Infants diagnosed with soft tissue tumors face a disproportionately high risk of dying from treatment toxicity rather than from cancer relapse, a new study reveals, AJMC reported. The research, analyzing data from the Cancer in Young People in Canada program, found that treatment-related mortality was 4 times higher in infants compared to older children, despite similar rates of severe side effects.
While relapse rates were comparable, infants had significantly lower 1-year (63.7% vs. 81.5%) and 5-year (56.9% vs. 62.0%) survival rates. The authors concluded that the survival disadvantage was driven by excess treatment-related toxicity, a finding that shows a critical, unmet need for age-adapted therapies.
Why Survival Diverges: The Toxicity-Relapse Nexus
The study, led by Sassine et al., provides a granular look at the outcomes for infants and older children with bone and soft tissue neoplasms. The central finding is a paradox: infants experience severe treatment-related complications at a rate similar to older children (13.7% vs. 14.9%), yet they are far more likely to die from them (4.8% vs. 1.5%).
This discrepancy points to a fundamental biological difference. The study notes that infants process drugs differently, which could make a toxicity of a given grade more dangerous at this age, even when it is graded as severe (Grade 3 or 4) in the same way it would be for an older child.
Subtype-Specific Outcomes and the Impact of Targeted Therapy
Survival outcomes varied dramatically by tumor subtype within the infant group, highlighting the need for precision medicine. At 5 years, survival was lowest for infants with Malignant Rhabdoid Tumors (MRT), at just 16.8%. In stark contrast, infants with fibrosarcoma had a 5-year survival rate of 92.7%, a dramatic difference driven largely by the advent of targeted therapy.
Larotrectinib (Vitrakvi; Bayer), approved by the FDA for solid tumors harboring NTRK gene fusions, has changed the management of NTRK fusion-positive infantile fibrosarcoma.
| Outcome Measure | Infants | Older Children | Statistical Significance (P-value) |
|---|---|---|---|
| Treatment-Related Mortality | 4.8% | 1.5% | .003 |
| Grade 3/4 Treatment Complications | 13.7% | 14.9% | .71 |
| 5-Year Overall Survival | 56.9% | 62.0% | < .001 |
| Enrollment in Clinical Trials | 8.4% | 19.8% | < .001 |
Bridging the Gap: A Call for Age-Adapted Care
The findings expose a systemic issue: infants are significantly less likely to be enrolled in clinical trials than older children (8.4% vs. 19.8%). This gap limits their access to innovative therapies, particularly for high-risk cancers like MRT. Early-phase trials of novel agents, such as the EZH2 inhibitor tazemetostat (Tazverik; Ipsen), have explicitly excluded infants younger than 1 year, creating a therapeutic dead end for the very patients who need it most.
The study's authors emphasize that progress requires using biologically informed diagnostics and risk stratification, implementing age-adapted therapeutic drug monitoring and supportive care, and expanding age limits in early-phase trials.
“These findings highlight the unmet need to identify novel treatment approaches that balance toxicity and efficacy, especially for infants with MRT,” the authors concluded. “Future progress will require to leverage biologically informed diagnostics and risk stratification, age-adapted therapeutic drug monitoring and supportive care, and expansion of age limit to include infants in early phase trials to provide access to innovative therapies for high-risk tumors that are prevalent during infancy.”
Sassine S, et al. Pediatr Blood Cancer. 2026.
In Plain English: The Clinical Takeaway
- For infants with soft tissue tumors, the biggest threat isn’t the cancer coming back, but the severe side effects from the treatment itself. Their bodies are more sensitive to chemotherapy and other drugs.
- Survival rates vary greatly depending on the type of tumor. While some, like fibrosarcoma, have excellent outcomes with new targeted drugs, others, like MRT, remain extremely deadly due to a lack of effective and safe treatments.
- To improve survival, doctors and researchers need new strategies. This includes creating safer treatment protocols for infants, including them in clinical trials for new drugs, and developing therapies specifically designed for their unique biology.
Contraindications & When to Consult a Doctor
The study serves as a crucial benchmark. Its retrospective design, while powerful for identifying trends, has limitations, including incomplete data and an inability to pinpoint which specific therapy caused each treatment-related death. However, its core message is clear and actionable: to close the survival gap for infants, the focus must shift to mitigating toxicity and developing age-appropriate therapies.
References
- Sassine S, Coltin H, Kondyli M, et al. Bone and soft tissue neoplasms in infants compared to older children: a study from the Cancer in Young People in Canada program. Pediatr Blood Cancer. Published online 2026:e70753.
- Sassine S, Coltin H, Kondyli M, et al. The frequency and results of cancer cases in infants across Canada: an analysis of the Cancer in Young People in Canada database. Pediatr Blood Cancer. 2026;73(2):e70050.
- The Cancer in Young People in Canada program. Public Health Agency of Canada. Updated June 9, 2026. Accessed November 6, 2026.
- Laetsch TW, Voss S, Ludwig K, et al. Larotrectinib administration for initial cases of infantile fibrosarcoma and other pediatric solid tumors with NTRK fusions (Children’s Oncology Group ADVL1823). J Clin Oncol. 2025;43(10):1188-1197.
