Technical Report: Diagnostic Scan-Based Planning (DSBP), A Method to Improve the Speed and Safety of Radiation Therapy for the Treatment of Critically Ill Patients

Diagnostic image-based treatment planning for online adaptive ultra-hypofractionated prostate cancer radiotherapy with MR-Linac

PURPOSE

A new workflow was investigated for Elekta Unity MR-Linac by removing the computed tomography (CT)-simulation step and using diagnostic CT (DCT) for reference plan generation.

MATERIALS AND METHODS

Ten patients with ultra-hypofractionated prostate cancer treated with magnetic resonance imaging (MRI)-guided adaptive radiotherapy were retrospectively enrolled. Targets and organs at risk (OARs) were recontoured on DCT, and Hounsfield unit conversions to relative electron density were calibrated for DCT. Reference plans were reoptimized and recalculated using DCT for Unity. Subsequent adaptive plans were designed through an adapt-to-shape workflow to edit targets and OARs via daily MRI to generate a new treatment plan. Bulk electron density information for Unity adaptive plan was compared between planning CT (PCT) and DCT for volumes of interest. Dosimetric parameters were evaluated between PCT- and DCT-based reference and adaptive plans for target coverage and OAR dose constraints.

RESULTS

Bulk relative electron density differences between PCT and DCT were within ±1% for targets and OARs, excepting the rectum. PCT and DCT-based reference plans did not significantly differ in mean target coverages or for OARs in dosimetric difference except for V36 Gy of the rectum. PCT- and DCT-based adaptive plans did not significantly differ for most dosimetric parameters of targets and OARs except for V29 Gy and V36 Gy of the rectum, V18.1 Gy of the bladder, and D50% of the urethra.

CONCLUSIONS

By removing the CT simulation step, it is feasible to use DCT for designing reference and adaptive plans in the Unity ATS workflow. The workflow increased adaptive radiotherapy efficiency and decreased patient waiting time and additional radiation dose.

Clinical feasibility of treatment planning on a diagnostic CT scan without or with single fraction plan adaptation in patients with stage II/III rectal cancer

BACKGROUND

With the ultimate aim of reducing time to start radiotherapy treatment in patients with rectal cancer, this study explores the feasibility of omitting a planning CT scan (pCT), by utilizing the diagnostic CT scan (dCT) for treatment planning, with or without plan adaption using online adaptive radiotherapy.

METHODS

Fifteen rectal cancer patients, with both dCT and pCT available, were included. Target volumes and organs at risk (OARs) were delineated on both scans, followed by treatment planning based on the dCT contours. Plans were recalculated on the pCT to assess dosimetric differences for target volumes and OARs. Additionally, five patients with HyperSight CBCT scans underwent a similar planning process. An online adaptive treatment workflow was simulated using the Ethos system, where the dCT and its plan served as the reference, and the HyperSight CBCT was used for adaptation.

RESULTS

dCT-based plans showed adequate target volume coverage. However, when recalculated on the pCT, median coverage decreased for both CTV and PTV, and OAR doses increased. None of the 15 plans met prescribed constraints without online adaptive radiotherapy. In contrast, for all five patients in the adaptive workflow, the treatment plans met target volume coverage and OAR constraints.

CONCLUSION

Using dCT-based treatment planning is feasible for rectal cancer patients but requires at least one online adaptive session. A prospective trial (MEC XXXX-XXXX) is ongoing in patients with rectal cancer, aiming to reduce time to start treatment, by omitting the pCT and using online adaptive radiotherapy workflow.

Real-World Implementation of Simulation-Free Radiation Therapy (SFRT-1000): A Propensity Score-Matched Analysis of 1000 Consecutive Palliative Courses Delivered in Routine Care

PURPOSE

The feasibility of simulation-free radiation therapy (SFRT) has been demonstrated but information regarding its routine care impact and scalability is lacking.

METHODS AND MATERIALS

In this single-institution, retrospective cohort study, all patients receiving palliative radiation therapy at an Australian tertiary cancer center were eligible for consideration of SFRT unless mask immobilization, a stereotactic technique, or a definitive dose was indicated. Coprimary endpoints were SFRT utilization, impact on consultation-to-RT time, and on-couch treatment duration. Timing metrics were compared with a contemporary local cohort that received simulation-based palliative radiation therapy using unadjusted Wilcoxon rank-sum tests and a propensity score-matched regression. Electronic patient-reported outcomes captured 2-week toxicity and pain response.  RESULTS:  Between April 2018 and February 2024, 2849 palliative radiation courses were delivered, of which 1904 were eligible. Of the 1904 courses, 1000 (52.5% SFRT utilization) received SFRT, including 668 using intensity-modulated radiation therapy/volumetric-modulated arc therapy. A total of 788 individual patients received SFRT and the median age was 71 years (IQR, 61-80) with 59% being male and 42% being Eastern Collaborative Oncology Group 2-4. SFRT utilization increased from 41% to 54% between years 2018-2019 and 2022-2024.  SFRT reduced median consultation-to-RT time from 7.0 to 5.1 days (P < .0001) corresponding to an adjusted average treatment effect in the treated of -2.1 days (95% CI, -2.8 to -1.3). SFRT increased median on-couch treatment duration from 17.8 to 20.5 minutes (P < .0001; adjusted average treatment effect in the treated 2.6 minutes, 95% CI, 1.3-3.9). Patient-Reported Outcomes Version of the Common Terminology Criteria for Adverse Events grade 3 acute toxicity was 9% and at 4 weeks after RT, patients with moderate/severe pain at baseline (≥5/10) had a mean pain reduction of 3.5 points (7.1-3.6; P < .0001).  CONCLUSIONS:  Using widely available technologies, the SFRT-1000 cohort demonstrates routine care scalability with patient-centered and workflow benefits. SFRT is an attractive new paradigm implementable in most settings following adaptation to local requirements. Thus, SFRT opens new avenues to potentially improve access to palliative RT, which remains a global area of need.

Outcomes of patients receiving urgent palliative radiotherapy for advanced lung cancer: an observational study

BACKGROUND

There is considerable variability in the management of patients with advanced lung cancer referred for palliative radiotherapy owing to uncertainties in prognosis and the benefit of treatment. This study presents the outcomes of patients seen in the Fast Track Lung Clinic, an urgent access palliative radiotherapy clinic, and aims to identify factors associated with treatment response and survival.

METHODS

Consecutive patients with advanced lung cancer seen in the Fast Track Lung Clinic between January 2014 and July 2020 were included. Patients who underwent radiotherapy were contacted beginning 30 days after radiotherapy to evaluate treatment response. Cluster bootstraps were used to compute confidence intervals for treatment response rate. Prognostic factors for treatment response and overall survival were identified using multivariable generalized estimating equations and Cox regression models, respectively.

RESULTS

A total of 558 patients were included, of whom 459 (82.3%) consented to palliative radiotherapy for 1053 indications. The overall treatment response rate was 70.0% (95% CI, 65.8-74.2) for indications with follow-up (70.8%). Higher response rates were observed in patients with better ECOG performance status (OR per point, 0.71; 95% CI, 0.55-0.93; P = 0.01 ) and EGFR-mutant non-small cell lung cancer (OR vs wild-type, 2.46; 95% CI, 1.35-4.51; P = 0.003 ), whereas patients treated for neurological symptoms had lower response rates (OR, 0.27; 95% CI, 0.16-0.45; P < 0.001 ). There was no difference in response rate between patients who died within 30 days of starting radiotherapy and those who survived longer (OR, 0.83; 95% CI, 0.42-1.67; P = 0.61 ). Age; ECOG performance status; smoking history; pathology; EGFR or ALK mutation status; and the presence of liver, adrenal, or brain metastases were associated with overall survival.

CONCLUSIONS

Palliative radiotherapy was effective for patients with advanced lung cancer, although response rates varied by patient characteristics and treatment indication. This study identified prognostic factors for radiotherapy response and overall survival that can inform treatment decisions in this population.

Palliative radiotherapy of soft tissue tumoral masses based on diagnostic instead of planning computed tomography scans

Background and purpose

Radiotherapy (RT) treatment planning is based on a planning computed tomography scan (pCT), while the decision to treat is often already established on a diagnostic CT scan (dCT). The objective of this study was to evaluate the usage of dCT for palliative radiation planning of soft tissue tumoral masses (STTMs), removing the need for a pCT scan and associated attendances.

Materials and methods

RT planning was performed retrospectively to 38 STTMs of 7 anatomical sites using volumetric modulated arc therapy techniques in dCT and transferred to pCT. The dose of clinical target volumes (CTV), D(95 %,50 %), were compared between the plans. The patient setup was assessed in cone-beam CT scans.

Results

The differences of D(95 %,50 %) between dCT and pCT plans were the lowest in the STTMs of the thoracic cage (0.9 %,0.9 %), STTMs in the inguinal area (0.8 %,1.3 %) and in mediastinal masses associated with superior vena cava syndrome (SVCS) (1.1 %,1.3 %), while the differences increased for other sites. The patient setup was acceptable for 88 % of mediastinal masses associated with SVCS and ≤ 60 % of cases in other sites comparing pCT and CBCT images with a strict margin of 6 mm, but all cases fitted to increased 2 cm margin.

Conclusions

This study demonstrated the possibility of using dCT scans for palliative RT planning of STTMs for mediastinal masses associated with SVCS and for STTMs in the thoracic cage and in the inguinal area, indicating the potential feasibility of this procedure for clinical use.

Feasibility of simulation free abdominal stereotactic adaptive radiotherapy using an expedited pre-plan workflow

Background and Purpose

Improved hounsfield-unit accuracy of on-board imaging may lead to direct-to-unit treatment approaches We aimed to demonstrate the feasibility of using only a diagnostic (dx) computed tomography (CT)-defined target pre-plan in an in silico study of simulation-free abdominal stereotactic adaptive radiotherapy (ART).

Materials and Methods

Eight patients with abdominal treatment sites (five pancreatic cancer, three oligometastases) were treated using an integrated adaptive O-Ring gantry system. Each patient's target was delineated on a dxCT. The target only pre-plan served primarily to seed the ART process. During the ART session, all structures were delineated. All simulated cases were treated to 50 Gy in 5 fractions to a planning target optimization structure (PTV_OPT) to allow for dose escalation within the planning target volume. Timing of steps during this workflow was recorded. Plan quality was compared between ART treatment plans and a plan created on a CT simulation scan using the traditional planning workflow.

Results

The workflow was feasible in all attempts, with organ-at-risk (OAR) constraints met in all fractions despite lack of initial OAR contours. Median absolute difference between the adapted plan and simulation CT plan for the PTV_Opt V95% was 2.0 %. Median absolute difference in the D0.5 cm3 between the adapted plan and simulation CT plan was -0.9 Gy for stomach, 1.2 Gy for duodenum, -5.3 Gy for small bowel, and 0.3 Gy for large bowel. Median end-to-end workflow time was 63 min.

Conclusion

The workflow was feasible for a dxCT-defined target-only pre-plan approach to stereotactic abdominal ART.

Prompt Pain Relief From Bone Metastases: The Virtual Simulation Program

Purpose

Rapid pain relief for patients with bone metastases can be a challenge due to the lengthy and complex radiation therapy workflow. The purpose of this study was to evaluate the time (in days) between initial radiation oncology consultation and start of palliative radiation treatment after implementing an alternative virtual simulation palliative workflow.

Methods and Materials

Patients meeting strict criteria were selected for virtual simulation, which included only those with painful bone metastases who were recommended palliative radiation therapy using standard anterior-posterior/posterior-anterior or opposed lateral fields. A recent (within 30 days) diagnostic computed tomography (CT) scan clearly visualizing the target volume was required for treatment planning. For comparison, a reference group of 40 consecutive patients with bone metastases who underwent in-person CT simulation before virtual simulation implementation was reviewed.

Results

Forty-five patients were treated for painful bone metastases as part of the virtual simulation program from May 2021 to October 2022. Regarding travel distance, 23 patients lived locally (<50 miles from the treatment center) and 22 patients were distant (≥50 miles from the treatment center). Average time from consultation to treatment for all patients undergoing virtual simulation was 3.7 days, compared with 7.5 days for patients undergoing in-person CT simulation (3.8 days sooner, on average; P ≤ .001). Before full implementation of the virtual simulation program, 5 eligible patients participated in a virtual simulation pilot from April 2021 to May 2021, in which each patient was contoured and planned on both a pre-existing diagnostic CT scan and a standard CT simulation scan. For virtual simulation-based plans, the average V90, V95, and V99 were 99.99%, 99.87%, and 96.70%. No significant planning target volume (PTV) coverage difference was found on subsequent in-person CT simulation scans.

Conclusions

The virtual simulation program decreased the time from consultation to start of treatment by more than 50% for patients recommended palliative radiation therapy for painful bone metastases. This benefit was most significant for outpatients traveling ≥50 miles for treatment. Virtual simulation-based planning can be considered for patients anxious to proceed with radiation therapy quickly or in underserved settings with limited transportation options to regional treatment centers.

Palliative intensity modulated radiotherapy of bone metastases based on diagnostic instead of planning computed tomography scans

Background and purpose

Radiotherapy (RT) treatment planning is as a standard based on a computed tomography (CT) scan obtained at the planning stage (pCT), while most of the decisions whether to treat by RT are based on diagnostic CT scans (dCT). Bone metastases (BM) are the most common palliative RT target. The objective of this study was to investigate if a palliative RT treatment plan of BMs could be made based on a dCT with sufficient accuracy and safety, without sacrificing any treatment quality.

Materials and methods

A retrospective study with 60 BMs of 8 anatomical sites was performed. RT planning was performed using intensity-modulated radiation therapy/volumetric modulated arc therapy techniques in dCT and transferred to pCT. The dose of clinical target volumes (CTVs), D(CTVV95%, V50%), were compared between plans for dCT and pCT. Patient setup was investigated in cone-beam CT scans.

Results

The differences of D(CTVV95%, V50%) between dCT and pCT plans were the lowest in the pelvis (1.0%, 1.1%), lumbar spine (0.6%, 0.7%) and thoracic spine (0.7%, 2.1%), while the differences were higher in cervical spine (3.7%, 1.9%), long bones (2.3%, 0.8%), and costae (1.6%, 1.4%). The patient set-up was acceptable for 100% of the pelvic and lumbar, for 92% of thoracic spine cases, and for <80% of cases in other sites.

Conclusion

This study showed the feasibility of using dCT images in palliative RT planning of BMs in thoracic, lumbar spine and pelvic sites, indicating the potential suitability of this strategy for clinical use.

Evaluation of a workflow for cone-beam CT-guided online adaptive palliative radiotherapy planned using diagnostic CT scans

PURPOSE

Single-visit radiotherapy (RT) is beneficial for patients requiring pain control and can limit interruptions to systemic treatments. However, the requirement for a dedicated planning CT (pCT)-scan can result in treatment delays. We developed a workflow involving preplanning on available diagnostic CT (dCT) imaging, followed by online plan adaption using a cone-beam CT (CBCT)-scan prior to RT-delivery, in order to account for any changes in anatomy and target position.

METHODS

Patients previously treated with palliative RT for bone metastases were selected from our hospital database. Patient dCT-images were deformed to treatment CBCTs in the Ethos platform (Varian Medical Systems) and a synthetic CT (sCT) generated. Treatment quality was analyzed by comparing a coverage of the V95% of the planning/clinical target volume and different organ-at-risk (OAR) doses between adapted and initial clinical treatment plans. Doses were recalculated on the CBCT and sCT in a separate treatment planning system. Adapted plan doses were measured on-couch using an anthropomorphic phantom with a Gafchromic EBT3 dosimetric film and compared to dose calculations.

RESULTS

All adapted treatment plans met the clinical goals for target and OARs and outperformed the original treatment plans calculated on the (daily) sCT. Differences in V95% of the target volume coverage between the initial and adapted treatments were <0.2%. Dose recalculations on CBCT and sCT were comparable, and the average gamma pass rate (3%/2 mm) of dosimetric measurements was 98.8%.

CONCLUSIONS

Online daily adaptive RT using dCTs instead of a dedicated pCT is feasible using the Ethos platform. This workflow has now been implemented clinically.

Same-day adaptive palliative radiotherapy without prior CT simulation: Early outcomes in the FAST-METS study

BACKGROUND AND PURPOSE

Standard palliative radiotherapy workflows involve waiting times or multiple clinic visits. We developed and implemented a rapid palliative workflow using diagnostic imaging (dCT) for pre-planning, with subsequent on-couch target and plan adaptation based on a synthetic computed tomography (CT) obtained from cone-beam CT imaging (CBCT).

MATERIALS AND METHODS

Patients with painful bone metastases and recent diagnostic imaging were eligible for inclusion in this prospective, ethics-approved study. The workflow consisted of 1) telephone consultation with a radiation oncologist (RO); 2) pre-planning on the dCT using planning templates and mostly intensity-modulated radiotherapy; 3) RO consultation on the day of treatment; 4) CBCT scan with on-couch adaptation of the target and treatment plan; 5) delivery of either scheduled or adapted treatment plan. Primary outcomes were dosimetric data and treatment times; secondary outcome was patient satisfaction.

RESULTS

47 patients were enrolled between December 2021 and October 2022. In all treatments, adapted treatment plans were chosen due to significant improvements in target coverage (PTV/CTV V95%, p-value < 0.005) compared to the original treatment plan calculated on daily anatomy. Most patients were satisfied with the workflow. The average treatment time, including consultation and on-couch adaptive treatment, was 85 minutes. On-couch adaptation took on average 30 min. but was longer in cases where the automated deformable image registration failed to correctly propagate the targets.

CONCLUSION

A fast treatment workflow for patients referred for painful bone metastases was implemented successfully using online adaptive radiotherapy, without a dedicated CT simulation. Patients were generally satisfied with the palliative radiotherapy workflow.

Simulation-Free Radiation Therapy: An Emerging Form of Treatment Planning to Expedite Plan Generation for Patients Receiving Palliative Radiation Therapy

Purpose

Herein we report the clinical and dosimetric experience for patients with metastases treated with palliative simulation-free radiation therapy (SFRT) at a single institution.

Methods and Materials

SFRT was performed at a single institution. Multiple fractionation regimens were used. Diagnostic imaging was used for treatment planning. Patient characteristics as well as planning and treatment time points were collected. A matched cohort of patients with conventional computed tomography simulation radiation therapy (CTRT) was acquired to evaluate for differences in planning and treatment time. SFRT dosimetry was evaluated to determine the fidelity of SFRT. Descriptive statistics were calculated on all variables and statistical significance was evaluated using the Wilcoxon signed rank test and t test methods.

Results

Thirty sessions of SFRT were performed and matched with 30 sessions of CTRT. Seventy percent of SFRT and 63% of CTRT treatments were single fraction. The median time to plan generation was 0.88 days (0.19-1.47) for SFRT and 1.90 days (0.39-5.23) for CTRT (P = .02). The total treatment time was 41 minutes (28-64) for SFRT and 30 minutes (21-45) for CTRT (P = .02). In the SFRT courses, the maximum and mean deviations in the actual delivered dose from the approved plans for the maximum dose were 4.1% and 0.07%, respectively. All deliveries were within a 5% threshold and deemed clinically acceptable.

Conclusions

Palliative SFRT is an emerging technique that allowed for a statistically significant lower time to plan generation and was dosimetrically acceptable. This benefit must be weighed against increased total treatment time for patients receiving SFRT compared with CTRT, and appropriate patient selection is critical.

A pilot study of same-day MRI-only simulation and treatment with MR-guided adaptive palliative radiotherapy (MAP-RT)

We conducted a prospective pilot study evaluating the feasibility of same day MRI-only simulation and treatment with MRI-guided adaptive palliative radiotherapy (MAP-RT) for urgent palliative indications (NCT#03824366). All (16/16) patients were able to complete 99% of their first on-table attempted fractions, and no grades 3-5 toxicities occurred.

Practical Implementation of Emergent After-Hours Radiation Treatment Process Using Remote Treatment Planning on Optimized Diagnostic CT Scans

The purpose of this report is to present the implementation of a process for after-hours radiation treatment (RT) utilizing remote treatment planning based on optimized diagnostic computed tomography (CT) scans for the urgent palliative treatment of inpatients. A standardized operating procedure was developed by an interprofessional panel to improve the quality of after-hours RT and minimize the risk of treatment errors. A new diagnostic CT protocol was created that could be performed after-hours on hospital scanners and would ensure a reproducible patient position and adequate field of view. An on-call structure for dosimetry staff was created utilizing remote treatment planning. The optimized CT protocol was developed in collaboration with the radiology department, and a novel order set was created in the electronic health system. The clinical workflow begins with the radiation oncologist notifying the on-call team (therapist, dosimetrist, and physicist) and obtaining an optimized diagnostic CT scan on a hospital-based scanner. The dosimetrist remotely creates a plan; the physicist checks the plan; and the patient is treated. Plans are intentionally simple (parallel opposed fields, symmetric jaws) to expedite care and reduce the risk of error. Education on the new process was provided for all relevant staff. Our process was successfully implemented with the use of an optimized CT protocol and remote treatment planning. This approach has the potential to improve the quality and safety of emergent after-hours RT by better approximating the normal process of care.

Dosimetry Comparison of Palliative Radiation Plans Generated From Available Diagnostic CT Images Versus Dedicated CT Simulation for Inpatients

Introduction The morbidity sequelae of advanced cancer are often irreversible. Early palliative radiation can prevent, delay, and even improve these consequences. Treatment may be delayed due to a packed computed tomography (CT) simulation schedule or other logistics, including the cost and burden of arranging ambulance transportation when radiation centers are off-site. Objectives The primary objective was to determine the feasibility of using a recent diagnostic CT scan in lieu of a dedicated simulation CT to generate an adequate plan without sacrificing dosimetric goals and subsequent efficacy or tolerability. Secondary objectives included how much the lesion has grown, and how much earlier treatment could start if planned on a diagnostic CT scan. Materials/Methods For each inpatient treated with palliative radiation, a prior recent diagnostic CT scan was imported into the RayStation (RaySearch Laboratories, Stockholm, Sweden) planning system. From these diagnostic scans, planning treatment volumes (PTV) and organs at risk (OAR) were contoured using the same technique as the patient's actual treatment. The primary outcome was to compare both the PTV coverage and OAR dose between the plan generated from the diagnostic CT compared to that from the simulation CT. Our secondary outcomes include the mean time between CT simulation and first treatment, change in tumor volume between diagnostic scan and CT simulation, and the hottest 1% of each plan (D1). Results Between May and August 2019, a total of 22 inpatients were treated palliatively. Of those 22 patients, 10 patients (ages 32-92 years, median 64.5 years, 50% spine) met study criteria and had a diagnostic CT scan that was obtained within 14 days of simulation CT that was also compatible with our planning software. In the plans that were delivered, a mean of 98.8% (range 94.4-100%) of PTV was covered by at least 95% prescription dose. In the diagnostic CT plans, a mean of 95.4% (range 84.5-100%) of PTV was covered by at least 95% prescription dose. The difference between plans trended towards significance (p=0.061). When looking at patients receiving treatment to the spine or having a diagnostic CT within four days of the simulation CT, there was no statistically significant difference between the two plans (p=0.032 and 0.030, respectively). The OARs received, on average, 1.4% less mean radiation dose in the hypothetical plans (p=0.911). All OAR constraints were met in both groups. The mean time between diagnostic CT and CT simulation was 5.9 days and between CT simulation and first treatment was 1.9 days (range 0-5 days). The mean change in tumor volume was 22.64% smaller in the diagnostic CT scan plan. The D1 was an average 1% hotter in the hypothetical plans (p=0.16). Conclusion In hospitalized patients with an indication for palliative radiation, treatment planning on a pre-existing recent diagnostic CT scan produces comparable dose distributions without increases in dose to OARs when compared to the use of CT simulation scans, particularly for the treatment of the spine or when a very recent diagnostic CT is available. Bypassing CT simulation in select cases allows for earlier delivery of radiation with less patient and logistical burden. In combination with daily image guidance, this may translate to more timely delivery of radiation, less cost and burden to critically ill patients, and improved palliative benefit.