From Fewer Fractions to Smarter Combinations: The State of Radiotherapy in Soft Tissue Sarcoma

Shorter, more convenient radiotherapy (RT) regimens are delivering outcomes equivalent to traditional treatment schedules for soft tissue sarcoma (STS), while novel combinations with immunotherapy and targeted agents are building a case for more personalized approaches, according to a review published in Current Oncology Reports.¹ The findings carry meaningful implications for managed care stakeholders navigating treatment authorization, site-of-care decisions, and the allocation of high-cost technologies such as proton beam therapy (PBT).

Soft tissue sarcomas account for roughly 1% of all adult malignancies but encompass more than 100 histological subtypes, creating significant complexity in treatment planning and coverage determinations. RT plays a central role in improving local control and, in some cases, overall survival (OS), particularly as an adjunct to surgery for high-risk disease.

Why Hypofractionation May Be Reshaping the Standard of Care

The clearest takeaway from the 2025 evidence base is the growing acceptance of hypofractionated RT, which are regimens using fewer, larger doses per fraction as a noninferior alternative to the conventional approach of 1.8 to 2.0 Gy per fraction over 35 to 39 fractions. Study data shows that hypofractionated preoperative RT, typically 45 to 50 Gy delivered in 15 to 20 fractions, achieved local control rates of 85% to 90% comparable to conventional fractionation, with similar postoperative complication rates.¹

The implications in the managed care space are direct: Hypofractionation cuts treatment duration by 30% to 40%, from 5 to 6 weeks down to 3 to 4 weeks, potentially reducing per-episode costs related to facility visits, ancillary services, and productivity loss. Crucially, these benefits may extend to underserved or rural populations with limited access to daily radiation appointments.

However, the recently updated European Society for Radiotherapy and Oncology (ESTRO)–American Society for Radiation Oncology (ASTRO) joint clinical practice guideline stopped short of endorsing hypofractionation as a formal standard pending randomized head-to-head data, while acknowledging its promise in prospective single-arm studies.²

What the Immunotherapy and Targeted Therapy Data Show

Beyond fractionation, the review highlights 2025 data supporting RT combinations with systemic agents. A phase 2 trial of pembrolizumab (anti-PD-1) plus neoadjuvant RT in patients with high-risk undifferentiated pleomorphic sarcoma (UPS) and dedifferentiated liposarcoma reported a pathological complete response (pCR) rate of 24% and a 2-year OS rate of 79%, with evidence of increased CD8+ T-cell infiltration in responding tumors.¹ Overall, the trial demonstrated a disease-free survival benefit from adding pembrolizumab to preoperative RT.²

On the targeted therapy side, a phase 1b study of olaparib, a PARP inhibitor, combined with concurrent RT in patients with advanced STS reported a disease control rate of 77% at a maximum tolerated olaparib dose of 100 mg twice daily, with manageable myelosuppression and fatigue as the primary grade 3+ toxicities.¹

These combinations raise questions about sequencing, concurrent compared with sequential use, and how emerging evidence should inform prior authorization criteria for immune checkpoint inhibitor use in STS—a rare cancer where biomarker-based patient selection tools remain nascent.

Where Equity and Access Concerns Intersect With Technology

The review also examines high-precision RT modalities such as stereotactic body radiotherapy and particle therapy, including PBT and carbon ion radiotherapy (CIRT). With these therapies the clinical case is strong, but the high cost and difficult access remain acute difficulties.

A meta-analysis of 8 studies covering 1245 pediatric patients with rhabdomyosarcoma found that PBT was associated with a 58% reduction in the risk of late grade 2+ toxicities compared with conventional photon RT, including a 64% lower risk of musculoskeletal toxicity, while achieving comparable OS and local control rates.¹ For a vulnerable population already at risk for growth retardation, organ dysfunction, and secondary malignancies, this toxicity benefit is clinically meaningful.

However, CIRT remains available at only a small number of centers worldwide, and PBT is far from universally accessible. The review's authors acknowledge that health economic analyses are needed to define which patient populations derive the greatest clinically meaningful benefit from particle therapy to justify its cost.

Patients with STS face many logistical barriers when accessing specialized treatment, and multidisciplinary care influences therapy choices but does not automatically overcome systemic access barriers.³ The COVID-19 pandemic-era adoption of hypofractionation, documented in a prospective cohort of 98 patients with STS, demonstrated that shorter schedules can be implemented in resource-limited settings without compromising outcomes. The results from this study serve as a proof of concept with direct implications for access-to-care policy.¹

What Biomarkers Mean for Future Coverage Decisions

A growing body of 2025 evidence points toward response assessment tools that could eventually support adaptive, biomarker-guided RT.

Advances in multiparametric MRI parameters (mpMRI) may also enable early response assessments and pave the way for personalized and adaptive RT. Results from a pilot study showed that mpMRI parameters correlated strongly with pathological response to neoadjuvant RT in a pilot study, with a combined scoring approach predicting pCR with 89% sensitivity and 83% specificity as early as 2 to 3 weeks into treatment.¹ Hyalinization, which is the replacement of tumor cells by acellular material, was identified as a novel pathologic marker associated with a 2-year local control rate of 89% in patients with UPS with high hyalinization vs 53% in those with low hyalinization. Tumor-infiltrating monocytes also emerged as an independent predictor of progression-free and OS in a phase 2 immunoradiotherapy trial.

If validated prospectively, these tools could support adaptive treatment modification, including dose escalation in nonresponders and de-escalation in strong responders. This could reduce unnecessary treatment exposure and its associated costs while concentrating resources on high-risk patients.

Looking ahead, the review identifies artificial intelligence integration into adaptive RT workflows, validation of surrogate end points, and expanded global access to advanced technologies as the field's primary unmet needs.

References

1. Yang YY, Xie L, Sun X, Xu J, Ren G. Advances in radiotherapy for soft tissue sarcomas in 2025: a review. Curr Oncol Rep. 2026;28:50. doi:10.1007/s11912-026-01787-2
2. Hohmann E. Preoperative radiotherapy remains standard of care for soft tissue sarcoma, new ESTRO-ASTRO guideline confirms. AJMC. May 7, 2026. Accessed May 20, 2026. https://www.ajmc.com/view/preoperative-radiotherapy-remains-standard-of-care-for-soft-tissue-sarcoma-new-estro-astro-guideline-confirms
3. McNulty R. The top 5 most-read soft tissue sarcoma articles of 2025. AJMC. December 29, 2025. Accessed May 20, 2026. https://www.ajmc.com/view/the-top-5-most-read-soft-tissue-sarcoma-articles-of-2025