Prognostic implications of advancing nodal stage in anal cancer: evaluating AJCC 8 staging changes through an NCDB...

In the AJCC8, nodal staging for squamous cell carcinoma of the anus (SCCA) has been changed to a binary format (N0 or N+), and overall stage groups have been redefined. We evaluated the effect of AJCC8 nodal stage by T stage and hypothesized similar survival regardless of the extent of AJCC7-defined nodal involvement.

The National Cancer Database (NCDB) was used to identify patients' SCCA. Overall survival (OS) for each T stage within the AJCC7 was compared with increasing nodal stage, as well as for the new AJCC8 overall stage groups and subsets.

There were 6738 patients analyzed. The 5-year OS by AJCC8 stage was I = 81%, IIA = 78%, IIB = 64%, IIIA = 69%, IIIB = 59%, IIIC = 57% (p < 0.0001). In AJCC8 IIIA (T1-2, N+), there was no difference in 5-year OS between T1N+ or T2N+ patients (70.3% vs 68.6%, p = 0.09). A significant survival difference was demonstrated between AJCC7 N1, N2, and N3 for patients with either T1 (p = 0.0047) or T2 (p = 0.0389) disease. In the AJCC 8 IIIC (T3-4, N+) group, there was no difference in 5-year OS between T3N+ and T4N+ (58% vs 55%, p = 0.81). There was no OS difference between AJCC7 N1-3 for either T3 (p = 0.19) or T4 (0.35) disease.

For earlier T stages, advancing nodal stage per AJCC7 retains prognostic implications for OS. Survival in AJCC8 stage IIIA is heterogeneous and is largely driven by burden of nodal disease in patients with T1-2 disease.