Single Fraction Radiation Treatment Research Articles

High-Dose Rate Interstitial Spine Brachytherapy Using an Intraoperative Mobile Computed Tomography-Guided Surgical Navigation System.

Up to 15% of previously irradiated metastatic spine tumors will progress. Re-irradiation of these tumors poses a significant risk of exceeding the radiation tolerance to the spinal cord. High-dose rate (HDR) brachytherapy is a treatment alternative. To develop a novel HDR spine brachytherapy technique using an intraoperative computed tomography-guided navigation (iCT navigation). Patients with progressive metastatic spine tumors were included in the study. HDR brachytherapy catheters were placed under iCT navigation. CT-based planning with magnetic resonance imaging fusion was performed to ensure conformal dose delivery to the target while sparing normal tissue, including the spinal cord. Patients received single fraction radiation treatment. Five patients with thoracolumbar tumors were treated with HDR brachytherapy. Four patients previously received radiotherapy to the same spinal level. Preimplant plans demonstrated median clinical target volume (CTV) D90 of 116.5% (110.8%-147.7%), V100 of 95.7% (95.5%-99.6%), and Dmax of 8.08 Gy (7.65-9.8 Gy) to the spinal cord/cauda equina. Postimplant plans provided median CTV D90 of 113.8% (93.6%-120.1%), V100 of 95.9% (87%-99%), and Dmax of 9.48 Gy (6.5-10.3 Gy) to cord/cauda equina. Patients who presented with back pain (n=3) noted symptomatic improvement at a median follow-up of 22 d after treatment. Four patients demonstrated local tumor control of spinal metastatic tumor at a median follow-up of 92 d after treatment. One patient demonstrated radiographic evidence of local tumor progression 2.7 mo after treatment. HDR spine brachytherapy with iCT navigation is a promising treatment alternative to induce local tumor control and reduce pain symptoms associated with metastatic spine disease.

The impact of COVID-19 pandemic on the practice of radiotherapy: A retrospective single-institution study

Background: The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 led to the imposition of a nationwide lockdown as a control measure, which in turn disrupted the diagnosis and treatment of other diseases including cancer.Objectives: The primary objective of this study was to assess the impact of the COVID-19 pandemic on patients receiving radiotherapy and whether it correlated with the patients' age, gender, site of disease, and intent of radiotherapy. The secondary objective was to assess the compliance to radiotherapy and the treatment modifications, if any.Materials and Methods: This is a retrospective analysis of all patients planned for radiotherapy at the Mahavir Cancer Sansthan, a tertiary cancer center, in Patna, India from January 1, 2020, to May 31, 2020. The study cohort was divided into two groups: Group A comprised patients who received radiotherapy in the period before the lockdown and Group B comprised patients who received radiotherapy during the lockdown. Data regarding the age, gender, site of disease, intent of treatment, completion of planned treatment, use of concurrent chemotherapy, and modifications of the radiation protocol, if any, were analyzed. The categorical variables were compared using the Chi-square test.Results: A total of 1412 patients were planned for radiotherapy during the study period. Of these, 1020 patients, 759 in Group A and 261 in Group B, actually received radiotherapy during the entire study period. The proportion of female patients decreased by 10.5% and that of patients receiving palliative intent radiotherapy increased by 12% during the lockdown. Head and neck, gynecological, and breast cancers were the most common cancer types in both the periods. There was no significant difference in the compliance to radiotherapy between the two groups (88.2% in Group A and 90.8% in Group B). Similar protocols were used during both the periods in patients being treated with a curative intent, but there was a significant increase in the use of single fraction radiation treatment in patients being treated with palliative intent with conventional fields.Conclusions: There was a sharp decline in the number of patients, especially women, during the lockdown. The number of patients being treated with palliative intent increased significantly, with an increased use of single-fraction radiation treatment.

How should radiation oncologists interpret the ASTRO evidence-based guideline and ASTRO Choosing Wisely campaign for the treatment of uncomplicated bone metastases?

In the article accompanying this commentary, Lutz and colleagues provide an updated American Society for Radiation Oncology (ASTRO) evidence-based guideline for palliative radiation therapy (RT) in the treatment of bone metastases. [1] Lutz S Berk L Chang E et al. Palliative radiotherapy for bone metastases: An ASTRO evidence-based guideline. Int J Radiat Oncol Biol Phys. 2011; 79: 965-976 Abstract Full Text Full Text PDF PubMed Scopus (655) Google Scholar The latest guideline summarizes important advances regarding the role of retreatment and highly conformal RT. However, the message around single fraction (SF) RT (Key questions 1-3) for uncomplicated bone metastases (UBM) remains unchanged when compared with the 2011 guideline. In brief, SF RT offers a similar rate of pain relief and a toxicity profile to multiple fraction (MF) RT. SF RT is associated with slightly higher rates of retreatment compared with MF RT; 20% versus 8%, as per the cited meta-analysis. [2] Chow E Zeng L Salvo N et al. Update on the systematic review of palliative radiotherapy trials for bone metastases. Clin Oncol. 2012; 24: 112-124 Abstract Full Text Full Text PDF PubMed Scopus (480) Google Scholar There are data from more than 25 randomized controlled trials (RCTs) and 3 meta-analyses supporting this observation. [1] Lutz S Berk L Chang E et al. Palliative radiotherapy for bone metastases: An ASTRO evidence-based guideline. Int J Radiat Oncol Biol Phys. 2011; 79: 965-976 Abstract Full Text Full Text PDF PubMed Scopus (655) Google Scholar The studies on efficacy and toxicity have further been strengthened by economic analyses, which highlight the cost-effectiveness of SF RT 3 Konski A James J Hartsell W et al. Economic analysis of Radiation Therapy Oncology Group (RTOG) 97-14: Multiple versus single fraction radiation treatment of patients with bone metastases. Am J Clin Oncol. 2009; 32: 423 Crossref PubMed Scopus (85) Google Scholar , 4 van den Hout van der Linden YM Steenland E et al. Single-versus multiple-fraction radiotherapy in patients with painful bone metastases: Cost–utility analysis based on a randomized trial. J NCI. 2003; 95: 222-229 Crossref PubMed Scopus (208) Google Scholar ; therefore, there has been a global push to adopt SF RT as an economical and efficacious standard in place of MF RT for UBM. Several guidelines and commentaries have highlighted the benefits of shorter treatment to both patient and society.

Tolosa-Hunt Syndrome: Another legitimate target for radiosurgery?

Reading articles describing the first application of a technique to a certain pathology often elicits two parallel emotions from the reader: an admiration for the bravery to be the first, followed by the realisation that it was based on previous successful or unsuccessful related interventions. The article by Lee et al. in this issue regarding Gamma Knife radiosurgery for TolosaHunt Syndrome (THS) is no exception. Considering the risks identified with treating nonneoplastic pathologies with radiation (the list is long), it is undoubtedly brave to use ionising radiation for THS. However, once one considers the often disabling degree of pain combined with other cranial nerve deficits suffered by these patients, as well as the undoubted complication rate of high-dose steroids and immunosuppressants, one fully understands why Gamma Knife radiosurgery was attempted for this pathology. The conventional treatment with steroids, particularly when the dose has to be escalated, often leads to acceptable aesthetic side effects, not to mention proximal myopathy, hypertension, and the rest. Radiosurgery, single-fraction radiation treatment, was indeed first-time reported for this pathology in the current article. Of course, there were forerunners. Radiotherapy has been used for pseudotumour of the orbit. Furthermore, as the authors describe, there have been others introducing radiation therapy for medically intractable recurrences of THS also. In the 1980s, radiosurgery was not yet available outside the pioneering clinic in Sweden, thus such radiotherapy was delivered to a broader field and in a fractionated manner. While it has proved successful, but must have carried the risks identified with fractionated radiotherapy for pituitary tumours: the risk of late malignancy. In order to minimise the risk to normal tissues included in the radiation field, often very long fractionation regimes were applied, accepting the inconvenience of lengthy treatment protocols. As for many pathologies both intraand extra-cranially, radiosurgery provides a very convenient way forward. The exquisite sub-millimetre precision of radiosurgery, particularly using Gamma Knife technology, offers a very dramatic reduction of the low-dose radiation volume into the normal tissues surrounding the target and, as a result, the risk of secondary oncogenesis is truly minimised [1]. At the same time, the one-day treatment offers such convenience that tolerance and compliance is vastly improved without compromising efficacy and safety. Whilst it is highly unlikely that this treatment would make steroid treatment as the first line outdated, Gamma Knife radiosurgery may be an alternative that should be, and will be, used as an early option for THS in the future. Given that this journal is predominantly read by neurosurgeons, one hopes that this information percolates through to our neurologist colleagues who may otherwise remain reluctant to utilise radiation even for resistant cases.

18F-EF5 PET Is Predictive of Response to Fractionated Radiotherapy in Preclinical Tumor Models.

We evaluated the relationship between pre-treatment positron emission tomography (PET) using the hypoxic tracer 18F-[2-(2-nitro-1-H-imidazol-1-yl)-N-(2,2,3,3,3- pentafluoropropyl) acetamide] (18F-EF5) and the response of preclinical tumor models to a range of fractionated radiotherapies. Subcutaneous HT29, A549 and RKO tumors grown in nude mice were imaged using 18F-EF5 positron emission tomography (PET) in order to characterize the extent and heterogeneity of hypoxia in these systems. Based on these results, 80 A549 tumors were subsequently grown and imaged using 18F-EF5 PET, and then treated with one, two, or four fraction radiation treatments to a total dose of 10–40 Gy. Response was monitored by serial caliper measurements of tumor volume. Longitudinal post-treatment 18F-EF5 PET imaging was performed on a subset of tumors. Terminal histologic analysis was performed to validate 18F-EF5 PET measures of hypoxia. EF5-positive tumors responded more poorly to low dose single fraction irradiation relative to EF5-negative tumors, however both groups responded similarly to larger single fraction doses. Irradiated tumors exhibited reduced 18F-EF5 uptake one month after treatment compared to control tumors. These findings indicate that pre- treatment 18F-EF5 PET can predict the response of tumors to single fraction radiation treatment. However, increasing the number of fractions delivered abrogates the difference in response between tumors with high and low EF5 uptake pre-treatment, in agreement with traditional radiobiology.

TU-F-CAMPUS-J-02: Evaluation of Textural Feature Extraction for Radiotherapy Response Assessment of Early Stage Breast Cancer Patients Using Diffusion Weighted MRI and Dynamic Contrast Enhanced MRI

Purpose: To investigate the feasibility of using classic textural feature extraction in radiotherapy response assessment, we studied a unique cohort of early stage breast cancer patients with paired pre - and post-radiation Diffusion Weighted MRI (DWI-MRI) and Dynamic Contrast Enhanced MRI (DCE-MRI). Methods: 15 female patients from our prospective phase I trial evaluating preoperative radiotherapy were included in this retrospective study. Each patient received a single-fraction radiation treatment, and DWI and DCE scans were conducted before and after the radiotherapy. DWI scans were acquired using a spin-echo EPI sequence with diffusion weighting factors of b = 0 and b = 500 mm2 /s, and the apparent diffusion coefficient (ADC) maps were calculated. DCE-MRI scans were acquired using a T1-weighted 3D SPGR sequence with a temporal resolution of about 1 minute. The contrast agent (CA) was intravenously injected with a 0.1 mmol/kg bodyweight dose at 2 ml/s. Two parameters, volume transfer constant (Ktrans ) and kep were analyzed using the two-compartment Tofts kinetic model. For DCE parametric maps and ADC maps, 33 textural features were generated from the clinical target volume (CTV) in a 3D fashion using the classic gray level co-occurrence matrix (GLCOM) and gray level run length matrix (GLRLM). Wilcoxon signed-rank test was used to determine the significance of each texture feature’s change after the radiotherapy. The significance was set to 0.05 with Bonferroni correction. Results: For ADC maps calculated from DWI-MRI, 24 out of 33 CTV features changed significantly after the radiotherapy. For DCE-MRI pharmacokinetic parameters, all 33 CTV features of Ktrans and 33 features of kep changed significantly. Conclusion: Initial results indicate that those significantly changed classic texture features are sensitive to radiation-induced changes and can be used for assessment of radiotherapy response in breast cancer.

Considerations for quality improvement in radiation oncology therapy for patients with uncomplicated painful bone metastases.

118 Background: Although American Society for Radiation Oncology (ASTRO) guidelines support single fraction radiation treatment for uncomplicated bone metastases, it is rarely used. Methods: We used modified RAND/UCLA appropriateness methodology to understand how radiation oncologists make decisions about single fraction treatment to inform quality improvement. We focused on uncomplicated bone metastases (defined by relevant RCT exclusion criteria) without prior irradiation, pathologic fracture, or spinal cord compression. Eight radiation oncologists with varying sub-specialties were provided ASTRO guidelines, a summary table of RCT’s and recent research on current practices. They rated the appropriateness of 8Gy Single Fraction treatment and 4 alternative regimens for clinical cases before and after a panel discussion that also included three palliative care physicians. Clinical cases varied by location of metastases (spine, humeral head, femur, rib), size of metastases, patient prognosis, travel distance to treatment site, and patient age. We report findings based on final median appropriateness ratings and qualitative evaluation of discussion. Results: Single fraction treatment (8Gy) was rated as the most appropriate treatment, regardless of other factors if prognosis was 6 months or less. However, participants noted that prognostic information is often not available at the point of care. Use of greater than 10 fractions was rated as inappropriate regardless of other factors. Older age and travel distance were factors that lead to favoring 8Gy single fraction treatment. There was less consensus concerning single fraction treatment and favoring of other treatment approaches for lesions located on the spine, especially large lesions, and for patients with oligometastases and a longer prognosis where goals may include local tumor control in addition to palliation. Conclusions: Improving specification and communication of prognostic information is an important quality improvement target to enhance the patient-centered nature of care for patients with painful bone metastases.

SU-E-T-262: Treatment Room Activation after 15 MV Single Fraction Radiation Treatments Delivered Using Varian's TrueBeam and Trilogy Linear Accelerators.

To measure radiation levels in treatment room due to activation after 15MV single fraction radiation treatment (SFRT) delivered to a solid water phantom. We performed radiation surveys of two LINAC treatment rooms immediately after 15 MV SFRT. We delivered a sequence of two 15 MV single fraction IMRT treatments to a phantom at the end of a typical treatment day. The first treatment delivered was 6201MU (about 12 Gy) and the second one, 15 minutes later was 12711 MU (24 Gy). Both were delivered to the pelvic region of a solid water anthropomorphic phantom. In a second technique, a 15 MV VMAT SFRT (4326 MU) was delivered using the Varian TrueBeam LINAC. Radiation measurements were recorded repetitively at four locations using a thin windowed Geiger Muller detector, a sodium iodide photon spectrometer and a pressurized ionization chamber. The four locations surveyed were: the top of the collimator head, the collimator window surface, the isocenter, and the inferior end of the patient support assembly. Radiation levels at the isocenter at the end of the treatment day and before the two IMRT SFRTs varied from 0.06 to 0.1 mR/h. Within 2-3 minutes after finishing the second IMRT SFRT the radiation levels were approximately 10 and 1.4 mR/h at isocenter for the TrueBeam and Trilogy rooms respectively and around 0.6 mR/h for the TrueBeam VMAT SFRT. Closing the MLC and the jaws significantly reduces the radiation level at isocenter. The average half life of the mixture of radionuclides produced is about 10 minutes. High dose single fraction IMRT treatments with 15 MV photons produce elevated treatment room activation as compared to conventional IMRT. In addition, activation levels varied between the TrueBeam and Trilogy for similar SFRT schemes. There is no funding support, disclosures, or conflict of interest.