High-Level Highlights
This Phase 2 nonrandomized clinical trial provides evidence that a condensed 5-day preoperative radiation therapy (RT) regimen (30 Gy in 5 fractions) for high-risk soft tissue sarcoma (STS) achieves a 2-year local control rate of 92.4%.
Late grade 2 or higher radiation toxic effects occurred in only 18.9% of patients at the 2-year mark, suggesting that the shorter course does not result in prohibitive long-term morbidity.
Major wound complications (MWC) were observed in 30.0% of the cohort, a rate consistent with historical data for standard 5-week preoperative radiation therapy.
The findings suggest that ultrahypofractionated RT could significantly reduce the logistical and financial burden on patients without compromising oncologic outcomes or safety.
The Clinical Challenge of Soft Tissue Sarcoma
Soft tissue sarcomas (STS) of the extremities and trunk are rare but aggressive malignancies that require a multidisciplinary approach. For decades, the standard of care for high-risk, localized STS has involved preoperative radiation therapy followed by wide surgical resection. Traditionally, this radiation is delivered in a fractionated manner—typically 50 Gy over 25 treatment sessions spanning 5 weeks.
While effective in maximizing local control, the 5-week duration presents significant challenges. Many patients must travel to high-volume academic centers for specialized sarcoma care, leading to substantial logistical hurdles, financial strain, and time away from work or family. In the era of value-based healthcare, there is an urgent need to investigate whether shorter, more intensive radiation schedules—known as hypofractionation—can offer equivalent outcomes while improving patient quality of life.
Study Design and Methodology
This Phase 2, single-group nonrandomized trial was conducted at a leading academic center in the United States to evaluate the long-term safety and efficacy of a 5-day preoperative RT regimen. The study enrolled 110 patients with histologically confirmed, high-risk extremity or trunk STS who were candidates for preoperative RT and surgery.
Intervention and Dosing
The intervention consisted of ultrahypofractionated RT, delivering a total dose of 30 Gy in 5 daily fractions of 6 Gy each. This dose is biologically equivalent to the standard 50 Gy in 25 fractions, assuming a low alpha/beta ratio for sarcoma cells, which suggests they may be more sensitive to larger doses per fraction.
Patient Cohorts and Endpoints
The analysis included an initial cohort of 50 patients (treated 2016-2018) and an expansion cohort of 60 patients (treated 2018-2023) who did not receive neoadjuvant chemotherapy. The primary endpoint was the rate of grade 2 or higher late radiation toxic effects at 2 years. Secondary endpoints included major wound complications (defined as those requiring secondary surgery or prolonged specialized care), local failure, distant progression, and overall survival.
Key Findings and Clinical Outcomes
The study results provide a robust look at both the oncologic efficacy and the safety profile of the 5-day regimen. With a median follow-up of 37.3 months across the entire group, several critical data points emerged.
Toxicity and Wound Complications
At the 2-year milestone, 18.9% of evaluable patients experienced grade 2 or higher late toxic effects. This is a favorable rate, particularly when compared to historical benchmarks for 5-week RT. Interestingly, the expansion cohort showed a lower rate of late toxicity (11.8%) than the initial cohort (25.0%), potentially reflecting improvements in radiation planning or surgical techniques over time.
Major wound complications (MWC) occurred in 30.0% of patients. This figure is strikingly similar to the 35% rate reported in the landmark SR2 trial that established preoperative RT as a standard. However, the study noted that time to wound closure exceeded 6 months in 13.6% of patients, particularly those who underwent local tissue advancement flaps (41.4% of that subgroup), highlighting a specific area for clinical vigilance.
Oncologic Control
The 2-year local control rate, adjusted for the competing risk of death, was 92.4% (95% CI, 86.3%-96.5%). This demonstrates that shortening the treatment window did not result in a loss of local tumor control. Furthermore, the rates of bone fracture (2.7%) and amputation (4.5%) remained low, suggesting that the high dose per fraction did not lead to catastrophic structural failure of the treated limbs.
Expert Commentary and Mechanistic Insights
The move toward hypofractionation in sarcoma is supported by the radiobiological principle that certain tumors, including many sarcomas, have a low alpha/beta ratio. This implies that they are highly sensitive to the size of the radiation dose per fraction. By increasing the fraction size to 6 Gy, clinicians can potentially achieve the same cell-killing effect in five days that previously took five weeks.
Current clinical guidelines are beginning to reflect this shift, partly influenced by the Polish 5×5 Gy trials and the UK’s HYPO-RT initiatives. However, this study adds significant value by providing long-term (2-year) toxicity data, which is essential for ensuring that the intensive 5-day course doesn’t lead to late-onset fibrosis, joint stiffness, or secondary fractures. The observed 30% MWC rate remains the ‘Achilles heel’ of preoperative radiation in STS, regardless of the fractionation schedule. Surgeons and radiation oncologists must continue to collaborate closely on tissue handling and flap reconstruction to mitigate these risks.
Study Limitations
While promising, the study is limited by its nonrandomized, single-center design. The lack of a direct head-to-head comparison with the 50 Gy/25 fraction standard means that definitive conclusions about superiority or non-inferiority cannot be drawn. Additionally, the exclusion of patients receiving neoadjuvant chemotherapy in the expansion cohort limits the generalizability of these findings to patients with the highest risk of systemic spread who require multi-modal therapy.
Conclusion and Future Directions
The results of this Phase 2 trial suggest that a 5-day, 30 Gy preoperative radiation regimen is a viable, safe, and effective alternative to the traditional 5-week course for patients with high-risk soft tissue sarcoma. It offers durable local control and a favorable late toxicity profile, with wound complication rates that mirror historical standards. For patients, the reduction in treatment time from 35 days to 5 days is transformative.
Looking ahead, large-scale randomized controlled trials are necessary to confirm these findings across diverse populations and to further refine which patients benefit most from this accelerated approach. For now, this data provides a strong foundation for clinicians to discuss shortened radiation courses as a feasible option in the shared decision-making process.
Funding and Clinical Trial Information
This research was supported by institutional funds and grants from the National Cancer Institute. ClinicalTrials.gov Identifier: NCT02701153.
References
1. Nikitas J, Kendal JK, Savjani RR, et al. Five-Day Preoperative Radiation Therapy for Patients With High-Risk Soft Tissue Sarcoma: A Nonrandomized Clinical Trial. JAMA Netw Open. 2025;8(12):e2550195. doi:10.1001/jamanetworkopen.2025.50195.
2. O’Sullivan B, Davis AM, Turcotte R, et al. Preoperative versus postoperative radiotherapy in soft-tissue sarcoma of the limbs: a randomised trial. Lancet. 2002;359(9325):2235-2241.
3. Folkert MR, Singer S, Brennan MF, et al. Comparison of local recurrence with conventional and intensity-modulated radiation therapy for primary soft-tissue sarcoma of the extremity. J Clin Oncol. 2014;32(29):3236-3243.
