Characteristics and outcomes of rhabdomyosarcoma patients with isolated lung metastases from IRS-IV

To better understand outcomes in children with rhabdomyosarcoma (RMS) and lung-only metastatic disease, the authors reviewed the experience from Intergroup Rhabdomyosarcoma Studies IV Pilot and IV. Patients with lung-only (n = 46) vs other sites of metastatic disease (n = 234) were reviewed using patient charts and the database of Children's Oncology Group (COG). Sixteen percent of patients with RMS and metastatic disease had isolated lung metastases. Thirty-one (67%) had more than 5 metastatic lung lesions. These were bilateral in 34 (74%). Only 6 patients were biopsied at diagnosis. Sixteen children (35%) did not receive any lung radiotherapy. Patients that received lung radiotherapy had fewer lung recurrences (P =. 04), although this has no significant impact on overall survival (OAS, 47% radiotherapy vs 31% no radiotherapy). Compared with patients with other sites of metastatic disease, patients with lung-only metastases have a greater proportion of favorable histology (67% vs 39%, P =. 0017), negative nodal involvement (67% vs 32%, P =. 0013), and parameningeal primaries (39% vs 12%) and a smaller proportion of extremity primaries (20% vs 33%, P =. 0005 for site of primary tumor). Overall survival at 4 years for lung-only metastases was not significantly different from other single-site metastasis (42% vs 34%). Survival was not improved for unilateral disease or fewer than 5 metastatic lesions. Factors associated with diminished OAS include unfavorable histology (P =. 0001) and age >10 years (P =. 015). Children with RMS and lung-only metastases usually present with extensive bilateral disease that is frequently not biopsied nor given protocol-recommended radiotherapy (XRT). However, outcome is comparable, although slightly better, than patients with other single-site metastasis.