Impact of Consolidative Radiation on Overall and Progression Free Survival in Pediatric, Adolescent and Young Adult Metastatic Sarcoma

PURPOSE/OBJECTIVE(S)

To determine the association between consolidative radiation and survival in pediatric, adolescent, and young adult (AYA) metastatic sarcoma MATERIALS/METHODS: Eligible patients included those diagnosed with metastatic bone or soft tissue sarcoma at ≤39 years of age. Patients whose cancer progressed prior to the time of local control were excluded. Consolidative radiation (RT) was defined as RT to all sites of metastatic disease. Kaplan Meier method was used to estimate overall survival (OS) and progression-free survival (PFS). Cox proportional hazards was used to account for confounding variables. To adjust for immortal time bias (ITB), end of local control was chosen as a landmark time.

RESULTS

Patients (n = 77) had a median age at diagnosis of 14.5 years (range: 1.7-29.7 years). The most common histology was Ewing sarcoma (49%), followed by rhabdomyosarcoma (30%). Median follow up was 28.5 months, without significant difference between patients treated with and without consolidative RT (23.7 vs. 21.5 months, p = 0.270). Median time to completion of consolidative RT from diagnosis was 8.5 months. Ewing sarcoma was more likely to be treated with consolidative RT compared to other histologies (p<0.001). Consolidative RT was associated with improved OS (2yr OS: 81.9% vs. 57.9%, p = 0.009) and PFS (2yr PFS: 71.2% vs. 30%, p = 0.001). On multivariate analysis, after accounting for age, histology, number, and type of metastases (lung, bone or other), consolidative RT remained independently associated with improved OS (hazard ratio (HR):0.36, 95% confidence interval [CI]: 0.17, 0.78, p = 0.010) and improved PFS (HR = 0.34, 95% CI = 0.16, 0.73, p = 0.006). The OS benefit for consolidative RT persisted after adjusting for ITB (1yr OS post-local control: 80.9% vs. 89.7%, p = 0.016). The effect of consolidative RT was validated in a dataset consisting of patients who were diagnosed with localized disease but had metastatic progression (n = 30). In this metachronous population, consolidative RT remained independently associated with improved OS (HR = 0.11, 95% CI = 0.03, 0.51, p = 0.004) after accounting for age.

CONCLUSION

ConsolidativeRT was independently associated with improved OS and PFS in pediatric and AYA patients with metastatic sarcoma at diagnosis. The OS benefit extended to those who underwent consolidative RT for metastatic progression. Future work should evaluate biomarkers to optimize patient selection and timing and dose of consolidative RT.

Patterns of Failure in Pediatric and Young Adult Rhabdomyosarcoma

PURPOSE/OBJECTIVE(S)

To characterize patterns of failure in pediatric and young adult patients with rhabdomyosarcoma (RMS) from a single institution with over 20 years of experience.

MATERIALS/METHODS

Patients diagnosed with RMS from 2000 to 2022 were identified retrospectively. Time to failure was calculated from diagnosis. Local only failure was defined as first failure at the primary site without distant failure. Distant failure was defined as first failure outside of the primary site with or without local failure. Cumulative incidence (CI) of failure was calculated using death as a competing risk. Fine-Gray regression was used to evaluate impact of prognostic factors.

RESULTS

Ninety-five patients were eligible. Median age was 7.28 years (range 0 - 35 years), 41% of patients were >10 years old. Median follow up was 33.3 months. Approximately half (n = 47, 49.5%) of the tumors demonstrated alveolar histology. FOXO1 fusion status was available in 76 (80%) patients, of which 7 out of 37 alveolar tumors (18.9%) were FOXO1 fusion negative. The majority of tumors presented with unfavorable primary site (n = 72, 75.8%) and advanced stage (Stage III and IV, n = 72, 75.8%). The 5-yr CI of local only failure and distant failure for the entire cohort was 19.0% (95% CI 11.3, 28.3) and 34.6% (24.0, 45.5%), respectively. The predominant pattern of failure by Group was: Groups 1&2: Local only (5yr CI 14.8%), Group 3: Distant (5yr CI: 25.9%), Group 4: Distant (5yr CI: 67.6%). CI of distant failure by primary site was higher in perianal/gluteal (n = 2/5, 5yr CI 60.0%) and extremity (n = 8/19, 5yr CI 45.9%) sites. Of the 28 distant failures, 10 (36%) also had a local failure component. CI of local only failure by primary site was higher in parameningeal head and neck (n = 6/25, 5yr CI 30%) and bladder/prostate (n = 2/12, 5yr CI 23%) sites. The following were associated with an increased CI of distant failures: increasing age (HR 1.08, p<0.01), alveolar vs. embryonal histology (HR 3.01, p = 0.0095), FOXO1 fusion positive vs. negative (HR 2.8, p = 0.02) and Group IV vs. Groups I/II (HR 7.7, p = 0.0007). FOXO1 fusion and alveolar histology were associated with older age and Group IV, both of which were independently associated with increased distant failure on multivariate analysis.

CONCLUSION

Failures were predominantly distant in older patients and patients with Group IV RMS, both of which were associated with FOXO1 fusion and alveolar histology, highlighting the need to improve therapies in this population. Local only failures were highest in parameningeal head and neck and bladder/prostate primaries, highlighting the need to improve local control strategies at these sites.

On a Volterra Cubic Stochastic Operator

We consider a class of Volterra cubic stochastic operators. We describe the set of fixed points, the invariant sets and construct several Lyapunov functions to use them in the study of the asymptotical behavior of the given Volterra cubic stochastic operators. A complete description of the set of limit points is given, and we show that such operators have the ergodic property.