have demonstrated inconsistent results. For example, among 13 studies published between 1977 and 2006 included in a 2007 systematic review by Ramos and colleagues, 10 found no association between the symptom-to-diagnosis interval (SDI) and survival and the other three found that increased delays resulted in better chances of survival. As for the relationship between SDI and tumor stage, among 18 studies, 11 found no association, four found that shorter delays were associated with an earlier stage at diagnosis and three paradoxically found that a greater delay was associated with an earlier stage at diagnosis. As noted by Ramos et al., the SDI risk function is likely nonlinear and multifaceted, reflecting a complex interaction between tumor biology and location, the clinical course, patient behavior, and the functioning of the healthcare system, and the studies have varied in their methods for adjusting for these confounding factors. These findings highlight the importance of detecting colorectal cancer through screening, before symptoms appear"--Publisher's description. |