Cancer as a Metabolic Disorder

I received an inquiry via Twitter “Has anyone thought about using a sugar medium (similar to PET scans) to deliver chemo drugs?”

Although no one would use PET scans nor the PET reagents as therapy, the question is actually profound. There is a growing recognition that cancer is not a genetic disease but instead a metabolic disorder. One could not attend a lecture at the American Association of Cancer Research without there being reference to Otto Warburg’s 1956 paper “On the Origin of Cancer Cells” that described the metabolic basis of human malignancy.

Despite our myopic focus on cancer genomics, there is a growing recognition that cancer represents dysregulated energy metabolism. The high utilization of glucose, a hallmark of malignantly transformed cells, (and the target of PET scan diagnostics), in part reflects the process of aerobic glycolysis, whereby cells provided ample oxygen nonetheless eschew the efficiency of mitochondrial oxidative phosphorylation in favor of seemingly inefficient lactate production.

Into this new realm of biochemically driven developments, a growing number of therapeutic agents that target glucose metabolism are finding their way into the clinic. To the dismay of some, the mutations that our molecular biologists identify are increasingly found to represent intermediates of cellular metabolism, forcing many to go back to relearn biochemistry. Thus, the avidity for glucose represented by uptake of the PET scan reagent F18 fluorodeoxyglucose by tumor cells, is a diagnostic application of what, in the future, may provide meaningful therapeutic opportunities.

Renal Cancer Patient Update

A few weeks ago, I discussed the case of a patient with metastatic renal cell carcinoma who upon arrival in my office for a consultation, appeared to be too ill to even consider further treatment. Determined to persevere, he provided us with a sample to test and underwent our suggested regimen. As was mentioned previously, the patient was delighted with his response and has now returned to many normal activities, including working out at the gym.

What I did not expect was to receive a letter a few weeks later from his treating oncologist in Northern California. He was thrilled with the patient’s “massive” response, even commenting that the carcinoma had reacted more like a lymphoma than the typically aggressive and non-responsive renal cancer. In fact, the patient is doing so well he is being considered for a kidney removal (a procedure that he couldn’t have possible survived just weeks earlier).

Working in tandem with treating physicians is a partnership that benefits patients. It is exhilarating for myself and my team to hear about such favorable outcomes.

Are New Cancer Drugs Always Better?

Few cancers instill a greater sense of fear in the medical oncologist that metastatic renal cell carcinoma, the most common form of which is known as clear cell cancer. This type of kidney cancer — driven by a mutation in a gene know as VHL — spreads rapidly, metastasizes to almost any and all organs and historically responded to almost no therapies. The development of Interleukin-2 (IL-2) in the 1980s offered a glimmer of hope. Yet, even this breakthrough ultimately yielded complete and durable responses in a mere 10 percent of patients.

By focusing on the hyper-vascular nature of this disease, investigators then developed a second line of defense that attacked the blood supply of these cancers. Following the introduction of Avastin, a number of small molecule VEGF inhibitors were introduced. Most recently, a class of drugs known as mTOR inhibitors gained popularity by providing objective responses and showing evidence of improved survival.

But what happens when all the really “hot new drugs” fail to provide benefit?

This was a question I confronted in a charming, 68-year-old neurologist who traveled to visit me from Stanford University where he received highly appropriate, yet unfortunately ineffective therapy. The patient presented in July 2010 with rapidly progressive kidney cancer that had overtaken his lungs. He was started on oral Sutent (the treatment of choice). His management was complicated by a hemolytic anemia. When I met the patient in October, I was concerned that he could not survive long enough to take on another treatment, no matter how effective it might ultimately prove to be.

As a physician, he beseeched me to study his tumor in the hope of finding any therapy to salvage him from his rapidly deteriorating course. A small biopsy was obtained with the help of one of our surgical colleagues. The results were striking — no evidence of activity for sorafenib, sunitinib (Sutent), nor the Rapalogs (Rapamycin derivatives). In one fell swoop, all of the newest therapies were swept aside with little likelihood of benefit. Despite the established literature, this patient was clearly sensitive to chemotherapeutics. It was evident to me that the treatment outline, a combination of three drugs, could provide meaningful clinical benefit if the patient could tolerate even the most modest associated side effects. With the kind cooperation of the treating physician in Northern California, our recipe was followed to a T.

The treating oncologist pulled no punches in his description of this patient’s prognosis. Nonetheless, he kindly assisted in the management of the treatment we described. While the cancer-related hemolytic anemia raged, and the patient fought for air, the treatments were delivered. Too ill to leave the hospital, his entire first course of therapy was delivered on an inpatient basis.

For several weeks, we anticipated the worst. And then, a phone call from a chipper-sounding patient. Breathing comfortable, his chest x-ray had cleared, his anemia had resolved and he was being readied for discharge. A short time later, an abdominal ultrasound revealed measurable improvement in the kidney cancer, further confirming objective response.

The patient, now home, could not be happier. The excellent outcome is as gratifying as it is unexpected. There is no question that no one else would have given this treatment. And there is further no question that the patient would not be alive today had he not received it. There are many lessons to be learned from this experience. Among them, that every patient deserves the opportunity to get better; that laboratory analyses can identify unexpected options for patients, even with the worst malignancies; that new drugs aren’t always better drugs; and finally, that nothing succeeds like success.

New Drugs Are Not Always Better Drugs

The most common form of renal carcinoma is the clear cell variant. These tumors are driven by mutations in the VHL gene and are associated with hyper-vascularity. Understanding the pathogenesis of this disease has enabled researchers to develop new classes of drugs that target VEGF, both at the protein level (Bevacizumab) and at the tyrosine kinase level (sorafenib, sunitinib, etc.). An additional class of drugs targets the intracellular metabolic pathway known as mTOR. Patients newly diagnosed with renal cell carcinoma of the clear cell type are treated with drugs that target these pathways. However, responses occur in the minority of patients. It is unclear why some patients respond to these interventions while others fail.

The EVA-PCD™ analysis is equally applicable to classic cytotoxic drugs and the newer classes of targeted agents, which include Sunitinib and Sorafenib and the rapalogs like Everolimus and Temsirolimus. This enables our lab to explore whether renal cell carcinoma patients are likely to respond to vascular or mTOR targeting classes of drugs. Interestingly, patients who do not respond to these classes of drugs may nonetheless have sensitivity to cytotoxic chemotherapeutic agents. One example currently undergoing therapy is a 51 year old male who was presented in February 2009 with widely metastatic renal cell carcinoma, and a destructive lesion of the right femur requiring open surgical stabilization. Tissue removed from the patient’s femur at the time of the orthopedic surgery was submitted for an EVA-PCD™ analysis. The results were highly instructive, indicating clear resistance to the VEGF targeting agents and the rapalogs but substantial sensitivity to a novel combination of cytotoxic drugs. The patient received an opinion from a renowned renal cell expert who immediately placed him on sunitinib (Sutent™). When he failed sunitinib he was then placed upon Everolimus (Afinitor). Again the patient failed to respond. Progression of his disease was heralded by brain metastases that required both neurosurgery and cranial irradiation. He then revealed rapidly progressive pulmonary metastases as well as large painful bilateral axillary lymphadenopathy and large painful subcutaneous lesions. In light of the patient’s failure of targeted agents, he was treated with a three-drug combination identified to be active in the EVA-PCD™ analysis. The response to date has been dramatic, with complete resolution of subcutaneous lesions and lymph nodes , and objective improvement in the pulmonary metastases by CT scan. The patient remains on therapy, with continued excellent response.

This is but one example of an unexpectedly good response to classic cytotoxic drugs following a failure to respond to the newest classes of targeted agents. These experiences reinforce the need for cancer therapies to be individualized. They also remind us, as physicians, that it is the good outcome of the patient not the therapy applied that constitute successful application of the healing arts.