Context: A number of authors have found that there exists a positive relationship between progression-free survival and overall survival in clinical trials of cancer treatments for particular types of metastatic cancer. However, such an outcome is consistent with an increase in progression-free survival generally leading to an increase, a decrease or no change in survival following disease progression (post-progression survival) and which of these theories is valid has yet to be thoroughly investigated.
Objective: To test theories of this nature in relation to the use of chemotherapy in treating four different types of metastatic cancer by performing a systematic search of published clinical trials.