A Survey of Survival Outcomes for Targeted Cancer Drugs Approved by the US Food and Drug Administration

The last two decades have witnessed the vigorous development of targeted cancer drugs and the potent therapeutic effects of these drugs have been validated by various true and surrogate end points. Overall survival (OS) and progression-free survival (PFS) outcomes were two important end points used in targeted cancer drugs clinical trials but investigation on which was rare as a consequence of inherent heterogeneity and complexity. Here, we present the review and analysis of OS and PFS outcomes of all targeted cancer drugs approved by the U.S. Food and Drug Administration (FDA) through December 31, 2019, in the setting of clinical studies.

The targeted cancer drug directory was accessed via NCI website. The survival outcomes of those drugs in the setting of clinical trials were collected from publicly available Package Inserts and ClinicalTrials.gov. Median overall (OS) and progression-free survival (PFS) outcomes were summarized for targeted cancer drugs that were evaluated as monotherapies in clinical trials, contributions of targeted drugs to combination therapies in terms of survival benefit were analyzed, survival outcomes of FDA-approved first-line targeted therapies in different cancers were investigated, and the correlation between the absolute OS gain (ΔOS) and PFS gain (ΔPFS) as well as the hazard ratios for PFS (HR_PFS) and OS (HR_OS) between comparative arms of available randomized clinical trials was evaluated.

A total of 223 indications for 126 targeted cancer drugs have been approved by the FDA through December 31, 2019, among which 28 indications of 23 drugs have been approved for first-line therapies. Eighty indications for leukemia, lymphoma, and rare cancer types without survival data were excluded in the investigation of survival outcomes. For the remaining 143 indications, 99 were approved as monotherapies and 72 were approved as combination therapies. Among monotherapy subset, 18 of 72 (25%) indications with available OS outcomes have maximum median OS less than 12 months, 55 of 72 (76%) drug indications have maximum median OS less than 24 months, and 67 of 72 (93%) have maximum median OS less than 36 months. Regarding PFS, 38 of 88 (43%) drug indications have maximum median PFS less than 6 months, 69 of 88 (78%) drug indications have maximum median PFS less than 12 months, and 84 of 88 (95%) drug indications have maximum median PFS less than 24 months. The addition of targeted drugs to combination regimens under FDA's approval provided notable survival benefit, but the median value of OS gain rate of the available combination regimens was lower than that of PFS. The univariate Spearman Rank correlation coefficient suggested a significant positive correlation between ΔOS and ΔPFS (R = 0.62) but a weak correlation between HR_OS and HR_PFS (R = 0.11) in 46 randomized clinical trials that investigated contributions of targeted cancer drugs to combination therapies with available data. A moderate correlation between ΔOS and ΔPFS (R = 0.43) and a rather weak correlation between HR_OS and HR_PFS (R = 0.07) were also found in other randomized clinical trials that included in our study with available data.

The survival benefit provided by targeted cancer drugs varied a lot among cancer types. Though targeted cancer drugs showed improvements in both OS and PFS in approved combination regimens, the median value of OS gain rate was lower than that of PFS. As only weak correlation was found between HR_PFS and HR_OS, the evidence supporting the use of PFS as a surrogate to OS in the setting of targeted cancer drugs might also be limited.