3764 - Improvements in Imaging Appear to Increase the Association between the Rates of Synchronous and Metachronous Metastases in Patients with Cancer

Materials/Methods: All the analyses were performed by using the the Surveillance, Epidemiology, and End Results (SEER)-8 dataset from 1975 to 2015. For each of 18 solid tumor types, the crude rates of synchronous and metachronous metastases were estimated as below:

The fraction of patients with synchronous metastases at the time of initial diagnosis is taken as the ratio of distant cases to the sum of localized, regional, and distant cases reported in SEER (distant / [localized + regional + distant]).

The fraction of patients developing metachronous metastases is estimated as the product of “The fraction of patients presenting with local or regional disease (clinical M0)” * “The cancer-related death rate in patients presenting with local or regional disease” (In the formulation we have defined, it is assumed that the majority of patients developing metachronous metastases harbored subclincial metastases at diagnosis).

For each patient cohort (1975, 1985, 1995, 2005, and 2015), and for each followup interval (5- 10-, and 15-years), simple linear regression analyses were done to quantify the relationship between the rates of metachronous metastasis (dependent variable) and synchronous metastasis (independent variable) across all cancer sites considered. Fisher’s z-transformation was applied to assess the significance of the difference between two correlation coefficients.

Results: Correlation coefficient (R) and p <span class="SpellE">values of regression analyses for 5-year, 10-year and 15-year data are demonstrated in Table 1. There is a statistical significance between R values of 1975 and 2015 of 5-year data (z= -1.7, one-tailed p=0.04, and two-tailed p= 0.09).

Conclusion: There is an increasing association between the rates of synchronous and metachronous distant metastases over time, and the difference of association between 1975 and 2015 is statistically significant. It is reasonable to conclude that these increasing associations are, to some extent, linked to the improved accuracy of staging studies, that are being more widely-applied across different types of cancer, over time. Abstract 3764 – Table 1: Correlation coefficient (R) and p <span>values of simple linear regression analysis between the rates of synchronous metastases and each of 5-year, 10-year and 15-year metachronous metastases