Case report: Intrafraction dose-guided tracking for gastrointestinal organ-at-risk isotoxicity delivery on an MR-guided radiotherapy system.

In the current era of high-precision radiation therapy, real-time magnetic resonance (MR)-guided tracking of the tumor and organs at risk (OARs) is a novel approach that enables accurate and safe delivery of high-dose radiation. Organ tracking provides a general sense of the need for daily online adaptation but lacks precise information regarding exact dosimetry. To overcome this limitation, we developed the methodology for monitoring intrafraction motion with real-time MR-guided isodose line-based tracking of an OAR in combination with anatomic tumor-based tracking and reported the first case treated with this approach. An isolated para-aortic (PA) nodal recurrence from carcinosarcoma of the endometrium was treated with an ablative dose of 50 Gy in five fractions using MR-guided radiotherapy (MRgRT). This report demonstrates the feasibility, workflow, dosimetric constraints, and treatment paradigm for real-time isodose line-based OAR tracking and gating to enable an isotoxicity delivery approach. This innovative treatment strategy effectively tracked the intrafraction motion of both the target and OAR independently and enhanced the accuracy of structure localization in time and space with a more precise dosimetric evaluation.

Quality assurance of an established online adaptive radiotherapy program: patch and software upgrade.

Introduction: The ability to dynamically adjust target contours, derived Boolean structures, and ultimately, the optimized fluence is the end goal of online adaptive radiotherapy (ART). The purpose of this work is to describe the necessary tests to perform after a software patch installation and/or upgrade for an established online ART program. Methods: A patch upgrade on a low-field MR Linac system was evaluated for post-software upgrade quality assurance (QA) with current infrastructure of ART workflow on (1) the treatment planning system (TPS) during the initial planning stage and (2) the treatment delivery system (TDS), which is a TPS integrated into the delivery console for online ART planning. Online ART QA procedures recommended for post-software upgrade include: (1) user interface (UI) configuration; (2) TPS beam model consistency; (3) segmentation consistency; (4) dose calculation consistency; (5) optimizer robustness consistency; (6) CT density table consistency; and (7) end-to-end absolute ART dose and predicted dose measured including interruption testing. Differences of calculated doses were evaluated through DVH and/or 3D gamma comparisons. The measured dose was assessed using an MR-compatible A26 ionization chamber in a motion phantom. Segmentation differences were assessed through absolute volume and visual inspection. Results: (1) No UI configuration discrepancies were observed. (2) Dose differences on TPS pre-/post-software upgrade were within 1% for DVH metrics. (3) Differences in segmentation when observed were small in general, with the largest change noted for small-volume regions of interest (ROIs) due to partial volume impact. (4) Agreement between TPS and TDS calculated doses was 99.9% using a 2%/2-mm gamma criteria. (5) Comparison between TPS and online ART plans for a given patient plan showed agreement within 2% for targets and 0.6 cc for organs at risk. (6) Relative electron densities demonstrated comparable agreement between TPS and TDS. (7) ART absolute and predicted measured end-to-end doses were within 1% of calculated TDS. Discussion: An online ART QA program for post-software upgrade has been developed and implemented on an MR Linac system. Testing mechanics and their respective baselines may vary across institutions, but all necessary components for a post-software upgrade QA have been outlined and detailed. These outlined tests were demonstrated feasible for a low-field MR Linac system; however, the scope of this work may be applied and adapted more broadly to other online ART platforms.

Cine MRI-based analysis of intrafractional motion in radiation treatment planning of head and neck cancer patients.

PURPOSE/OBJECTIVE(S): To investigate intrafraction motion of (HN) target volumes and to determine patient-specific planning target volume (PTV) margins. MATERIALS/METHODS: MR-cine imaging was performed for radiation treatment planning in HN cancer patients treated with definitive EBRT (n = 62) or SBRT (n = 4) on a 1.5 T MRI between 2017-2019. Dynamic MRI scans (sagittal orientation, 2 × 82 × 7 mm3 resolution), ranging from 3-5 min and 900-1500 images, were acquired. The position of the maximum tumor displacement along each direction in the anterior/posterior (A/P) and superior/inferior (S/I) position was recorded and analyzed to determine average PTV margins. RESULTS: Primary tumor sites (n = 66) were oropharynx (n = 39), larynx (n = 24) and hypopharynx (n = 3). PTV margins for A/P/S/I positions were 4.1/4.4/5.0/6.2 mm and 4.9/4.3/6.7/7.7 mm for oropharyngeal and laryngeal/hypopharyngeal cancers when accounting for all motion. V100 for PTV was calculated and compared to the original plans. The mean drop in PTV coverage was in most cases under 5%. For a subset of patients with 3 mm plans available, V100 for PTV had more substantial decreases in coverage averaging 8.2% - and 14.3% for oropharyngeal and laryngeal/hypopharynx plans, respectively. CONCLUSION: The use of MR-cine in treatment planning allows for quantification of tumor motion during swallow and resting periods and should be accounted for during treatment planning. With motion considered, the derived margins may exceed the commonly used 3-5 mm PTV margins. Quantification and analysis of tumor and patient-specific PTV margins is a step towards real-time MRI guidance adaptive radiotherapy.

Opioid consumption and pain in patients with gynecological cancer who underwent spinal anesthesia vs. general anesthesia for interstitial brachytherapy.

AIMS: Interstitial brachytherapy (ISBT) is an effective option for delivering conformal high dose radiation to the target volume with better organ-at risk sparing but is thought to be more invasive and painful than other methods. This study investigated pain levels and opioid consumption in patients who received spinal anesthesia (SA) or general anesthesia (GA) for their ISBT. MATERIALS AND METHODS: Patients that underwent ISBT from April 2014 to September 2018 were analyzed from a prospective institutional database. The most prevalent malignancies were cervical (45%), recurrent endometrial (27%) and vaginal (20%) cancers. Baseline patient characteristics, radiation treatment details, anesthesia records, and inpatient charts were obtained. Opioid consumption was quantified as oral morphine equivalent per day (OMEq/day) from implantation until removal. Pain score levels were collected by using an 11-point scoring system. RESULTS: Ninety nine patients received GA and 40 patients received SA as their anesthesia for ISBT. During their first admission, 76 patients (55%) required intravenous opioids. Patients receiving SA had significantly lower mean pain scores on the morning of their procedure 6 (Interquartile range [IQR] 2-8) vs. 0 (IQR: 0-1); p < 0.001]. Pain did not significantly differ between cohorts at any other time. During the first admission, SA patients had a lower median opioid usage of 23 (IQR: 9-47) mg/day compared to GA patients at 38 (IQR: 21-71) mg/day (p = 0.011). No difference in opioid consumption was seen during subsequent admissions. CONCLUSIONS: In patients undergoing ISBT, SA provides better immediate pain control post insertion compared to GA. Patients who received SA used lower amounts of opioids during their first ISBT insertion.

3D image-guided interstitial brachytherapy for primary vaginal cancer: A multi-institutional experience.

PURPOSE/OBJECTIVES: High dose rate (HDR) interstitial brachytherapy (ISBT) boost is integral for definitive radiation treatment of primary vaginal cancer. Technological advances with CT or MRI guidance provide improved precision and ability to treat more extensively invasive tumors over historical techniques, but reported experience is limited. We sought to provide updated outcome and toxicity data for women with primary vaginal cancer undergoing treatment with a modern ISBT technique. MATERIAL/METHODS: Databases of primary vaginal carcinoma patients treated at two Canadian academic cancer institutions were combined including patient, tumor and treatment characteristics, and survival outcomes and toxicity data. Descriptive statistics, survival estimates based on the Kaplan-Meier method, and univariable/multivariable Cox proportional hazards regression analyses are reported. RESULTS: Between 2002 and 2017, 67 women with primary vaginal cancer were treated with 3D HDR ISBT. FIGO stage distribution was I (22.4%), II (50.8%), III (17.9%), IVa (9.0%). All patients received external beam radiotherapy and HDR ISBT of 500-750 cGy per fraction over 2-4 fractions. Median follow-up was 2.68 years (95% confidence interval: 2.04-6.04). Cumulative rate of grade 3-4 genitourinary/gastrointestinal toxicity was 10.4%. Four patients developed vaginal fistula. Progression-free survival at 2 and 3 years was 73.5% and 66.4% for all patients, 78.3% and 75.0% for stage I-II and 61.6% and 46.2% for stage III-IVa, respectively (log-rank p = 0.252). CONCLUSIONS: Use of 3D image-guided HDR ISBT boost was safe and resulted in improved survival outcomes compared to historical rates in this series of primary vaginal cancer patients. Prospective study is warranted to better define clinical and dosimetric predictors of local control.

Exploring Tobacco Use and Smoking Cessation Best Practices From the Perspectives of Individuals With Lung Cancer and Health Care Professionals.

BACKGROUND: Lung cancer patients who continue to smoke after diagnosis are at increased risk of treatment toxicity, residual/recurrent disease, future malignancies, and all-cause mortality. Guidelines including those from National Comprehensive Cancer Network and Cancer Care Ontario advocate for screening, counseling, and access to smoking cessation services for all cancer patients; however, barriers from both patient and health care professional (HCP) perspectives contribute to lack of implementation. OBJECTIVE: The objective of this study was to identify the different perspectives among patients and HCPs in how the promotion of person-centred approaches may be used when offering smoking cessation services to patients who are receiving care within a regional cancer centre. METHODS: Qualitative data were generated using various methods, including focus groups with HCPs and interviews with patients. In total, 16 HCPs participated in three focus groups: including nine radiation therapists, five registered nurses, one registered dietitian, and one physiotherapist. Of 55 patients accrued, 19 were interviewed. Both focus groups and interviews were audio recorded, and the recordings were transcribed verbatim. Transcripts were then analyzed using narrative thematic analysis to define and identify themes. RESULTS: The identified themes were categorized into three topic areas: knowledge (eg, impact of smoking on illness and why they should not smoke); individual decision to quit (eg, motivators), and the social unacceptability of smoking (eg, the public perception of smoking over the last 40 years). HCP-identified themes included identification of smokers, triggers to start a conversation, approach, gaps and barriers to cessation, rationale for cessation, and judgment. Patient-identified themes included knowledge, individual decision to quit, and the social unacceptability of smoking. CONCLUSION: Understanding patient and HCP perspectives on smoking cessation will help influence practice to ensure that patients are not judged, assumptions are not made, and individualized and person-centred care is provided. HCP awareness of these themes and the patient perspective may challenge assumptions and values.

Stereotactic Body Radiotherapy (SBRT) for Oligometastatic Spine Metastases: An Overview.

The oligometastatic state is hypothesized to represent an intermediary state of cancer between widely metastatic disease and curable, localized disease. Advancements in radiotherapy have allowed for delivery of high precision, dose escalated treatment known as stereotactic body radiotherapy (SBRT) to targets throughout the body with excellent rates of local control. Recently, the first phase II randomized trial comparing conventional radiotherapy to comprehensive SBRT of oligometastatic disease demonstrated an overall survival and progression free survival advantage. The spine is a common site of metastasis, and a complex site for SBRT given the adjacent spinal cord and the tumor embedded within the bone tissue putting the patient at risk of fracture. Although there are expert spine SBRT guidelines for practice, there are as yet no reported randomized trials that proves superiority as compared to conventional radiation. The use of SBRT in patients with oligometastatic disease and spinal metastases is the focus of this review.

Three-dimensional-guided perineal-based interstitial brachytherapy in cervical cancer: A systematic review of technique, local control and toxicities.

OBJECTIVE: To evaluate local control and toxicities of perineal-based interstitial brachytherapy (P-ISBT) in cervical cancers treated with three-dimensional (3D) image-based planning through a systematic review. The secondary objective of this review is to summarize the implant and dosimetric techniques in 3D P-ISBT. METHODS: Systematic review of the literature using the PRISMA guideline was conducted through a search of Medline, EMBASE and Cochrane databases. This search resulted in 19 relevant manuscripts. Selected studies evaluated the role of perineal ISBT in cervical tumours treated using 3D planning. Eleven of nineteen manuscripts contained sufficient information for LC and toxicity calculations. Data were extracted by at least two investigators. RESULTS: A total of 672 cervical cancer patients were treated with P-ISBT and planned with 3D image-based planning. Clinical outcomes could be identified for 392 patients and 60% were staged IIIB or higher. Most patients received 45-50.4Gy EBRT to the pelvis followed by a P-ISBT boost with a range of dose between 28 and 48Gy EQD2Gy. Overall LC was 79% (310/392) with a median follow-up ranging from 14 to 55months. Almost half of the patients (48%) had a median follow-up ≥35months. Patients treated to a lower tumour EQD2Gy total dose had inferior LC. Procedure-related complications were rare (7 infections and 7 episodes of bleeding) and limited. Combined late gastro-intestinal, genitourinary and vaginal grade 3 and 4 toxicity was 12.1%. CONCLUSION: Promising LC rates were found in patients with cervical cancers treated with perineal ISBT with 3D image-based planning. In this systematic review, 60% had stage IIIB disease or higher and yet a LC rate of 79% was found. LC seemed to correlate with the dose delivered to the tumour, while toxicity rates were similar to other cervical cancer series using 3D image-based brachytherapy. Perineal ISBT with 3D planning seems to be an effective and safe treatment for large advanced cervical tumours and may be a reasonable alternative to the increasingly more standard and modern intracavitary/interstitial (IC/IS) approaches such as the 'Vienna' applicator.