Nonrhabdomyosarcoma soft tissue sarcomas in children: is age at diagnosis an important variable?

The associations between age at diagnosis, tumor characteristics, and outcome in children diagnosed with nonrhabdomyosarcoma soft tissue sarcoma (NRSTS) were studied.

Retrospective review was conducted of 192 children from 1962 through 1996. Patients were divided into groups: birth to 1 year (n = 13), 1 to 5 years (n = 26), 5 to 10 years (n = 49), 10 to 15 years (n = 55), and older than 15 years (n = 49) of age at diagnosis. Characteristics including IRS group, histological grade and pattern, tumor size, and invasiveness were investigated. Survival rate was estimated by age group. The median follow-up was 8.8 years (range, 2 to 28 years).

There were 81 group I patients, 40 group II, 41 group III, and 30 group IV. A significant difference of IRS groups among the age groups was seen (P = .034). There were no IRS group IV patients less than 1 year of age; 50% of IRS group IV patients were older than 15 years. A significant difference in the distribution of histological grade among the age groups (P = .032) was seen. Ten of 13 (77%) children less than 1 year of age had low-grade tumors, whereas 42%, 45%, 60%, and 37% of patients aged 1 to 5, 5 to 10, 10 to 15, and older than 15 years, respectively, had low-grade tumors. Patients older than 15 years had the highest incidence of invasive tumors (59%). Histological pattern also varied with age. The most prevalent histology in the less-than-1-year age group was infantile fibrosarcoma. No predominant histology was seen in the 1- to 5-year age group. Malignant fibrous histiocytoma was the most frequent histological subtype in children between 5 and 10 years of age. In the 10- to 15-year age group and children older than 15 years the malignant peripheral nerve sheath tumor and synovial sarcoma were the most prevalent subtypes. Without adjusting for any other factors, age group was prognostic of survival (P = .007). Patients less than 1 year at diagnosis had the best outcome, with a 5-year survival rate of 92% +/- 9%. Five-year estimates were lowest for patients older than 15 years (49% +/- 7%).

Significant differences in IRS group, histological grade, and histological subtype were observed in different age groups. Infants with NRSTS were more likely to have low grade, less invasive, and lower stage tumors. These characteristics may account for their improved prognosis.