Predicting outcome in patients with rhabdomyosarcoma: role of [(18)f]fluorodeoxyglucose positron emission tomography. Int J Radiat Oncol Biol Phys. 2014;90:1136-1142. [PMID: 25539372 DOI: 10.1016/j.ijrobp.2014.08.005]

Local Control for Intermediate-Risk Rhabdomyosarcoma: Results From D9803 According to Histology, Group, Site, and Size: A Report From the Children's Oncology Group

PURPOSE

To determine local control according to clinical variables for patients with intermediate-risk rhabdomyosarcoma (RMS) treated on Children's Oncology Group protocol D9803.

PATIENTS AND METHODS

Of 702 patients enrolled, we analyzed 423 patients with central pathology-confirmed group III embryonal (n=280) or alveolar (group III, n=102; group I-II, n=41) RMS. Median age was 5 years. Patients received 42 weeks of VAC (vincristine, dactinomycin, cyclophosphamide) or VAC alternating with VTC (T = topotecan). Local therapy with 50.4 Gy radiation therapy with or without delayed primary excision began at week 12 for group III patients. Patients with group I/II alveolar RMS received 36-41.4 Gy. Local failure (LF) was defined as local progression as a first event with or without concurrent regional or distant failure.

RESULTS

At a median follow-up of 6.6 years, patients with clinical group I/II alveolar RMS had a 5-year event-free survival rate of 69% and LF of 10%. Among patients with group III RMS, 5-year event-free survival and LF rates were 70% and 19%, respectively. Local failure rates did not differ by histology, nodal status, or primary site, though there was a trend for increased LF for retroperitoneal (RP) tumors (P=.12). Tumors ≥5 cm were more likely to fail locally than tumors <5 cm (25% vs 10%, P=.0004). Almost all (98%) RP tumors were ≥5 cm, with no difference in LF by site when the analysis was restricted to tumors ≥5 cm (P=.86).

CONCLUSION

Local control was excellent for clinical group I/II alveolar RMS. Local failure constituted 63% of initial events in clinical group III patients and did not vary by histology or nodal status. The trend for higher LF in RP tumors was related to tumor size. There has been no clear change in local control over RMS studies, including IRS-III and IRS-IV. Novel approaches are warranted for larger tumors (≥5 cm).

Radiotherapy is Important for Local Control at Primary and Metastatic Sites in Pediatric Rhabdomyosarcoma

Purpose: The current recommended practice for pediatric patients with metastatic rhabdomyosarcoma includes full-dose radiotherapy to each metastatic site. We wished to question this practice, which can cause side-effects and is often logistically challenging, by studying the pattern of failure in our pediatric and teenage patient population.

Methods and Materials: Our institution’s cancer registry was queried for patients diagnosed with rhabdomyosarcoma aged 18 or less from January 1990 until January 2014. Twenty-nine patients were found and, of these, six had metastatic disease. Five of the six were treated with standard chemotherapy together with radiotherapy to the primary and metastatic sites with doses and fractionation according to the site. Progression-free survival was calculated from the end of radiotherapy until radiological or pathological evidence of disease progression or death.

Results: Median age was 13 years (range: 12-18). Three were girls. All had alveolar histology and unfavorable primary sites. Twelve metastatic sites were treated with radiotherapy. Doses used were 41.4 - 50.4 Gy in 1.8 Gy fractions for most sites, and 15 Gy in 1.5 Gy fractions for whole lung radiotherapy. The median number of sites treated per patient was two (range: 1 - 6). Median time to progression was 10.1 months (range: 1.9 - 15.7). Local control was 100% for all metastatic sites. Median overall survival (OS) was 31.8 months (range: 20.4 – 95.4 months). Three patients developed progressive disease outside the treated field. One patient died from a secondary hematological malignancy without evidence of disease progression. One patient remains progression-free at 88.6 months post-radiotherapy.

Conclusions: Radiotherapy to metastatic disease sites prevented in-field progression in all five patients with metastatic alveolar rhabdomyosarcoma. However, failure at sites outside of the radiotherapy volume occurred in three of five of patients and overall survival was very poor despite aggressive treatment to all sites of disease. Radiotherapy has a role in metastatic disease, although future studies evaluating dose and fractionation are needed.

Current management of pediatric soft tissue sarcomas

Pediatric soft tissue sarcomas are a group of malignant neoplasms arising within embryonic mesenchymal tissues during the process of differentiation into muscle, fascia and fat. The tumors have a biphasic peak for age of incidence. Rhabdomyosarcoma (RMS) is diagnosed more frequently in younger children, whereas adult-type non-RMS soft tissue sarcoma is predominately observed in adolescents. The latter group comprises a variety of rare tumors for which diagnosis can be difficult and typically requires special studies, including immunohistochemistry and molecular genetic analysis. Current management for the majority of pediatric sarcomas is based on the data from large multi-institutional trials, which has led to great improvements in outcomes over recent decades. Although surgery remains the mainstay of treatment, the curative aim cannot be achieved without adjuvant treatment. Pre-treatment staging and risk classification are of prime importance in selecting an effective treatment protocol. Tumor resectability, the response to induction chemotherapy, and radiation generally determine the risk-group, and these factors are functions of tumor site, size and biology. Surgery provides the best choice of local control of small resectable tumors in a favorable site. Radiation therapy is added when surgery leaves residual disease or there is evidence of regional spread. Chemotherapy aims to reduce the risk of relapse and improve overall survival. In addition, upfront chemotherapy reduces the aggressiveness of the required surgery and helps preserve organ function in a number of cases. Long-term survival in low-risk sarcomas is feasible, and the intensity of treatment can be reduced. In high-risk sarcoma, current research is allowing more effective disease control.

Recent advances in understanding and managing rhabdomyosarcoma

Rhabdomyosarcoma is the most common childhood soft tissue sarcoma and the fourth most common pediatric solid tumor. For most patients, treatment consists of a multimodality approach, including chemotherapy, surgery, and/or radiotherapy. To guide treatment, patients with rhabdomyosarcoma are risk stratified based on a number of factors. These factors include clinical group, which depends largely on the extent of resection and nodal involvement, and stage, which takes into account tumor size, invasion, nodal involvement, and disease site. Histology of the tumor and age at diagnosis are also factored into risk stratification. Recent advances in understanding the biology of the disease have allowed for the further sub-classification of rhabdomyosarcoma. In addition, elucidation of additional clinical features associated with poor prognosis has allowed for better understanding of risk and provides more clarity regarding those patients who require more intensive therapy. Many areas of active investigation are ongoing, including the following: further delineation of the biological underpinnings of the various disease subtypes with the possibility of molecularly targeted therapy; a better understanding of clinical risk factors, including the evaluation and management of potentially involved lymph nodes; determination of the appropriate role of post-treatment imaging and assessment of response to therapy; and incorporation of advanced radiotherapeutic techniques, including conformal intensity-modulated photon and proton therapy.