Background/objectives: Non-small cell lung cancer and pleural mesothelioma are among the most lethal and therapy-resistant tumors in humans. These tumors are diagnosed late, frequently present pleural effusion and develop drug resistance, and the treatment is often inefficient and largely alliative. Therefore, there is an urgent need to refine the selection of drugs and patients for personalized treatment. Methods: To progress the field, we performed a systematic literature review in line with the PRISMA guidelines followed by a narrative synthesis approach to identify themes. Results: The literature to date shows, in general, a positive correlation between the drug-sensitivity of patient-derived cells ex vivo and the clinical outcome. However, only a handful of these studies show a numerical correlation. This, along with the vast diversity of correlated techniques and parameters makes it difficult to directly compare the findings. To build a common knowledge base for future studies, we therefore offer a comprehensive summary of the literature, identify gaps, and suggest future avenues for research. Conclusions: We present unified recommendations for the collection, preparation, and ex vivo sensitivity testing of samples for the future development of personalized medicine.