Time Dependency of the Influence of Prognostic Factors on Relapse in Breast Cancer

Background: A number of factors concerning the prognosis of cancer patients have been reported, but the evaluation of individual factors is not always consistent. The author considered that the discrepancies may lie in part in that factors may have a changing influence on relapse with time. The present study was intended to reveal the phenomenon and its clinical significance in patients with breast cancer.

Methods: Eleven pathological prognostic factors in 462 patients with primary breast cancer were analysed with special reference to the influence on relapse and its changes with time. The Cox regression analysis was performed for whole and three stratified non-overlapping observation period (within 2, 2-5 and 5 years more), using factors including extent of nodal involvement (N), nuclear grade (NG), tumor infiltrating lymphocytes (TIL), tumor size, fat infiltration (F) and others.

Results: Cox regression analysis for whole observation period showed N followed by NG, TIL, F and others as the most important factors on relapse. But the analysis performed for 3 stratified intervals revealed that the influence on relapse decreased with time for N and NG, but tended to increase with time for F. The suppressive effect of TIL on relapse was not evident up to 2 years but was significantly emphasized after 2 years postoperatively.

Conclusions: In conclusion, a distinct time-dependency with varied patterns was found in the influence of some prognostic factors on relapse, which implies the assessment of prognostic factors may vary according to the length of the observation period.