Local Therapy Modality Does Not Independently Predict Recurrence in Nonmetastatic Ewing Sarcoma

In a contemporary analysis of the phase 3 AEWS1031 study (NCT01231906), treatment modality was not found to independently predict local recurrence—the rates of which were also found to be historically low for prospective trials— in patients with nonmetastatic Ewing sarcoma treated with interval compression chemotherapy.¹ Instead, tumor size, age, and axial location emerged as the principal predictors of recurrence, supporting individualized decision-making based on resectability and anticipated functional outcomes rather than concern for inferior control with radiation alone, according to R. Lor Randall, MD, FACS.

“The take-home message in this modern multi-modality therapy study is that future efforts should focus on identifying and intensifying treatment for the high-risk subsets, rather than debating modality alone,” Randall stated in an interview with OncLive®

During the interview, Randall detailed the key results and implications of this report, including the 6% 5-year rate of cumulative incidence of local recurrence, and identified patients with large volume and axial tumors as high-risk candidates for intensified local approaches based on these findings.

Randall is the David Linn Endowed Chair for Orthopedic Surgery, the chair of the Department of Orthopedic Surgery, and a professor at UC Davis Comprehensive Cancer Center in Sacramento, California.

OncLive: What was the rationale for evaluating clinical and treatment variables associated with local recurrence risk in nonmetastatic Ewing sarcoma treated with interval compression therapy?

Randall: This is a…compelling analysis from the Children’s Oncology Group [COG]. This study addresses a long-standing question in Ewing sarcoma: What factors are associated with local recurrence in the modern era of interval-compressed chemotherapy, and does the local therapy modality matter? Local therapy—whether it is surgery, radiation therapy, or a combination—remains a cornerstone of curative treatment in nonmetastatic Ewing sarcoma. Historically, surgery has been associated with lower local recurrence rates and radiation with higher rates. Combined therapy is generally reserved for margin-positive or complex cases, but those data largely come from older, cooperative group trials.

In patients receiving interval-compressed chemotherapy for nonmetastatic Ewing sarcoma, what clinical or tumor-related factors most strongly influence the choice between surgery, radiation, or combined modality local therapy?

This study was a contemporary phase 3 trial using interval compression chemotherapy [that] examined 588 patients who completed induction and initiated local therapy.^1,2 The primary end point was the cumulative incidence of local recurrence from the start of local therapy.

There are several key findings.¹ First, the overall 5-year cumulative incidence of local recurrence was just 6%. This is the lowest reported rate to date in a prospective Ewing sarcoma trial. It reflects meaningful progress in multimodality care, including chemotherapy intensification, imaging, radiation planning, and advanced surgical techniques. Secondly, when comparing local therapy modalities, there was no statistically significant difference in 5-year local recurrence rates: for surgery alone, it was 5%; for radiation alone, it was 8.4%; and for surgery plus radiation, it was 5.6%. Importantly, these differences were not statistically significant. This suggests that in the era of interval compression and modern radiation delivery, outcomes with radiation are substantially improved compared with older datasets.

Third, and perhaps most clinically relevant, the strongest predictors of local failure were not the modality, but tumor biology and burden. Three factors stood out: tumor volume greater than 200 mL, a maximum tumor dimension of 8 cm [or greater], and older age at enrollment. On multivariate analysis, axial tumor location was associated with a higher risk compared with extremity tumors. For example, a tumor greater than 200 mL had an 11% local recurrence rate vs 3.9% for smaller tumors; larger tumors, particularly those 8 cm [or larger], also demonstrated significantly higher local [recurrence] risks. This reinforces the principle that tumor size and disease burden remain dominant drivers of risk even in the modern era. Interestingly, the randomized chemotherapy backbone also showed a signal: patients receiving VDC-IE [vincristine, doxorubicin, cyclophosphamide with ifosfamide, etoposide]/

VTC [vincristine, topotecan, cyclophosphamide] had numerically lower local recurrence rates compared with VDC-IE alone, though the study was not powered for this as an end point.

What are the implications of these findings for navigating treatment decisions in nonmetastatic Ewing sarcoma?

First, these data support thoughtful, individualized local therapy decision-making. Since modality did not independently predict local recurrence, decisions can be more heavily guided by resectability, anticipated morbidity, functional outcomes, and patient preference, rather than a fear of inferior local control with radiation alone. Second, we must pay particular attention to patients with large-volume and axial tumors. These patients remain at higher risk and may be candidates for intensified local approaches, such as clinical trials evaluating dose escalation or novel biologically targeted strategies. Third, the findings suggest that advances in radiation planning—such as IMRT, proton therapy, improved imaging, and tighter margins—have meaningfully narrowed historical differences between surgery and radiation outcomes.

Putting this all together, this contemporary COG analysis demonstrated historically low local recurrence rates in nonmetastatic Ewing sarcoma treated with interval compression chemotherapy. Local therapy modality did not significantly impact local recurrence; instead, tumor size, age, and axial location were the dominant risk factors.

What are the unanswered questions that remain about local as optimizing local control while minimizing long-term morbidity?

Both radiation therapy and surgery have made major advances over the last couple of decades in terms of being more precise with less scatter, whether that is through radiation therapy or the tissue dissections a surgeon performs to resect a tumor. I believe that the modality is much less important now in terms of the local recurrence rate, but we do need to take a nuanced approach to every case. What is the morbidity of the resection vs the adverse effects of using even more refined radiation to ablate the tumor?

Another consideration if we use radiation is that one of the challenges with surveillance is that because the tumor is left in situ, there are going to be signal abnormalities in surveillance. We don’t always know if those signals mean the tumor is coming alive again—for example, if there are residual clones that are active. What does that signal mean when you have a tumor that hasn’t been physically removed? That reflects a surgical assumption and bias, but all of us would like to know that the tumor is out and the margins are known for our surveillance.

References

1. Ahmed SK, Binitie O, Krailo M, et al. Factors associated with primary site local therapy in patients with nonmetastatic Ewing sarcoma treated with interval-compressed chemotherapy: a report from the Children's Oncology Group. Int J Radiat Oncol Biol Phys. Published online November 22, 2025. doi:10.1016/j.ijrobp.2025.11.010
2. Leavey PJ, Laack NN, Krailo MD, et al. Phase III trial adding vincristine-topotecan-cyclophosphamide to the initial treatment of patients with nonmetastatic Ewing sarcoma: a Children's Oncology Group report. J Clin Oncol. 2021;39(36):4029-4038. doi:10.1200/JCO.21.00358