Validation of the AJCC 8th lung cancer staging system among patients with small cell lung cancer

The current study tried to validate the prognostic significance of the 8th American Joint Committee on Cancer (AJCC) staging system among small cell lung cancer (SCLC) patients recorded within the surveillance, epidemiology, and end results (SEER) database.

SEER database (2004-2014) has been queried through SEER*Stat program, and both AJCC 7th and 8th edition stages were constructed. Cancer-specific and overall survival analyses according to both editions were performed through Kaplan-Meier analysis. The cause-specific Cox regression hazard for both AJCC editions (adjusted for age, gender, race, and surgery) was calculated and pair-wise comparisons of hazard ratios were conducted.

A total of 39,286 patients with SCLC were recruited in the period from 2004 to 2014. For overall and cancer-specific survival assessment, according to the AJCC 7th edition, P values for all pair-wise comparisons among different stages were significant (<0.0001) except for the comparisons between stage IB vs. stage IIA, and stage IIB vs. stage IIIA. For overall survival assessment, according to AJCC 8th, P values for all pair-wise comparisons were significant (<0.05) except for IA2 vs. IA3, IA3 vs. IB, IB vs. IIA, IIA vs. IIB, and IIIB vs. IIIC. For cancer-specific survival, according to AJCC 8th, P values for all pair-wise comparisons among different stages were significant (<0.05) except IA1 vs. IA2, IA2 vs. IA3, and IIA vs. IIB. When conducting pair-wise hazard ratio comparisons among different AJCC stages (for both editions), similar findings to the Kaplan-Meier analyses were reported.

While there is a clear improvement for both the AJCC 7th and 8th systems compared to the old veterans' administration system, there is a modest improvement for the 8th compared to the 7th system among patients with SCLC.