Abstract
Background/Aims AJCC Tumor (T), Nodal (N) and Metastatic (M) staging is commonly used in clinical practice for treatment decisions. However before 2004, most cancer registries following the North American Association of Central Cancer Registries (NAACR) standards reported only SEER Summary Staging, including the Kaiser Permanente Northern California Cancer Registry (KPNCCR). Information on extent of disease (EOD; extent and size of primary tumor, presence of metastases, lymph node involvement) was recorded as required by NAACR and SEER. The KP Southern California Cancer Registry (KPSCCR) also recorded TNM staging since 1988, in accordance with the American College of Surgeons. We developed an algorithm to map EOD to AJCC TNM stages for female breast cancer cases diagnosed from 1988–2003 identified from the KPNCCR. This algorithm was validated using KPSCCR data from 1996–2003 (n=17,135 cases) with available EOD and TNM information.
Methods : The SEER Comparative Staging Guide for Cancer (1993) and the AJCC Cancer Staging Manual 6th edition (2002) were used to derive TNM stages (AJCC Version 6) from KPNCCR EOD variables for breast cancer cases diagnosed from 1988–2003. This algorithm was then applied to KPSCCR EOD variables for breast cancer cases diagnosed from 1996–2003. T, N, M and stage from this algorithm were compared to T, N, M and stage (“gold standard”) available in the KPSCCR. Test characteristics (percent agreement, Cohen’s kappa, sensitivity, specificity) were calculated. KPNC and KPSC distributions of cancer diagnoses by stage from 1996–2003 were compared.
Results Agreement between the derived and available T, N, M variables was excellent (percent agreement and Cohen’s kappa): T 93% and 0.91; N 96% and 0.94; M 100% and 0.93. Consistent high sensitivity and specificity were observed except for somewhat lower sensitivity for Stage III (sensitivity, specificity): Stage 0 (0.99, 1.00), Stage I (0.97, 0.98), Stage II (0.91, 0.96), Stage III (0.69, 0.99), Stage IV (0.92, 1.00), Overall (0.92, 0.89). Distributions of derived TNM staging of KPNC and KPSC cases from 1996–2003 were similar.
Discussion SEER EOD variables for breast tumors available in SEER-accredited cancer registries can be used to accurately map to AJCC TNM staging for conduct of epidemiologic studies using cancer registry data.
