Interindividual variability is yet to be fully characterized, and for this, optimum patient stratification and companion diagnostics are still lacking. Especially when complex disease phenotypes and/or polygenic diseases are considered, patient monitoring and disease management become rather challenging, while acquired resistance to therapy and/or toxicity events are among the unmet needs in the clinic. No doubt, biomarkers are of great importance to disease management and tailor-made theranostics. Microfluidics has gathered great attention lately, mostly due to its low-invasive nature compared to tissue biopsies. Low invasiveness becomes greatly advantageous for microfluidics practices as the latter mirror cell biology revolutionizing cancer diagnostics and management. Recent advances in microfluidics hold the promise of robust clinical diagnostics after they have demonstrated effective exosome separation. We feel that microfluidics-based exosome isolation techniques, if cost-effective, could be implemented in the clinic and/or resource-scarce settings. This article (a) discusses exosomes, (b) comments on the first microfluidic advances in the field of cancer theranostics, (c) presents such advances in exosomes as complementary to liquid biopsies with an emphasis on circulating tumor cells, and (d) proposes a road map for future developments.