Nomograms Help Predict Survival Outcomes in Osteosarcoma Patients

July 29, 2015

A retrospective study was used to develop nomograms predictive of both metastasis-free and overall survival for patients with nonmetastatic osteosarcoma.

A retrospective study was used to develop predictive nomograms for patients with non-metastatic osteosarcoma. Using six clinical and pathologic variables, the nomograms were useful in predicting both metastasis-free survival (MFS) and overall survival (OS).

“The long-term survival of osteosarcoma patients has improved dramatically because of the introduction of effective systemic chemotherapy,” wrote study authors led by Koichi Ogura, MD, of the National Cancer Center Hospital in Tokyo. In spite of those improvements, many patients do develop metastases or suffer tumor-related death, and current clinical staging guidelines do not include some factors that have been shown to correlate with survival.

In the new study, researchers analyzed data from a large national cohort study, including 1,070 osteosarcoma patients treated with neoadjuvant chemotherapy and surgery, to develop prognostic nomograms. Results were published online ahead of print in Cancer.

Of this cohort, 557 were used in a “training set” to determine factors to include, and 553 were then considered a validation set. The 3-year and 5-year OS rates were 87% and 82%, respectively; the rates for MFS were 69% and 64%, respectively.

Based on multivariate analyses showing significant associations between certain factors and MFS and OS, researchers created nomograms that included the following variables, weighted in different ways: age, sex, tumor size, tumor site, necrotic rate, and presence of pathologic fracture. The point values assigned to each of these differed for the MFS and OS nomograms.

A score of approximately 15 points would yield a 3-year metastasis-free survival probability of about 90%, while a score close to 90 points would yield a probability near 10%. For OS, a point score of just under 50 corresponds with the 90% survival probability, while a score of about 90 again corresponds to about a 10% 3-year survival probability.

Calibration plots showed a concordance index of 0.631 for the MFS nomogram and of 0.679 for the OS nomogram.

“It is not unusual for musculoskeletal oncologists to encounter patients who develop distant metastasis or suffer tumor-related death even though they receive identical definitive treatment, and the ability to identify such higher risk patients would undoubtedly be valuable,” study authors concluded. “Our nomograms make it easier to derive individualized predictions of patient outcome; they allow physicians to recognize the risk of distant metastasis or tumor-related death after treatment and provide a more informative explanation for their patients.”

They added that the study is limited by its retrospective nature, but that this tool can be used for patient counseling and establishing post-surgical surveillance strategies.