Number of affected lymph nodes predicts outcome in extremity rhabdomyosarcoma

Rhabdomyosarcoma (RMS) of the extremity has poor outcomes due to its high potential for lymphatic and haematogenic spread.

Data were selected from the SEER17 registry 2000-2020 for non-pleomorphic extremity rhabdomyosarcoma (all ages and stages).

473 cases were identified, 181 at upper and 292 at lower extremity. Median age was 14years. Histology was alveolar in 250. The median tumor size was 7 cm. 144 tumors were localized, 131 regional and 178 distant (20 unknown). Median follow-up for 229 survivors was 8.17years. 5-year-DSS and OS was 49.7 % ± 4.9(95 % CI) and 46.3 % ± 4.9, respectively. A total of 169 patients underwent pathological examination of regional lymph nodes. In 51, one node was examined, in 24 two and in 63 ≥ 3 nodes were examined. Overall, 85 patients had pathologically positive nodes: 36 had one positive regional lymph node, 12 had two and 15 had ≥3. When adjusted for age, histology, size and stage, involvement of ≥3 lymph nodes was independently associated with worse survival. This observation was also applicable to the Cox regression analysis, which exclusively considered the 275 cases of localized/regional stage.

The number of regional lymph nodes affected correlates with survival, suggesting the extent of lymph node involvement as a new and crucial predictive factor. Further analysis of the extent of regional lymph node involvement is advisable. This includes identifying the most effective methods for detecting affected nodes and establishing how many nodes need to be examined to obtain representative results.