The Many Reasons Why Personalized Medicine Is So Tricky

The European Multidisciplinary Cancer Congress is the gift that keeps on giving. It’s with an almost predictable rhythm these days that articles either praising the promise of personalized medicine (that is, medical treatment tailored to your specific make-up, genetic and otherwise) or expressing disappointment about how it hasn’t lived up to that promise pop up.

But a more interesting question than will it or won’t it is: why. Why exactly is personalized medicine such a challenge? The reasons might seem obvious — genes are really, really small; it’s hard to get enough people to study any particular target; cancer, the disease in which personalized therapy has been most touted, probably results from a combination of many genetic mutations and it’s hard to know just which one to blame. But reading through a list of explanations given by Gordon Mills, of the Institute for Personalized Cancer Therapy at M. D. Anderson Cancer Center, I was struck by the nice feeling of having something explained to me that I didn’t realize I needed to have explained. In case you might feel likewise, here are a few of the reasons he gave today during his EMCC talk:

• Among the many genetic aberrations discovered during genomic sequencing, it’s hard to know which ones can be drugged.

• Along those same lines, it’s hard to know which mutations are driving cancer and which are passive abnormalities that either happen as cancer progresses or just happen to be present with no connection to cancer at all. For example, most patients with advanced cancer have p53 mutations. Right now, there is no drug that targets p53, and there’s no saying that taking aim at p53 will be useful.

• Targeted therapy often leads to short-lived responses, and it’s not easy to move these into meaningful extensions in healthy survival.

• When you target one abnormality or pathway, the cancer cells will develop another means of growth, a process also known as treatment resistance.

• Genomic tests: 70% are true positive and 70% are true negative. His words, not mine.

• Slow downs stemming from reimbursement issues and the drug approval process.

• The costs associated with gene sequencing, including storing the data. Gene sequencing costs about $10,000 per patient, but handling and storage add extra charges. Mills estimates that the cost could go up to $100,000 per patient when you take interpreting the results into account.

Several studies presented at EMCC underscore the points above, with targeted drugs failing to deliver tangible, meaningful results. Of course, that doesn’t mean the end of personalized therapy for cancer or other diseases. If that were the case, how would all the biotech companies stay afloat? There were some glimmers of hope among the gene-targeting studies reported at EMCC, such as one phase III clinical trial in which breast cancer resistant to the aromatase inhibitors letrozole or anastrozole, was effectively treated with another aromatase inhibitor plus everolimus, an mTOR inhibitor. Of course, it needs to be said that this trial was called BOLERO-2 and with a name like that, failure is not really an option.

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