Rhabdomyosarcoma with unknown primary tumor site. A report from European
Pediatric Soft Tissue Sarcoma Study Group (EpSSG)
Abstract
BACKGROUND: Rhabdomyosarcoma (RMS) is an aggressive malignancy, and 20%
of children present with metastases at diagnosis. Patients presenting
with disseminated disease very occasionally have no clear evidence of a
primary tumor mass. Since these patients have rarely been investigated,
we report on a series of patients with RMS and unknown primary tumor
site registered in the MTS 2008 protocol (October 2008 - December 2016)
coordinated by the European pediatric Soft tissue sarcoma Study Group.
METHODS: Patients were administered 9 cycles of induction chemotherapy,
and 48 weeks of maintenance chemotherapy. Surgery and/or radiotherapy
was planned after the first assessment of tumor response, and
implemented after six cycles of chemotherapy. If feasible, radiotherapy
to all sites of metastasis was recommended. RESULTS: We identified 10
patients with RMS and unknown primary site, most of them adolescents
(median age 15.8 years, range 4.6-20.4). Nine had fusion-positive
alveolar RMS. Multiple organ involvement was identified in 7 patients, 2
only had bone marrow disease, and 1 only had leptomeningeal
dissemination. All patients were given chemotherapy, 4 were irradiated,
and none had surgery. Three patients underwent allogeneic bone marrow
transplantation. At the time of this analysis, only 2 patients are alive
in complete remission: 1 had received radiotherapy; and 1 had a bone
marrow transplant. CONCLUSIONS: RMS with unknown primary tumor occurs
mainly in adolescents and is typically fusion-positive alveolar.
Radiotherapy may be important, but survival is poor and patients should
be offered enrollment in investigational trials.