Endpoints for agents that slow tumor growth

Area of Science:

• Oncology
• Clinical Trial Design
• Mathematical Modeling

Background:

• Traditional oncology endpoints like time to progression/progression-free survival (TTP/PFS) were developed for cytotoxic agents.
• Current cancer therapies increasingly combine cytostatic and cytotoxic agents.
• Tumor growth dynamics can be complex, influenced by agent type and tumor volume.

Purpose of the Study:

• To evaluate the sensitivity of TTP/PFS as an endpoint for cytostatic drugs used in combination with cytotoxic agents.
• To explore alternative endpoints that may better capture cytostatic agent activity.
• To analyze the impact of combined therapies on tumor growth kinetics.

Main Methods:

• Utilized mathematical models of tumor growth, incorporating Gompertzian kinetics.
• Simulated the effects of chemotherapy (cytotoxic) and cytostatic agents on tumor growth over time.
• Applied a clinical trial of an angiogenesis inhibitor in metastatic breast cancer as a case study.

Main Results:

• Demonstrated that TTP/PFS may be insensitive to the effects of active cytostatic agents when combined with chemotherapy.
• Identified that time to regrowth is a more sensitive measure for detecting cytostatic agent activity in such combinations.
• Mathematical models supported the masking effect of cytotoxic agents on cytostatic efficacy via TTP/PFS.

Conclusions:

• TTP/PFS may underestimate or obscure the efficacy of cytostatic agents in combination regimens.
• Clinical trial designs should consider alternative endpoints like time to regrowth for evaluating cytostatic agents.
• Accurate assessment of cytostatic drug efficacy requires careful endpoint selection, especially in combination therapies.