Relationship of DNA ploidy to histology and prognosis in rhabdomyosarcoma. Comparison of flow cytometry and image analysis.

BACKGROUND

Although DNA ploidy correlates with prognosis in certain childhood cancers, e.g., neuroblastoma, its significance in rhabdomyosarcoma (RMS) is unclear and controversial.

METHODS

Ploidy by flow cytometry (FCM) and image analysis (IA) in 26 of 27 children with RMS (17 embryonal, 3 mixed embryonal/alveolar, 5 alveolar, 1 anaplastic, 1 ectomesenchymoma) and 4 adults with pleomorphic RMS were evaluated. Statistical comparisons were analyzed between DNA content and gender, age, localization, Intergroup Rhabdomyosarcoma Study (IRS) group, and histopathologic subtype. Survival analyses were performed by the Kaplan-Meier test using the approximate chi-square statistic for the log rank test.

RESULTS

The concordance rate between FCM and IA was 26 of 30 (87%); FCM was not performed in one tumor. Image analysis was more sensitive than FCM in detecting aneuploidy. Furthermore, DNA content was associated significantly with histologic subtype (P = 0.031); embryonal histology commonly was hyperdiploid (mean, 1.44; median, 1.27), whereas alveolar histology usually was near-tetraploid (mean, 1.83; median, 1.95). All four adult patients with pleomorphic RMS were aneuploid, with one showing multiple DNA peaks. No correlation between DNA content and survival was observed in the children with RMS. However, IRS group (P = 0.011) and patient age (P = 0.036) were independent prognostic indicators significantly related to survival. All adult patients died of their disease.

CONCLUSIONS

Although ploidy correlates with histologic subtype, DNA content is not significantly predictive of prognosis in patients with RMS. Age at diagnosis and IRS group are independent predictors of clinical outcome in children with RMS.