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Purpose. Extraskeletal osteosarcoma represents an unusual soft-tissue sarcoma that historically is reported to carry an exceptionally poor prognosis. The objectives of this study were to use a prospectively gathered sarcoma database to test the prevailing clinical bias and more accurately describe the natural history, characterize the prognostic features, estimate survival and evaluate treatment strategies for this unusual sarcoma. Patients and methods. From a large database of nearly 4000 sarcomas at a single institution, 15 patients with pathologically confirmed extraskeletal osteosarcoma were analysed. Results and discussion. Extraskeletal osteosarcoma usually occurs as a large, deep, high-grade lesion in the lower extremity of older patients. Overall and disease-specific survival at 5 years was 50%, with a median follow-up of 35 months (range 3-200 months). Use of adjuvant chemotherapy or radiation therapy did not appear to influence survival, but an effect may have been missed by the relatively low numbers in each group. When matched to a comparable group of patients with stage III extremity sarcomas, there was no significant difference in overall or disease-specific survival between groups. Treatment for extraskeletal osteosarcoma should follow established guidelines for treatment of soft-tissue sarcomas, with the decision regarding adjuvant therapy to be based on individual risk factors. [ABSTRACT FROM AUTHOR]

Summary: Background: Adjuvant imatinib mesylate prolongs recurrence-free survival (RFS) after resection of localised primary gastrointestinal stromal tumours (GIST). We aimed to develop a nomogram to predict RFS after surgery in the absence of adjuvant therapy to help guide patient selection for adjuvant imatinib therapy. Methods: A nomogram to predict RFS based on tumour size (cm), location (stomach, small intestine, colon/rectum, or other), and mitotic index (<5 or ≥5 mitoses per 50 high-power fields) was developed from 127 patients treated at Memorial Sloan-Kettering Cancer Center (MSKCC), New York, NY, USA. The nomogram was tested in patients from the Spanish Group for Research on Sarcomas (GEIS; n=212) and the Mayo Clinic, Rochester, MN, USA (Mayo; n=148). The nomogram was assessed by calculating concordance probabilities and testing calibration of predicted RFS with observed RFS. Concordance probabilities were also compared with those of three commonly used staging systems. Findings: The nomogram had a concordance probability of 0·78 (SE 0·02) in the MSKCC dataset, and 0·76 (0·03) and 0·80 (0·02) in the validation cohorts. Nomogram predictions were well calibrated. Inclusion of tyrosine kinase mutation status in the nomogram did not improve its discriminatory ability. Concordance probabilities of the nomogram were better than those of the two NIH staging systems (0·76 [0·03] vs 0·70 [0·04, p=0·04] and 0·66 [0·04, p=0·01] in the GEIS validation cohort; 0·80 [0·02] vs 0·74 [0·02, p=0·04] and 0·78 [0·02, p=0·05] in the Mayo cohort) and similar to those of the AFIP-Miettinen staging system (0·76 [0·03] vs 0·73 [0·004, p=0·28] in the GEIS cohort; 0·80 [0·02] vs 0·76 [0·003, p=0·09] in the Mayo cohort). Nomogram predictions of RFS seemed better calibrated than predictions made with the AFIP-Miettinen system. Interpretation: The nomogram accurately predicts RFS after resection of localised primary GIST and could be used to select patients for adjuvant imatinib therapy. Funding: National Cancer Institute, Bethesda, MD, USA. [Copyright &y& Elsevier]