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Failure to include skeletal staging in newly diagnosed soft-tissue sarcoma (STS) would have missed a majority of bone metastases and 40% of all patients with metastatic disease, a large retrospective review showed.

Overall, 4.1% of almost 29,000 patients had bone metastases at diagnosis, whereas 7.8% had lung metastases for which routine screening is currently recommended. However, more than half of patients with bone metastases did not have lung metastases.

The findings suggest that skeletal staging should be considered for patients with newly diagnosed STS, particularly those with certain histologies, Christopher D. Collier, MD, of the University of Chicago, reported during the .

"The RACE -- rhabdomyosarcoma, angiosarcoma, clear cell sarcoma, epithelioid sarcoma -- mnemonic is frequently taught to convey the STS histologies most a risk for regional lymph node metastasis," he said in conclusion. "Based on these findings, the RACE mnemonic also applies to STS histologies most at risk for metastasis to bone at diagnosis and serves as a simple reminder to evaluate for bone metastases in these patients."

Presence of skeletal or lung metastasis at diagnosis conferred worse prognosis as compared with other metastatic sites, he added.

Historically, staging for newly diagnosed STS patients includes computed tomography scans of the lungs and bone scintigraphy, which encompasses the two most common sites of metastasis. However, some specialists have questioned the value of routine bone scintigraphy, and National Comprehensive Cancer Network guidelines do not recommend skeletal imaging for newly diagnosed STS, Collier noted.

To address the issue, he and his co-investigators performed an extensive retrospective review to determine the incidence of bone metastases in patients with newly diagnosed STS and identify factors associated with bone metastasis at diagnosis. The team also examined the impact of bone metastasis at diagnosis on survival in STS.

Data for the analysis came from the , which captures 70% of all new cancer diagnoses in the U.S. and has 90% follow-up. The researchers queried the database for all patients with new diagnoses of primary STS during 2010-2015. After excluding patients without documented metastasis at diagnosis, the team analyzed data for 28,687 patients.

The most common histologies included in the analysis were undifferentiated pleomorphic sarcoma (UPS, 10,319 patients), liposarcoma (5,996), myxofibrosarcoma (3,188), synovial sarcoma (2,297), angiosarcoma (2,121), rhabdomyosarcoma (1,968), malignant peripheral nerve sheath tumor (1,863), epithelioid sarcoma (660), and clear cell sarcoma (275).

The study population had a median follow-up of 27 months.

The data showed that 6.2% of all patients had regional lymph node involvement at diagnosis, and 4.1% had bone metastases. Histologies most often associated with bone metastasis were rhabdomyosarcoma (15.3%), angiosarcoma (8.3%), clear cell sarcoma (5.5%), and epithelioid sarcoma (6.5%).

Factors associated with metastasis to bone at diagnosis were:

• Age over 30 -- OR 0.79, P=0.02

• Non-white or Black race -- OR 1.35, P=0.03

• Pelvic location (vs lower extremity) -- OR 2.07, P<0.01

• Trunk location -- OR 1.7, P<0.01

• Rhabdomyosarcoma (vs UPS) -- OR 2.77, P<0.01

• Angiosarcoma -- OR 2.22, P<0.01

• Clear cell sarcoma -- OR 1.68, P=0.08

• Epithelioid sarcoma -- OR 1.59, P=0.01

• Regional lymph node metastasis -- OR 2.55, P<0.01

• Lung metastasis -- OR 8.59, P<0.01

Absence of bone or lung metastasis at diagnosis was associated with a 5-year survival rate of 55-60% versus about 5-20% for patients with bone metastasis, lung metastasis, or both (P<0.01).

"The majority of patients with bone metastases did not have lung metastasis," Collier and co-authors concluded. "Failure to recognize extrapulmonary metastatic disease, which is associated with poor survival outcomes, misinforms prognosis and may alter treatment."

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