Prospective Evaluation of Implementation of a Tattoo-less Workflow for Non-Spine Bone SBRT

PURPOSE/OBJECTIVE(S)

Oligometastatic disease has expanded the clinical indications for non-spine bone (NSB) SBRT. Optical surface monitoring systems (OSMS) may reduce treatment time if it represents an effective surrogate for bone intrafraction motion monitoring. We aimed to identify whether OSMS could substitute for 2D-3D mid-imaging and enable a tattoo-less set up in NSB SBRT.

MATERIALS/METHODS

Beginning 11/2019, OSMS was incorporated in parallel with an existing workflow using CBCT and mid 2D-3D kV/kV imaging for pre- and mid-imaging for NSB SBRT. The ability of OSMS to detect both observed out-of-tolerance (>2mm/>2deg) shifts and manual couch shifts was analyzed. A workflow incorporating OSMS reference captures, CBCT for pre-treatment verification and OSMS/triggered imaging (TI) for intrafraction monitoring was developed and deployed for rib/sternum SBRT beginning 11/2021 and all NSB SBRT beginning 2/2022. All NSB SBRT treatment appointments were analyzed through statistical process control (SPC) with use of an XmR chart of average set up and total treatment time per quarter from 2/2019 to 2/2023. Special cause rules were based on IHI rules and conduced with spreadsheet software.

RESULTS

From 2/2019 to 2/2023, 1962 NSB SBRT fractions were delivered, including 337 rib, 150 sternum, 197 femur, 266 ilium, 222 multi-site. Over 104 femur and 87 ilium images, there were no over tolerance intra-fraction events detected with 2D-3D or OSMS. Over 20 manual shifts, OSMS could detect 2mm shifts to within 0.4mm 67% of the time and 0.8mm 95% of time. There was no difference in treatment set up time following adoption of an OSMS/TI workflow as a replacement for 2D-3D mid-imaging. A reduction in rib SBRT delivery and multi-site treatment set-up times was significantly associated with the adoption of OSMS/TI and OSMS, respectively, as assessed based on special cause variation with 8 consecutive points below the mean.

CONCLUSION

Integration of OSMS and triggered imaging has enabled the transition to a completely tattoo-less workflow, thus sparing patients the need for permanent tattoos whilst also allowing more continuous motion monitoring and reduced radiation exposure related to unnecessary 2D-3D or CBCT mid-imaging. Treatment times were significantly reduced for patients receiving rib SBRT or multi-site NSB SBRT with this workflow.

A Prospective Study Assessing the Efficacy and Toxicity of Stereotactic Body Radiation Therapy for Oligometastatic Bone Metastases

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) is a promising treatment for oligometastatic disease in bone due to its delivery of high dose to target tissue and minimal dose to surrounding tissue. The purpose of this study is to assess efficacy and toxicity of this treatment in patients with previously unirradiated oligometastatic bony disease.

MATERIALS/METHODS

In this prospective phase II trial, patients with oligometastatic bone disease, defined as ≤3 active sites of disease, were treated with SBRT at one of two academic institutions between December 2016 and May 2019. Local progression-free survival (LPFS), progression-free survival (PFS), prostatic specific antigen (PSA) progression, and overall survival (OS) were reported. Treatment-related toxicity was also reported.

RESULTS

A total of 98 patients and 131 lesions arising from various tumor histologies were included in this study. The median age of patients enrolled in the study was 72.8 years (80.6% male, 19.4% female). Median follow-up was 26.7 months. The most common histology was prostate cancer (68.4%, 67/98). The most common dose prescriptions were 27/30 Gy in 3 fractions (26.0%, 34/131), 30 Gy in 5 fractions (19.1%, 25/131), or 30/35 Gy in 5 fractions (16.0%, 21/131). Multiple doses per treatment regimen reflect dose painting employing the lower dose to the clinical target volume (CTV) and higher dose to the gross tumor volume (GTV). Four patients (4.1%, 4/98) experienced local progression at one site for each patient (3.1%, 4/131). Among patients who progressed locally, the median time to local recurrence was 25.8 months (31.0 months among prostate cancer patients, N = 2, and 14.5 months among non-prostate cancer patients, N = 2). Among the entire cohort, 2-year LPFS (including death without local progression) was 85.0%, 2-year PFS (including deaths as well as local, distant, and PSA-based progression) was 47.0%, and 2-year OS was 87.5%. Twenty-seven patients (27.6%, 27/98) developed treatment-related toxicities, and most were Grade 1 (19.4%, 19/98) and 2 (4.1%, 4/98). Four patients (4.1%, 4/98) developed Grade 3 toxicities; there were no Grade 4 toxicities. The most common toxicity was fatigue (10.2%, 10/98). Of 68 treated spine metastases, there were four (5.9%, 4/68) vertebral fractures. Among these four patients, median time to fracture was 23.5 months (range 14.2-39.2 months).

CONCLUSION

Our study supports existing literature in showing that SBRT is effective and tolerable in patients with oligometastatic bone disease. Larger phase III trials are necessary and reasonable to determine long-term efficacy and toxicities.

Outcomes of Stereotactic Body Radiation Therapy (SBRT) for Femur Oligometastases

PURPOSE/OBJECTIVE(S)

Stereotactic body radiation therapy (SBRT) is increasingly used for oligometastatic bone disease, but there is limited data regarding the clinical outcomes of utilizing SBRT in treatment for femur metastases, which was excluded from SABR-COMET. We aimed to identify patient or treatment factors associated with clinical outcomes among patients treated with SBRT to femur metastases for oligometastatic disease control or re-irradiation.

MATERIALS/METHODS

We identified 50 patients with 56 femur lesions consecutively treated with SBRT at a single institution May 2017-June 2022. The Kaplan-Meier method was used to characterize time-to-event endpoints and Cox proportional hazards models were performed to evaluate the associations between baseline factors and clinical outcomes. Local control was defined as the absence of regional tumor progression at treated area or need for surgical fixation post radiation.

RESULTS

Most patients had ECOG 0-1 (90%), prostate (50%) or breast/lung (16%) cancer, and 1-3 lesions (100%), including 30 proximal and 5 distal. 55% of lesions received concurrent systemic therapy, including ADT (n = 18) or immunotherapy (n = 6). Median PTV volume was 54.7cc (range, 6.6 to 387cc). PTV V100(%) was 99% (range 71.5-100). Fractionation included 18-20 Gy/1F, 27-30 Gy/3F, 25-40 Gy/5F, and 50 Gy/10F. 43% of lesions had Mirel's score ≥ 7 and 91% of lesions did not have extraosseous bone extension on diagnostic CT and/or MRI. Acute toxicities included grade 1 fatigue (14.3%), pain flare (7.1%), and decreased blood counts (1.8%). Late toxicities included fracture (1.8%) at 1.5 years and 2 patients with radiation-induced osteonecrosis (3.6%) from dose of 40 Gy in 5F and 30 Gy in 5F (after prior 30 Gy/10F). One patient (n = 2%) required fixation post-radiation due to progression of disease or symptoms. With median follow up 19.4 months, 1 and 2-year rates of local control were 84% and 69%, progression-free survival were 55% and 27%, and overall survival were 91% and 74%.

CONCLUSION

There was no significant association between patient or treatment characteristics and local control outcomes. Femur SBRT for oligometastatic disease control in well-selected patients was associated with good outcomes with minimal rates of acute and late toxicity. Further prospective study is warranted.

Multi-Institutional Analysis of Metastasis Directed Therapy with or without Androgen Deprivation Therapy in Oligometastatic Castration Sensitive Prostate Cancer

PURPOSE/OBJECTIVE(S)

Several prospective trials in oligometastatic castration sensitive prostate cancer (omCSPC) have shown metastasis-directed therapy (MDT) can delay time to progression and initiation of androgen deprivation therapy (ADT) compared to observation. However, the optimal integration of ADT with MDT remains unclear. Here we report a multi-national, multi-institutional retrospective cohort of omCSPC treated with MDT to characterize the long-term outcomes of patients treated with MDT alone or in combination with ADT.

MATERIALS/METHODS

Patients with a controlled primary site and omCSPC (defined as ≤ 5 lesions on conventional imaging) treated with MDT with or without concurrent ADT and with at least 36 months follow-up were retrospectively screened across 13 institutions. The primary endpoints included biochemical progression free survival (bPFS) and radiographic progression free survival (rPFS) calculated using Kaplan-Meier method and stratified by treatment group (MDT alone vs MDT + ADT). Multivariable Cox regression was performed adjusted for variables found to be prognostic on univariate analysis.

RESULTS

Among 414 patients screened, a total of 263 patients treated between 2003 and 2018 met inclusion criteria and included. Of these, 105 received MDT alone and 158 received MDT+ADT, with median follow-up of 49.5 and 54.5 months, respectively. The majority were metachronous (90%) and had bone lesions (60%). Median ADT duration was 21.3 months (IQR 12.0- 31.9). Patients who received ADT vs. no ADT had poorer prognostic features including 23% vs. 1% synchronous (p<0.001), and 55% vs 40% Gleason 8-10 (p = 0.012). ADT use was associated with a better 5-year bPFS 24% vs 11% (p<0.0001) and rPFS 41% vs 29% (p<0.001). On multivariable Cox regression adjusting for post-MDT PSA nadir and salvage therapy, ADT use maintained significance for both bPFS (HR 0.51 (0.36, 0.71), p<0.001) and rPFS (HR 0.67, 95% CI 0.46-0.96, p = 0.03).

CONCLUSION

Long-term outcomes with MDT alone suggest a small proportion of patients experience sustained disease control. The addition of ADT appears to improve rPFS, however prospective studies are needed in order to allow for personalization of care in patients with omCSPC.

Clinical Outcomes with Stereotactic Body Radiation Therapy for Oligometastatic Prostate Cancer: Results from a Prospective Registry Trial

PURPOSE/OBJECTIVE(S)

Metastasis-directed radiation therapy using stereotactic body radiation therapy (SBRT) in oligometastatic prostate cancer (Oligo PCa) has a demonstrated benefit for local control and biochemical recurrence free survival for men with oligorecurrent PCa; however, the impact of SBRT within other oligometastatic states and in the context of systemic therapy remains poorly characterized. In this study, we investigate prognostic factors for clinical outcomes in a prospective cohort of Oligo PCa patients treated with metastasis-directed SBRT.

MATERIALS/METHODS

Using a single-institution registry trial, we analyzed a prospective cohort of 86 patients with Oligo PCa (≤5 metastatic lesions) and treated with metastasis-directed SBRT between 2017- 2022. Patients were classified as synchronous, metachronous, or induced oligometastatic disease as per the ESTRO guidelines. We evaluated the time to radiographic progression (TTRP), defined as the time from SBRT start date to radiographic progression, as well as time to initiation of new treatment (TTNT), defined as the time from SBRT end date to initiation of new therapy (systemic or radiation therapy). Time to event (TTE) was defined as the time from SBRT start date to radiographic progression or initiation of new therapy, whichever occurred first. Patients without documented events were censored at the date of last disease assessment. Comparative analyses were performed using Kaplan-Meier and Cox proportional hazards regression methods.

RESULTS

Eighty-six men with Oligo PCa treated with SBRT were followed for a median of 16.4 months with M0 (73%), Oligo PCa (21%) or polymetastatic PCa (6%) GS > = 8 (63%) at initial diagnosis. At the time of treatment with initial SBRT, 21% had synchronous oligometastatic disease, 63% had metachronous or repeat oligorecurrence or oligoprogression, and 16% had induced oligometastatic disease. Most patients were treated to 1-3 sites (94%), which predominantly included bone (86%), and the median dose was 35 Gy/5F. Concurrent systemic therapy during SBRT was seen in 85% of patients, including (60.5% with new generation androgen receptor signaling inhibitors). Overall survival at 1-year and 2-years was 96.9% [95% CI, 88.2-99.2%] and 94.4% [95% CI, 83.2-98.2%]. Using univariable analysis, those who did not receive systemic treatment during SBRT had significantly shorter TTRP (HR 3.67, [95% CI, 1.62-8.32], p = 0.002), TTNT (HR 3.24, 95% CI [1.49-7.06], p = 0.003), and TTE (HR 3.05, [95% CI, 1.44-6.45], p = 0.004). Additionally, patients treated with SBRT for metachronous (HR 2.89, [95% CI 0.68-12.30]) and induced metastatic disease (HR 8.96, [95% CI 1.85-43.37]) had significantly shorter TTE compared to synchronous oligometastatic disease (p = 0.006).

CONCLUSION

Using a prospective registry cohort of men with Oligo PCa treated with SBRT, we identify an association of oligometastatic state and the use of concurrent systemic therapy with improved TTRP and TTNT. Further prospective studies are warranted.

Deep Learning-Based Automated Quality Assurance for Palliative Spinal Treatment Planning in Radiotherapy

PURPOSE/OBJECTIVE(S)

Robustquality assurance (QA) for palliative spine radiation therapy (RT) remains critical due to the risk of wrong anatomic level treatment on account of human error in enumerating vertebral bodies accurately based on morphology with incomplete imaging of the spine and prevalence of anatomic variants (10%). We propose a rapid, fully automated deep learning-based QA (DL-QA) tool for segmenting and enumerating vertebral structures from image data, capable of identifying misalignment based on discrepancies in calculated dose coverage.

MATERIALS/METHODS

Ina retrospective cohort of 514 patients who received palliative spine radiation treatment at a single institution for spinal metastases, vertebral volumes for each individual spine level were automatically segmented on RT planning computed tomography scans using a publicly available deep learning algorithm, Total Segmentator (TS) deployed in the treatment planning system (Wasserthal et al, 2022). Departmental policy requires that the prescription/plan name include all spinal levels that receive a prescribed dosimetric threshold of V50% > 50%. By comparing the intended spine level target in the prescription and plan name against the TS volumes, the DL-QA flagged all cases for which any target vertebrae did not receive this threshold dose and/or any non-targeted vertebrae that received V50% > 50%. To detect spine anomalies, cases were also flagged if any vertebrae volume was not within ±1σ of the entire population of vertebrae volumes. Flagged cases were either categorized as: (1) wrong spine level RT error; (2) documentation error, in which treatment was correct but the prescription/plan name did not follow Departmental policy; or (3) potential spinal geometric error. All flagged cases were verified manually by checking the original images and treatment planning data.

RESULTS

Outof 514 patients, 29 cases were flagged as potential errors. Manual review revealed that one of these was a previously discovered true treatment error (due to anatomic variant with 4 lumbar bodies) while 10 were treated as intended but showed documentation errors due to variants in the number of vertebral bodies, kyphosis of the spine causing non-targeted vertebrae to appear in the treatment field, or improper observation of the Departmental plan naming policy. The remaining 18 cases were associated with flagged vertebrae volumes. Reviewing those patients, we identified spinal anomalies where TS attempted to account for extra or missing vertebrae (N = 9) and cases where TS made segmentation errors (N = 9).

CONCLUSION

Theproposed automated DL-QA system successfully identified patients with spine anomalies, flagged documentation errors, verified the correct target levels of spine RT treatments, and detected a known misadministration. The next phase will involve prospective testing of the system in a clinical setting upstream of treatment delivery.