month local control was 98.5%±1.4, reaching primary aim; median DFS time,1,2,3,4,5-year PFS rates were 12 months(95%CI 8-16 months), 50%±7.5, 19.5%±6.6, 11.7%±5.8, 11.7%±5.8, and 11.7%±5.8, respectively. Median OS time,1,2,3,4,5-year OS rates were 49 months(95%CI 24-49 months), 88.6%±4.7, 66.7±7.6, 56.8%±8.4, 53.0%±8.6, and 48.2%±9.1, respectively. Prognostic factors recorded as significantly impacting survival were age, grade of primary sarcoma, interval time from diagnosis to occurrence of LMs, and number of LMs. No severe pulmonary toxicity(grade 3-4) occurred.

CONCLUSIONS

We found a local control of LMs in almost all patients treated, with negligible toxicity. Survival was also highly satisfactory. Well-designed randomized trials comparing surgery with SBRT for lung metastatic sarcoma patients are needed to confirm this preliminary data.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier XXXXXX.

MRI features of treated hepatocellular carcinoma following locoregional therapy: a pictorial review

Hepatocellular carcinoma (HCC) is a leading cause of cancer death worldwide and within the United States. Liver transplant or partial liver resection is the definitive treatment of choice for HCC; however, the majority of cases are detected in advanced stages due to its early-stage asymptomatic nature, often precluding surgical treatment. Locoregional therapy plays an essential role in HCC management, including curative intent, as a bridge to transplant, or in some cases palliative therapy. Radiologists play a critical role in assessing tumor response following treatment to guide further management that may potentially impact transplantation eligibility; therefore, it is important for radiologists to have an understanding of different locoregional therapies and the variations of imaging response to different therapies. In this review article, we outline the imaging response to ablative therapy (AT), transarterial chemoembolization (TACE), selective internal radiation therapy (SIRT), and stereotactic body radiation therapy (SBRT). We will also briefly discuss the basic concepts of these locoregional therapies. This review focuses on the imaging features following locoregional treatment for hepatocellular carcinoma following AT, TACE, SIRT, and SBRT.

Stereotactic body radiation therapy for the treatment of locally recurrent pancreatic cancer after surgical resection

Background

To report on a cohort of radiation-naïve patients with pancreatic cancer who developed isolated local recurrence following surgical resection and were subsequently treated with stereotactic body radiation therapy (SBRT).

Methods

Patients with pancreatic cancer who were treated with SBRT for isolated local recurrence after surgical resection were retrospectively reviewed. Clinical outcomes were calculated from completion of SBRT and included overall survival (OS), local progression-free survival (LPFS), distant metastasis-free survival (DMFS), and progression-free survival (PFS). Univariate (UVA) analysis was performed to identify variables associated with clinical outcomes. Kaplan-Meier method was used for survival outcomes. Toxicity was assessed using the Common Terminology Criteria for Adverse Events version 4.0.

Results

From September 2012 to November 2018, a total of 19 patients with localized pancreatic cancer were treated with SBRT for isolated local recurrence after initial surgical resection. No patients had prior radiation. The median biologically effective dose (BED10) was 54.8 Gy (range, 37.5-54.8 Gy). Median OS was 17.1 months, with 6-month and 1-year OS rates of 94.4% and 69.6%, respectively. Nine patients (47.4%) developed local failure after SBRT. Pattern of first failure after SBRT was distant in 7 patients (46.7%), local in 5 patients (33.3%), and synchronous distant and local in 3 patients (20.0%). One patient developed local failure after developing distant disease first. Of the 9 local failures, 3 (33.3%) were out-of-field. Median LPFS was 22.2 months, with 6-month and 1-year LPFS rates of 86.9% and 63.2%, respectively. A BED10 <54.8 Gy was associated with inferior LPFS (1-year, 25.0% vs. 80.2%, P<0.009). Median DMFS and PFS were 15.6 months. There was 1 case (5.3 %) of grade 3 gastric perforation. There were no cases of grade 4-5 toxicity events.

Conclusions

SBRT for locally recurrent pancreatic cancer after initial curative resection is safe and feasible. A BED10 <54.8 Gy was significantly associated with inferior local control. Further studies investigating dose escalation and optimal treatment volumes in the locally recurrent setting are warranted.

High neutrophil-to-lymphocyte ratio following stereotactic body radiation therapy is associated with poor clinical outcomes in patients with borderline resectable and locally advanced pancreatic cancer

BACKGROUND

The purpose of this study is to report on the prognostic role of pre- and post-stereotactic body radiation therapy (SBRT) neutrophil-to-lymphocyte ratio (NLR) in a cohort of patients with borderline resectable (BRPC) and locally advanced pancreatic cancer (LAPC) who was treated with multi-agent induction chemotherapy followed by five-fraction SBRT.

METHODS

Patients treated with multi-agent induction chemotherapy followed by SBRT from August 2016 to January 2019 and who had laboratory values available for review were included in the study. Univariate (UVA) and multivariate analyses (MVA) were performed to determine associations between pre-/post-SBRT NLR and overall survival (OS), local progression-free survival (LPFS), distant metastasis-free survival (DMFS), and progression-free survival (PFS).

RESULTS

A total of 156 patients were treated with multi-agent induction chemotherapy followed by SBRT and had laboratory values available for review. On UVA, chemotherapy duration ≥4 months, poorly differentiated disease, inability to undergo resection, pre-SBRT ANC ≥3.7 No./µL, pre-SBRT NLR ≥2.3, and post-SBRT NLR ≥2.6 were associated with worse OS. Patients with post-SBRT NLR ≥2.6 had a median OS of 16.7 months versus median OS not yet reached in patients with post-SBRT <2.6 (P=0.009). On MVA, poorly differentiated disease [hazard ratio (HR) =1.82, 95% CI: 1.04-3.18, P=0.035], inability to undergo resection (HR =2.17, 95% CI: 1.25-3.70, P=0.006), and post-SBRT NLR ≥2.6 (HR =2.55, 95% CI: 1.20-5.45, P=0.015) were associated with inferior OS. On UVA, baseline CA 19-9 ≥219 U/mL, pre-SBRT platelet count ≥157×1,000/µL, and post-SBRT NLR ≥2.6 were associated with inferior LPFS. Patients with post-SBRT NLR ≥2.6 had a median LPFS of 18.3 months versus median LPFS not yet reached in patients with post-SBRT <2.6 (P=0.028). On MVA, only post-SBRT NLR ≥2.6 was associated with worse LPFS (HR =3.22, 95% CI: 1.04-9.98, P=0.043).

CONCLUSIONS

Post-SBRT NLR ≥2.6 predicted for inferior OS and LPFS in BRPC/LAPC patients treated with multi-agent chemotherapy and SBRT. These findings highlight the importance of further elucidating the immunologic effects of radiation therapy in this setting, which may have significant implications on both radiation design as well as combination strategies.

Refining the definition of biochemical failure in the era of stereotactic body radiation therapy for prostate cancer: The Phoenix definition and beyond

BACKGROUND AND PURPOSE

The Phoenix definition for biochemical failure (BCF) after radiotherapy uses nadir PSA (nPSA) + 2 ng/mL to classify a BCF and was derived from conventionally fractionated radiotherapy, which produces significantly higher nPSAs than stereotactic body radiotherapy (SBRT). We investigated whether an alternative nPSA-based threshold could be used to define post-SBRT BCFs.

MATERIALS AND METHODS

PSA kinetics data on 2038 patients from 9 institutions were retrospectively analyzed for low- and intermediate-risk PCa patients treated with SBRT without ADT. We evaluated the performance of various nPSA-based definitions. We also investigated the relationship of relative PSA decline (rPSA, PSA_18month/PSA_6month) and timing of reaching nPSA + 2 with BCF.

RESULTS

Median follow-up was 71.9 months. BCF occurred in 6.9% of patients. Median nPSA was 0.16 ng/mL. False positivity of nPSA + 2 was 30.2%, compared to 40.9%, 57.8%, and 71.0% for nPSA + 1.5, nPSA + 1.0, and nPSA + 0.5, respectively. Among patients with BCF, the median lead time gained from an earlier nPSA + threshold definition over the Phoenix definition was minimal. Patients with BCF had significantly lower rates of early PSA decline (mean rPSA 1.19 vs. 0.39, p < 0.0001) and were significantly more likely to reach nPSA + 2 ≥ 18 months (83.3% vs. 21.1%, p < 0.0001). The proposed criterion (rPSA ≥ 2.6 or nPSA + 2 ≥ 18 months) had a sensitivity and specificity of 92.4% and 81.5%, respectively, for predicting BCF in patients meeting the Phoenix definition and decreased its false positivity to 6.4%.

CONCLUSION

The Phoenix definition remains an excellent definition for BCF post-SBRT. Its high false positivity can be mitigated by applying additional criteria (rPSA ≥ 2.6 or time to nPSA + 2 ≥ 18 months).

SEOR SBRT-SG stereotactic body radiation therapy consensus guidelines for non-spine bone metastasis

The use of stereotactic body radiation therapy (SBRT) to treat non-spine bone metastases (NSBM) is becoming increasingly common in clinical practice. The clinical advantages of SBRT include good pain control and high local control rates, although only limited data are available. The Spanish Society of Radiation Oncology (SEOR) SBRT group recently convened a task force of experts in the field to address key questions related to SBRT for NSBM, including treatment indications, planning, techniques, and dose fractionation. The task force reviewed the available literature to develop evidence-based recommendations for the safe application of NSBM SBRT and to standardize and optimize SBRT processes. The present document provides a comprehensive analysis of the available data, including ongoing clinical trials and controversies, providing clinically applicable recommendations.

Five-year outcomes of stereotactic body radiation therapy (SBRT) for prostate cancer: the largest experience in China

Objective

To evaluate the efficacy and safety of SBRT for localized prostate cancer (PCa) with CyberKnife in China. Moreover, it is the largest-to-date pilot study to report 5-year outcomes of SBRT for localized PCa from China.

Methods

In this retrospective study, 133 PCa patients in our center were treated by SBRT with CyberKnife (Accuray Inc., Sunnyvale, USA) from October 2012 to July 2019. Follow-up was performed every 3 months for efficacy and toxicity evaluation. Biochemical progression-free survival (bPFS) and toxicities were assessed using the Phoenix definition and the Common Terminology Criteria for Adverse Events (CTCAE) v.5.0, respectively. Factors predictive of bPFS were identified with COX regression analysis.

Results

133 patients (10 low-, 21 favorable intermediate-, 31 unfavorable intermediate-, 45 high-, and 26 very high risk cases on the basis of NCCN risk classification) with a median age of 76 years (range 54–87 years) received SBRT. The median dose was 36.25 Gy (range 34–37.5 Gy) in 5 fractions. Median follow-up time was 57.7 months (3.5–97.2 months). The overall 5-year bPFS rate was 83.6% for all patients. The 5-year bPFS rate of patients with low-, favorable intermediate-, unfavorable intermediate-, high-, and very high risk PCa was 87.5%, 95.2%, 90.5%, 86.3%, and 61.6%, respectively. Urinary symptoms were all alleviated after SBRT. All patients tolerated SBRT with 1 (0.8%) patient reporting grade-3 acute and 1 (0.8%) patient reporting grade-3 late genitourinary (GU) toxicity, respectively. There were no grade 4 toxicities. Gleason score (P < 0.001, HR = 7.483, 95%CI: 2.686–20.846) was the independent predictor of bPFS rate after multivariate analysis.

Conclusion

SBRT is an efficient and safe treatment modality for localized PCa with high 5-year bPFS rates and acceptable toxicities.

A narrative review of combined stereotactic ablative radiotherapy and immunotherapy in metastatic non-small cell lung cancer

Immune checkpoint inhibitors (ICIs) have significantly improved overall survival (OS) in metastatic non-small cell lung cancer (m-NSCLC). However, not all patients with m-NSCLC benefit from ICIs, and resistance to ICIs is an emerging challenge. The tumour microenvironment (TME) is immunosuppressive, and provides a myriad of mechanisms to facilitate escape of cancer cells from immune surveillance. The TME may also dampen the response to ICIs by inhibiting T cell effector responses. The poor prognosis of m-NSCLC has led to investigation of ICIs combined with other treatments with the intention of modulating the TME and sensitizing tumours to the effects of ICIs. Stereotactic ablative radiotherapy (SABR) in combination with ICIs is an area of intense interest. SABR is thought to evoke a pro-immunogenic response in the TME, with the capacity to turn a “cold”, unresponsive tumour to “hot” and receptive to ICI. In addition to improved local response, SABR is postulated to produce a heightened systemic immune response when compared to conventional radiotherapy (RT). Preclinical studies have demonstrated a synergistic effect of SABR + ICIs, and clinical studies in m-NSCLC showed safety and promising efficacy compared to systemic therapies alone. To optimize ICI + SABR, ICI choice, combinations, dosing and length of treatment, as well as sequencing of ICI + SABR all require further investigation. Appropriate sequencing may depend on the ICI(s) being utilized, with differing sites of metastases possibly eliciting differing immune responses. Single versus multisite radiation is controversial, whilst effects of irradiated tumour volume and nodal irradiation are increasingly recognized. Taken together, there is strong preclinical and biological rationale, with emerging clinical evidence, supporting the strategy of combining SABR + ICIs in m-NSCLC.

Stereotactic radiotherapy for early stage non-small cell lung cancer: current standards and ongoing research

Stereotactic body radiation therapy (SBRT) allows for the non-invasive and precise delivery of ablative radiation dose. The use and availability of SBRT has increased rapidly over the past decades. SBRT has been proven to be a safe, effective and efficient treatment for early stage non-small cell lung cancer (NSCLC) and is presently considered the standard of care in the treatment of medically or functionally inoperable patients. Evidence from prospective randomized trials on the optimal treatment of patients deemed medically operable remains owing, as three trials comparing SBRT to surgery in this cohort were terminated prematurely due to poor accrual. Yet, SBRT in early stage NSCLC is associated with favorable toxicity profiles and excellent rates of local control, prompting discussion in regard of the treatment of medically operable patients, where the standard of care currently remains surgical resection. Although local control in early stage NSCLC after SBRT is high, distant failure remains an issue, prompting research interest to the combination of SBRT and systemic treatment. Evolving advances in SBRT technology further facilitate the safe treatment of patients with medically or anatomically challenging situations. In this review article, we discuss international guidelines and the current standard of care, ongoing clinical challenges and future directions from the clinical and technical point of view.

Survival Benefits and Disparities in Adjuvant Radiation Therapy for Patients with Pancreatic Cancer

BACKGROUND

The effects of adjuvant radiation therapy on pancreatic cancer outcomes after resection are not well defined in the literature.

METHODS

We abstracted data from the Surveillance, Epidemiology, and End Result (SEER) database to explore the impact of adjuvant radiation on cancer-specific survival in pancreatic cancer patients who received surgical resection.

RESULTS

A total of 10,224 patients met our inclusion criteria with 6768 (66.2%) patients treated with surgery only and 3456 (33.8%) treated with surgery plus adjuvant radiation. Surgery followed by adjuvant radiation was associated with significantly improved survival (HR: 0.753, CI: 0.718-0.789, p<0.001). Additionally, female gender and married status were both independently associated with better survival (p<0.05), while advanced age, Caucasian race, higher TNM stage, and higher grade had worse survival outcomes (p<0.05) Asian and Spanish-Hispanic-Latino patients were less likely to receive adjuvant radiotherapy (p<0.05).

CONCLUSION

Adjuvant radiation was associated with significantly improved survival after resection for pancreatic cancer. There are significant differences in the patient populations who receive adjuvant radiation.

New Potential Options for SBRT in Pancreatic Cancer

Stereotactic body radiotherapy (SBRT) is an emerging treatment option for patients with pancreatic cancer, as it can provide a therapeutic benefit with significant advantages for patients' quality of life over standard conventional chemoradiation (CRT). The objective of this review is to present alternative clinical settings in which SBRT may benefit patients with pancreatic cancer. These include palliation of pain, elderly patients who are not surgical candidates, local therapy in oligometastatic cases and salvaging local failures after surgery or external beam radiation. We will review these individually and provide supporting literature for each.

Stereotactic body radiation therapy (SBRT) for patients with stage I non-small cell lung cancer is applicable to more tumors than sublobar resection

Background

Virtually all patients with medically inoperable stage I non-small cell lung cancer (NSCLC) can receive stereotactic body radiation therapy. However, the percentage of such patients in whom sublobar resection is technically feasible is unknown. This discrepancy can confound clinical trial eligibility and designs comparing stereotactic body radiation therapy vs. sublobar resection.

Methods

A total of 137 patients treated with stereotactic body radiation therapy for lung lesions (3/2013–11/2017) underwent retrospective review. Diagnostic CT chest and PET/CT images, stereotactic body radiation therapy dates, and demographic data were collected on 100 of 137 patients. Two experienced board-certified thoracic surgeons independently reviewed anonymized patients’ pre-stereotactic body radiation therapy diagnostic imaging and completed a custom survey about the technical feasibility of sublobar resection for each patient. Interrater agreement was measured using Cohen’s kappa coefficient by bootstrap methodology. Summary statistics were performed for baseline demographics and tumor characteristics.

Results

Of the 100 patients, 57% were female, with median age of 75 years (range, 52–95 years) and Karnofsky Performance Status of 80 (range, 40–100). Most patients (61%) had Stage IA1, T1a tumors. For interrater agreement analysis, one patient was removed from each cohort due to inability to locate tumor on images, leaving 98 patients analyzed. Comparing Surgeon #1 vs. Surgeon #2, 64 (65.3%) vs. 69 (70.3%) of tumors were thought eligible for sublobar resection, respectively (κ=0.414).

Conclusions

Stereotactic body radiation therapy for stage I NSCLC is applicable to more tumors than sublobar resection, with ~30–35% of stereotactic body radiation therapy patients unable to undergo sublobar resection assessed by pretreatment diagnostic imaging based on technical grounds. This study illustrates that clinical trials comparing stereotactic body radiation therapy vs. sublobar resection are limited to only a subpopulation of patients with stage I NSCLC.

A phase II trial proposal of total neoadjuvant treatment with primary chemotherapy, stereotactic body radiation therapy, and intraoperative radiation therapy in borderline resectable pancreatic adenocarcinoma

BACKGROUND

The current management guidelines recommend that patients with borderline resectable pancreatic adenocarcinoma (BRPC) should initially receive neoadjuvant chemotherapy. The addition of advanced radiation therapy modalities, including stereotactic body radiation therapy (SBRT) and intraoperative radiation therapy (IORT), could result in a more effective neoadjuvant strategy, with higher rates of margin-free resections and improved survival outcomes.

METHODS/DESIGN

In this single-center, single-arm, intention-to-treat, phase II trial newly diagnosed BRPC will receive a "total neoadjuvant" therapy with FOLFIRINOX (5-fluorouracil, irinotecan and oxaliplatin) and hypofractionated SBRT (5 fractions, total dose of 30 Gy with simultaneous integrated boost of 50 Gy on tumor-vessel interface). Following surgical exploration or resection, IORT will be also delivered (10 Gy). The primary endpoint is 3-year survival. Secondary endpoints include completion of neoadjuvant treatment, resection rate, acute and late toxicities, and progression-free survival. In the subset of patients undergoing resection, per-protocol analysis of disease-free and disease-specific survival will be performed. The estimated sample size is 100 patients over a 36-month period. The trial is currently recruiting.

TRIAL REGISTRATION

NCT04090463 at clinicaltrials.gov.

Natural history of hepatocellular carcinoma after stereotactic body radiation therapy

PURPOSE

To determine the long-term natural history of size change in SBRT-treated HCC to identify an imaging biomarker to help assess treatment response.

METHODS

This was a retrospective cohort study of consecutive HCCs treated with SBRT from January 2008 to December 2016 with either 2 years post-treatment MRI follow-up or post-treatment resection histology. Size, major features for HCC, and mRECIST and LI-RADS v.2018 treatment response criteria were assessed at each post-treatment MRI. Local progression, distant progression, and survival were modeled with Kaplan Meier analyses.

RESULTS

56 HCCs met inclusion criteria. Mean baseline HCC diameter was 30 mm (range: 9-105 mm). At 3 months, 76% (N = 43) of treated HCCs decreased in size (mean reduction: 8 mm, range: 5-99 mm) and 0% (N = 0) increased in size. By 24 months, 11% (N = 5) had increased in size and were considered local progression. APHE remained in 77% (43/56) at 3 months, 38% (19/50) at 12 months, and 23% (11/47) at 24 months. mRECIST-defined viable disease was observed in 77% (43/56) at 3 months and 20% (9/47) at 24 months. LI-RADS v.2018 criteria identified viable or equivocal disease in 0% at 3 months and 10% (5/47) at 24 months.

CONCLUSION

Gradual loss of APHE and slow decrease in size are normal findings in HCCs treated with SBRT, and persistent APHE does not indicate viable disease. mRECIST is not accurate in the assessment of HCC after SBRT due to an overreliance on APHE to define viable disease. Increasing mass size or new nodular APHE at the treatment site may indicate local progression.

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.

Feasibility of High-Intensity Focused Ultrasound for Hepatocellular Carcinoma after Stereotactic Body Radiation Therapy: Initial Experience

The purpose of this initial clinical observation was to investigate the safety and effect of high-intensity focused ultrasound (HIFU) for patients with hepatocellular carcinoma (HCC) after stereotactic body radiation therapy (SBRT). Twenty patients who had been treated with SBRT, with 24 local residuals, received HIFU ablation. The changes of periphery blood cell count and serum biochemistry were observed before HIFU and 1 week after. Contrast-enhanced magnetic resonance imaging before HIFU and 2 weeks after was performed to assess the effect of HIFU. All patients received follow-up. The mean ± standard deviation follow-up time was 19.3 ± 18.0 mo. The median survival time and 1-y survival rate were 21 mo and 76.2%. Seventeen residual lesions (70.8%) received complete ablation and seven received partial ablation, with a mean ablation ratio of 75.8% ± 18.2%. No significant differences were found in periphery blood cell counts or serum biochemistry 1 week after HIFU compared with before HIFU. No severe adverse reactions related to HIFU were observed. Thus, we believe that HIFU can safely and effectively ablate residual HCC after SBRT, which may be a feasible option for patients with HCC who have local residuals after SBRT.

Pulmonary oligometastases treated by stereotactic body radiation therapy (SBRT): a single institution's experience

Background

To investigate the effect of stereotactic body radiation therapy (SBRT) on pulmonary oligometastases and to analyze the clinical factors and dose parameters affecting local recurrence-free survival (LRFS) and overall survival (OS).

Methods

This study retrospectively enrolled a total of 84 patients (148 lesions) treated in our department from May 2015 to November 2018. Pulmonary oligometastases was defined as up to 5 metastatic lesions in the lung and with both the primary tumor and any extra-thoracic metastases being controlled. Patients receiving a BED₁₀ (biological effective dose, α/β =10) of SBRT ≥75 Gy and a dose/fraction ≥4 Gy were enrolled. The patient group consisted of 52 men (61.9%) and 32 women (38.1%), with a median age 56 years (range, 29-80 years). Median tumor diameter was 1.71cm (range, 1.2-5.0 cm). The BED₁₀ was 75-119 Gy in 4-15 fractions. Univariate and multivariate Cox regression analyses were performed on factors predicting the outcomes.

Results

All patients completed the treatment as planned, and the median follow-up time was 20.3 months. The median OS for the entire group was 34.3 months, with an actuarial 1-, 2-, 3- and 5-year OS of 74.7%, 59.4%, 49.7%, and 36.8%, respectively. Among the 148 lesions in the whole group, 19 (12.8%) lesions had local recurrence (LR). The median LRFS time for all patients was 56.9 months. The LRFS rate was 93.6%, 83.5%, 81.4%, and 76.6% at 1, 2, 3, and 5 years, respectively. No patient developed acute grade 3 or 4 toxicity. On univariate analysis, age ≥63 years old, primary site of colorectal cancer, BED₁₀ <85.2 Gy, pathological type of adenocarcinoma, planning target volume (PTV) min BED₁₀ <76.6 Gy, and gross tumor volume (GTV) ≥8.8 cc, were significantly associated with poorer LRFS. Multivariate analysis showed that age ≥63 years old, primary site of colorectal cancer, and PTV min BED₁₀ <76.6 Gy were significant risk factors affecting LRFS.

Conclusions

SBRT is feasible for pulmonary oligometastasis with favorable local control and minimal toxicity. Multiple dose parameters, instead of a prescription dose only, in combination with clinical parameters, should be considered for optimal local control.

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.

SBRT combined with PD-1/PD-L1 inhibitors in NSCLC treatment: a focus on the mechanisms, advances, and future challenges

Immune checkpoint inhibitors targeting programmed cell death 1 (PD-1), programmed cell death ligand-1 (PD-L1), and others have shown potent clinical efficacy and have revolutionized the treatment protocols of a broad spectrum of tumor types, especially non–small-cell lung cancer (NSCLC). Despite the substantial optimism of treatment with PD-1/PD-L1 inhibitors, there is still a large proportion of patients with advanced NSCLC who are resistant to the inhibitors. Preclinical and clinical trials have demonstrated that radiotherapy can induce a systemic antitumor immune response and have a great potential to sensitize refractory “cold” tumors to immunotherapy. Stereotactic body radiation therapy (SBRT), as a novel radiotherapy modality that delivers higher doses to smaller target lesions, has shown favorable antitumor effects with significantly improved local and distant control as well as better survival benefits in various solid tumors. Notably, research has revealed that SBRT is superior to conventional radiotherapy, possibly because of its more powerful immune activation effects. Thus, PD-1/PD-L1 inhibitors combined with SBRT instead of conventional radiotherapy might be more promising to fight against NSCLC, further achieving more favorable survival outcomes. In this review, we focus on the underlying mechanisms and recent advances of SBRT combined with PD-1/PD-L1 inhibitors with an emphasis on some future challenges and directions that warrant further investigation.

Dosimetric comparison between RapidArc and HyperArc techniques in salvage stereotactic body radiation therapy for recurrent nasopharyngeal carcinoma

Background

To evaluate dosimetric differences of salvage irradiations using two commercially available volumetric modulated arc therapy (VMAT) stereotactic body radiation therapy (SBRT) techniques: RapidArc (RA) and HyperArc (HA), for recurrent nasopharyngeal carcinoma (NPC) after initial radiation therapy.

Methods

Ten patients with recurrent NPC status previously treated with radiation therapy were considered suitable candidates for salvage SBRT using VMAT approach. Two separate treatment plans were created with HA and RA techniques for each case, with dosimetric outcomes compared with respect to tumor target coverage and organs-at-risk (OARs) sparing. Furthermore, the cumulative radiobiological effects to the relevant OARs from the original radiotherapy to the respective salvage SBRT plans were analyzed in terms of biologically effective dose (BED).

Results

Treatment with HA exhibited similar target dose coverage as with RA, while delivering a higher mean dose to the targets. Using RA technique, the mean maximal doses to optic apparatus and the mean brain dose were reduced by 1 to 1.5 Gy, comparing to HA technique. The conformity index, gradient radius, and intermediate dose spillage in HA plans were significantly better than those in RA. With HA technique, the volume of brain receiving 12 Gy or more was reduced by 44%, comparing to RA technique. The cumulative BEDs to spinal cord and optic apparatus with RA technique were 1 to 2 Gy₃ less than those with HA. HA technique significantly reduced the volume within body that received more than 100 Gy.

Conclusions

With better dose distribution than RA while maintaining sufficient target dose coverage, HA represents an attractive salvage SBRT technique for recurrent NPC.

Medically inoperable Merkel cell carcinoma of the head and neck treated with stereotactic body radiation therapy: a case report

Merkel cell carcinoma (MCC) is a rare but aggressive neuroendocrine tumour of the skin. MCC is the second most common cause of death from non-melanoma skin cancer and the most aggressive cutaneous malignancy. An 88-year-old male presented with a large, bleeding skin tumour located on the right temple and pre-auricular region. A biopsy confirmed MCC; immunohistochemistry (IHC) was positive for synaptophysin and CK20. The patient was assessed by a head and neck surgical oncologist and not deemed to have operable disease due to medical co-morbidities and extent of disease. The patient underwent a single fraction of electron treatment, followed by stereotactic body radiation therapy (SBRT) to a total dose of 40 Gy in 5 fractions over 2 weeks. Bleeding stopped and the patient tolerated treatment well with no reported side effects other than fatigue. There was symptomatic improvement within 2 weeks and a complete clinical response within 4 weeks of treatment. There are limited data on the use of radiotherapy in unresected/ inoperable MCC. For elderly, medically frail patients who cannot undergo surgery, SBRT may be an option to alleviate symptoms and control the tumour in a relatively short number of treatments; further study is warranted.

Strategies to Mitigate Toxicities From Stereotactic Body Radiation Therapy for Spine Metastases

Improvements in systemic therapy are translating into more patients living longer with metastatic disease. Bone is the most common site of metastasis, where spinal lesions can result in significant pain impacting quality of life and possible neurological dysfunction resulting in a decline in performance status. Stereotactic body radiation therapy (SBRT) of the spine has emerged as a promising technique to provide durable local control, palliation of symptoms, control of oligoprogressive sites of disease, and possibly augment the immune response. SBRT achieves this by delivering highly conformal radiation therapy to allow for dose escalation due to a steep dose gradient from the planning target volume to nearby critical organs at risk. In our review, we provide an in-depth review and expert commentary regarding seminal literature that defined clinically meaningful toxicity endpoints with actionable dosimetric limits and/or clinical management strategies to mitigate toxicity potentially attributable to SBRT of the spine. We placed a spotlight on radiation myelopathy (de novo, reirradiation after conventional external beam radiation therapy or salvage after an initial course of spinal SBRT), plexopathy, vertebral compression fracture, pain flare, esophageal toxicity, myositis, and safety regarding combination with concurrent targeted or immune therapies.

A systematic review and meta-analysis of stereotactic body radiation therapy for colorectal pulmonary metastases

Background

There is growing evidence to support the hypothesis that radical treatment of pulmonary oligometastatic disease with stereotactic body radiation therapy (SBRT) can improve oncological outcomes. However, some reports suggest colorectal cancer (CRC) pulmonary metastases are associated with radioresistance. The present systematic review aimed to assess the local control (LC), overall survival (OS), and progression-free survival (PFS) of patients with CRC pulmonary metastases treated by SBRT. Secondary outcomes included assessment of peri-procedural complications and identification of prognostic factors on LC.

Methods

Electronic databases were systematically searched from their dates of inception using predefined criteria. Summative statistical analysis was performed for patients with CRC pulmonary metastases, and comparative meta-analysis was performed for patients with CRC versus non-CRC pulmonary metastases.

Results

Using predefined criteria, 18 relevant studies were identified from the existing literature. LC for CRC pulmonary metastases treated by SBRT at 1-, 2-, and 3-year were estimated to be 81%, 66%, and 60%, respectively. OS and PFS at 3-year were 52% and 13%, respectively. Patients with CRC pulmonary metastases were associated with significantly lower LC compared to non-CRC pulmonary metastases [HR, 2.93; 95% confidence interval (CI), 1.93-4.45; P<0.00001], but higher OS (HR, 0.61; 95% CI, 0.45-0.82; P=0.001). There were no reported periprocedural mortalities and low incidences of periprocedural morbidities.

Conclusions

These findings may have implications for patient and treatment selection, dose fractionation, and support the hypothesis that CRC pulmonary metastases may require higher biological effective doses while respecting normal tissue constraints when treated with SBRT.

The Evolving Field of Stereotactic Body Radiation Therapy in Pancreatic Cancer

Pancreatic cancer remains a devastating disease with dismal outcomes despite the development of novel chemotherapeutic regimens and radiation techniques. Stereotactic body radiation therapy (SBRT) offers an advantage both in image guidance and radiation dose delivery to direct ablative doses to tumors with acceptable toxicity compared to conventional techniques. Recent literature is clustered with data pertaining to SBRT in patients with resectable, borderline resectable and locally advanced pancreatic tumors. We here present a summary of the current data and highlight the limitations and potential for future growth. Further clinical study in the form of multi-institutional trials is warranted to establish the role of SBRT in combination with new chemo- therapeutic agents as well as a non-invasive alternative to surgery.

Management of local recurrences and regional failure in early stage non-small cell lung cancer after stereotactic body radiation therapy

Stereotactic body radiation therapy (SBRT) is a very effective way to treat early stage non-small cell lung cancer (NSCLC) and small oligometastatic lung lesions with consistently high rates of local control, but both local and regional/distant recurrences still occur. The management of recurrences remains unsettled and may entail repeat SBRT, conventionally fractionated external beam RT (EF-EBRT), chemotherapy or surgery. Most patients with local recurrences [within the initial planning target volume (PTV)] can be salvaged successfully with good cancer specific survival. Nonetheless, proximity of the initial SBRT delivery to organs at risk (ribs, blood vessels, airways) may make retreatment more difficult. With attention to detail and careful patient selection, both surgery and reirradiation can be performed safely and effectively. Strategies for management of regional (nodal) recurrences may require conventional therapies tailored to the patterns of failure. The role of immunotherapy in salvage has not been elucidated as yet. We review here data on the available literature concerning salvage of SBRT lung patients.

The role of biological dose-escalation for pancreatic cancer

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High local control rates even for LAPC with biological dose-escalation using SBRT.

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MR-guided adaptive SBRT optimal technique pursuing further dose-escalation.

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High-dose constraints of adjacent OARs will remain the limiting factor.

The role of chemo-radiotherapy for treatment of locally advanced pancreatic cancer (LAPC) has been discussed for many years, and the absence of an overall survival benefit compared to gemcitabine chemotherapy alone in the recent LAP07 study seems to have increased the controversy. However, even in this study, chemo-radiotherapy resulted in decreased local progression (p = 0.03). In combination with increased efficacy of novel systemic therapy consisting of oxaliplatin, irinotecan, fluorouracil and leucovorin (FOLFIRINOX), radiation dose-escalation may show to be beneficial in LAPC. Stereotactic body radiation therapy (SBRT) can be expected to be the most suitable approach to perform local radiation dose-escalation, and has been shown to be both effective and tolerable at doses of 25–35 Gy in 3–5 fractions. Whether further dose-escalation for LAPC will be both feasible and useful is debatable, because of dose restrictions to adjacent critical organs at risk, and the observation that thus far a benefit of delivering BED₁₀ in excess of 70 Gy has not shown to improve local control significantly. If an attempt to further dose-escalate is performed, stereotactic MR-guided adaptive radiation therapy (SMART) theoretically has the highest potential. In addition to superior soft-tissue setup without the need for implanted fiducial markers and online MR-guidance during delivery with minimal safety margins, daily plan adaptation directed at avoiding undue high doses to critical organs such as the duodenum, stomach and bowel are advantages of this technique over current SBRT. This paper aims to illustrate the SMART technique, which has been delivered in 300 fractions for LAPC or locally recurrent pancreatic cancer at Amsterdam UMC since early 2016.

Comparing stereotactic ablative radiotherapy (SABR) versus re-trans-catheter arterial chemoembolization (re-TACE) for hepatocellular carcinoma patients who had incomplete response after initial TACE (TASABR): a randomized controlled trial

Background

Hepatocellular carcinoma (HCC) accounts for 75–85% of primary liver cancers and is prevalent in the Asia-Pacific region. Till now, trans-arterial chemoembolization (TACE) is still one of common modalities in managing unresectable intermediate-stage HCC. However, post-TACE residual viable HCC is not uncommon, resulting in unsatisfied overall survival after TACE alone. Recently, stereotactic ablative radiotherapy (SABR) has been suggested to manage HCC curatively. However, evidence from phase-III trials is largely lacking.

Hence, the present phase III randomized trial is designed to compare clinical outcomes between SABR and re-TACE for unresectable HCC patients who had incomplete response after initial TACE.

Methods

The present study is an open-label, parallel, randomized controlled trial. A total of 120 patients will be included into two study groups, i.e., SABR and re-TACE, with a 1:1 allocation rate. A 3-year allocating period is planned. Patients with incomplete response after initial TACE will be enrolled and randomized. The primary endpoint is 1-year freedom-form-local-progression rate. Secondary endpoints are disease-progression-free survival, overall survival, local control, response rate, toxicity, and duration of response of the treated tumor.

Discussion

SABR has been reported as an effective modality in managing intermediate-stage HCC patients, but evidence from phase-III randomized trials is largely lacking. As a result, conducting randomized trials to demarcate the role of SABR in these patients is warranted, especially in the Asia-Pacific region, where HBV- and HCV-related HCCs are prevalent.

Trial registration

Before enrolling participants, the present study was registered prospectively on ClinicalTrials.gov (trial identifier, NCT02921139) on Sep. 29, 2016. This study is ongoing.

Empiric Radiotherapy for Lung Cancer Collaborative Group multi-institutional evidence-based guidelines for the use of empiric stereotactic body radiation therapy for non-small cell lung cancer without pathologic confirmation

The standard of care for managing early stage non-small cell lung cancer (NSCLC) is definitive surgical resection. Stereotactic body radiation therapy (SBRT) has become the standard treatment for patient who are medically inoperable, and it is increasingly being considered as an option in operable patients. With the growing use of screening thoracic CT scans for patients with a history of heavy smoking, as well as improved imaging capabilities, the discovery of small lung nodes has become a common dilemma. As a result, clinicians are increasingly faced with managing lung nodules in patients in whom diagnostic biopsy is not safe or feasible. Herein, we describe the scope of the problem, tools available for predicting the probability that a lung nodule is a malignancy, staging procedures, benefits of pathology-proven and empiric SBRT, considerations of safety based on location of the lesion of concern, and overall efficacy of SBRT.

Stereotactic body radiation therapy (SBRT) for early-stage lung cancer in the elderly

Early-stage non-small cell lung cancer (NSCLC) is on the rise due to the implementation of screening guidelines for patients at risk for developing lung cancer. It is anticipated that as the US population continues to age, there will be a higher percentage of medically inoperable early-stage lung cancer patients. For this reason, noninvasive ablative therapies are necessary. Stereotactic body radiation therapy (SBRT) is an effective modality in addressing early-stage NSCLC. SBRT consists of high-dose radiation delivered over 3-5 treatments. Several randomized trials comparing surgery to SBRT in early-stage operable patients have unfortunately closed early due to poor accrual. However, a recent pooled analysis from 2 randomized trials (StereoTActic Radiotherapy and Radiosurgery Or Surgery for operable Early-stage non-small cell Lung cancer) comparing surgery to SBRT did show comparable local control and overall survival rates between surgery and SBRT, offering a very effective, noninvasive modality for older adult patients with early-stage NSCLC. In this review, we summarize the role of SBRT in early-stage NSCLC, in particularly applied to the older adult population.

Emerging technologies in stereotactic body radiotherapy

Stereotactic body radiation therapy (SBRT) stems from the initial developments of intra-cranial stereotactic radiosurgery (SRS). Despite similarity in their names and clinical goals of delivering a sufficiently high tumoricidal dose, maximal sparing of the surrounding normal tissues and a short treatment course, SBRT technologies have transformed from the early days of body frame-based treatments with X-ray verification to primarily image-guided procedures with cone-beam CT or stereoscopic X-ray systems and non-rigid body immo-bilization. As a result of the incorporation of image-guidance systems and multi-leaf col-limators into mainstream linac systems, and treatment planning systems that have also evolved to allow for routine dose calculations to permit intensity modulated radiotherapy and volumetric modulated arc therapy (VMAT), SBRT has disseminated rapidly in the community to manage many disease sites that include oligometastases, spine lesions, lung, prostate, liver, renal cell, pelvic tumors, and head and neck tumors etc. In this article, we review the physical principles and paradigms that led to the widespread adoption of SBRT practice as well as technical caveats specific to individual SBRT technologies. From the perspective of treatment delivery, we categorically described (I) C-arm linac-based SBRT technologies; (II) robotically manipulated X-band CyberKnife® technology; and (III) emerging specialized systems for SBRT that include integrated MRI-linear accelerators and the imaged-guided Gamma Knife Perfexion Icon system with expanded multi-isocenter treatments of skull-based tumors, head-and-neck and cervical-spine lesions.

[Radiotherapy of bone metastases in France: A descriptive monocentric retrospective study]

PURPOSE

Bone metastases cause pain and affect patients' quality of life. Radiation therapy is one of the reference analgesic treatments. The objective of this study was to compare the current practices of a French radiotherapy department for the treatment of uncomplicated bone metastases with data from the literature in order to improve and optimize the management of patients.

MATERIAL AND METHODS

A retrospective monocentric study of patients who underwent palliative irradiation of uncomplicated bone metastases was performed.

RESULTS

Ninety-one patients had 116 treatments of uncomplicated bone metastases between January 2014 and December 2015, including 44 men (48%) and 47 women (52%) with an average age of 63years (25-88years). Primary tumours most commonly found were breast cancer (35%), lung cancer (16%) and prostate cancer (12%). The regimens used were in 29% of cases 30Gy in ten fractions (group 30Gy), in 21% of cases 20Gy in five fractions (group 20Gy), in 22% of cases 8Gy in one fraction (group 8Gy) and in 28% of cases 23.31Gy in three fractions of stereotactic body irradiation (stereotactic group). The general condition of the patient (P<0.001), pain score and analgesic (P<0.001), oligometastatic profile (P=0.003) and practitioner experience (P<0.001) were factors influencing the choice of the regimen irradiation. Age (P=0.46), sex (P=0.14), anticancer treatments (P=0.56), concomitant hospitalization (P=0.14) and the distance between the radiotherapy centre and home (P=0.87) did not influence the decision significantly. A total of three cases of spinal compression and one case of post-therapeutic fracture were observed, occurring between one and 128days and 577days after irradiation, respectively. Eight percent of all irradiated metastases were reirradiated with a delay ranging between 13 and 434days after the first irradiation. The re-irradiation rate was significantly higher after 8Gy (P=0.02). The rate of death was significantly lower in the stereotactic arm (P<0.001) and overall survival was significantly greater in the stereotactic arm (P<0.001).

CONCLUSION

This study showed that patients' analysed was comparable to the population of different studies. Predictive factors for the choice of the treatment regimen were identified. Non-fractionnated therapy was underutilised while stereotactic treatment was increasingly prescribed, showing an evolution in the management of patients.

Medically inoperable stage I non-small cell lung cancer: best practices and long-term outcomes

Early-stage non-small cell lung cancer (ES-NSCLC) currently represents a minority of all NSCLC diagnoses but, with ongoing refinement and improvement of treatment approaches, is a group with increasing likelihood of long-term disease control and survival. A significant proportion of this population will not be optimal candidates for definitive surgical resection due to tumor characteristics, patient frailty, or comorbid status. The clinical evidence to support the use of stereotactic body radiation therapy (SBRT) in patients with medically inoperable stage I NSCLC is growing as long-term data are obtained. In this review, initial workup, SBRT delivery considerations, recent trial data, and post-treatment surveillance of this population are discussed.

Stereotactic body radiotherapy as salvage treatment for recurrence of non-small cell lung cancer after prior surgery or radiotherapy

Treatment options for thoracic recurrences of non-small cell lung cancer (NSCLC) are limited. Stereotactic body radiation therapy (SBRT) is an emerging, potentially effective technology to manage recurrent NSCLC, although with limited prospective studies. This work reviews the outcomes of patients undergoing salvage SBRT for pulmonary recurrences after prior resection or prior radiotherapy for NSCLC. Following salvage SBRT, after prior external beam radiation (SBRT or conventionally fractionated), the 2-year overall survival (OS) ranged from 37% to 79% in 11 of the studies (397 patients) reviewed here, while the 2-year local control (LC) ranged from 37% to 90% in 6 studies that reported that outcome. Toxicity risks are acceptable albeit with appreciable risks of severe to potentially fatal toxicity, necessitating the need to weigh risks vs. benefits in the re-irradiation setting. There were fewer studies on the use of SBRT after prior resection. Following salvage SBRT, after prior resection, the 2-year OS ranged from 56% to 68% in 4 studies (131 patients) reviewed here, while the 2-year LC ranged from 83% to 100% in 3 of these studies. SBRT in the salvage setting after prior resection appeared to be well-tolerated, with toxicity risks comparable to historical patients treated with SBRT alone (i.e., SBRT without prior resection, which is not reviewed here). The data are limited due to the retrospective nature of published studies (all but 4 with <40 patients), with various clinical scenarios (i.e., original NSCLC stage, prior treatment, location of target amenable to salvage SBRT) and a range of SBRT dosing and techniques. More studies are needed to better understand the tumor control, survival and toxicity of SBRT for salvage therapy of NSCLC patients, as well as the potentially prognostic factors that could affect these outcomes.

Combining stereotactic body radiation therapy with immunotherapy: current data and future directions

Stereotactic body radiation therapy (SBRT) offers excellent local control of early-stage non-small cell lung cancer (NSCLC), but there currently is a need for tolerable systemic therapy to address regional and distant disease progression. One potential option is immunotherapy, which in metastatic NSCLC has shown promise for sustained disease control in a subset of patients. There is also growing evidence for a clinical synergy between radiation and immunotherapy, with several ongoing trials studying the abscopal effect. This review summarizes the current data in the fast-changing field of immuno-radiation therapy, highlighting updates from recent clinical trials.

Radiological differential diagnosis between fibrosis and recurrence after stereotactic body radiation therapy (SBRT) in early stage non-small cell lung cancer (NSCLC)

Background

Parenchymal changes after stereotactic body radiation therapy (SBRT) make differential diagnosis between treatment outcomes and disease recurrence often difficult. The purpose of our study was to identify the radiographic features detectable at computed tomography (CT) scan [high-risk features (HRFs)] that allow enough specificity and sensitivity for early detection of recurrence.

Methods

We retrospectively evaluated patients who underwent SBRT for inoperable early stage non-small cell lung cancer (NSCLC). The median delivered dose performed was 50 Gy in 5 fractions prescribed to 80% isodose. All patients underwent chest CT scan before SBRT and at 3, 6, 12, 18, 24 months after, and then annually. Each CT scan was evaluated and benign and HRFs were recorded. ¹⁸F-fluorodeoxyglucose-CT was not used routinely.

Results

Forty-five patients were included (34 males, 11 females; median age: 77 years; stage IA: 77.8%, stage IB: 22.2%; median follow-up: 21.7 months). Two year and actuarial local control was 77%. HRFs were identified in 20 patients. The most significant predictor of relapse was an enlarging opacity at 12 months (P<0.001) with 84.6% sensitivity and 71.8% specificity. The presence of ≥2 HRFs demonstrated a high sensibility (92.3%) and specificity (71.9%) (P<0.0001).

Conclusions

Detection of HRFs is predictive of relapse with a sensibility that increases with the number of HRFs observed. This observation may allow to better define the diagnostic follow algorithm up suggesting to performing further exams only in patients with >2 HRFs.

Stereotactic body radiation therapy for liver metastasis - The linac-based Greater Poland Cancer Centre practice

AIM

The main purpose of this work is to give a technical description and present the properties of the liver SBRT protocol implemented in the Greater Poland Cancer Centre (GPCC) in Poznan, Poland.

BACKGROUND

Stereotactic body radiation therapy (SBRT) for liver metastasis is a non-invasive therapeutic option which enables irradiation of a small target in the body with a high dose.

MATERIALS AND METHODS

This study presents details of our linac-based liver SBRT protocol. Special emphasis has been placed on fiducial implantation, patient preparation (CT scanning, immobilization), treatment planning, and its implementation.

RESULTS

The liver SBRT treatment course implemented in the GPCC consists of three fractions to deliver a total of 45 Gy. Fraction delivery details with description of patient positioning (localization of liver metastasis) are presented below.

CONCLUSIONS

The literature validation of the assumptions concerning the steps of the GPCC linac-based liver SBRT procedure show their potential for an effective and patient friendly implementation.

Dosimetric and radiobiological comparison of Cyberknife and Tomotherapy in stereotactic body radiotherapy for localized prostate cancer

BACKGROUND AND PURPOSE

As recent studies have suggested relatively low α/β for prostate cancer, the interest in hypofractionated stereotactic body radiotherapy (SBRT) for prostate cancer is rising. The aim of this study is to compare dosimetric results of Cyberknife (CK) with Tomotherapy (HT) in SBRT for localized prostate cancer. Furthermore, the radiobiologic consequences of heterogeneous dose distribution are also analyzed.

MATERIAL AND METHOD

A total of 12 cases of localized prostate cancer previously treated with SBRT were collected. Treatments had been planned and delivered using CK. Then HT plans were generated for comparison afterwards. The prescribed dose was 37.5Gy in 5 fractions. Dosimetric indices for target volumes and organs at risk (OAR) were compared. For radiobiological evaluation, generalized equivalent uniform dose (gEUD) and normal tissue complication probability (NTCP) were calculated and compared.

RESULT

Both CK and HT achieved target coverage while meeting OAR constraints adequately. HT plans resulted in better dose homogeneity (Homogeneity index: 1.04±0.01 vs. 1.21±0.01; p = 0.0022), target coverage (97.74±0.86% vs. 96.56±1.17%; p = 0.0076) and conformity (new vonformity index: 1.16±0.05 vs. 1.21±0.04; p = 0.0096). HT was shown to predict lower late rectal toxicity as compared to CK. Integral dose to body was also significantly lower in HT plans (46.59±6.44 Gy'L vs 57.05±11.68 Gy'L; p = 0.0029).

CONCLUSION

Based on physical dosimetry and radiobiologic considerations, HT may have advantages over CK, specifically in rectal sparing which could translate into clinical benefit of decreased late toxicities.

A phase-I trial of pre-operative, margin intensive, stereotactic body radiation therapy for pancreatic cancer: the 'SPARC' trial protocol

BACKGROUND

Standard therapy for borderline-resectable pancreatic cancer in the UK is surgery with adjuvant chemotherapy, but rates of resection with clear margins are unsatisfactory and overall survival remains poor. Meta-analysis of single-arm studies shows the potential of neo-adjuvant chemo-radiotherapy but the relative radio-resistance of pancreatic cancer means the efficacy of conventional dose schedules is limited. Stereotactic radiotherapy achieves sufficient accuracy and precision to enable pre-operative margin-intensive dose escalation with the goal of increasing rates of clear resection margins and local disease control.

METHODS/DESIGN

SPARC is a "rolling-six" design single-arm study to establish the maximum tolerated dose for margin-intensive stereotactic radiotherapy before resection of pancreatic cancer at high risk of positive resection margins. Eligible patients will have histologically or cytologically proven pancreatic cancer defined as borderline-resectable per National Comprehensive Cancer Network criteria or operable tumour in contact with vessels increasing the risk of positive margin. Up to 24 patients will be recruited from up to 5 treating centres and a 'rolling-six' design is utilised to minimise delays and facilitate ongoing recruitment during dose-escalation. Radiotherapy will be delivered in 5 daily fractions and surgery, if appropriate, will take place 5-6 weeks after radiotherapy. The margin-intense radiotherapy concept includes a systematic method to define the target volume for a simultaneous integrated boost in the region of tumour-vessel infiltration, and up to 4 radiotherapy dose levels will be investigated. Maximum tolerated dose is defined as the highest dose at which no more than 1 of 6 patients or 0 of 3 patients experience a dose limiting toxicity. Secondary endpoints include resection rate, resection margin status, response rate, overall survival and progression free survival at 12 and 24 months. Translational work will involve exploratory analyses of the cytological and humoral immunological responses to stereotactic radiotherapy in pancreatic cancer. Radiotherapy quality assurance of target definition and radiotherapy planning is enforced with pre-trial test cases and on-trial review. Recruitment began in April 2015.

DISCUSSION

This prospective multi-centre study aims to establish the maximum tolerated dose of pre-operative margin-intensified stereotactic radiotherapy in pancreatic cancer at high risk of positive resection margins with a view to subsequent definitive comparison with other neoadjuvant treatment options.

TRIAL REGISTRATION

ISRCTN14138956 . Funded by CRUK.

What is the best way to radiate the prostate in 2016?

Prostate cancer treatment with definitive radiation therapy (RT) has evolved dramatically in the past 2 decades. From the initial 2-dimensional planning using X-rays, advances in technology led to 3-dimensional conformal RT, which used computerized tomography-based planning. This has allowed delivery of higher doses of radiation to the prostate while reducing dose to the surrounding organs, resulting in improved cancer control. Today, intensity-modulated RT (IMRT) is considered standard, where radiation beams of different shapes and intensities can be delivered from a wide range of angles, thus further decreasing doses to normal organs and likely reducing treatment-related toxicity. In addition, image guidance ascertains the location of the prostate before daily treatment delivery. Brachytherapy is the placement of radioactive seeds directly in the prostate, and has a long track record as a monotherapy for low-risk prostate cancer patients with excellent long-term cancer control and quality of life outcomes. Recent studies including several randomized trials support the use of brachytherapy in combination with external beam RT for higher-risk patients. RT for prostate cancer continues to evolve. Proton therapy has a theoretical advantage over photons as it deposits most of the dose at a prescribed depth with a rapid dose fall-off thereafter; therefore it reduces some doses delivered to the bladder and rectum. Prospective studies have shown the safety and efficacy of proton therapy for prostate cancer, but whether it leads to improved patient outcomes compared to IMRT is unknown. Hypofractionated RT delivers a larger dose of daily radiation compared to conventional IMRT, and thus reduces the overall treatment time and possibly cost. An extreme form of hypofractionation is stereotactic body radiation therapy where highly precise radiation is used and treatment is completed in a total of 4 to 5 sessions. These techniques take advantage of the biological characteristic of prostate cancer, which is more sensitive to larger radiation doses per fraction, and therefore could be more effective than conventional IMRT. Multiple randomized trials have demonstrated noninferiority of moderately hypofractionated RT compared to conventional fractionation. There is also a growing body of data demonstrating the safety and efficacy of stereotactic body radiation therapy for low- and intermediate-risk prostate cancer.

Developing oxygen-enhanced magnetic resonance imaging as a prognostic biomarker of radiation response

Oxygen-Enhanced Magnetic Resonance Imaging (OE-MRI) techniques were evaluated as potential non-invasive predictive biomarkers of radiation response. Semi quantitative blood-oxygen level dependent (BOLD) and tissue oxygen level dependent (TOLD) contrast, and quantitative responses of relaxation rates (ΔR1 and ΔR2*) to an oxygen breathing challenge during hypofractionated radiotherapy were applied. OE-MRI was performed on subcutaneous Dunning R3327-AT1 rat prostate tumors (n=25) at 4.7 T prior to each irradiation (2F × 15 Gy) to the gross tumor volume. Response to radiation, while inhaling air or oxygen, was assessed by tumor growth delay measured up to four times the initial irradiated tumor volume (VQT). Radiation-induced hypoxia changes were confirmed using a double hypoxia marker assay. Inhaling oxygen during hypofractionated radiotherapy significantly improved radiation response. A correlation was observed between the difference in the 2nd and 1st ΔR1 (ΔΔR1) and VQT for air breathing rats. The TOLD response before the 2nd fraction showed a moderate correlation with VQT for oxygen breathing rats. The correlations indicate useful prognostic factors to predict tumor response to hypofractionation and could readily be applied for patient stratification and personalized radiotherapy treatment planning.

The use of isodose levels to interpret radiation induced lung injury: a quantitative analysis of computed tomography changes

BACKGROUND

Patients treated with stereotactic body radiation therapy (SBRT) for lung cancer are often found to have radiation-induced lung injury (RILI) surrounding the treated tumor. We investigated whether treatment isodose levels could predict RILI.

METHODS

Thirty-seven lung lesions in 32 patients were treated with SBRT and received post-treatment follow up (FU) computed tomography (CT). Each CT was fused with the original simulation CT and treatment isodose levels were overlaid. The RILI surrounding the treated lesion was contoured. The RILI extension index [fibrosis extension index (FEI)] was defined as the volume of RILI extending outside a given isodose level relative to the total volume of RILI and was expressed as a percentage.

RESULTS

Univariate analysis revealed that the planning target volume (PTV) was positively correlated with RILI volume at FU: correlation coefficient (CC) =0.628 and P<0.0001 at 1(st) FU; CE =0.401 and P=0.021 at 2(nd) FU; CE =0.265 and P=0.306 at 3(rd) FU. FEI -40 Gy at 1(st) FU was significantly positively correlated with FEI -40 Gy at subsequent FU's (CC =0.689 and P=6.5×10(-5) comparing 1(st) and 2(nd) FU; 0.901 and P=0.020 comparing 2(nd) and 3(rd) FU. Ninety-six percent of the RILI was found within the 20 Gy isodose line. Sixty-five percent of patients were found to have a decrease in RILI on the second 2(nd) CT.

CONCLUSIONS

We have shown that RILI evolves over time and 1(st) CT correlates well with subsequent CTs. Ninety-six percent of the RILI can be found to occur within the 20 Gy isodose lines, which may prove beneficial to radiologists attempting to distinguish recurrence vs. RILI.

The radiobiological targets of SBRT: tumor cells or endothelial cells?

The development of stereotactic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) techniques has revolutionized the practice of radiation oncology. The radiobiological targets that alter the therapeutic response to SBRT remain a subject of debate. The prevailing perspective has been that the radiation-induced damage to endothelial cells and changes in microvasculature facilitate tumor response to SBRT. A provocative study by Moding et al. (PMID: 25761890), challenged this notion by elucidating the role of tumor cells versus endothelial cells in mediating sarcoma eradication following high-dose SBRT. Using dual recombinase technology, they generated primary sarcomas in genetically engineered mouse models (GEMMs). They also modulated the apoptotic pathway and radiosensitization profile using targeted mutations in either tumor cells or endothelial cells. Unlike transplanted tumor models, the findings here suggest that deletion of the pro-apoptotic gene Bax or of the DNA-damage response gene ATM in endothelial cells did not result in tumor eradication to high dose SBRT, despite extensive endothelial cell death. On the other hand, genetic targeting of ATM gene in tumor cells achieved local sarcoma control and tumor eradication. These findings imply that tumor cells rather than endothelial cells act as prime targets affecting a tumor eradication response to SBRT. The translational implications of these findings are of great potential significance. When targeting endothelial cells, delivery of SBRT irradiation can only result in tumor growth delay. The benefit of targeting ATM in this setting will be radiation dose dependent. Curative intent, tumor eradication and local control, on the other hand, are only possible by targeting tumor cells with high dose SBRT (50 Gy in 1 fraction) and with radiosensitization by ATM deletion. In the absence of radiosensitization, only palliation is possible with high dose SBRT. Whether these provocative findings can be extrapolated to other translational tumor models or proved valid in clinical trials remains the subject of future studies. The mechanisms by which tumors compensate to SBRT's endothelial cell damage, such as new vascular recruitment, and/or recruitment of other immune and stromal components, are also critical questions for the field of radiobiology to address. Such mechanistic understanding of the key cellular players mediating SBRT response in a model system that recapitulates human disease will be essential in designing targeted radiosensitizers ultimately aimed at improving the therapeutic ratio.