Of the 7759 patients with STS (4309 male and 3450 women) identified, 210 (2.7%) were aged ≤14 years (children), 1467 (18.9%) were aged 15–39 years (AYAs), 2771 (35.7%) were aged 40–64 years (adults), and 3311 (42.7%) were aged ≥65 years (elderly). The common histologic subtypes were undifferentiated pleomorphic sarcomas, 2030 (26.2%); myxoid/round cell liposarcomas (MRLS), 956 (12.3%); synovial sarcomas (SySa), 555 (7.2%); and malignant peripheral nerve sheath tumors (MPNST), 478 (6.2%). Meanwhile, the histologic subtypes with a higher ratio in AYA patients were MRLS, 286 (19.5%); SySa, 259 (17.7%); MPNST, 130 (8.9%); primitive neuroectodermal tumor (PNET), 111 (7.6%); and rhabdomyosarcoma (RMS), 94 (6.4%).
Table 1 shows the patient characteristics and treatments according to the age groups. The most predominant subtype among the AYA patients was MRLS, 286(19.5%), followed by SySa, 259 (17.7%). No other categories demonstrated differences in prevalence in the AYA patient groups when compared to the same categories in other age groups.
Table 2 shows the overall 5-year cancer survival rates among patients with STS with unadjusted and adjusted hazard ratios (HRs) derived from Cox proportional hazard models. The cancer survival rates of AYA patients with STS were poorer than those of adult age groups. However, they were not poorer than that of the child and the elderly age groups. On multivariate analysis, age was not a prognostic factor for poor cancer survival among AYA patients with STS.
Overall, the prognostic factors for poor cancer survival in patients with STS were age 40-64 years (HR: 1.35, 95% confidence interval [CI]: 1.11–1.65, P=0.003), age ≥65 years (HR: 2.28, 95% CI: 1.47–2.34, P<0.001), high tumor grade (HR: 3.41, 95% CI: 2.37-4.91, P<0.001), tumor size >5 cm and ≤10 cm and >10 cm (HR: 1.71 and 2.57, 95% CI: 1.38-2.12 and 2.06-3.19, P<0.001, respectively), multiple tumor location (HR: 2.32, 95% CI: 1.59-3.39, P=0.014), non-surgical treatment compared with surgery (HR: 0.58, 95% CI: 0.49-0.69, P<0.001), amputation (HR: 1.69, 95% CI: 1.35-2.11, P<0.001), positive surgical margins (HR: 1.65, 95% CI: 1.27-2.14, P<0.001), chemotherapy (HR: 1.59, 95% CI: 1.35-1.87, P<0.001), radiation (HR: 1.38, 95% CI: 1.20-1.59, P<0.001), the presence of metastases (HR: 4.68, 95% CI: 3.97-5.51, P<0.001), and deep tumor location (HR: 1.34, 95% CI: 1.07-1.67, P=0.041). The prevalence of these poor prognostic factors excluding age was not higher among the AYA patients compared with other age groups.
Figure 1 shows the Kaplan-Meier plots for cancer survival rates in patients with STS in general and its subtypes. The cancer survival rates of AYA patients with MPNST were poorer than those of other age groups, whereas those for AYA patients with other histologic subtypes were not significantly different from those of other age groups. Therefore, data from AYA patients with MPNST were analyzed to better understand the factors that caused these poor outcomes.
Table 3 shows the characteristics of MPNST based on age groups. MPNST was more prevalent in male AYA patients, had a larger tumor size, appeared predominantly on the head and neck and in deeper layers, had a higher rate of positive surgical margins, and presented with more metastatic lesions at the first visit in AYA patients than in other age groups.
Table 4 shows the results of univariate and multivariate analyses of the prognostic factors for cancer survival in patients with MPNST. The cancer survival rates of AYA patients with MPNST were poorer than those of other age groups on univariate analyses. Tumor size >5 cm and ≤10 cm (HR: 2.20, 95% CI: 1.01–4.77, P=0.046), tumor size >10 cm (HR: 2.54, 95% CI: 1.17–5.50, P=0.018), non-surgical treatment compared with surgery (HR: 0.51, 95% CI: 0.29-0.92, P=0.024), radiation (HR: 1.70, 95% CI: 0.67-2.06, P=0.035), the presence of metastases (HR: 3.11, 95% CI: 1.76-5.51, P<0.001), and deep tumor location (HR: 2.71, 95% CI: 1.23–5.98, P=0.014) were prognostic factors for poor cancer survival in patients with MPNST, but who were not AYA.