Retroperitoneal sarcoma (RPS) high risk gross tumor volume boost (HR GTV boost) contour delineation agreement among NRG sarcoma radiation and surgical oncologists

NRG Oncology Assessment of Artificial Intelligence Deep Learning-Based Auto-segmentation for Radiation Therapy: Current Developments, Clinical Considerations, and Future Directions

Deep learning neural networks (DLNN) in Artificial intelligence (AI) have been extensively explored for automatic segmentation in radiotherapy (RT). In contrast to traditional model-based methods, data-driven AI-based models for auto-segmentation have shown high accuracy in early studies in research settings and controlled environment (single institution). Vendor-provided commercial AI models are made available as part of the integrated treatment planning system (TPS) or as a stand-alone tool that provides streamlined workflow interacting with the main TPS. These commercial tools have drawn clinics' attention thanks to their significant benefit in reducing the workload from manual contouring and shortening the duration of treatment planning. However, challenges occur when applying these commercial AI-based segmentation models to diverse clinical scenarios, particularly in uncontrolled environments. Contouring nomenclature and guideline standardization has been the main task undertaken by the NRG Oncology. AI auto-segmentation holds the potential clinical trial participants to reduce interobserver variations, nomenclature non-compliance, and contouring guideline deviations. Meanwhile, trial reviewers could use AI tools to verify contour accuracy and compliance of those submitted datasets. In recognizing the growing clinical utilization and potential of these commercial AI auto-segmentation tools, NRG Oncology has formed a working group to evaluate the clinical utilization and potential of commercial AI auto-segmentation tools. The group will assess in-house and commercially available AI models, evaluation metrics, clinical challenges, and limitations, as well as future developments in addressing these challenges. General recommendations are made in terms of the implementation of these commercial AI models, as well as precautions in recognizing the challenges and limitations.

Update on Dosing and Fractionation for Neoadjuvant Radiotherapy for Localized Soft Tissue Sarcoma

OPINION STATEMENT

Neoadjuvant radiotherapy (RT) over 5-6 weeks with daily doses of 1.8-2.0 Gy to a total dose of 50-50.4 Gy is standard of care for localized high-grade soft tissue sarcomas (STS) of the extremities and trunk wall. One exception is myxoid liposarcomas where the phase II DOREMY trial applying a preoperative dose of 36 Gy in 2 Gy fractions (3-4 weeks treatment) has achieved excellent local control rates of 100% after a median follow-up of 25 months.Hypofractionated preoperative RT has been investigated in a number of phase II single-arm studies suggesting that daily doses of 2.75-8 Gy over 1-3 weeks can achieve similar oncological outcomes to conventional neoadjuvant RT. Prospective data with direct head-to-head comparison to conventional neoadjuvant RT investigating oncological outcomes and toxicity profiles is eagerly awaited.For the entire group of retroperitoneal sarcomas, RT is not the standard of care. The randomized multi-center STRASS trial did not find a benefit in abdominal recurrence-free survival by the addition of preoperative RT. However, for the largest histological subgroup of well-differentiated and grades I and II dedifferentiated liposarcomas, the STRASS trial and the post-hoc propensity-matched STREXIT analysis have identified a possible benefit in survival by preoperative RT. These patients deserve to be informed about the pros and cons of preoperative RT while the longer follow-up data from the STRASS trial is awaited.

Neoadjuvant Simultaneous Integrated Boost Radiation Therapy Improves Clinical Outcomes for Retroperitoneal Sarcoma

PURPOSE

Neoadjuvant radiation therapy (RT) with standard techniques (ST) offers a modest benefit in retroperitoneal sarcoma (RPS). As the high-risk region (HRR) at risk for a positive surgical margin and recurrence is posterior and away from radiosensitive organs at risk, using a simultaneous integrated boost (SIB) allows targeted dose escalation to the HRR while sparing these organs. We hypothesized that neoadjuvant SIB RT can improve disease control compared with ST, without increasing toxicity.

METHODS AND MATERIALS

We retrospectively identified patients with resectable nonmetastatic RPS from 2000 to 2021 who received neoadjuvant RT of 180 to 200 cGy/fraction to standard volumes. SIB patients received 205 to 230 cGy/fraction to the appropriate HRR. Clinical endpoints included abdominopelvic control (APC), recurrence-free survival (RFS), overall survival (OS), and acute toxicity.

RESULTS

With a median follow-up of 57 months (95% confidence interval [CI], 50-64), there were 103 patients with RPS who received either ST (n = 69) or SIB (n = 34) RT. Median standard volume dose was 5000 cGy (ST) and 4500 cGy (SIB), with a median HRR SIB dose of 5750 cGy. Liposarcomas (79% vs 53%; P = .004) and cT4 tumors (59% vs 19%; P < .001) were more common in the SIB cohort, without a significant difference in the rate of resection (82% vs 81%; P = .88) or R1 margin (53.5% vs 50%; P = .36); there were no R2 resections. SIB was associated with a significant improvement in 5-year APC (96% vs 70%; P = .046) and RFS (60.2% vs 36.3%; P = .036), with a nonsignificant OS difference (90.1% vs 67.5%; P = .164). On multivariable analysis, SIB remained a predictor for APC (hazard ratio, 0.07; 95% CI, 0.01-0.74; P = .027) and RFS (hazard ratio, 0.036; 95% CI, 0.13-0.98; P = .045). SIB showed no significant detriment in toxicity, albeit with a lower rate of overall grade 3 acute toxicity (3% vs 22%; P = .023) compared with ST.

CONCLUSIONS

In RPS, dose escalation with neoadjuvant SIB RT may be independently associated with improved APC and RFS, without a detriment in toxicity, compared with ST. With the addition of standard RT having only a modest benefit compared with surgery alone, our study suggests that future prospective studies evaluating for the benefit of SIB RT should be considered.

Comparative In Silico Analysis of Ultra-Hypofractionated Intensity-Modulated Photon Radiotherapy (IMRT) Versus Intensity-Modulated Proton Therapy (IMPT) in the Pre-Operative Treatment of Retroperitoneal Sarcoma

BACKGROUND

While pre-operative radiation did not improve abdominal recurrence-free survival for retroperitoneal sarcoma (RPS) in the randomized STRASS trial, it did reduce rates of local recurrence. However, the risk of toxicity was substantial and the time to surgery was prolonged. A combination of hypofractionation and proton therapy may reduce delays from the initiation of radiation to surgery and limit the dose to surrounding organs at risk (OARs). We conducted a dosimetric comparison of the pre-operative ultra-hypofractionated intensity-modulated photon (IMRT) and proton radiotherapy (IMPT).

METHODS

Pre-operative IMRT and IMPT plans were generated on 10 RPS patients. The prescription was 25 Gy radiobiological equivalents (GyEs) (radiobiological effective dose of 1.1) to the clinical target volume and 30 GyEs to the margin at risk, all in five fractions. Comparisons were made using student T-tests.

RESULTS

The following endpoints were significantly lower with IMPT than with IMRT: mean doses to liver, bone, and all genitourinary and gastrointestinal OARs; bowel, kidney, and bone V5-V20; stomach V15; liver V5; maximum doses to stomach, spinal canal, and body; and whole-body integral dose.

CONCLUSIONS

IMPT maintained target coverage while significantly reducing the dose to adjacent OARs and integral dose compared to IMRT. A prospective trial treating RPS with pre-operative ultra-hypofractionated IMPT at our institution is currently being pursued.

Preoperative Dose-Escalated Intensity-Modulated Radiotherapy (IMRT) and Intraoperative Radiation Therapy (IORT) in Patients with Retroperitoneal Soft-Tissue Sarcoma: Final Results of a Clinical Phase I/II Trial

BACKGROUND

To report the final results of a prospective, one-armed, single-center phase I/II trial (NCT01566123).

METHODS

Between 2007 and 2017, 37 patients with primary or recurrent (N = 6) retroperitoneal sarcomas were enrolled. Treatment included preoperative IMRT of 45-50 Gy with a simultaneous integrated boost of 50-56 Gy, surgery and IORT. The primary endpoint was local control (LC) at 5 years. The most common histology was dedifferentiated liposarcoma (51%), followed by leiomyosarcoma (24%) and well-differentiated liposarcoma (14%). The majority of lesions were high-grade (FNCLCC G1: 30%, G2: 38%, G3: 27%, two missing). Five patients were excluded from LC analysis per protocol.

RESULTS

The minimum follow-up of the survivors was 62 months (median: 109; maximum 162). IORT was performed for 27 patients. Thirty-five patients underwent gross total resection; the pathological resection margin was mostly R+ (80%) and, less often, R0 (20%). We observed 10 local recurrences. The 5-year LC of the whole cohort was 59.6%. Eleven patients received a dose > 50 Gy plus IORT boost; LC was 64.8%; the difference, however, was not significant (p = 0.588). Of 37 patients, 15 were alive and 22 deceased at the time of final analysis. The 5-year OS was 59.5% (68.8% per protocol).

CONCLUSIONS

The primary endpoint of a 5-year LC of 70% was not met. This might be explained by the inclusion of recurrent disease and the high rate of G3 lesions and leiomyosarcoma, which have been shown to profit less from radiotherapy. Stratification by grading and histology should be considered for future studies.

Role of Radiation Therapy in Retroperitoneal Sarcoma

Retroperitoneal sarcoma comprises a small subset of all soft tissue sarcoma and includes various histopathologic subtypes, each with unique patterns of behavior and differential risks for local recurrence and hematogenous metastatic spread. The primary treatment modality is surgery, although even with complete macroscopic resection, recurrence is common. The rationale for the addition of radiotherapy to resection is to improve local control; however, the use of radiation therapy for retroperitoneal sarcoma is controversial, and existing data are suboptimal to guide management. Treatment decisions should be determined with multidisciplinary input and shared decision-making. When used in selected patients, radiation therapy should be delivered preoperatively; postoperative treatment is not recommended.

Soft Tissue Sarcoma, Version 2.2022, NCCN Clinical Practice Guidelines in Oncology

Soft tissue sarcomas (STS) are rare malignancies of mesenchymal cell origin that display a heterogenous mix of clinical and pathologic characteristics. STS can develop from fat, muscle, nerves, blood vessels, and other connective tissues. The evaluation and treatment of patients with STS requires a multidisciplinary team with demonstrated expertise in the management of these tumors. The complete NCCN Clinical Practice Guidelines in Oncology (NCCN Guidelines) for Soft Tissue Sarcoma provide recommendations for the diagnosis, evaluation, and treatment of extremity/superficial trunk/head and neck STS, as well as retroperitoneal/intra-abdominal STS, desmoid tumors, and rhabdomyosarcoma. This portion of the NCCN Guidelines discusses general principles for the diagnosis and treatment of retroperitoneal/intra-abdominal STS, outlines treatment recommendations, and reviews the evidence to support the guidelines recommendations.

Genomic identification of sarcoma radiosensitivity and the clinical implications for radiation dose personalization

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Soft tissue sarcomas have traditionally been treated with a one-size fits all approach, despite a wide range of histologies and clinical outcomes.

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The radiosensitivity index has demonstrated that soft tissue sarcomas are in general radioresistant, however exhibit a wide range of radiosensitivity.

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These differences in radiosensitivity are associated with decreased locoregional control in patients with radioresistant histologies.

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Using the radiosensitivity index we identify specific histologies of soft tissue sarcoma that may be more radioresistant, and suggest a genomic-based radiation dosing framework.

Background

Soft-tissue sarcomas (STS) are heterogeneous with variable response to radiation therapy (RT). Utilizing the radiosensitivity index (RSI) we estimated the radiobiologic ratio of lethal to sublethal damage (α/β), genomic-adjusted radiation dose(GARD), and in-turn a biological effective radiation dose (BED).

Methods

Two independent cohorts of patients with soft-tissue sarcoma were identified. The first cohort included 217 genomically-profiled samples from our institutional prospective tissue collection protocol; RSI was calculated for these samples, which were then used to dichotomize the population as either highly radioresistant (HRR) or conventionally radioresistant (CRR). In addition, RSI was used to calculate α/β ratio and GARD, providing ideal dosing based on sarcoma genomic radiosensitivity. A second cohort comprising 399 non-metastatic-STS patients treated with neoadjuvant RT and surgery was used to validate our findings.

Results

Based on the RSI of the sample cohort, 84% would historically be considered radioresistant. We identified a HRR subset that had a significant difference in the RSI, and clinically a lower tumor response to radiation (2.4% vs. 19.4%), 5-year locoregional-control (76.5% vs. 90.8%), and lower estimated α/β (3.29 vs. 5.98), when compared to CRR sarcoma. Using GARD, the dose required to optimize outcome in the HRR subset is a BED_α/β=3.29 of 97 Gy.

Conclusions

We demonstrate that on a genomic scale, that although STS is radioresistant overall, they are heterogeneous in terms of radiosensitivity. We validated this clinically and estimated an α/β ratio and dosing that would optimize outcome, personalizing dose.

Role of Radiation Therapy for Newly Diagnosed Retroperitoneal Sarcoma

OPINION STATEMENT

Soft tissue sarcomas (STS) are rare, aggressive, and heterogenous tumors, comprising approximately 1% of adult cancers with over 50 different subtypes. The mainstay of treatment for retroperitoneal sarcomas (RPS) includes surgical resection. The addition of radiation therapy (RT), either preoperatively or postoperatively, has been used to potentially decrease the risk of local recurrence. The recently published results from STRASS (EORTC-STBSG 62092-22092), which randomized patients to receive or not receive preoperative radiation, indicate no abdominal recurrence-free survival benefit (primary endpoint) nor overall survival benefit to date from the addition of preoperative RT prior to surgical resection in patients with RPS. Keeping in mind caveats of subgroup analyses, the data show a significant reduction in local recurrence with radiation therapy in resected patients and non-significant trends toward improved abdominal recurrence-free survival in all patients and improved local control and abdominal recurrence-free survival in patients with liposarcoma and low-grade sarcoma. Given the high rate of local failure with surgery alone, it is possible that higher RT dose and/or selective RT dose painting may improve outcomes. Prior to treatment, the authors encourage multidisciplinary review and discussion of management options at a sarcoma center for patients with RPS. Selective use of RT may be considered for patients at high risk of local recurrence.

The Future of Radiation Oncology in Soft Tissue Sarcoma

Radiotherapy (RT) is an important component of the treatment of soft tissue sarcomas (STS) and has been traditionally incorporated with a homogenous approach despite the reality that STS displays a known heterogeneity in clinicopathologic features and treatment outcomes. In this article, we explore the principle components of personalized medicine, including genomics, radiomics, and treatment response, along with their impact on the future of radiation therapy for STS. We propose a shift in the treatment paradigm for STS from a one-size-fits-all technique to one that implements the tenets of personalized medicine and includes the framework for a potential clinical trial technique in this heterogeneous disease.

Intensity modulated radiation therapy and surgery for Management of Retroperitoneal Sarcomas: a single-institution experience

BACKGROUND

Peri-operative radiation of retroperitoneal sarcomas (RPS) is an important component of multidisciplinary treatment. All retrospective series thus far included patients treated with older radiation therapy (RT) techniques including 2D and 3DRT. Intensity modulated radiation therapy (IMRT) allows for selective dose escalation while sparing adjacent organs. We therefore report the first series of patients with RPS treated solely with IMRT, surgery and chemotherapy. We hypothesized that IMRT would permit safe dose escalation and superior rates of local control (LC) in this high-risk patient population.

METHODS

Thirty patients with RPS treated with curative intent between 2006 and 2015 were included in this retrospective study. RT was administered either pre- or post-operatively and IMRT was used in all patients. Statistical comparisons, LC, distant metastasis (DM), and overall survival (OS) were calculated by Kaplan-Meier analysis and univariate Cox regression.

RESULTS

Median follow-up time after completion of RT was 36 months (range 1.4-112). Median tumor size was 14 cm (range 3.6 - 28 cm). The most prevalent histologies were liposarcoma in 10 (33%) patients and leiomyosarcoma in 10 (33%) with 21 patients (70%) having high-grade disease. Twenty-eight (93%) patients had surgical resection with 47% having positive margins. Chemotherapy was administered in 9 (30%) patients. RT was delivered pre-operatively in 11 (37%) patients, and post-operatively in 19 (63%) with 60% of patients receiving a simultaneous integrated boost. Pre-operative median RT dose to the high-risk area was 55 Gy (range, 43-66 Gy) while median post-operative dose was 60.4 Gy (range, 45-66.6 Gy). There was one acute grade 3 and one late grade 3 toxicity and no grade 4 or 5 toxicities. Three year actuarial LC, freedom from DM, and OS rates were 84%, 64%, and 68% respectively. Positive surgical margins were associated with a higher risk of local recurrence (p = 0.02) and decreased OS (p = 0.04). Pre-operative RT was associated with improved LC (p = 0.1) with a 5-year actuarial LC of 100%. Administration of chemotherapy, timing of RT, histology or grade was not predictive of OS.

CONCLUSIONS

Patients with RPS treated with peri-operative IMRT at our institution had excellent local control and low incidences of toxicity.

Phase 1 trial of preoperative image guided intensity modulated proton radiation therapy with simultaneously integrated boost to the high risk margin for retroperitoneal sarcomas

PURPOSE

To conduct phase 1 and 2 trials with photon intensity modulated radiation therapy and intensity modulated proton therapy (IMPT) arms to selectively escalate the retroperitoneal sarcoma preoperative radiation dose to tumor volume (clinical target volume [CTV] 2) that is judged to be at a high risk for positive margins and aim to reduce local recurrence. We report on the IMPT study arm in phase 1.

METHODS AND MATERIALS

Patients aged ≥18 years with primary or locally recurrent retroperitoneal sarcoma were treated with preoperative IMPT, 50.4 GyRBE in 28 fractions, to CTV1 (gross tumor volume and adjacent tissues at risk of subclinical disease) with a simultaneous integrated boost to CTV2 to doses of 60.2, 61.6, and 63.0 GyRBE in 28 fractions of 2.15, 2.20, and 2.25 GyRBE, respectively. The primary objective of the phase 1 study was to determine the maximum tolerated dose to CTV2, which will be further tested in the phase 2 study.

RESULTS

Eleven patients showed increasing IMPT dose levels without acute dose limiting toxicities that prevented dose escalation to maximum tolerated dose. Acute toxicity was generally mild with no radiation interruptions. No unexpected perioperative morbidity was noted. Eight months postoperatively, one patient developed hydronephrosis that was treated by stent with ureter dissected off tumor and received 57.5 GyRBE. Retained ureter(s) was (were) subsequently constrained to 50.4 GyRBE without further problem. With an 18-month median follow-up, there were no local recurrences.

CONCLUSIONS

IMPT dose escalation to CTV2 to 63 GyRBE was achieved without acute dose limiting toxicities. The phase 2 study of IMPT will accrue patients to that dose. Parallel intensity modulated radiation therapy phase 1 arm is currently accruing at the initial dose level. Ureters that undergo a high dose radiation and/or surgery are at risk for late hydro-ureter. Future studies will constrain retained ureters to 50.4 GyRBE to avoid ureteral stricture.

Retroperitoneal Sarcoma Target Volume and Organ at Risk Contour Delineation Agreement Among NRG Sarcoma Radiation Oncologists

PURPOSE

The purpose of this study was to evaluate the variability in target volume and organ at risk (OAR) contour delineation for retroperitoneal sarcoma (RPS) among 12 sarcoma radiation oncologists.

METHODS AND MATERIALS

Radiation planning computed tomography (CT) scans for 2 cases of RPS were distributed among 12 sarcoma radiation oncologists with instructions for contouring gross tumor volume (GTV), clinical target volume (CTV), high-risk CTV (HR CTV: area judged to be at high risk of resulting in positive margins after resection), and OARs: bowel bag, small bowel, colon, stomach, and duodenum. Analysis of contour agreement was performed using the simultaneous truth and performance level estimation (STAPLE) algorithm and kappa statistics.

RESULTS

Ten radiation oncologists contoured both RPS cases, 1 contoured only RPS1, and 1 contoured only RPS2 such that each case was contoured by 11 radiation oncologists. The first case (RPS 1) was a patient with a de-differentiated (DD) liposarcoma (LPS) with a predominant well-differentiated (WD) component, and the second case (RPS 2) was a patient with DD LPS made up almost entirely of a DD component. Contouring agreement for GTV and CTV contours was high. However, the agreement for HR CTVs was only moderate. For OARs, agreement for stomach, bowel bag, small bowel, and colon was high, but agreement for duodenum (distorted by tumor in one of these cases) was fair to moderate.

CONCLUSIONS

For preoperative treatment of RPS, sarcoma radiation oncologists contoured GTV, CTV, and most OARs with a high level of agreement. HR CTV contours were more variable. Further clarification of this volume with the help of sarcoma surgical oncologists is necessary to reach consensus. More attention to delineation of the duodenum is also needed.