In a Viewpoint column in this week's Journal of the American Medical Association, Eric Topol, Kelly Bethel, and Laura Goetz of the Scripps Translational Science Institute and the Scripps Clinic say that pathologists must change the way they handle tissue samples in order to take full advantage of genomic sequencing in cancer care.
The Scripps physicians recommend that cancer tissue samples be frozen, rather than fixed in formalin, to improve tissue processing for whole-genome sequencing.
"It is now clear that thousands of somatic genomic changes occur in many solid adult tumors, and in many patients, the critical driver mutations and biologic pathways can be determined," the authors write. However, "discovering this level of crucial detail is possible only with whole genome and exome sequencing of frozen tissue."
The authors acknowledge that procuring frozen samples will add an extra step to the current process of formalin fixation and also may require obtaining additional tissue. "This is a significant concern in today's world of less invasive procedures retrieving smaller and smaller amounts of tissue," they concede. "Yet the potential for discovering clinically actionable driver and passenger mutations and also for analyzing tumor heterogeneity suggest consideration for more rather than less tissue procurement."
Changing practices within the pathology and oncology communities will likely be difficult, they note, but they argue that the field has no choice but to embrace the requirements of genomic medicine.
"As genomic testing becomes part of routine care and patients become increasingly informed, medicine will have to adapt to meet the demands of the next generation of patients with cancer, now informed about sequencing options for their particular malignancy," they write. "Rather than being beholden to this consumer-driven approach, a transformation from within the medical community is necessary."
Gary Robbins at the San Diego Union-Tribune says the proposed changes are "controversial" because the method "has not undergone clinical trials, and it would increase the cost of such sampling because the tumors would have to be refrigerated."
Topol tells the Union-Tribune that most pathologists "are very much against" procuring frozen tissue due to the additional expense of storing the samples and the lack of reimbursement to do so.
But Steven Gonias, chairman of the department of pathology at the University of California San Diego, takes issue with Topol's characterization of the pathology field, noting that his department has "invested in new biorepository facilities so that all of our diagnostic specimens can be stored and processed by conventional methods and by multiple state-of-the-art tissue-freezing methods, facilitating techniques like genome sequencing."