Abstract P6-06-11: The Will Rogers phenomenon in breast cancer - How does the change from AJCC 5th edition to AJCC 6th edition affect cancer survival?

Abstract

Abstract Introduction: Staging of cancers are important to select appropriate treatment and to estimate prognosis. The most extensive and significant revisions that have ever been made in the breast cancer staging system occurred when the 5th Edition (AJCC5) was updated to the 6th Edition (AJCC6) in Jan 2003. The principal changes were related to the size, number, and location of metastases to the lymph nodes. AJCC6 takes into account the number of lymph nodes involved, and if 4 or more lymph nodes are involved, a Stage 2 breast cancer under AJCC5 is upstaged to Stage 3 under AJCC6. The presence of a supraclavicular lymph node in the absence of other metastases was considered a Stage 4 under AJCC5, but under AJCC6, patients with a supraclavicular lymph node is downstaged to Stage 3. The Will Rogers phenomenon to describe the effect of the “stage migration” has been described as one of the most important biases limiting the use of historical cohorts when comparing survival or treatment. In breast cancer, when we move the “poor prognosis” Stage 2’s, with 4 or more nodes involved, to Stage 3, the Stage 2's remaining will be a “better prognosis” Stage 2, and hence survival should improve. These “poor prognosis” Stage 2's will then be the “better prognosis” Stage 3's and hence the survival of Stage 3 should improve. The aim of this study is to investigate how the change from AJCC5 to AJCC6 affected stage-specific survival in a group of Asian breast cancer patients. Patients and Methods: 3127 new cases of breast cancer cases presenting to the University Malaya Medical Centre between Jan 1993 and Dec 2007 were prospectively registered into the UMMC Breast Cancer Database. Non-epithelial cancers and ductal carcinoma in situ were excluded. All patients were restaged into AJCC5 and AJCC6 Results: Comparison of Staging by AJCC5 and AJCC6StageAJCC5AJCC61706 (22.6%)706 (22.6%)21553 (49.7%)1230 (39.3%)3511 (16.3%)854 (27.3%)4357 (11.4%)337 (10.8%)Total31273127 Discussion: It is important to compare stage-specific survival in different time periods to determine whether survival has improved, usually due to timely and optimal treatment. Out of 1553 women classified into Stage 2 breast cancer, 323 or 20.8%, were moved to Stage 3 under AJCC6. The shift from Stage 4 to 3 is less significant because only 20 out of 357 women (5.6%) had supraclavicular lymph node metastases only. The survival of AJCC 5 Stage 2 breast cancer had a 5 year survival rate of 82.9% compared to a 86.1% with AJCC6 Stage 2. Similarly, the 5 year survival of AJCC5 Stage 3 was 50.6% compared to 59% with AJCC6 Stage 3. Conclusion: Similar to other studies, the stage specific survival in women with Stage 2 and 3 breast cancer improves significantly when AJCC6 is used for staging in the same cohort of patients, again underlying the importance of standardizing the stage when comparing survival from two time periods. Comparison of 5-year relative survival by AJCC5 and AJCC6StageAJCC5AJCC6196.996.9282.986.1350.659414.412.6 Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P6-06-11.