On the same day that the personalized medicine testing market was reported to have exceeded $28 billion in 2011, the New England Journal of Medicine (NEJM) also reported a perceived stumble to the use of genomic tests that serve personalized medicine.
According to the NEJM report, “Intratumor Heterogeneity and Branched Evolution Revealed by Multiregion Sequencing” (Gerlinger et al., N. Engl. J. Med. 366:883-92 (2012)) intratumor heterogeneity may hinder personalized-medicine strategies that depend on results from single tumor-biopsy samples. Using various techniques, from exome sequencing, chromosome aberration analysis and ploidy profiling, genetic analysis was performed on samples isolated from primary renal carcinomas and associated metastatic sites from renal cell carcinoma patients treated with everolimus (Zortress, a drug marketed by Novartis). The researchers found that even within the same tumor gene expression varied. For example, mutational intratumoral heterogeneity was observed for multiple tumor-suppressor genes. Gene-expression signatures of good and poor prognosis were detected in different regions of the same tumor. The authors concluded that:
“Intratumor heterogeneity can lead to underestimation of the tumor genomics landscape portrayed from single tumor-biopsy samples and may present major challenges to personalized-medicine and biomarker development. Intratumor heterogeneity, associated with heterogeneous protein function, may foster tumor adaption and therapeutic failure through Darwinian selection.”
Is this the end of the road for personalized medicine ? No, others in the industry say the end is not near. The Personalized Medicine Coalition’s Amy Abernethy told ABC News that “There might be concern that the personalized medicine story has created a false sense of hope I don’t think it is false hope, but rather a false sense of the simplicity.” Moreover, personalized medicine is more than genetic tests on tumor samples. Companion diagnostics are being developed that utilize genomic polymorphisms rather than somatic mutations as studied in the NEJM report. In addition to the advantage of providing a test using a patient’s blood sample rather than a tumor biopsy, there is no issue of heterogeneity. Kalorama Information’s report on the personalized medicine testing market to have exceeded $28 billion in 2011, characterized personalized medicine not only as tissue-based tests to aid drug therapy decisions similar to that reported by the NEJM, but also tests that identify the characteristics of a disease, condition, or disorder to specifically determine what type of treatment is appropriate. Other tests include those that are the basis for selecting a safe and efficacious therapeutic dose, identified as likely the oldest application of personalized medicine that has been in use in clinical laboratories for at least 50 years.