Adjuvant volumetric modulated arc therapy compared to 3D conformal radiation therapy for newly diagnosed soft tissue sarcoma of the extremities: outcome and toxicity evaluation

Toxicity, normal tissue and dose-volume planning parameters for radiotherapy in soft tissue sarcoma of the extremities: A systematic review of the literature

BACKGROUND

Patients with soft tissue sarcoma of the extremities (STSE) are left with high incidence of toxicities after Radiotherapy (RT). Understanding the normal tissue dose relationship with the development of long-term toxicities may enable better RT planning in order to reduce treatment toxicities for STSE. This systematic review of the literature aims at reporting the incidence of acute and late toxicities and identifying RT delineation guidance the normal tissues structures and dose-volume parameters for STSE.

METHODS

A literature search of PUBMED-MEDLINE for studies that reported data on RT toxicity outcomes, delineation guidelines and dose-volume parameters for STSE from 2000 to 2022. Data has been tabulated and reported.

RESULTS

Thirty of 586 papers were selected after exclusion criteria. External beam RT prescriptions ranged from 30 to 72 Gy. The majority of studies reported the use of Intensity Modulated RT (IMRT) (27%). Neo-adjuvant RT was used in 40%. The highest long-term toxicities were subcutaneous and lymphoedema, reported when delivering 3DCRT. IMRT had a lower incidence of toxicities. Normal tissue outlining such as weight-bearing bones, skin and subcutaneous tissue, corridor and neurovascular bundle was recommended in 6 studies. Nine studies recommended the use of dose-volume constraints, but only one recommended evidence-based dose-volume constraints.

CONCLUSION

Although the literature is replete with toxicity reports, there is a lack of evidence-based guidance on normal tissue and dose-volume parameters and strategies to reduce the normal tissues irradiation when optimising RT plans for STSE are poor compared to other tumour sites.

Early outcomes of ultra-hypofractionated preoperative radiation therapy for soft tissue sarcoma followed by immediate surgical resection

BACKGROUND

There is increasing interest in shorter courses of radiation therapy (RT) in the management of soft tissue sarcoma (STS). We report our institutional experience for patients undergoing ultra-hypofractionated preoperative RT followed by immediate resection.

METHODS

An IRB approved review of patients treated with preoperative 5 fraction, once daily RT followed by immediate resection (within 7 days) for STS of the extremity or trunk was conducted. The primary endpoints are major wound complications and local control (LC). Secondary endpoints include grade ≥ 2 toxicity, metastasis free survival (MFS), and overall survival (OS).

RESULTS

Twenty-two patients with a median age of 67 years (range 30-87) and median follow-up of 24.5 months (IQR 17.0-35.7) met eligibility criteria; 18/22 patients (81.8 %) had ≥ 1 year follow-up. Primary tumor location was lower extremity in 15 patients (68.2 %), upper extremity in 5 (22.7 %), and trunk in 2 (9.1 %). All patients received 30 Gy in 5 fractions. The median time to resection following RT was 1 day (range 0-5). The median time from biopsy to resection was 34 days (range 20-69). Local control was 100 %; in patients with localized disease, 2-year MFS and OS were 71.3 % and 76.9 %, respectively. Major wound complications occurred in 9 patients (40.9 %), with wound complications requiring reoperation occurring in 8 patients (36.4 %). Other acute and late grade ≥ 2 toxicities were seen in 0 and 4 patients (18.2 %), respectively.

CONCLUSION

Ultra-hypofractionated preoperative RT followed by immediate resection permits expedited completion of oncologic therapy with early results demonstrating excellent local control and acceptable toxicity. Prospective data with long-term follow-up is needed.

Dosimetric Comparison of VMAT and IMRT Pre-Operative Radiotherapy for Soft Tissue Sarcoma of the Extremities

PURPOSE

Radiotherapy is a standard part of limb conserving therapy for extremity soft tissue sarcoma (STS) at high risk of recurrence. Toxicities increase with radiation dose and volume of normal tissue irradiated. This study sought to compare dosimetry of volumetric modulated arc radiotherapy (VMAT), with intensity modulated radiotherapy (IMRT) and to investigate the optimal planning technique.

METHODS AND MATERIALS

Twenty patients with extremity STS who underwent preoperative radiotherapy (50 Gy in 25 fractions) between 2016 and 2020 at a sarcoma specialist centre were included. The original treatment techniques were sliding window IMRT or 3D conformal. VMAT plans were retrospectively generated according to the original tumour and organ at risk constraints. Quality assurance was performed as per departmental protocol. Wilcoxon signed-rank test was used to compare dosimetric parameters (for planning target volume, in-field bone, and soft tissue structures), monitor units (MU) and treatment time.

RESULTS

Median patient age was 65 years and majority were male (n=14, 70%). Commonest subtype was undifferentiated pleomorphic sarcoma (n=14, 70%) and most tumours were located on the thigh (n=12, 60%). Median PTV volume was 1110 cm³ and median volume of in-field bone 236 cm³. VMAT plans had significantly lower average MU (480 vs 862 MU, p<0.001) and overall treatment time (300 vs 153 seconds, p<0.001). PTV coverage favoured VMAT, with marginally higher mean, minimum, and maximum doses, and higher Conformity Index. However, differences were not statistically significant. Dose to infield bone and soft tissue structures were similar or slightly lower with VMAT.

CONCLUSIONS

In extremity soft tissue sarcoma, VMAT plans demonstrated a favourable trend toward tumour coverage and dose conformity compared to IMRT along with significantly lower monitor units and half the overall treatment time.

Preoperative Stereotactic Body Radiation Therapy for Soft-Tissue Sarcoma: Results of Phase 2 Study

Purpose

Preoperative radiation followed by surgical resection is a standard treatment for soft-tissue sarcomas (STS). We report on 2 consecutive, phase 2, single-arm studies evaluating 5 fraction stereotactic body radiation therapy (SBRT) treatments followed by surgical resection for STS (clinical trails.gov NCT02706171).

Methods and Materials

A total of 16 patients were treated with preoperative SBRT. Tumor size in the greatest dimension was a median 6.7 cm (maximum: 14 cm) and the majority of STS were in the extremities. SBRT consisted of 35 to 40 Gy in 5 fractions every other day.

Results

Median follow-up time was 1719 days (4.7 years). Grade ≥3 acute toxicity occurred in 1 patient (grade 3 skin changes). Fifteen patients proceeded with surgical resection. Three patients had a wound complication after surgery, 1 patient had grade ≥3 late toxicity (grade 4 requiring surgical intervention). There was 1 local recurrence and 5 distant recurrences.

Conclusions

Long-term follow-up on SBRT for STS found acceptable control and toxicity rates, and warrants further evaluation.

Radiation Therapy for Treatment of Soft Tissue Sarcoma in Adults: Executive Summary of an ASTRO Clinical Practice Guideline

PURPOSE

This guideline provides evidence-based recommendations addressing the indications for radiation therapy (RT), sequencing of local therapies, and appropriate dose and planning techniques for management of primary, operable, localized, soft tissue sarcoma (STS) in adults.

METHODS

The American Society for Radiation Oncology convened a task force to address 5 key questions focused on the use of RT for management of STS. These questions included indications for RT for STS of the extremity and superficial trunk; considerations for sequencing of RT with respect to surgery, dose of RT, appropriate treatment volumes and techniques; and the role of RT in management of retroperitoneal sarcoma. Recommendations were based on a systematic literature review and created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength.

RESULTS

Multidisciplinary evaluation and decision making are recommended for all cases of STS. RT is recommended for patients in whom there is increased risk of local recurrence of resected STS, particularly if close or microscopically positive margins are anticipated or have occurred. When RT is indicated, preoperative RT is strongly recommended over postoperative RT. Postoperative RT is conditionally recommended in specific clinical circumstances (eg, uncontrolled pain or bleeding) or when the risk of wound complications outweighs that of late toxicity from RT. Routine use of RT in addition to oncologic resection for retroperitoneal sarcoma is conditionally not recommended. When RT is used for retroperitoneal sarcoma, preoperative RT is recommended, whereas postoperative RT is not recommended.

CONCLUSIONS

Based on currently published data, the American Society for Radiation Oncology task force has proposed evidence-based recommendations regarding the use of RT for STS in adults. Future studies will ascertain whether alterations in dosing and sequencing may optimize outcomes and quality of life.

Significance of intraoperative radiation therapy and high cumulative radiation doses in retroperitoneal soft tissue sarcoma

INTRODUCTION

In retroperitoneal soft tissue sarcoma (STS) local recurrence (LR) rates remain high despite more aggressive surgical approaches. Since wide resection margins cannot be achieved in all patients, application of intraoperative radiation therapy (IORT) has been frequently discussed. Still, the significance of IORT in multimodal treatment of retroperitoneal STS remains unclear.

MATERIAL AND METHODS

Patients undergoing resection of primary or recurrent retroperitoneal STS at the University of Heidelberg Department of General, Visceral and Transplantation Surgery were retrospectively analyzed. Univariate Kaplan-Meyer and multivariate Cox regression analyses were performed to identify predictors of LR-free survival and to investigate the impact of IORT and high cumulative radiation doses. Analyses with propensity-score matched subgroups for IORT and cumulative radiation dose were performed to control for selection bias. Subgroup analyses for patients with retroperitoneal liposarcoma were likewise performed.

RESULTS

272 patients were identified. Recurrent tumors, histology of dedifferentiated liposarcoma or unclassified sarcoma and microscopically incomplete resection were associated with decreased LR-free survival. In liposarcoma, only recurrent and dedifferentiated tumors were confirmed as poor prognostic factors concerning LR. IORT and cumulative radiation doses exceeding 60 Gy did not influence LR rates (estimated 5-year LR-free survival: IORT: 39%, non-IORT: 46%; p = 0.79).

CONCLUSION

In this retrospective evaluation, additional application of IORT does not significantly influence oncological outcome in retroperitoneal soft tissue sarcoma. Randomized trials are needed to clarify the benefit of IORT.