Epidemiology, trends, and survival of ocular and orbital rhabdomyosarcoma: a nationwide study in the USA (1996-2018) : Ocular and orbital rhabdomyosarcoma in the USA.

Background: Rhabdomyosarcoma (RMS) is a rare malignancy that affects both children and young adults. Therefore, the current incidence and mortality rates of ocular and orbital rhabdomyosarcoma (ORMS) need to be clarified. We aimed to explore the epidemiology, trends, and survival outcomes of ORMS in the United States population spanning over two decades, from 1996 to 2018.

Methods: We retrospectively reviewed 92,633 patients with ocular and adnexal malignancies and identified 640 ORMS cases from the North American Association of National Cancer Registries. Demographics, tumor characteristics, treatment modalities, and survival outcomes were analyzed.

Results: Most ORMS cases (71.7%) were reported in children aged-0-9 years. The age-adjusted incidence of ORMS was 0.1 per million population (ppm), with males demonstrating a higher incidence (0.12 ppm) than females (0.09 ppm). Whites had the highest incidence rate (0.11 ppm). Embryonal ORMS is the most common histological subtype. The incidence trend over the 22-year study period revealed a decline in ORMS from 0.124 to 0.076, in contrast with the incidence of whole-body RMS, which showed an insignificant increase. The 5-year relative survival rates of patients with ORMS were 89.7%, whereas the 10-year relative survival rate was 87.2%. The 5-year relative survival trend for ORMS increased but was insignificant.

Conclusions: ORMS primarily affects young children and males, with the embryonal subtype being the most common. Despite the declining incidence, survival rates have remained stable, underscoring the need for further research on the risk factors, diagnostics, and management strategies to improve patient outcomes.

Key Messages: What is known Ocular and Orbital Rhabdomyosarcoma (ORMS) predominantly affects children, especially males, and is the most frequent primary tumor in the  orbit during childhood. The embryonal subtype is the most common histological subtype of ORMS. What is new A significant decline in the incidence of ORMS was observed over the 22-year study period, in contrast to the overall incidence of whole-body  rhabdomyosarcoma. It has a characteristic bigeminal distribution with a peak at 3-4 and another at 6  years. Patients receiving combined treatment modalities showed improved survival  rates, while those undergoing surgery alone had poorer outcomes. Despite advancements in treatment, there has been no significant increase in  the 5-year relative survival trends for ORMS.