Children and adolescents diagnosed with cancer can now expect an average 85% 5-year overall survival, with significant improvements in longer-term morbidity and mortality reported over the past several decades. However, the long-term impact of therapeutic agents and modalities introduced in recent years remains unclear and will require dedicated follow-up in the years ahead. The Children's Oncology Group (COG), a part of the NCI's National Clinical Trials Network, with over 200 sites across North America and beyond, enrolls more than 10,000 patients onto research protocols annually, inclusive of first-line clinical trials and nontherapeutic studies. COG provides a platform to conduct survivorship research with several unique strengths: (i) a huge catchment to ascertain relatively rare but important adverse events, (ii) study populations that are otherwise too rare to study in smaller consortia, including access to highly diverse patient populations, (iii) long-term follow-up of clinical trial populations linked to the original trial data, and (iv) a natural platform for intervention research. Enhancements in COG infrastructure facilitate survivorship research, including a COG patient registry (Project:EveryChild), availability of a long-term follow-up tracking resource, and successful deployment of various remote-based study procedures to reduce the burden on participants and participating institutions.

Background

Ewing sarcoma survivors (ESSs) are at increased risk for treatment-related complications. The incidence of treatment-related morbidity and late mortality with aging is unknown.

Methods

This study reports survival probabilities, estimated with the Kaplan-Meier method, and the cumulative incidence of cause-specific mortality and chronic conditions among ESSs in the Childhood Cancer Survivor Study who were treated between 1970 and 1986. Piecewise exponential models were used to estimate relative rates (RRs) and 95% confidence intervals (CIs) for these outcomes. Chronic conditions were graded with the Common Terminology Criteria for Adverse Events (version 4.03).

Results

Among 404 5-year ESSs (median age at last follow-up, 34.8 years; range, 9.1-54.8 years), the 35-year survival rate was 70% (95% CI, 66%-74%). Late recurrence (cumulative incidence at 35 years, 15.1%) was the most common cause of death, and it was followed by treatment-related causes (11.2%). There were 53 patients with subsequent neoplasms (SNs; cumulative incidence at 35 years, 24.0%), and 38 were malignant (14.3% at 35 years). The standardized incidence ratios were 377.1 (95% CI, 172.1-715.9) for osteosarcoma, 28.9 (95% CI, 3.2-104.2) for acute myeloid leukemia, 14.9 (95% CI, 7.9-25.5) for breast cancer, and 13.1 (95% CI, 4.8-28.5) for thyroid cancer. Rates of chronic conditions were highest for musculoskeletal (RR, 18.1; 95% CI, 12.8-25.7) and cardiac complications (RR, 1.8; 95% CI, 1.4-2.3). Thirty-five years after the diagnosis, the cumulative incidences of any chronic conditions and 2 or more chronic conditions were 84.6% (95% CI, 80.4%-88.8%) and 73.8% (95% CI, 67.8%-79.9%), respectively.

Conclusions

With extended follow-up, ESSs' risk for late mortality and SNs does not plateau. Treatment-related chronic conditions develop years after therapy, and this supports the need for lifelong follow-up. Cancer 2017;123:2551-60. © 2017 American Cancer Society.