The oligometastatic state - separating truth from wishful thinking

Stereotactic ablative body radiation for oligometastatic and oligoprogressive disease

Stage IV non-small cell lung cancer (NSCLC) exists on a spectrum, with a subset of patients presenting with oligometastatic disease involving only a limited number of distant sites. For these patients, local consolidative therapy (LCT) has been demonstrated to improve outcomes through ablation or cytoreduction of metastatic disease, as shown in an increasing number of randomized controlled trials. In particular, stereotactic ablative body radiation (SABR) has emerged as a feasible treatment modality for elimination of oligometastatic sites. This focused review examines the underlying biologic mechanisms and clinical data in support of SABR in the setting of oligometastatic NSCLC. Following a comprehensive evaluation of the pertinent retrospective, prospective, and anticipated trials to date, we summarize the evidence regarding patient selection, treatment safety, and technical considerations to provide guidance of this approach for clinicians.

Stereotactic Body Radiotherapy for Oligometastasis: Opportunities for Biology to Guide Clinical Management

Oligometastasis refers to a state of limited metastatic disease burden, in which surgical or ablative treatment to all known visible metastases holds promise to extend survival or even effect cure. Stereotactic body radiotherapy is a form of radiation treatment capable of delivering a high biologically effective dose of radiation in a highly conformal manner, with a favorable toxicity profile. Enthusiasm for oligometastasis ablation, however, should be counterbalanced against the limited supporting evidence. It remains unknown to what extent (if any) ablation influences survival or quality of life. Rising clinical equipoise necessitates the completion of randomized controlled trials to assess this, several of which are underway. However, a lack of clear identification criteria or biomarkers to define the oligometastatic state hampers optimal patient selection.This narrative review explores the evolutionary origins of oligometastasis, the steps of the metastatic process at which oligometastases may arise, and the biomolecular mediators of this state. It discusses clinical outcomes with treatment of oligometastases, ongoing trials, and areas of basic and translational research that may lead to novel biomarkers. These efforts should provide a clearer, biomolecular definition of oligometastatic disease and aid in the accurate selection of patients for ablative therapies.

Radiotherapy for Oligometastatic Lung Cancer

Non-small cell lung cancer (NSCLC) typically presents at an advanced stage, which is often felt to be incurable, and such patients are usually treated with a palliative approach. Accumulating retrospective and prospective clinical evidence, including a recently completed randomized trial, support the existence of an oligometastatic disease state wherein select individuals with advanced NSCLC may experience historically unprecedented prolonged survival with aggressive local treatments, consisting of radiotherapy and/or surgery, to limited sites of metastatic disease. This is reflected in the most recent AJCC staging subcategorizing metastatic disease into intra-thoracic (M1a), a single extra thoracic site (M1b), and more diffuse metastases (M1c). In the field of radiation oncology, recent technological advances have allowed for the delivery of very high, potentially ablative, doses of radiotherapy to both intra- and extra-cranial disease sites, referred to as stereotactic radiosurgery and stereotactic body radiotherapy (or SABR), in much shorter time periods compared to conventional radiation and with minimal associated toxicity. At the same time, significant improvements in systemic therapy, including platinum-based doublet chemotherapy, molecular agents targeting oncogene-addicted NSCLC, and immunotherapy in the form of checkpoint inhibitors, have led to improved control of micro-metastatic disease and extended survival sparking newfound interest in combining these agents with ablative local therapies to provide additive, and in the case of radiation and immunotherapy, potentially synergistic, effects in order to further improve progression-free and overall survival. Currently, despite the tantalizing potential associated with aggressive local therapy in the setting of oligometastatic NSCLC, well-designed prospective randomized controlled trials sufficiently powered to detect and measure the possible added benefit afforded by this approach are desperately needed.

[A randomized controlled trial of metastases-directed treatment in patients with metastatic prostate cancer using stereotactic body irradiation: A GETUG-AFU trial]

The goal of treatment of metastatic prostate cancer remains palliation. The oligometastatic state could be the right time to intensify therapy by introducing metastases directed treatments. The aim of this trial was to evaluate the benefit of radiotherapy to all macroscopic metastatic sites and to the primary disease in patients with hormone sensitive oligometastatic prostate cancer.

Outcome of oligoprogressing metastatic renal cell carcinoma patients treated with locoregional therapy: a multicenter retrospective analysis

Locoregional treatment with radical intent should be considered during therapy with targeted agents in patients with metastatic renal cell carcinoma (mRCC) in order to achieve a complete response, especially in the setting of an oligo-progression in one or more metastatic sites.

We retrospectively enrolled 55 patients who experienced a disease oligo-progression after at least 6 months from the beginning of first-line therapy in one or more metastatic sites radically treated with locoregional treatments. Post-first-oligo-progression overall survival (PFOPOS) and post-first-oligo-progression free survival (PFOPFS) were evaluated.

The global median PFOPOS and PFOPFS were 37 months and 14 months respectively. Patients who continued the same therapy after a locoregional treatment on a site of progression had a significantly longer mPFOPOS compared to patients who changed therapy (39 vs 11 months, p=0.014). An advantage in mPFOPOS was also observed in patients with a Memorial Sloan-Kettering Cancer Center (MSKCC) good risk score compared to patients of the intermediate risk group (39 vs 29 months, p=0.036); patients with bone metastases had a longer mPFOPOS compared to those with visceral metastases (not reached vs 31 months, p=0.045). The only independent predictor of poor prognosis, in terms of PFOPOS at multivariate analysis (p=0.007), proved out to be change of treatment after first progression.

In this paper we aim to illustrate that continuing the same systemic therapy, after a radical locoregional treatment on a site of progression, seems to be associated with a prolongation of mPFOPOS.

If a picture is worth a thousand words, take a good look at the picture: Survival after liver metastasectomy for colorectal cancer

INTRODUCTION

An analysis of NHS data published in by Morris et al. in 2010 is widely used as evidence in support of liver metastasectomy for colorectal cancer and its wider application. Recent evidence concerning better overall survival for patients with metastatic colorectal cancer challenges the notional assumptions about what survival would be without metastasectomy. Earlier detection of metastases for local treatments has not resulted in a survival benefit.

MATERIALS AND METHODS

The interpretation of its central graphical display is critically reviewed and the common the limitations of the analysis of registry data and resulting immortal time bias are explored.

RESULTS AND DISCUSSION

Recent evidence, including the 2017 CLOCC trial report make the original interpretation of the analysis suspect. Randomised trials are essential to detect a treatment effect of specific interventions among variable disease progression, selection bias, and multiple and repeated treatments that are inherent in the management of advanced cancer.

Incremental diagnostic utility of systematic double-bed SPECT/CT for bone scintigraphy in initial staging of cancer patients

Background

SPECT/CT has been shown to increase the diagnostic performance of bone scintigraphy for staging of malignancies. A systematic double-bed SPECT/CT of the trunk may allow further improvement. However, this would be balanced by higher dosimetry and longer acquisition time. The objective was to assess the incremental diagnostic utility of a systematic double-bed SPECT/CT acquisition for bone scintigraphy in initial staging of cancer patients, especially compared with the usual approach consisting in a whole body planar scan (WBS) plus one single-bed targeted SPECT/CT.

Methods

One hundred two consecutive patients referred for bone scintigraphy for initial staging of malignancy were analyzed. All patients underwent a double-bed SPECT/CT acquisition of the trunk. Images were interpreted by two nuclear medicine physicians in a 3-step procedure. Firstly, only WBS planar images were used; secondly, one additional single-bed SPECT/CT chosen based on planar images was used; finally, WBS planar and double-bed SPECT/CT images were interpreted. Lesions were classified as benign, equivocal or suspicious for metastasis. A per-lesion, per-anatomical region and per-patient analysis was performed.

Results

In a per-lesion analysis, the number of equivocal and suspicious lesions was 91 and 241 using WBS planar images, 17 and 259 using a single-bed SPECT/CT acquisition and 11 and 269 using double-bed SPECT/CT images, respectively. In a per-patient analysis, the diagnostic conclusion was negative, equivocal or suspicious for malignancy in 35, 53 and 14 patients using WB planar images, 77, 6 and 19 patients using an additional single-bed SPECT/CT and 76, 7 and 19 using double-bed SPECT/CT images, respectively.

Seventeen lesions unseen on WBS images were interpreted as suspicious (n = 12) or equivocal (n = 5) on double-bed SPECT/CT images. Six lesions unseen on “WBS + targeted single-bed SPECT/CT” were interpreted as suspicious on double-bed SPECT/CT, with no shift in the metastatic status of patients.

Conclusion

A systematic double-bed SPECT/CT acquisition has a limited incremental diagnostic value over an oriented single-bed SPECT/CT in terms of specificity and conclusiveness of bone scintigraphy in the initial staging of cancer patients. However, it slightly improved the sensitivity of the test by detecting unseen lesions on WBS, which may be of value for initial staging of cancer.

Patterns of initial and intracranial failure in metastatic EGFR-mutant non-small cell lung cancer treated with erlotinib

OBJECTIVES

Patients with metastatic EGFR-mutant (mEGFRmt) NSCLC have favorable survival when treated with erlotinib. We hypothesized that treatment failure in most patients is limited to initial sites of disease, in which case incorporating local therapy such as radiation might further delay progression. We therefore analyzed patterns and predictors of failure in a large cohort of such patients.

MATERIALS AND METHODS

We reviewed 189 patients treated with erlotinib for mEGFRmt NSCLC. We classified first pattern of failure as involving initial sites only (ISF), new sites only (NSF), or the combination (CSF), and used competing-risks regression to identify factors associated with ISF, progression and overall survival (OS). We also separately analyzed intracranial and intrathoracic failure.

RESULTS

Of 171 patients who progressed, 103 (60.2%) had ISF, 30 (17.5%) had NSF, and 38 (22.2%) had CSF. Younger age and lack of initial CNS involvement independently correlated with ISF, with a trend for higher T and N stage. Higher T and N stage was also a significant predictor of progression. Factors predicting shorter OS were female gender, weight loss, initial intracranial involvement, and ≥4 extracranial metastases. Intrathoracic progression was a component of first failure in 61%, and three-year cumulative incidence of brain metastasis was 30%.

CONCLUSION

The main pattern of progression in mEGFRmt NSCLC on erlotinib is in the initial sites of disease. Younger patients and those without brain involvement are particularly likely to develop ISF. This suggests a role for incorporating local therapy into treatment of selected patients with mEGFRmt NSCLC.

Oligometastatic Disease in Upper Gastrointestinal Cancer - How to Proceed?

BACKGROUND

In the present study we review and discuss the current evidence and suggest how to proceed in the management of oligometastatic disease in upper gastrointestinal cancer.

METHODS

An electronic search of the PubMed database for relevant articles was performed.

RESULTS

Both the search for 'oligometastasis', 'oligometastases', 'oligometastatic', 'oligometastatic disease' as well as 'esophageal' and 'esophageal cancer' and the search for 'oligometastasis', 'oligometastases', 'oligometastatic', 'oligometastatic disease' as well as 'gastric', 'gastric cancer', 'stomach', and 'stomach cancer' yielded very few studies. Most data need to be extrapolated in general studies on oligometastatic diseases of different origins. No randomized controlled trial could be found.

CONCLUSION

In the absence of data to formulate recommendations on how to proceed in the treatment of oligometastatic disease in upper gastrointestinal cancer, a more aggressive treatment of oligometastatic disease can be considered in patients whose tumors show a more favorable neoplastic behavior after the 'test of time'. The RENAISSANCE study will certainly deliver important data regarding this aspect.

Liver Metastases in Colorectal Cancer

Resection of colorectal liver metastases is a treatment standard because patients experience long-term disease-free survival or are even cured after undergoing this procedure. Improved surgical techniques for liver resection in combination with downsizing liver metastases by chemotherapy, interventions to induce liver hypertrophy before resection, and the use of ablative techniques have allowed us to expand the indications for liver surgery and local treatment in situations with limited metastatic colorectal cancer. Resectability and identification of patients who might benefit from liver surgery and local ablative techniques are key factors for the treatment of patients with colorectal cancer. Despite the wide acceptance of liver surgery and ablative techniques, there are many open questions on the management of limited metastatic disease, such as which patients benefit from an aggressive surgical approach, what the indications for ablative and other local techniques are, and what the role of chemotherapy is for patients with resectable or resected disease. Unfortunately, results of randomized trials are only available for a limited number of these questions.

Stereotactic radiation therapy for oligometastases or oligorecurrence within mediastinal lymph nodes

Aims

This study evaluated the safety and efficacy of stereotactic radiation therapy (SRT) for the treatment of patients with oligometastases or oligorecurrence within mediastinal lymph nodes (MLNs) originating from different tumors.

Methods

Between October 2006 and May 2015, patients with MLN oligometastases or oligorecurrence were enrolled and treated with SRT at our hospital. The primary endpoint was MLN local control (LC). Secondary endpoints were time to symptom alleviation, overall survival (OS) after SRT, and toxicity using the Common Terminology Criteria for Adverse Events (CTCAE v4.0).

Results

Eighty-five patients with 98 MLN oligometastases or oligorecurrences were treated with SRT. For the entire cohort, the 1-year and 5-year actuarial LC rates were 97% and 77%, respectively. Of 53 symptomatic patients, symptom alleviation was observed in 47 (89%) after a median of 5 days (range, 3-30 days). The median OS was 27.2 months for all patients. For patients with non-small cell lung cancer, univariate and multivariate analyses revealed that a shorter interval between diagnosis of primary tumors and SRT and larger MLN SRT volume were associated with worse OS. CTCAE v4.0 ≥ Grade 3 toxicities occurred in six patients (7%), with Grade 5 in three patients (all with RT history to MLN station 7).

Conclusions

SRT is a safe and efficacious treatment modality for patients with oligometastases or oligorecurrence to MLNs originating from different tumors, except for patients who received radiotherapy to MLN station 7. Further investigation is warranted to identify the patients who benefit most from this treatment modality.

Local consolidative therapy versus maintenance therapy or observation for patients with oligometastatic non-small-cell lung cancer without progression after first-line systemic therapy: a multicentre, randomised, controlled, phase 2 study

BACKGROUND

Evidence from retrospective studies suggests that disease progression after first-line chemotherapy for metastatic non-small-cell lung cancer (NSCLC) occurs most often at sites of disease known to exist at baseline. However, the potential effect of aggressive local consolidative therapy for patients with oligometastatic NSCLC is unknown. We aimed to assess the effect of local consolidative therapy on progression-free survival.

METHODS

In this multicentre, randomised, controlled, phase 2 study, eligible patients from three hospitals had histological confirmation of stage IV NSCLC, three or fewer metastatic disease lesions after first-line systemic therapy, an Eastern Cooperative Oncology Group performance status score of 2 or less, had received standard first-line systemic therapy, and had no disease progression before randomisation. First-line therapy was four or more cycles of platinum doublet therapy or 3 or more months of EGFR or ALK inhibitors for patients with EGFR mutations or ALK rearrangements, respectively. Patients were randomly assigned (1:1) to either local consolidative therapy ([chemo]radiotherapy or resection of all lesions) with or without subsequent maintenance treatment or to maintenance treatment alone, which could be observation only. Maintenance treatment was recommended based on a list of approved regimens, and observation was defined as close surveillance without cytotoxic treatment. Randomisation was not masked and was balanced dynamically on five factors: number of metastases, response to initial therapy, CNS metastases, intrathoracic nodal status, and EGFR and ALK status. The primary endpoint was progression-free survival analysed in all patients who were treated and had at least one post-baseline imaging assessment. The study is ongoing but not recruiting participants. This study is registered with ClinicalTrials.gov, number NCT01725165.

FINDINGS

Between Nov 28, 2012, and Jan 19, 2016, 74 patients were enrolled either during or at the completion of first-line systemic therapy. The study was terminated early after randomisation of 49 patients (25 in the local consolidative therapy group and 24 in the maintenance treatment group) as part of the annual analyses done by the Data Safety Monitoring Committee of all randomised trials at MD Anderson Cancer Center, and before a planned interim analysis of 44 events. At a median follow-up time for all randomised patients of 12·39 months (IQR 5·52-20·30), the median progression-free survival in the local consolidative therapy group was 11·9 months (90% CI 5·7-20·9) versus 3·9 months (2·3-6·6) in the maintenance treatment group (hazard ratio 0·35 [90% CI 0·18-0·66], log-rank p=0·0054). Adverse events were similar between groups, with no grade 4 adverse events or deaths due to treatment. Grade 3 adverse events in the maintenance therapy group were fatigue (n=1) and anaemia (n=1) and in the local consolidative therapy group were oesophagitis (n=2), anaemia (n=1), pneumothorax (n=1), and abdominal pain (n=1, unlikely related).

INTERPRETATION

Local consolidative therapy with or without maintenance therapy for patients with three or fewer metastases from NSCLC that did not progress after initial systemic therapy improved progression-free survival compared with maintenance therapy alone. These findings suggest that aggressive local therapy should be further explored in phase 3 trials as a standard treatment option in this clinical scenario.

FUNDING

MD Anderson Lung Cancer Priority Fund, MD Anderson Cancer Center Moon Shot Initiative, and Cancer Center Support (Core), National Cancer Institute, National Institutes of Health.

What do radiation oncologists require for future advancements in lung SBRT?

Stereotactic Body Radiotherapy (SBRT) is a well established therapeutic option for patients affected with peripheral early stage non-small cell lung cancer (NSCLC), given the positive clinical evidence accumulated so far on its efficacy and safety. SBRT is regarded as the best choice for inoperable patients, and could also be offered as an alternative to surgery to selected operable patients. More recently, its use for lung metastases progressively increased, and SBRT is now regarded as a low toxic and highly effective local therapy for lung oligometastases from different primary tumors, especially colorectal cancer. Improved planning and delivery techniques have facilitated over the years its use on large and/or centrally located primary tumors, and multiple nodules. Given the successful applications and the current wide dissemination of this technique, clinicians are now faced with an increasingly complex and multi-variable decision process. Some clinically relevant factors are still uncertain, and strategies are needed to reduce the risk of both local and distant failures. Secondly, aspects related to target delineation, dose prescription, image guidance and treatment planning still need to be fully addressed; this may hamper, at least for now, the standardization of SBRT procedures through different Institutions making any kind of direct outcomes comparison difficult. We here aim to provide a perspective on the current role of lung SBRT and its critical aspects, highlighting the potential future developments.

New Strategies in Stereotactic Radiotherapy for Oligometastases

Patients with metastatic solid tumors are usually treated with palliative intent. Systemic therapy and palliative radiation are often used, with the goals of prolonging survival or maintaining quality of life, but not of cure. In contrast to this paradigm, the theory of oligometastasis suggests that some patients who have a small number of metastases may be amenable to cure if all lesions can be eradicated. Aggressive treatment of patients with oligometastases, using either surgery or radiotherapy, has become more common in the past decade, yet in most situations, no randomized evidence is available to support such an approach. Stereotactic ablative radiotherapy (SABR) is a novel treatment for oligometastases, delivering large doses of radiotherapy in only a few treatments, with excellent rates of local control, and appears to be an excellent noninvasive alternative to surgical resection of metastases. This article reviews recent biologic and clinical data that support the existence of the oligometastatic state and discusses gaps in this evidence base. The emerging role for SABR in the management of this challenging patient population is discussed with a focus on ongoing clinical trials in an attempt to improve overall survival, delay progression, or induce immunologic anticancer effects through the abscopal effect.

A critical review of recent developments in radiotherapy for non-small cell lung cancer

Lung cancer is the leading cause of cancer mortality, and radiotherapy plays a key role in both curative and palliative treatments for this disease. Recent advances include stereotactic ablative radiotherapy (SABR), which is now established as a curative-intent treatment option for patients with peripheral early-stage NSCLC who are medically inoperable, or at high risk for surgical complications. Improved delivery techniques have facilitated studies evaluating the role of SABR in oligometastatic NSCLC, and encouraged the use of high-technology radiotherapy in some palliative settings. Although outcomes in locally advanced NSCLC remain disappointing for many patients, future progress may come about from an improved understanding of disease biology and the development of radiotherapy approaches that further reduce normal tissue irradiation. At the moment, the benefits, if any, of radiotherapy technologies such as proton beam therapy remain unproven. This paper provides a critical review of selected aspects of modern radiotherapy for lung cancer, highlights the current limitations in our understanding and treatment approaches, and discuss future treatment strategies for NSCLC.

Imaging oligometastatic cancer before local treatment

With the advent of novel treatment strategies to help widen the therapeutic window for patients with oligometastatic cancer, improved biomarkers are needed to reliably define patients who can benefit from these treatments. Multimodal imaging is one such option and should be optimised to comprehensively assess metastatic sites, disease burden, and response to neoadjuvant treatment in each disease setting. These features will probably remain important prognostic biomarkers, and are crucial in planning multidisciplinary treatment. There are opportunities to extract additional phenotypic information from conventional imaging, while novel imaging techniques can also reveal specific aspects of tumour biology. Imaging can both characterise and localise the phenotypic heterogeneity of multiple tumour sites. Novel approaches to existing imaging datasets and correlation with tumour biology will be important in realising the potential of imaging to guide treatment in the oligometastatic setting. In this Personal View, we discuss the current status and future directions of imaging before treatment in patients with extracranial oligometastases.

Oligo-recurrence predicts favorable prognosis of brain-only oligometastases in patients with non-small cell lung cancer treated with stereotactic radiosurgery or stereotactic radiotherapy: a multi-institutional study of 61 subjects

Background

To investigate the prognostic value of oligo-recurrence in patients with brain-only oligometastases of non-small cell lung cancer (NSCLC) treated with stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT).

Methods

Patients treated with SRS or SRT for brain-only NSCLC oligometastases in 6 high-volume institutions in Japan between 1996 and 2008 were reviewed. Eligible patients met 1), 2), and 4) or 1), 3), and 4) of the following: 1) NSCLC with 1 to 4 brain metastases on magnetic resonance imaging (MRI) treated with SRS or SRT; 2) control of the primary lesions (thorax) at the time of SRS or SRT for brain metastases (patients meeting this criterion formed the oligo-recurrence group); 3) with SRS or SRT for brain metastases, concomitant treatment for active primary lesions (thorax) with curative surgery or curative stereotactic body radiotherapy (SBRT), or curative chemoradiotherapy (sync-oligometastases group); and 4) Karnofsky performance status (KPS) ≥70.

Results

The median overall survival (OS) of all 61 patients was 26 months (95 % CI: 17.5–34.5 months). The 2-year and 5-year overall survival rates were 60.7 and 15.7 %, respectively. Stratified by oligostatus, the sync-oligometastases group achieved a median OS of 18 months (95 % CI: 14.8–21.1 months) and a 5-year OS of 0 %, while the oligo-recurrence group achieved a median OS of 41 months (95 % CI: 27.8–54.2 months) and a 5-year OS of 18.6 %. On multivariate analysis, oligo-recurrence was the only significant independent factor related to a favorable prognosis (hazard ratio: 0.253 (95 % CI: 0.082–0.043) (p = 0.025).

Conclusions

The presence of oligo-recurrence can predict a favorable prognosis of brain-only oligometastases in patients with NSCLC treated with SRS or SRT.

Oligometastatic bone disease in prostate cancer patients treated on the TROG 03.04 RADAR trial

BACKGROUND

It remains unclear whether eradication of oligometastases by stereotactic body radiation therapy or other means will result in cure or prolongation of survival in some cases, or merely provide palliation. We address this issue with prospectively collected progression and treatment data from the TROG 03.04 RADAR randomised controlled trial for men with locally advanced prostate cancer (PC).

METHODS

Three Fine and Gray competing risk survival models with time-dependent covariates were used to determine whether metastatic progression status at first diagnosis of bony metastases, i.e. number of bony sites involved and presence of prior or simultaneous other sites of progression, impacts on prostate cancer-specific mortality (PCSM) when adjusted for baseline prognostic factors and allocated primary treatment.

RESULTS

Between 2003 and 2014, 176 of the 1071 subjects developed bone metastases, 152 developed other sites of progression and 91 died of PC. All subjects received secondary treatment using androgen suppression but none received extirpative treatments. The three models found evidence: 1 - of a clear prognostic gradient according to number of bony metastatic sites; 2 - that other sites of progression contributed to PCSM to a lesser extent than bone progression; and 3 - that further bony metastatic progression in men with up to 3 bony metastases had a major impact on PCSM.

CONCLUSION

Randomised trials are essential to determine the value of extirpative treatment for oligometastatic bony metastases due to PC.

Clinical applications of stereotactic radiation therapy for oligometastatic cancer patients: a disease-oriented approach

Oligometastases from solid tumors are currently recognized as a distinct clinical entity, corresponding to an intermediate state between local and widespread disease. It has been suggested that local ablative therapies (including surgery, radiofrequency ablation and radiation therapy) play an important role in this setting, in combination or not with systemic therapies, particularly in delaying disease progression and hopefully in increasing the median survival time. Stereotactic body radiation therapy (SBRT) rapidly emerged in recent years as one of the most effective and less toxic local treatment modalities for lung, liver, adrenal, brain and bone metastases. The aim of this review was to focus on its clinical role for oligometastatic disease in four major cancer subtypes: lung, breast, colorectal and prostate. On the basis of the available evidence, SBRT is able to provide high rates of local tumor control without significant toxicity. Its global impact on survival is uncertain; however, in specific subpopulations of oligometastatic patients there is a trend towards a significant improvement in progression-free and overall survival rates; these important data might be used as a platform for clinical decision-making and establish the basis for the current and future prospective trials investigating its role with or without systemic treatments.

Clinical and molecular markers of long-term survival after oligometastasis-directed stereotactic body radiotherapy (SBRT)

BACKGROUND

The selection of patients for oligometastasis-directed ablative therapy remains a challenge. The authors report on clinical and molecular predictors of survival from a stereotactic body radiotherapy (SBRT) dose-escalation trial for oligometastases.

METHODS

Patients who had from 1 to 5 metastases, a life expectancy of >3 months, and a Karnofsky performance status of >60 received escalating SBRT doses to all known cancer sites. Time to progression, progression-free survival, and overall survival (OS) were calculated at the completion of SBRT, and clinical predictors of OS were modeled. Primary tumor microRNA expression was analyzed to identify molecular predictors of OS.

RESULTS

Sixty-one evaluable patients were enrolled from 2004 to 2009. The median follow-up was 2.3 years for all patients (range, 0.2-9.3 years) and 6.8 years for survivors (range, 2.0-9.3 years). The median, 2-year, and 5-year estimated OS were 2.4 years, 57%, and 32%, respectively. The rate of progression after SBRT was associated with an increased risk of death (hazard ratio [HR], 1.44; 95% confidence interval [CI], 1.24-1.82). The time from initial cancer diagnosis to metastasis (HR, 0.98; 95% CI, 0.98-0.99), the time from metastasis to SBRT (HR, 0.98; 95% CI, 0.98-0.99), and breast cancer histology (HR, 0.12; 95% CI, 0.07-0.37) were significant predictors of OS. In an exploratory analysis, a candidate classifier using expression levels of 3 microRNAs (miR-23b, miR-449a, and miR-449b) predicted survival among 17 patients who had primary tumor microRNA expression data available.

CONCLUSIONS

A subset of oligometastatic patients achieves long-term survival after metastasis-directed SBRT. Clinical features and primary tumor microRNA expression profiling, if validated in an independent dataset, may help select oligometastatic patients most likely to benefit from metastasis-directed therapy. Cancer 2016;122:2242-50. © 2016 American Cancer Society.

Immunotherapy and stereotactic ablative radiotherapy (ISABR): a curative approach?

Conventional radiotherapy, in addition to its well-established tumoricidal effects, can also activate the host immune system. Radiation therapy modulates tumour phenotypes, enhances antigen presentation and tumour immunogenicity, increases production of cytokines and alters the tumour microenvironment, enabling destruction of the tumour by the immune system. Investigating the combination of radiotherapy with immunotherapeutic agents, which also promote the host antitumour immune response is, therefore, a logical progression. As the spectrum of clinical use of stereotactic radiotherapy continues to broaden, the question arose as to whether the ablative radiation doses used can also stimulate immune responses and, if so, whether we can amplify these effects by combining immunotherapy and stereotactic ablative radiotherapy (SABR). In this Perspectives article, we explore the preclinical and clinical evidence supporting activation of the immune system following SABR. We then examine studies that provide data on the effectiveness of combining these two techniques - immunotherapy and SABR - in an approach that we have termed 'ISABR'. Lastly, we provide general guiding principles for the development of future clinical trials to investigate the efficacy of ISABR in the hope of generating further interest in these exciting developments.

Exploratory Analysis on Overall Survival after Either Surgery or Stereotactic Radiotherapy for Lung Oligometastases from Colorectal Cancer

AIMS

Lung metastasectomy and, more recently, stereotactic body radiotherapy (SBRT), are frequently proposed to stage IV oligometastatic colorectal cancer (CRC) patients. In the absence of a randomised comparison between the two treatments, we aimed to retrospectively explore the effect on overall survival and progression-free survival (PFS) in a comparative cohort study.

MATERIALS AND METHODS

We included patients who consecutively underwent surgery (n = 142) or SBRT (n = 28) as first local therapy at the time of lung progression, between 2005 and 2012. Both overall survival and PFS functions according to treatment were calculated using the Kaplan-Meier method and compared using the Log-rank test. The effect of treatment on overall survival and PFS was estimated by Cox models using different adjustment methods.

RESULTS

Patients receiving SBRT were older and were treated more recently, whereas the two cohorts were similar for most baseline prognostic factors. Overall survival at 1 and 2 years was 0.89 and 0.77 for SBRT and 0.96 and 0.82 for surgery (P = 0.134), respectively. Multivariable analyses did not highlight a clear treatment effect on overall survival (adjusted hazard ratioSBRT versus surgery = 1.71; 95% confidence interval 0.82-3.54; P = 0.149) and even smaller differences using the inverse probability treatment weighting method (hazard ratioSBRT versus surgery = 1.28, 95% confidence interval 0.58-2.82; P = 0.547). The results of PFS were unreliable because different follow-up protocols were applied in the two cohorts.

CONCLUSION

With limitations consisting in the retrospective observational design and different sample sizes, the results of this explorative analysis indicate that overall survival probability after SBRT is similar to surgery for the first 2 years from treatment. This finding supports the need for high-quality trials comparing different treatment modalities for lung oligometastases from CRC.

Is Surgery Warranted for Oligometastatic Disease?

The development of metastases after curative treatment can be seen as a failure. A common justification for the removal of metastases is that the knowledge that they are there may cause psychological distress, a real symptom that may be relieved by their removal. Although it is a commonly used justification for metastasectomy, the authors are unaware of any studies confirming or quantifying the health gain. This article strongly challenges the belief in clinical effectiveness and demonstrates that it is supported neither by a sound biological rationale nor by any good evidence. Reasons are suggested why this unfounded belief has become so prevalent.

14q32-encoded microRNAs mediate an oligometastatic phenotype

Oligometastasis is a clinically distinct subset of metastasis characterized by a limited number of metastases potentially curable with localized therapies. We analyzed pathways targeted by microRNAs over-expressed in clinical oligometastasis samples and identified suppression of cellular adhesion, invasion, and motility pathways in association with the oligometastatic phenotype. We identified miR-127-5p, miR-544a, and miR-655-3p encoded in the 14q32 microRNA cluster as co-regulators of multiple metastatic pathways through repression of shared target genes. These microRNAs suppressed cellular adhesion and invasion and inhibited metastasis development in an animal model of breast cancer lung colonization. Target genes, including TGFBR2 and ROCK2, were key mediators of these effects. Understanding the role of microRNAs expressed in oligometastases may lead to improved identification of and interventions for patients with curable metastatic disease, as well as an improved understanding of the molecular basis of this unique clinical entity.

Stereotactic ablative radiotherapy for centrally located early stage non-small-cell lung cancer: what we have learned

Image-guided stereotactic ablative radiotherapy (SABR; also called stereotactic body radiotherapy or radiosurgery) has become a standard treatment for medically inoperable peripherally located stage I non-small-cell lung cancer (NSCLC) and can achieve local control rates in excess of 90%. However, the role of SABR for centrally located lesions remains controversial because of concerns about the potential for severe toxic effects. When cutting-edge technologies and knowledge-based optimization of SABR planning that considers both target coverage and normal tissue sparing are used, some patients with central lesions can be safely and effectively cured of early stage NSCLC. However, delivery of ablative doses of radiation to critical structures such as bronchial tree, esophagus, major vessels, heart, and the brachial plexus/phrenic nerve could produce severe, potentially lethal toxic effects. Here, we address the current understanding of indications, dose regimens, planning optimization, and normal tissue dose-volume constraints for using SABR to treat central NSCLC.

The role of stereotactic ablative radiotherapy (SBRT) in the management of oligometastatic non small cell lung cancer

Our understanding of metastatic disease has evolved significantly in the last 20 years. Considered strictly a systemic issue, local treatment would only have significant impact in terms of palliation. However, Hellman and Weichselbaum stated that there might be an intermediate state, in which controlling limited metastatic sites could improve oncologic outcomes. This is called an oligometastatic state, a point between locally confined cancer and widespread disease [1,2]. As treatment with chemotherapy alone for non small cell lung cancer (NSCLC) yields median survivals of 8-11 months [3] and minimal chances of long term survival, new strategies are needed to offer better odds for metastatic patients. Outcomes tend to be better in patients with low volume metastatic disease. [4,5], leading us to question whether the oligometastatic group of patients will gain from a more radical treatment paradigm. In this setting, ablative treatments like surgery or SBRT may provide longer survival and better local control times. There is a rationale for the use of ablative local treatments, as most failures after chemotherapy occur at sites initially affected by disease, and these sites could be a source of further dissemination. Also, chemotherapy resistance can adversely impact resolution of metastatic disease [6]. In rare cases, the abscopal effect (an immune effect arising after radiotherapy in non irradiated metastatic sites) has been described [7,8]. In this review article, we address the impact of SBRT in oligometastatic NSCLC, the most relevant prognostic factors, indications and a site specific review. This review will focus on SBRT for extracranial disease as the role for intracranial SBRT is established.

Stereotactic radiotherapy for early lung cancer: Evidence-based approach and future directions

AIM

To review key studies evaluating stereotactic radiotherapy in the setting of early-stage non-small cell lung cancer (NSCLC) for inoperable or high-risk patients, and discuss areas of ongoing research and clinical trials.

BACKGROUND

The use of stereotactic radiotherapy for the treatment of early stage non-small cell lung cancer (NSCLC) has increased rapidly over the past decade. Numerous studies have reported outcomes for patients treated with SBRT who are unfit for surgical resection, or at high risk of surgical complications.

MATERIALS AND METHODS

A narrative review.

RESULTS

The preponderance of evidence suggests that SBRT is associated with excellent local control (∼90% at 3 years) and a favorable toxicity profile. In patients with higher operative risks, such as the elderly and patients with severe COPD, SBRT may provide a less-toxic treatment than surgery with similar oncologic outcomes. Ongoing studies are evaluating the use of SBRT for locally advanced or oligometastatic NSCLC.

CONCLUSIONS

A large body of evidence now exists to support the use of SBRT for early-stage NSCLC. Decisions regarding the optimal choice of treatment should be individualized, and made in the context of a multidisciplinary team.

Synchronous Oligometastatic Non-Small Cell Lung Cancer and Isolated Renal Cell Carcinoma: A Case Report and Literature Review

A 58-year-old gentleman presenting with a progressive headache, visual disturbance, decreased appetite, and weight loss was found to have a localized clear cell carcinoma of the kidney and synchronous Stage IV non-small cell lung cancer with a solitary brain metastasis. This case illustrates the challenges in distinguishing between primary and metastatic disease in a patient with both renal cell carcinoma and lung cancer. We highlight the uncertainties in the diagnosis and management of this unique clinical scenario and the potential implications on prognosis.

Increasing the Therapeutic Ratio of Stereotactic Ablative Radiotherapy by Individualized Isotoxic Dose Prescription

To obtain a favorable tradeoff between treatment benefits and morbidity ("therapeutic ratio"), radiotherapy (RT) dose is prescribed according to the tumor volume, with the goal of controlling the disease while respecting normal tissue tolerance levels. We propose a new paradigm for tumor dose prescription in stereotactic ablative radiotherapy (SABR) based on organ-at-risk (OAR) tolerance levels called isotoxic dose prescription (IDP), which is derived from experiences and limitations of conventionally fractionated radiotherapy. With IDP, the radiation dose is prescribed based on the predefined level of normal tissue complication probability of a nearby dose-limiting OAR at a prespecified dose-volume constraint. Simultaneously, the prescribed total tumor dose (TTD) is maximized to the technically highest achievable level in order to increase the local tumor control probability (TCP). IDP is especially relevant for tumors located at eloquent locations or for large tumors in which severe toxicity has been described. IDP will result in a lower RT dose or a treatment scheduled with more fractions if the OAR tolerance level is exceeded, and potential dose escalation occurs when the OAR tolerance level allows it and when it is expected to be beneficial (if TCP < 90%). For patients with small tumors at noneloquent sites, the current SABR dose prescription already results in high rates of local control at low toxicity rates. In this review, the concept of IDP is described in the context of SABR.

Extending the Frontiers Beyond Thermal Ablation by Radiofrequency Ablation: SBRT, Brachytherapy, SIRT (Radioembolization)

Metastatic spread of the primary is still defined as the systemic stage of disease in treatment guidelines for various solid tumors. This definition is the rationale for systemic therapy. Interestingly and despite the concept of systemic involvement, surgical resection as a local treatment has proven to yield long-term outcomes in a subset of patients with limited metastatic disease, supporting the concept of oligometastatic disease. Radiofrequency ablation has yielded favorable outcomes in patients with hepatocellular carcinoma and colorectal metastases, and some studies indicate its prognostic potential in combined treatments with systemic therapies. However, some significant technical limitations apply, such as size limitation, heat sink effects, and unpredictable heat distribution to adjacent risk structures. Interventional and non-invasive radiotherapeutic techniques may overcome these limitations, expanding the options for oligometastatic patients and cytoreductive concepts. Current data suggest very high local control rates even in large tumors at any given location in the human body. The article focusses on the characteristics and possibilities of stereotactic body radiation therapy, interstitial high-dose-rate brachytherapy, and Yttrium-90 radioembolization. In this article, we discuss the differences of the technical preferences as well as their impact on indications. Current data is presented and discussed with a focus on application in oligometastatic or cytoreductive concepts in different tumor biologies.