“We have evolved our understanding of cancer from that of a diseased organ, which must be removed to be cured, to a cellular disease that spreads through the lymphatic and blood systems, and now to a genomic disease, where mutated genes governing particular molecular pathways lead to developing cancer.” said Dr. Bruce Feinberg, vice president and chief medical officer for Cardinal Health Specialty Solutions.
Feinberg added that this evolution in understanding has transformed cancer care, as breast cancer treatment illustrates. He explained that when cancer was believed to be the result of a diseased organ, the treatment for breast cancer was radical mastectomy. When cancer was understood to be a cellular disease, treatment for breast cancer shifted to the lumpectomy, with or without chemo-hormonal therapy to kill the microscopic cells circulating outside the breast. As we gain further understanding of cancer’s genomic basis, treatment standards are likely to change again.
The critical insight of precision medicine is that mutations within the cancer genome result in altered protein expression that can give rise to unique, readily identifiable molecular targets within, or on the surface of, cancer cells. These specific targetable proteins may not be limited to one type of cancer. "Some mutations are commonly found in a variety of cancers, can be present in both genders, in different histologies, and so forth," explained Dr. Chadi Nabhan, vice president and chief medical officer for Cardinal Health Specialty Solutions. "For example, one target, one mutated gene called Her2 is found in both some breast cancer and some stomach cancer patients, and these patients are being treated with the same drug. Twenty years ago, that was unthinkable."
So far, multiple targeted therapies have been approved by the Food & Drug Administration to treat a variety of cancers. Many more currently exist in late-phase clinical trials. Precision medicine has shown success in the treatment of small diseases subsets. For example, the drug Gleevec (generic name Imatinib) approved in 2002 to treat chronic myeloid leukemia appears to cure or control disease in the majority of patients who otherwise would have had a limited life expectancy of less than five years unless transplanted successfully. This so-called “medical miracle” created unbridled optimism for the precision medicine approach, which over the past two decades has seen other successes, but not on the Gleevec scale.
So now the question is: Will targeted therapy of cancer be the revolution it was once believed to be, or will it be eclipsed by the emerging field of Immuno-oncology? And more importantly, will these therapies be safer and more effective treatments than chemotherapy in the broader cancer patient population? Precision medicine argues that treating the “target” is a better, safer, and potentially more cost-effective strategy. Data to support this hypothesis remain sparse and studies are ongoing.