Performance Analysis of the AJCC Latest-Edition Staging System for Sarcoma
A recent analysis examined whether changes to the latest American Joint Committee on Cancer (AJCC) cancer staging manual on retroperitoneal sarcoma have improved staging system performance, published in Annals of Surgical Oncology (online October 20, 2017; doi:10.1245/s1043).
The AJCC recently published the 8th edition of the AJCC Cancer Staging Manual, which featured significant changes to the staging algorithm for retroperitoneal sarcoma. However, whether or not these changes have improved staging system performance has yet to be determined.
Justin M M Cates, MD, PhD, department of pathology, microbiology, and immunology, Vanderbilt University Medical Center (Nashville, TN), conducted a retrospective analysis to determine whether recommendations in the 8th edition of the staging manual have positively impacted sarcoma staging. A total of 3703 adult patients with retroperitoneal sarcoma were sampled from the Surveillance, Epidemiology, and End Results (SEER) database. The analysis compared a novel staging system that incorporated a histologic subtype of sarcoma with current and prior AJCC soft-tissue sarcoma staging systems.
Flexible, non-linear Cox proportional hazard regression—using restricted cubic splines and fractional polynomials—was used to assess the effect of tumor size on sarcoma-specific survival.
Dr Cates reported that the relationship between the covariate-adjusted log hazard for disease-specific survival and tumor size is non-linear. “Although the new AJCC classification approximates this hazard fairly well, the overall prognostic impact of tumor size is limited after accounting for other predictive factors,” he explained.
Furthermore, Dr Cates found that the predictive accuracy and concordance indices of the AJCC latest edition staging system for retroperitoneal sarcoma are significantly low, compared to that of the prior 7th edition.
In his concluding remarks, Dr Cates recommends that AJCC committees should not revise tumor staging algorithms without prior evidence that the proposed changes improve the staging system. A proposed staging system—which incorporates histologic grade, tumor size, and histologic subtype—is superior to both the AJCC 7th and 8th editions in predicting sarcoma-specific survival, he attests.—Zachary Bessette