Intensity Modulating and Other Radiation Therapy Devices for Dose Painting

Radiation and Immune Checkpoint Inhibitors: Combination Therapy for Treatment of Hepatocellular Carcinoma

The liver tumor immune microenvironment has been thought to possess a critical role in the development and progression of hepatocellular carcinoma (HCC). Despite the approval of immune checkpoint inhibitors (ICIs), such as programmed cell death receptor 1 (PD-1)/programmed cell death ligand 1 (PD-L1) and cytotoxic T lymphocyte associated protein 4 (CTLA-4) inhibitors, for several types of cancers, including HCC, liver metastases have shown evidence of resistance or poor response to immunotherapies. Radiation therapy (RT) has displayed evidence of immunosuppressive effects through the upregulation of immune checkpoint molecules post-treatment. However, it was revealed that the limitations of ICIs can be overcome through the use of RT, as it can reshape the liver immune microenvironment. Moreover, ICIs are able to overcome the RT-induced inhibitory signals, effectively restoring anti-tumor activity. Owing to the synergetic effect believed to arise from the combination of ICIs with RT, several clinical trials are currently ongoing to assess the efficacy and safety of this treatment for patients with HCC.

Molecular imaging of tumor hypoxia: Evolution of nitroimidazole radiopharmaceuticals and insights for future development

Though growing evidence has been collected in support of the concept of dose escalation based on the molecular level images indicating hypoxic tumor sub-volumes that could be radio-resistant, validation of the concept is still a work in progress. Molecular imaging of tumor hypoxia using radiopharmaceuticals is expected to provide the required input to plan dose escalation through Image Guided Radiation Therapy (IGRT) to kill/control the radio-resistant hypoxic tumor cells. The success of the IGRT, therefore, is heavily dependent on the quality of images obtained using the radiopharmaceutical and the extent to which the image represents the true hypoxic status of the tumor in spite of the heterogeneous nature of tumor hypoxia. Available literature on radiopharmaceuticals for imaging hypoxia is highly skewed in favor of nitroimidazole as the pharmacophore given their ability to undergo oxygen dependent reduction in hypoxic cells. In this context, present review on nitroimidazole radiopharmaceuticals would be immensely helpful to the researchers to obtain a birds-eye view on what has been achieved so far and what can be tried differently to obtain a better hypoxia imaging agent. The review also covers various methods of radiolabeling that could be utilized for developing radiotracers for hypoxia targeting applications.

Non-Surgical Locoregional Therapies Alone or in Combination with Systemic Therapy in Patients with Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer, representing the third-leading cause of cancer-related deaths worldwide. Curative intent treatment options for patients with HCC include liver transplantation, resection and ablation of small lesions. Other potentially curative therapies include cryoablation, microwave ablation and percutaneous alcohol injection. For locally advanced disease, different arterially directed therapies including transarterial chemoembolization and selective internal radiation therapy, plus external beam radiation including three-dimensional conformal radiation therapy, intensity-modulated radiation therapy, stereotactic body radiation therapy and proton beam therapy, are available or studied. Systemic therapies based on checkpoint inhibitors and tyrosine kinase inhibitors are available for the management of metastatic HCC and sometimes for locally advanced disease. Combinations of locoregional therapies with systemic drugs are currently the subject of several clinical trials.

Treatment-integrated imaging, radiomics, and personalised radiotherapy: the future is at hand

Since the introduction of computed tomography for planning purposes in the 1970s, we have been observing a continuous development of different imaging methods in radiotherapy. The current achievements of imaging technologies in radiotherapy enable more than just improvement of accuracy on the planning stage. Through integrating imaging with treatment machines, they allow advanced control methods of dose delivery during the treatment. This article reviews how the integration of existing and novel forms of imaging changes radiotherapy and how these advances can allow a more individualised approach to cancer therapy. We believe that the significant challenge for the next decade is the continued integration of a range of different imaging devices into linear accelerators. These imaging modalities should show intra-fraction changes in body morphology and inter-fraction metabolic changes. As the use of these more advanced, integrated machines grows, radiotherapy delivery will become more accurate, thus resulting in better clinical outcomes: higher cure rates with fewer side effects.

Developing quality assurance tests for simultaneous Positron Emission Tomography - Magnetic Resonance imaging for radiotherapy planning

Background and purpose Simultaneous Positron Emission Tomography - Magnetic Resonance (PET-MR) imaging can potentially improve radiotherapy by enabling more accurate tumour delineation and dose painting. The use of PET-MR imaging for radiotherapy planning requires a comprehensive Quality Assurance (QA) programme to be developed. This study aimed to develop the QA tests required and assess their repeatability and stability. Materials and methods QA tests were developed for: MR image quality, MR geometric accuracy, electromechanical accuracy, PET-MR alignment accuracy, Diffusion Weighted (DW)-MR Apparent Diffusion Coefficient (ADC) accuracy and PET Standard Uptake Value (SUV) accuracy. Each test used a dedicated phantom and was analysed automatically or semi-automatically, with in-house software. Repeatability was evaluated by three same-day measurements with independent phantom positions. Stability was assessed through 12 monthly measurements. Results The repeatability Standard Deviations (SDs) of distortion for the MR geometric accuracy test were ⩽ 0.7 mm . The repeatability SDs in ADC difference from reference were ⩽ 3 % for the DW-MR accuracy test. The PET SUV difference from reference repeatability SD was 0.3 % . The stability SDs agreed within 0.6 mm , 1 percentage point and 1.4 percentage points of the repeatability SDs for the geometric, ADC and SUV accuracy tests respectively. There were no monthly trends apparent. These results were representative of the other tests. Conclusions QA Tests for radiotherapy planning PET-MR have been developed. The tests appeared repeatable and stable over a 12-month period. The developed QA tests could form the basis of a QA programme that enables high-quality, robust PET-MR imaging for radiotherapy planning.

The History of Neurosurgical Spinal Oncology: From Inception to Modern-Day Practices

The neurosurgical management of spinal neoplasms has undergone immense development in parallel with advancements made in general spine surgery. Laminectomies were performed as the first surgical procedures used to treat spinal neoplasms. Since then, neurosurgical spinal oncology has started to incorporate techniques that have developed from recent advances in minimally invasive spine surgery. Neurosurgery has also integrated radiotherapy into the treatment of spine tumors. In this historical vignette, we present a vast timeline spanning from the Byzantine period to the current day and recount the major advancements in the management of spinal neoplasms.

Advances in Radiobiology of Stereotactic Ablative Radiotherapy

Radiotherapy (RT) has been developed with remarkable technological advances in recent years. The accuracy of RT is dramatically improved and accordingly high dose radiation of the tumors could be precisely projected. Stereotactic radiosurgery (SRS) and stereotactic body radiotherapy (SBRT), also known as stereotactic ablative radiotherapy (SABR), are rapidly becoming the accepted practice in treating solid small sized tumors. Compared with the conventional fractionation external beam radiotherapy (EBRT), SABR with very high dose per fraction and hypo-fractionated irradiation yields convincing and satisfied therapeutic effects with low toxicity, since tumor cells could be directly ablated like radiofrequency ablation (RFA). The impressive clinical efficacy of SABR is greater than expected by the linear quadratic model and the conventional radiobiological principles, i.e., 4 Rs of radiobiology (reoxygenation, repair, redistribution, and repopulation), which may no longer be suitable for the explanation of SABR's ablation effects. Based on 4 Rs of radiobiology, 5 Rs of radiobiology emphasizes the intrinsic radiosensitivity of tumor cells, which may correlate with the responsiveness of SABR. Meanwhile, SABR induced the radiobiological alteration including vascular endothelial injury and the immune activation, which has been indicated by literature reported to play a crucial role in tumor control. However, a comprehensive review involving these advances in SABR is lacking. In this review, advances in radiobiology of SABR including the role of the 4 Rs of radiobiology and potential radiobiological factors for SABR will be comprehensively reviewed and discussed.

Radiomics for radiation oncologists: are we ready to go?

Radiomics have emerged as an exciting field of research over the past few years, with very wide potential applications in personalised and precision medicine of the future. Radiomics-based approaches are still however limited in daily clinical practice in oncology. This review focus on how radiomics could be incorporated into the radiation therapy pipeline, and globally help the radiation oncologist, from the tumour diagnosis to follow-up after treatment. Radiomics could impact on all steps of the treatment pipeline, once the limitations in terms of robustness and reproducibility are overcome. Major ongoing efforts should be made to collect and share data in the most standardised manner possible.

CT-based dose recalculations in head and neck cancer radiotherapy: comparison of daily dose recalculations to less time-consuming approaches

BACKGROUND

The goal of this study was to investigate if daily dose recalculations are necessary or if less time-consuming approaches can be used to identify dose differences to the planned dose in patients with head and neck cancers (H&N).

METHODS

For 12 H&N patients treated with helical tomotherapy, daily dose calculations were performed retrospectively. Four different summation doses (SuDo) were calculated: DayDo (daily dose calculation), MVCTx2, MVCTx5, and MVCTx10 (dose calculations every second, fifth, and tenth fraction). Dose recalculations were depicted on the last contoured mega voltage CT (MVCT). The DayDo was compared to the planned dose and to the less time-consuming SuDo scenarios. The doses were assessed for the planning target volume (PTV) and the organs at risk (OARs): mandible (mand), spinal cord (SC), spinal cord +5 mm (SC+5 mm), parotid glands (PG).

RESULTS

The ipsilateral PG, contralateral PG, and PTV volume decreased by -22.5% (range: -34.8 to 5.2%), -19.5% (-31.5 to 15.8%), and -2.6% (-16.7 to 0.2%), respectively. There was a significant median mean dose (Dmean) dose difference for DayDo compared to the planned dose for PG total of 1.9 Gy (-3.3 to 7.3 Gy). But less time-consuming SuDo compared to DayDo showed statistically significant but not clinically relevant (<2%) dose differences for several organs. Hence the small dose difference to the gold standard (DayDo), we recommend dose recalculations every fifth MVCT in order to identify the occurrence of dose differences compared to the planned dose.

CONCLUSION

Daily dose calculations are the most precise to assess dose differences between actual and planned dose. Dose recalculations on every fifth MVCT (i. e., weekly control CTs) are an applicable and time-saving way of identifying patients with significant dose differences compared to the planned dose.

Oxygen Sensing, Hypoxia Tracing and in Vivo Imaging with Functional Metalloprobes for the Early Detection of Non-communicable Diseases

Hypoxia has been identified as one of the hallmarks of tumor environments and a prognosis factor in many cancers. The development of ideal chemical probes for imaging and sensing of hypoxia remains elusive. Crucial characteristics would include a measurable response to subtle variations of pO2 in living systems and an ability to accumulate only in the areas of interest (e.g., targeting hypoxia tissues) whilst exhibiting kinetic stabilities in vitro and in vivo. A sensitive probe would comprise platforms for applications in imaging and therapy for non-communicable diseases (NCDs) relying on sensitive detection of pO2. Just a handful of probes for the in vivo imaging of hypoxia [mainly using positron emission tomography (PET)] have reached the clinical research stage. Many chemical compounds, whilst presenting promising in vitro results as oxygen-sensing probes, are facing considerable disadvantages regarding their general application in vivo. The mechanisms of action of many hypoxia tracers have not been entirely rationalized, especially in the case of metallo-probes. An insight into the hypoxia selectivity mechanisms can allow an optimization of current imaging probes candidates and this will be explored hereby. The mechanistic understanding of the modes of action of coordination compounds under oxygen concentration gradients in living cells allows an expansion of the scope of compounds toward in vivo applications which, in turn, would help translate these into clinical applications. We summarize hereby some of the recent research efforts made toward the discovery of new oxygen sensing molecules having a metal-ligand core. We discuss their applications in vitro and/or in vivo, with an appreciation of a plethora of molecular imaging techniques (mainly reliant on nuclear medicine techniques) currently applied in the detection and tracing of hypoxia in the preclinical and clinical setups. The design of imaging/sensing probe for early-stage diagnosis would longer term avoid invasive procedures providing platforms for therapy monitoring in a variety of NCDs and, particularly, in cancers.

Recent advances in radiation oncology

Radiotherapy (RT) is very much a technology-driven treatment modality in the management of cancer. RT techniques have changed significantly over the past few decades, thanks to improvements in engineering and computing. We aim to highlight the recent developments in radiation oncology, focusing on the technological and biological advances. We will present state-of-the-art treatment techniques, employing photon beams, such as intensity-modulated RT, volumetric-modulated arc therapy, stereotactic body RT and adaptive RT, which make possible a highly tailored dose distribution with maximum normal tissue sparing. We will analyse all the steps involved in the treatment: imaging, delineation of the tumour and organs at risk, treatment planning and finally image-guidance for accurate tumour localisation before and during treatment delivery. Particular attention will be given to the crucial role that imaging plays throughout the entire process. In the case of adaptive RT, the precise identification of target volumes as well as the monitoring of tumour response/modification during the course of treatment is mainly based on multimodality imaging that integrates morphological, functional and metabolic information. Moreover, real-time imaging of the tumour is essential in breathing adaptive techniques to compensate for tumour motion due to respiration. Brief reference will be made to the recent spread of particle beam therapy, in particular to the use of protons, but also to the yet limited experience of using heavy particles such as carbon ions. Finally, we will analyse the latest biological advances in tumour targeting. Indeed, the effectiveness of RT has been improved not only by technological developments but also through the integration of radiobiological knowledge to produce more efficient and personalised treatment strategies.

Intensity-modulated radiotherapy for hepatocellular carcinoma: dosimetric and clinical results

Since the introduction of 3-dimensional conformal radiotherapy (3DCRT), new radiotherapy techniques have expanded the indication of radiotherapy for the treatment of hepatocellular carcinoma (HCC), from the hitherto palliative to a now curative-intent purpose. Intensity-modulated radiotherapy (IMRT), currently the most advanced radiotherapy technique, is considered an attractive option for the treatment of HCC, and is more widely applied because it can deliver a higher dose to the tumor than 3DCRT while sparing surrounding normal organs. However, the advantages and potential disadvantages of IMRT for treating HCC have not been fully established. This article deals with three different IMRT techniques, including static IMRT and volumetric modulated arc therapy using conventional multileaf collimator (MLC) mounted linear accelerators, and helical IMRT using binary MLC mounted helical tomotherapy machine. We review dosimetric and clinical studies for these IMRT techniques for the treatment of HCC.

Pulmonary injury associated with radiation therapy - Assessment, complications and therapeutic targets

Pulmonary injury is more common in patients undergoing radiation therapy for lungs and other thoracic malignancies. Recently with the use of most-advanced technologies powerful doses of radiation can be delivered directly to tumor site with exquisite precision. The awareness of technical and clinical parameters that influence the chance of radiation induced lung injury is important to guide patient selection and toxicity minimization strategies. At the cellular level, radiation activates free radical production, leading to DNA damage, apoptosis, cell cycle changes, and reduced cell survival. Preclinical research shows the potential for therapies targeting transforming growth factor-β (TGF-B), Toll like receptor (TLRs), Tumour necrosis factor-alpha (TNF-alpha), Interferon gamma (IFN-γ) and so on that may restore lung function. At present Amifostine (WR-2721) is the only approved broad spectrum radioprotector in use for patients undergoing radiation therapy. Newer techniques also offer the opportunity to identify new biomarkers and new targets for interventions to prevent or ameliorate these late effects of lung damage.

Variations in target volume definition and dose to normal tissue using anatomic versus biological imaging (18 F-FDG-PET) in the treatment of bone metastases: results from a 3-arm randomized phase II trial

INTRODUCTION

To report the impact on target volume delineation and dose to normal tissue using anatomic versus biological imaging (¹⁸ F-FDG-PET) for bone metastases.

METHODS

Patients with uncomplicated painful bone metastases were randomized (1:1:1) and blinded to receive either 8 Gy in a single fraction with conventionally planned radiotherapy (ConvRT-8 Gy) or 8 Gy in a single fraction with dose-painting-by-numbers (DPBN) dose range between 6 and 10 Gy) (DPBN-8 Gy) or 16 Gy in a single fraction with DPBN (dose range between 14 and 18 Gy) (DPBN-16 Gy). The primary endpoint was overall pain response at 1 month. Volumes of the gross tumour volume (GTV) - both biological (GTV_PET ) and anatomical (GTV_CT ) -, planning target volume (PTV), dose to the normal tissue and maximum standardized-uptake values (SUV_MAX ) were analysed (secondary endpoint).

RESULTS

Sixty-three percent of the GTV_CT volume did not show ¹⁸ F-FDG-uptake. On average, 20% of the GTV_PET volume was outside GTV_CT . The volume of normal tissue receiving 4 Gy, 6 Gy and 8 Gy was at least 3×, 6× and 13× smaller in DPBN-8 Gy compared to ConvRT-8 Gy and DPBN-16 Gy (P < 0.05).

CONCLUSION

Positron emitting tomography-information potentially changes the target volume for bone metastases. DPBN between 6 and 10 Gy significantly decreases dose to the normal tissue compared to conventional radiotherapy.

Evaluating the four-dimensional cone beam computed tomography with varying gantry rotation speed

OBJECTIVE

The purpose of this work was to evaluate the four-dimensional cone beam CT (4DCBCT) imaging with different gantry rotation speed.

METHODS

All the 4DCBCT image acquisitions were carried out in Elekta XVI Symmetry™ system (Elekta AB, Stockholm, Sweden). A dynamic thorax phantom with tumour mimicking inserts of diameter 1, 2 and 3 cm was programmed to simulate the respiratory motion (4 s) of the target. 4DCBCT images were acquired with different gantry rotation speeds (36°, 50°, 75°, 100°, 150° and 200° min(-1)). Owing to the technical limitation of 4DCBCT system, average cone beam CT (CBCT) images derived from the 10 phases of 4DCBCT were used for the internal target volume (ITV) contouring. ITVs obtained from average CBCT were compared with the four-dimensional CT (4DCT). In addition, the image quality of 4DCBCT was also evaluated for various gantry rotation speeds using Catphan(®) 600 (The Phantom Laboratory Inc., Salem, NY).

RESULTS

Compared to 4DCT, the average CBCT underestimated the ITV. The ITV deviation increased with increasing gantry speed (-10.8% vs -17.8% for 36° and 200° min(-1) in 3-cm target) and decreasing target size (-17.8% vs -26.8% for target diameter 3 and 1 cm in 200° min(-1)). Similarly, the image quality indicators such as spatial resolution, contrast-to-noise ratio and uniformity also degraded with increasing gantry rotation speed.

CONCLUSION

The impact of gantry rotation speed has to be considered when using 4DCBCT for ITV definition. The phantom study demonstrated that 4DCBCT with slow gantry rotation showed better image quality and less ITV deviation.

ADVANCES IN KNOWLEDGE

Usually, the gantry rotation period of Elekta 4DCBCT system is kept constant at 4 min (50° min(-1)) for acquisition, and any attempt of decreasing/increasing the acquisition duration requires careful investigation. In this study, the 4DCBCT images with different gantry rotation speed were evaluated.

Intensity-modulated radiotherapy for head and neck surgeons

The development of intensity-modulated radiotherapy (IMRT) has played a major role in improving outcomes and decreasing morbidity in patients with head and neck cancer. This review addresses this vital modality with a focus on the important role of the head and neck surgeon. The technique as well as its benefits and points of caution are outlined, the definitions of tumor and treatment volumes are discussed, and the dose and fractionation are detailed. Following this are several sections dedicated to the role of the head and neck surgeon in the planning of both definitive and postoperative radiotherapy to the primary site and neck. There is a focus throughout on anatomic and surgical considerations; commonly encountered situations are illustrated. With a deeper understanding of this technique and their own pivotal contribution to target delineation, head and neck surgeons will be poised to expand their role and improve cancer care for their patients. © 2015 Wiley Periodicals, Inc. Head Neck 38: E2368-E2373, 2016.

Dose painting with Gamma Knife: Two techniques for delivering different doses to areas of recurrent or residual tumor after resection of brain metastases

PURPOSE

We investigated the feasibility of using Gamma Knife (GK) radiosurgery for "dose painting" to deliver higher doses to residual or recurrent nodules and surgical cavity after resection of brain metastases.

METHODS AND MATERIALS

Two integrated boost techniques were developed with GK. The single-target technique delineated both the surgical cavity (cavity) and gross disease (nodule) as a single target. Dose was prescribed to the target with the goal of covering the nodule with a higher dose. The 2-target technique delineated the cavity and nodule as separate target volumes, each prescribed to its own dose and planned separately. Two cases were used to illustrate each technique. The single-target technique was used to deliver 16 Gy to a smaller cavity (7 cm(3)) and a 20-Gy integrated boost to 2 nodules (case 1). The 2-target technique was used to deliver 12 Gy to a larger cavity (21.5 cm(3)) and 20 Gy to a single nodule (case 2).

RESULTS

For both cases, the cavity coverage with the prescribed dose was 100% with the standard plan and integrated boost techniques. For case 1, compared with a standard plan, the single-target technique improved the 20-Gy nodule coverage from 89.7% (nodule 1) and 97.9% (nodule 2) to 100% (both) and increased the minimum dose from 16.6 Gy to 20.8 Gy (nodule 1) and from 19.4 Gy to 20.8 Gy (nodule 2). For case 2, compared with a standard plan, the 2-target technique improved the 20-Gy nodule coverage from 4% to 100% and the minimum dose from 13.8 Gy to 21 Gy.

CONCLUSIONS

Both GK integrated boost approaches allowed for effective delivery of higher doses to residual or recurrent nodules in a surgical cavity. In our experience, the single-target technique works well for small cavities, whereas the 2-target technique is well suited for larger cavities.

Non-invasive MR assessment of macroscopic and microscopic vascular abnormalities in the rectal tumour-surrounding mesorectum

OBJECTIVES

To evaluate the MRI macroscopic and microscopic parameters of mesorectal vasculature in rectal cancer patients.

METHODS

Thirteen patients with rectal adenocarcinoma underwent a dynamic contrast-enhanced MRI at 1.5 T using a blood pool agent at the primary staging. Mesorectal macrovascular features, i.e., the number of vascular branches, average diameter and length, were assessed from baseline-subtracted post-contrast images by two independent readers. Mesorectal microvascular function was investigated by means of area under the enhancement-time curve (AUC). Histopathology served as reference standard of the tumour response to CRT.

RESULTS

The average vessel branching in the mesorectum around the tumour and normal rectal wall was 8.2 ± 3.8 and 1.7 ± 1.3, respectively (reader1: p = 0.001, reader2: p = 0.002). Similarly, the tumour-surrounding mesorectum displayed circa tenfold elevated AUC (p = 0.01). Interestingly, patients with primary node involvement had a twofold higher number of macrovascular branches compared to those with healthy nodes (reader1: p = 0.005 and reader2: p = 0.03). A similar difference was observed between good and poor responders to CRT, whose tumour-surrounding mesorectum displayed 10.7 ± 3.4 and 5.6 ± 1.5 vessels, respectively (reader1/reader2: p = 0.02).

CONCLUSIONS

We showed at baseline MRI of rectal tumours a significantly enhanced macrovascular structure and microvascular function in rectal tumour-surrounding mesorectum, and the association of primary mesorectal macrovascular parameters with node involvement and therapy response.

KEY POINTS

• Vascular MRI reveals macrovascular and microvascular abnormalities in the rectal tumour-surrounding mesorectum. • Formation of highly vascular stroma precedes the actual tumour invasion. • High macrovascular parameters are associated with node involvement. • Mesorectal vascular network differs for good and poor responders.

Dosimetric verification of gated delivery of electron beams using a 2D ion chamber array

The purpose of this study was to compare the dosimetric characteristics; such as beam output, symmetry and flatness between gated and non-gated electron beams. Dosimetric verification of gated delivery was carried for all electron beams available on Varian CL 2100CD medical linear accelerator. Measurements were conducted for three dose rates (100 MU/min, 300 MU/min and 600 MU/min) and two respiratory motions (breathing period of 4s and 8s). Real-time position management (RPM) system was used for the gated deliveries. Flatness and symmetry values were measured using Imatrixx 2D ion chamber array device and the beam output was measured using plane parallel ion chamber. These detector systems were placed over QUASAR motion platform which was programmed to simulate the respiratory motion of target. The dosimetric characteristics of gated deliveries were compared with non-gated deliveries. The flatness and symmetry of all the evaluated electron energies did not differ by more than 0.7 % with respect to corresponding non-gated deliveries. The beam output variation of gated electron beam was less than 0.6 % for all electron energies except for 16 MeV (1.4 %). Based on the results of this study, it can be concluded that Varian CL2100 CD is well suitable for gated delivery of non-dynamic electron beams.

Validation of functional imaging as a biomarker for radiation treatment response

Major advances in radiotherapy techniques, increasing knowledge of tumour biology and the ability to translate these advances into new therapeutic approaches are important goals towards more individualized cancer treatment. With the development of non-invasive functional and molecular imaging techniques such as positron emission tomography (PET)-CT scanning and MRI, there is now a need to evaluate potential new biomarkers for tumour response prediction, for treatment individualization is not only based on morphological criteria but also on biological tumour characteristics. The goal of individualization of radiotherapy is to improve treatment outcome and potentially reduce chronic treatment toxicity. This review gives an overview of the molecular and functional imaging modalities of tumour hypoxia and tumour cell metabolism, proliferation and perfusion as predictive biomarkers for radiation treatment response in head and neck tumours and in lung tumours. The current status of knowledge on integration of PET/CT/MRI into treatment management and bioimage-guided adaptive radiotherapy are discussed.

Alterations in anatomic and functional imaging parameters with repeated FDG PET-CT and MRI during radiotherapy for head and neck cancer: a pilot study

Background

The use of imaging to implement on-treatment adaptation of radiotherapy is a promising paradigm but current data on imaging changes during radiotherapy is limited. This is a hypothesis-generating pilot study to examine the changes on multi-modality anatomic and functional imaging during (chemo)radiotherapy treatment for head and neck squamous cell carcinoma (HNSCC).

Methods

Eight patients with locally advanced HNSCC underwent imaging including computed tomography (CT), Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography (PET)-CT and magnetic resonance imaging (MRI) (including diffusion weighted (DW) and dynamic contrast enhanced (DCE)) at baseline and during (chemo)radiotherapy treatment (after fractions 11 and 21). Regions of interest (ROI) were drawn around the primary tumour at baseline and during treatment. Imaging parameters included gross tumour volume (GTV) assessment, SUV_max, mean ADC value and DCE-MRI parameters including Plasma Flow (PF). On treatment changes and correlations between these parameters were analysed using a Wilcoxon rank sum test and Pearson’s linear correlation coefficient respectively. A p-value <0.05 was considered statistically significant.

Results

Statistically significant reductions in GTV-CT, GTV-MRI and GTV-DW were observed between all imaging timepoints during radiotherapy. Changes in GTV-PET during radiotherapy were heterogeneous and non-significant. Significant changes in SUV_max, mean ADC value, Plasma Flow and Plasma Volume were observed between the baseline and the fraction 11 timepoint, whilst only changes in SUV_max between baseline and the fraction 21 timepoint were statistically significant. Significant correlations were observed between multiple imaging parameters, both anatomical and functional; 20 correlations between baseline to the fraction 11 timepoint; 12 correlations between baseline and the fraction 21 timepoints; and 4 correlations between the fraction 11 and fraction 21 timepoints.

Conclusions

Multi-modality imaging during radiotherapy treatment demonstrates early changes (by fraction 11) in both anatomic and functional imaging parameters. All functional imaging modalities are potentially complementary and should be considered in combination to provide multi-parametric tumour assessment, to guide potential treatment adaptation strategies.

Trial Registration

ISRCTN Registry: ISRCTN34165059. Registered 2nd February 2015.

Radiation oncology: physics advances that minimize morbidity

ABSTRACT 

Radiation therapy has become an ever more successful treatment for many cancer patients. This is due in large part from advances in physics including the expanded use of imaging protocols combined with ever more precise therapy devices such as linear and particle beam accelerators, all contributing to treatments with far fewer side effects. This paper will review current state-of-the-art physics maneuvers that minimize morbidity, such as intensity-modulated radiation therapy, volummetric arc therapy, image-guided radiation, radiosurgery and particle beam treatment. We will also highlight future physics enhancements on the horizon such as MRI during treatment and intensity-modulated hadron therapy, all with the continued goal of improved clinical outcomes.

Intensity-modulated radiotherapy, not 3 dimensional conformal, is the preferred technique for treating locally advanced lung cancer

When used to treat lung cancer, intensity-modulated radiotherapy (IMRT) can deliver higher dose to the targets and spare more critical organs in lung cancer than can 3-dimensional conformal radiotherapy. However, tumor-motion management and optimized radiotherapy planning based on 4-dimensional computed tomography scanning are crucial to maximize the benefit of IMRT and to eliminate or minimize potential uncertainties. This article summarizes these strategies and reviews published findings supporting the safety and efficacy of IMRT for lung cancer.

Combining ultrasmall gadolinium-based nanoparticles with photon irradiation overcomes radioresistance of head and neck squamous cell carcinoma

Gadolinium based nanoparticles (GBNs, diameter 2.9±0.2nm), have promising biodistribution properties for theranostic use in-vivo. We aimed at demonstrating the radiosensitizing effect of these GBNs in experimental radioresistant human head and neck squamous cell carcinoma (SQ20B, FaDu and Cal33 cell lines). Combining 0.6mM GBNs with 250kV photon irradiation significantly decreased SQ20B cell survival, associated with an increase in non-reparable DNA double-strand breaks, the shortening of G2/M phase blockage, and the inhibition of cell proliferation, each contributing to the commitment of late apoptosis. Similarly, radiation resistance was overcome for SQ20B stem-like cells, as well as for FaDu and Cal33 cell lines. Using a SQ20B tumor-bearing mouse model, combination of GBNs with 10Gy irradiation significantly delayed tumor growth with an increase in late apoptosis and a decrease in cell proliferation. These results suggest that GBNs could be envisioned as adjuvant to radiotherapy for HNSCC tumors.

Targeted radiotherapy with gold nanoparticles: current status and future perspectives

Radiation therapy (RT) is the treatment of cancer and other diseases with ionizing radiation. The ultimate goal of RT is to destroy all the disease cells while sparing healthy tissue. Towards this goal, RT has advanced significantly over the past few decades in part due to new technologies including: multileaf collimator-assisted modulation of radiation beams, improved computer-assisted inverse treatment planning, image guidance, robotics with more precision, better motion management strategies, stereotactic treatments and hypofractionation. With recent advances in nanotechnology, targeted RT with gold nanoparticles (GNPs) is actively being investigated as a means to further increase the RT therapeutic ratio. In this review, we summarize the current status of research and development towards the use of GNPs to enhance RT. We highlight the promising emerging modalities for targeted RT with GNPs and the corresponding preclinical evidence supporting such promise towards potential clinical translation. Future prospects and perspectives are discussed.

A phase I study of concurrent weekly carboplatin and paclitaxel combined with intensity-modulated pelvic radiotherapy as an adjuvant treatment for early-stage cervical cancer patients with positive pelvic lymph nodes

OBJECTIVES

The objective of this study was to determine the maximum tolerated dose (MTD) and acute dose-limiting toxicities (DLTs) of intravenous carboplatin plus paclitaxel combined with intensity-modulated pelvic radiotherapy (pelvic IMRT) as an adjuvant treatment for early-stage cervical cancer patients with positive pelvic lymph nodes.

METHODS

Women with uterine cervical cancer who were treated with radical hysterectomy and pelvic lymphadenectomy and displayed positive pelvic lymph nodes were eligible for this study. The patients were postoperatively treated with pelvic IMRT (50.4 Gy). The concurrent weekly chemotherapy consisted of carboplatin (area under the curve [AUC], 2) and paclitaxel (starting at 35 mg/m² and escalating by 5 mg/m² in 3 patient cohorts). The primary end point of the escalation study was acute DLT that occurred within 30 days of the completion of radiation therapy.

RESULTS

Nine patients were enrolled and treated at 2 dose levels until DLT occurred. The median age of the patients was 47 years (range, 28-66 years). The median radiotherapy treatment time was 39.5 days (range, 38-64 days). At dose level I (35 mg/m² paclitaxel), 2 grade 3 leukopenia and a neutropenia were observed, but no DLT occurred. At dose level II (40 mg/m² paclitaxel), the first patient experienced a grade 2 hypersensitive reaction, which resulted in discontinuation of planned treatment. Thus, 2 more patients were evaluated at this dose level. Of these, 1 patient experienced febrile neutropenia, which was considered to be a DLT, and the other patient experienced long-lasting grade 3 leukopenia and grade 3 neutropenia, which resulted in the discontinuation of chemotherapy for 2 weeks (a DLT). We then evaluated 3 more patients at dose level 1, but no DLT occurred. The MTD of paclitaxel and carboplatin was thus defined as 35 mg/m² and an AUC of 2.0, respectively.

CONCLUSIONS

Weekly paclitaxel/carboplatin and pelvic IMRT is a reasonable adjuvant treatment regimen for cervical cancer patients after radical hysterectomy. The MTD of paclitaxel and carboplatin for future phase II trials of this regimen is 35 mg/m² and an AUC of 2.0, respectively.

Locally advanced rectal cancer: new findings in anticancer therapy

SUMMARY Rectal cancer accounts for nearly a third of colorectal cancer cases, with a mortality of 4–10 cases per 100,000 per year, thus accounting for 9% of cancer deaths both in males and in females in western countries. Management of locally advanced rectal cancer has undergone and continues to undergo significant progress in the last two decades: in particular, new multimodality strategies have contributed to marked improvements in terms of reduction of both local and distant recurrence rates. This review focuses and summarizes the effectiveness of multimodality approaches in the standard treatment programs for locally advanced rectal cancer and also discusses the ongoing research to improve these regimens.

Rational use of intensity-modulated radiation therapy: the importance of clinical outcome

During the last 2 decades, intensity-modulated radiation therapy (IMRT) became a standard technique despite its drawbacks of volume delineation, planning, robustness of delivery, challenging quality assurance, and cost as compared with non-IMRT. The theoretic advantages of IMRT dose distributions are generally accepted, but the clinical advantages remain debatable because of the lack of clinical assessment of the effort that is required to overshadow the disadvantages. Rational IMRT use requires a positive advantage/drawback balance. Only 5 randomized clinical trials (RCTs), 3 in the breast and 2 in the head and neck, which compare IMRT with non-IMRT (2-dimensional technique in four fifths of the trials), have been published (as of March 2011), and all had toxicity as the primary endpoint. More than 50 clinical trials compared results of IMRT-treated patients with a non-IMRT group, mostly historical controls. RCTs systematically showed a lower toxicity in IMRT-treated patients, and the non-RCTs confirmed these findings. Toxicity reduction, counterbalancing the drawbacks of IMRT, was convincing for breast and head and neck IMRT. For other tumor sites, the arguments favoring IMRT are weaker because of the inability to control bias outside the randomized setting. For anticancer efficacy endpoints, like survival, disease-specific survival, or locoregional control, the balance between advantages and drawbacks is fraught with uncertainties because of the absence of robust clinical data.

Therapeutic implications of molecular imaging with PET in the combined modality treatment of lung cancer

Molecular imaging with PET, and certainly integrated PET-CT, combining functional and anatomical imaging, has many potential advantages over anatomical imaging alone in the combined modality treatment of lung cancer. The aim of the current article is to review the available evidence regarding PET with FDG and other tracers in the combined modality treatment of locally advanced lung cancer. The following topics are addressed: tumor volume definition, outcome prediction and the added value of PET after therapy, and finally its clinical implications and future perspectives. The additional value of FDG-PET in defining the primary tumor volume has been established, mainly in regions with atelectasis or post-treatment effects. Selective nodal irradiation (SNI) of FDG-PET positive nodal stations is the preferred treatment in NSCLC, being safe and leading to decreased normal tissue exposure, providing opportunities for dose escalation. First results in SCLC show similar results. FDG-uptake on the pre-treatment PET scan is of prognostic value. Data on the value of pre-treatment FDG-uptake to predict response to combined modality treatment are conflicting, but the limited data regarding early metabolic response during treatment do show predictive value. The FDG response after radical treatment is of prognostic significance. FDG-PET in the follow-up has potential benefit in NSCLC, while data in SCLC are lacking. Radiotherapy boosting of radioresistant areas identified with FDG-PET is subject of current research. Tracers other than (18)FDG are promising for treatment response assessment and the visualization of intra-tumor heterogeneity, but more research is needed before they can be clinically implemented.

Improving bladder cancer treatment with radiotherapy using separate intensity modulated radiotherapy plans for boost and elective fields

The aim of this study is to investigate to what extent IMRT can decrease the dose to the organs at risk in bladder cancer treatment compared with conformal treatment while making separate treatment plans for the elective field and the boost. Special attention is paid to sparing small intestines. Twenty patients who were treated with the field-in-field technique (FiF) were re-planned with intensity modulated radiotherapy (IMRT) using five and seven beams, respectively. Separate treatment plans were made for the elective field (including the pelvic lymph nodes) and the boost, which enables position correction for bone and tumour separately. The prescribed dose was 40 Gy to the elective field and 55 or 60 Gy to the planning target volume (PTV). For bladder and rectum, V(45Gy) and V(55Gy) were compared, and for small intestines, V(25Gy) and V(40Gy.) The dose distribution with IMRT conformed better to the shape of the target. There was no significant difference between the techniques in dose to the healthy bladder. The median V(40Gy) of the small intestines decreased from 114 to 66 cc (P = 0.001) with five beam IMRT, and to 55 cc (P = 0.001) with seven beam IMRT compared with FiF. V(45Gy) for rectum decreased from 34.2% to 17.5% (P = 0.004) for both five and seven beam plans, while V(55Gy) for rectum remained the same. With IMRT, a statistically significant dose decrease to the small intestines can be achieved while covering both tumour and elective PTV adequately.

["Dose-painting": myth or reality?]

"Dose-painting" radiotherapy allows for a heterogeneous delivery of radiation within the tumour volume by targeting radioresistant areas defined by functional imaging. Within gross tumour volume, it is possible to define one or more target volumes based on biology (biological target volume [BTV]) and to apply a strategy of intensity modulated radiation therapy (IMRT) that will deliver a higher dose to these regions. In this review of the literature, we will highlight the biological elements responsible for radioresistance, and how to image them, then we will detail the radiotherapy techniques necessary for this approach, before presenting clinical results in various situations (head and neck tumours, prostate, brain tumours, etc.). Despite many difficulties that make dose-painting IMRT unusable in routine nowadays, biology-guided radiation therapy represents one of the major pathways of development of radiotherapy in the coming years.

Adaptive dose painting by numbers for head-and-neck cancer

PURPOSE

To investigate the feasibility of adaptive intensity-modulated radiation therapy (IMRT) using dose painting by numbers (DPBN) for head-and-neck cancer.

METHODS AND MATERIALS

Each patient's treatment used three separate treatment plans: fractions 1-10 used a DPBN ([(18)-F]fluoro-2-deoxy-D-glucose positron emission tomography [(18)F-FDG-PET]) voxel intensity-based IMRT plan based on a pretreatment (18)F-FDG-PET/computed tomography (CT) scan; fractions 11-20 used a DPBN plan based on a (18)F-FDG-PET/CT scan acquired after the eighth fraction; and fractions 21-32 used a conventional (uniform dose) IMRT plan. In a Phase I trial, two dose prescription levels were tested: a median dose of 80.9 Gy to the high-dose clinical target volume (CTV(high_dose)) (dose level I) and a median dose of 85.9 Gy to the gross tumor volume (GTV) (dose level II). Between February 2007 and August 2009, 7 patients at dose level I and 14 patients at dose level II were enrolled.

RESULTS

All patients finished treatment without a break, and no Grade 4 acute toxicity was observed. Treatment adaptation (i.e., plans based on the second (18)F-FDG-PET/CT scan) reduced the volumes for the GTV (41%, p = 0.01), CTV(high_dose) (18%, p = 0.01), high-dose planning target volume (14%, p = 0.02), and parotids (9-12%, p < 0.05). Because the GTV was much smaller than the CTV(high_dose) and target adaptation, further dose escalation at dose level II resulted in less severe toxicity than that observed at dose level I.

CONCLUSION

To our knowledge, this represents the first clinical study that combines adaptive treatments with dose painting by numbers. Treatment as described above is feasible.

Improving radiation conformality in the treatment of non-small cell lung cancer

One of the many challenges of lung cancer radiotherapy is conforming the radiation dose to the target due to tumor/organ motion and the need to spare surrounding critical structures. Evolving radiotherapy technologies, such as four-dimensional (4-D) image-based motion management, daily on-board imaging and adaptive radiotherapy, have enabled us to improve the therapeutic index of radiation therapy for lung cancer by permitting the design of personalized treatments that deliver adequate doses conforming to the target while sparing the surrounding critical normal tissues. Four-dimensional computed tomography (CT) image-based motion management provides an opportunity to individualize target motion margins and reduce the risk of a geographical target miss. Daily on-board imaging and adaptive radiotherapy reduce set-up and motion/anatomy uncertainties over the course of radiotherapy. These achievements in image guidance have permitted the implementation in lung cancer patients of highly conformal treatment delivery techniques that are exquisitely sensitive to organ motion and anatomic change such as intensity-modulated radiation therapy, stereotactic body radiation therapy, and proton therapy. More clinical studies are needed to further optimize conformal radiotherapy using individualized treatment adaptations based on changes in anatomy and tumor motion during the course of radiotherapy and using functional and biological imaging to selectively escalate doses to radioresistant subregions within the tumor.

New developments in arc radiation therapy: a review

Arc therapies have gained widespread clinical interest in radiation oncology over the past decade. Arc therapies have several potential advantages over standard techniques such as intensity-modulated radiation therapy, with implications for patients, administrators, and oncologists. This review focuses on the rationale for arc therapy, descriptions of the modern arc techniques that are currently clinically available, and highlights some distinguishing features of arc therapies, such as dose distributions, treatment times, and imaging capabilities. Arc therapies are exciting examples of progress in radiotherapy through technological innovation, aimed at ultimately improving the therapeutic ratio for patients receiving radiation.

Reducing biochemical recurrence rates in EBRT-treated prostate cancer patients: the influence of dose and dose per fraction

In the last 15-20 years, technological improvements in radiation treatment planning and delivery have allowed radiation oncologists to increase the total dose to the prostate gland. The results of four randomized trials using conventional daily doses (1.8-2 Gy) demonstrate that higher total doses lead to lower rates of biochemical recurrence, but with a modest increase in late toxicity. Preclinical data suggest that treatment schedules relying on fewer, larger daily fractions of radiotherapy (hypofractionation) may increase the therapeutic ratio. Early results from several uncontrolled trials indicate that schedules that rely on larger daily doses are associated with low toxicity, provided some form of daily target localization and sophisticated treatment delivery are used. The results of several randomized trials that compare hypofractionated regimens to conventionally fractionated regimens will be available in the next 5-10 years.