Conclusion

In summary, although numerous studies provide a clear rationale for monitoring drug levels of oral small molecule anticancer drugs, the lack of trials clearly showing significant improvement in outcomes with TDM prevents this approach from being embraced by the oncology community. Well-designed randomized controlled trials comparing drug level monitoring with the standard of care, which are sufficiently powered to demonstrate an effect on survival are desperately needed. Numerous completed and ongoing studies on TDM of oral small molecule anticancer drugs have prepared the precision oncology field for such a trial. The time has come to take the next step.