The prognostic significance of anaplasia in childhood rhabdomyosarcoma: A report from the Children's Oncology Group.

BACKGROUND

Established prognostic indicators in rhabdomyosarcoma (RMS), the most common childhood soft tissue sarcoma, include several clinicopathologic features. Among pathologic features, anaplasia has been suggested as a potential prognostic indicator, but the clinical significance of anaplasia remains unclear.

METHODS

Patients enrolled on one of five recent Children's Oncology Group clinical trials for RMS (D9602, n = 357; D9802, n = 80; D9803, n = 462; ARST0331, n = 335; and ARST0531, n = 414) with prospective central pathology review were included in this study. Clinicopathologic variables including demographic information, risk group, histologic subtype, and anaplasia were recorded along with overall survival (OS) and failure-free survival (FFS) with failure defined by recurrence, progression, or death. The log-rank test was used to compare OS and FFS.

RESULTS

Anaplasia was more common in embryonal RMS (27% of all embryonal RMS) than other subtypes of RMS (11% for alveolar RMS, 7% for botryoid RMS, 11% for spindle cell RMS). On multivariate analyses, anaplasia was not an independent prognostic factor in RMS (OS:hazard ratio (HR) = 1.12, p = 0.43; FFS:HR = 1.07, p = 0.56) across all subtypes or within embryonal RMS only (OS:HR = 1.41, p = 0.078; FFS:HR = 1.25, p = 0.16). Among tumors with TP53 mutations, 69% had anaplasia, while only 24% of tumors with anaplasia had a tumoral TP53 mutation.

CONCLUSIONS

Anaplasia is not an independent indicator of adverse outcomes in RMS. Emerging information on the prognostic significance of TP53 mutations raises the possibility that anaplasia may be a surrogate marker of TP53 mutations in some cases. Tumoral TP53 mutation status may be investigated as a prognostic indicator in future studies.