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.

Is There a Role for Maintenance Therapy in Cancer Treatment?

There is a long tradition of maintenance therapy in pediatric oncology. Children with acute lymphoblastic leukemia uniformly receive three stages of therapy: induction, consolidation, and finally maintenance. The maintenance stage consists of weekly, or even daily therapies.

The historical experiences of relapse in this population lead investigators to consistently expose these patients to drugs for a period of years. Despite the apparent success of this approach in childhood cancers, long-term maintenance therapy did not gain popularity in adult oncology. Why?

There are probably several reasons. One reason is that childhood leukemia is among the most chemo-responsive diseases in medicine. As such, there are many active drugs available for treatment and many non-cross-resistant maintenance schedules that can be employed.

A second reason is the relative tolerability of drugs like oral thioguanine or mercaptopurine that are used in chronic maintenance therapy. By contrast adult tumors rarely achieve complete remissions. The number of active drugs has historically been very limited and the tolerance of long-term treatments characteristically poor.

Despite this, there is an appealing rational for maintenance therapy. Once we recognized and incorporated the tenents of apoptosis and programmed cell death into cancer management, we were forced to reconsider many of the principles of older treatment protocols.

Conceptually, maintenance allows for a cytotoxic exposure when the cell enters a “chemosensitive” period in its life cycle.  Cancer cells that are “out surviving” their normal counterparts often do so in a quiescent stage (G0 Gx). In order to capture these cells, drugs must be present in the body when these cells awaken from their dormancy. As we have now achieved increasingly durable remissions in diseases like breast cancer, small cell lung and ovarian, we are confronting patients in long-term complete remission. When you add to this newfound population the availability of comparably mild agents, like the low dose Gemcitabine/Cisplatin doublet, we now have at our disposal active drugs that can be safely continued for long periods of time.

Using laboratory selection to identify first line (induction), second line (consolidation) and finally third line (maintenance) schedules, we can now offer our patients well-tolerated combinations that offer the hope of more durable remissions.

The GOG 178, in which continued taxol dosing provided more durable remission in ovarian cancer, provided the first inklings of this. Unfortunately, taxol is toxic. And the more durable remissions came at an increasingly high price: neuropathy, myelosuppression, alopecia, fatigue and malaise, which greatly limited the utility of this approach. Yet it does not limit its theoretical attractiveness as we continue to develop targeted agents with more selective activity and modified toxicity profiles. We anticipate maintenance therapies will become more widespread.

Based upon our experiences to date, we are successfully using this approach with our patients who achieve good clinical remissions.

You can find more information about our use of maintenance therapy, in Chapter 14 of the book Outliving Cancer.

This blog was originally posted in August 2011.

Cancer Patients: Cure the Curable, Treat the Treatable and Avoid Futile Care

During my interview with Jeff Michaels on the March 28, 5:00 P.M. Fox News, we explored the themes of my current book, Outliving Cancer. One of the points that most interested my interviewer was the appropriate use of our laboratory platform for the selection of therapy. He asked, “Are there some patients for whom there is no cure?” I responded by explaining what it is, that our laboratory test is designed to do: “Cure the curable, treat the treatable, and avoid futile care.” Jeff Michaels stopped me and asked that I might repeat what I had just said. It seemed that my succinct description resonated.

However simple this distillation of our work may seem, I realized it was actually rather profound. After all, we are confronting an escalating crisis in medicine. How do we meet the needs of a growing population of cancer patients with shrinking resources? How do we allocate treatments to those most likely to respond and finally, how do we avoid the misadventures of toxic and ineffective therapies for those destined to fail chemotherapeutic intervention? On every level, laboratory models can assist us. For those patients with early stage breast cancer, ovarian cancer, small cell lung cancer, non-Hodgkin lymphoma and many leukemias, the expectation of a cure is well within our reach. These patients must receive the very best treatments from the start.

The larger population of patients we confront are those with diseases like gastric, colon, non-small cell lung, recurrent breast, recurrent ovarian or sarcoma for whom cures are less likely and effective therapies must be tolerable so that they can provide benefit without undue toxicity. These are the patients for whom cancer can become a “chronic disease.”

Finally, we must all confront patients for whom treatments offer little likelihood of benefit, yet significant risks of toxicity. These heavily pretreated patients, or those who present with refractory malignancies like pancreatic, kidney cancer or melanoma – represent a special subset. Here the role of the physician is to decide that almost Shakespearean question, “To treat or not to treat.”

This is a particularly delicate circumstance as it forces the doctor, the patient and the family to confront the most difficult question of all, “Am I dying?” The answer is “maybe.” Without seeming flip, every patient no matter what diagnosis, has some chance of response to therapy. If we examine the performance characteristic of our laboratory analyses, they consistently double response rates. With this group however a doubling of response rate may still provide a rather low likelihood of meaningful benefit. If the laboratory finds drug resistance in this group, it is a near certainty that the patient will not respond.

However distressing this data may be, it may be comforting to know that the patient has left no stone unturned. For those patients where a treatment appears active, despite their diagnosis or treatment history, then the discussion surrounding tolerance, toxicity and realistic likelihood of benefit can be undertaken intelligently. This is the embodiment of rational therapeutics.

Gee (G719X) Whiz: Novel Mutations and Response to Targeted Therapies

In a recent online forum a patient described her experience using Tarceva as a therapy for an EGFR mutation negative lung cancer. For those of you familiar with the literature you will know that Lynch and Paez both described the sensitizing mutations that allow patients with certain adenocarcinoma to respond beautifully to the small molecule inhibitors.  The majority of these mutations are found in Exon 19 and Exon 21, within the EGFR domain. Response rates for the EGFR-TKI (gefitinib and erlotinib) clearly favor mutation positive patients. Depending upon the study, mutation positive patients have response rates from 53 – 100 percent, generally around 70 percent, while mutation negative response patients have a response rate of 0 – 25 percent, generally about 10 percent.

So why don’t all the mutation positive patients respond and conversely why do some mutation negative patients respond?

The story outlined in this online forum gives some insight. The individual in question carried a rare, and only recently recognized, Exon 18 mutation known as a G719X. This uncommon form of mutation had previously been unknown and few laboratories knew to test for it. Nonetheless, G719X positive patients respond to erlotinib and related agents. Indeed, there may be reason to believe that the more potent irreversible EGFR/HER2 dual inhibitor HKI-272, may be even more selective for this point mutation.

The excellent and durable response described by this individual, would not have been possible had the patient’s first physician followed the rules. That is, had her physician refused to give erlotinib to an (putatively) EGFR mutation negative patient she might well not be here to tell her story. More to the point, her good response (a clinical observation) led to the next level of investigation, namely the identification of this specific EGFR variant

The lessons from this experience are numerous. The first is that cancer biology is complex and, to paraphrase E.O. Wilson, was not put on earth for us to necessarily figure it out. The second, is that molecular biologists can only seek and identify that which they know about apriori.  To wit, if you don’t know about it (G719X) and you don’t have a test for it, and you don’t know to look for it, then it’s a virtual certainty that you aren’t going to find it.

The premise of our work at Rational Therapeutics is that the observation of a biological signal identifies a candidate for therapy whether we understand or recognize the target. Crizotinib was originally developed as a clinical therapy for patients who carried the CMET mutation. Serendipity led to the recognition that the responding subpopulation was actually carrying a heretofore-unrecognized ALK gene rearrangement. Sorafenib was originally evaluated for the treatment of BRAF mutation positive diseases. Yet it was the drug’s cross-reactivity with the VGEF tyrosine kinases that lead to its broad clinical applications. Each of these phenomena represents accidental successes. Were it not for the clinical observation of response in patients, the investigators conducting these trials would have been unlikely to make the discoveries that today provide such good clinical responses in others.

To put it quite simply, these patients and their disease entities educated the molecular biologists.

When we first identified lung cancer as a target for gefitinib, and began to administer the closely related erlotinib to lung cancer patients, neither Lynch nor Paez had identified the sensitizing EGFR mutations. That had absolutely no impact upon the excellent responses that we observed. It didn’t matter why it worked, but that it worked.  While the EGFR story has now been well-described, might we not use functional analytical platforms (functional profiling) to gain insights into the next, and the next generation of drugs and therapies that target pathways like MEK, ERK, SHH, FGFR, PI3K, etc., etc., etc. . . .

Cancer Medicine – A Humbling Experience

In his brilliant 1998 book, Consilience, Edward O. Wilson, notes: “The cost of scientific advance is the humbling recognition that reality was not constructed to be easily grasped by the human mind.”

This sententious point has remained a guiding principle in my thinking about human cancer. It is critically important for scientific investigators to be humble. We are explorers in a field more complex than any man-made system. We must be instructed by biology – as biological events will always find a way to outsmart our best efforts to explain them.

I was reminded of E.O. Wilson, when a colleague forwarded a recent publication from Molecular Cancer Therapy, “Molecular Profiling of Patient with Colorectal Cancer and Matched Targeted Therapy in Phase I Clinical Trials,” Dienstmann, R. et al MOL CANCER THER Sept 2012. The study conducted by the Molecular Therapeutics Research Unit at Vall d’Hebron Institute of Oncology in Barcelona, Spain, evaluated 254 patients for evidence of specific genetic aberrations. Their genomic analyses included, KRAS, BRAF, PIK3CA, PTEN, and pMET. Patients were then provided clinical therapy trials that matched the targeted agents (drugs with activity against the specific mutation) with their individual mutation profiles

In all, 68 patients received treatment constituting a total of 82 different molecularly targeted therapies. The clinical response rate for this population of patients who received molecularly selected therapy was 1.2%. No that isn’t a typo; it was really one point two percent.

While I applaud the scientific concept of this trial and must admit that I might have expected a somewhat higher response rate, I am not surprised by the result. In keeping with E. O. Wilson’s quote, human biology is not a puzzle designed to be solved by humans; it is instead the complex product of a billion years of evolution. Rather than demanding that cancer patients respond to those treatments we have selected for them based on genetic information, we should be instructed by the tumor’s behavior of each patient and use those insights to select amongst active drugs, whatever genetic elements they may have been originally designed to target. In my lectures, I describe this approach as the wisdom of whole cell experimental models.

I am continually humbled by the complexity of human tumor biology and delighted to have the insights that my patient’s cancer cells provide through the functional profile created by our EVA-PCD assay. Not only do I gain exciting scientific knowledge, but my patients have very good responses to the drugs we select. Not a bad day’s work.

Outliving Cancer: Surviving Even the Deadliest Forms of Cancer

My book of the same title (Outliving Cancer, Basic Health 2013) is an exploration of cancer biology through the lens of individual patients.

The conceptual framework within which my laboratory operates, reflects the basic premise that cancer doesn’t grow too much it dies too little. Thus, effective cancer therapy (regardless of contemporary wisdom) provides benefit only when the drugs induce cell death. While the forms of cell death may vary from necrotic, to apoptotic, autophagic and others, it is, in the end, the death of the cell that heralds a successful outcome.

We, along with a small group of collaborators, have pioneered the concept of individualized cancer care using each patient’s tumor as the study model. Fresh biopsies exposed to chemotherapies and signal transduction inhibitors, live or die depending upon their relative sensitivity to the drugs in question.

The simple elegance of our platform has provided immense insight into cancer biology, insights we describe in the book, which may ultimately lead to a greater understanding of all human diseases.

Having successfully applied this approach in many diseases, we have published findings in leukemia, breast, ovarian, and most recently, in lung cancers. We are now very excited by observations in one of the most difficult cancers – pancreatic. Ongoing work in this disease will be the subject of upcoming clinical trials.

One patient with pancreatic cancer comes to mind. Steve Lockwood presented to medical attention in the Spring of 2010 with weight loss, abdominal pain, and unrelenting low back pain. He was seen by a local medical oncologist after a CT scan revealed a large mass in the pancreas, extensive liver metastases and disease throughout the abdomen. He then sought the opinion of UCLA and the City of Hope.  Neither institution could offer any solutions. Luckily his wife, a nurse, had heard about our work and brought him to Rational Therapeutics.

His tumor markers were doubling every week. He couldn’t eat and required daily intravenous hydration, as well as high dose narcotics to get through each day. He was deteriorating so rapidly that I had concerns that he might be too ill for me to help. We decided to conduct an open liver biopsy. As his tumor markers, CA19.9, climbed into the multiple thousands, we found a three-drug combination to be the most active for his tumor.

Within a week, the pain began to subside. After two weeks, it was demonstrably better. By the time we began treatment cycle two, he had begun to gain weight and came off pain medications entirely.

Two cycles later, his tumor markers were normal and his PET CT remarkably improved. An additional cycle later, his PET CT was normal.

While there are many difficult cancers, metastatic pancreatic cancer figures among the worst. The fact that we could find a treatment was cause for celebration. The fact that Steven now remains in remission, after three years, is nothing short of a miracle. As I have written before, there are two kinds of cancer patients: those we can treat and those we can’t. Steve Lockwood turned out to be one of those patients we could.

Like Niebuhr’s Serenity prayer, oncologists need the serenity to accept the cancers they cannot treat, the courage to treat those that they can, and the wisdom to know the difference. It is our use of laboratory assays to select treatments that provides us with that particular form of wisdom.

HER2 Two

I met a charming patient in my office this week. A gentleman with advanced gastric cancer. Upon further examination of his cancer, the adenocarcinoma cells were found to be strongly positive for human epidermal growth factor receptor 2 (HER2).

Many of my readers are familiar with this surface receptor, a member of the epidermal growth factor family. It’s discovery, and the subsequent development of treatments directed toward this target, are well described in the literature. While most people are familiar with this protein in breast cancer, it is only in the last several years that we have recognized the importance of HER2 expression in diseases like gastric and esophageal cancer.

Discussing the implications with the patient and his sons, I realized that this attractive therapeutic target might not be available for use due to the patient’s underlying heart disease. One of the toxicities of HER2-targeted therapies is congestive heart failure. As I pondered the dilemma, I was reminded of one of my patients from 16 years earlier.

At that time, a strapping 69-year-old woman arrived in my office with a large, high-grade breast cancer and 13 positive lymph nodes. She was also HER2 positive. The problem was that in 1997, the drug trastuzumab was not widely available and never (not ever), used in the adjuvant setting. With that as a backdrop, I treated the patient based on laboratory analysis using the best combinations I could identify. Now, 16 years later, still free of disease, she represents a rare success for someone afflicted with such aggressive (and yes, HER2-positive) disease.

The reason this former patient came to mind was that her excellent success 16 years earlier had not required the use of HER2-directed therapy. Ingrid Ottesen had done very well using assay-directed therapy chemotherapy without the addition of trastuzumab.  All we needed for Ingrid was the best use of available drugs. Despite the possible contraindication for trastuzumab in this gentleman’s case, we can still hope for a good outcome if we use the available drugs that best meet his need. After all, it worked perfectly for Ingrid.

You can read about Ingrid in Chapter 14 in Outliving Cancer, to be released later this month.

Chemosensitivity Testing Captures Attention of “Nature Biotechnology”

An interesting editorial appeared in the February 2013 issue of Nature Biotechnology titled “Dishing out cancer treatment.” The lead line reads, “Despite their limitations, in-vitro assays are a simple means for assessing the drug sensitivity of a patient’s cancer . . . we think assays deserve a second look.”

The author describes the unequivocal appeal of laboratory analyses that are capable of selecting drugs and combinations for individual patients. At a time when 100’s of new drugs are in development, drug discovery platforms that can mimic human tumor response in the laboratory are becoming increasingly attractive to patients and the pharmaceutical industry. While the author, rooted in contemporary molecular biology, examines the field through the lens of genomic, transcriptomic, proteomic and metabolomic profiling, he recognizes that these analyte-based approaches cannot capture the tumor in its microenvironment, yet we now recognize that these micro-environmental influences are critical to accurate response prediction.

As one reads this piece, it is instructive to remember that no other platform can examine the dynamic interaction between cells and their microenvironment. No other platform can examine drug synergy. And no other platform can examine drug sequence.

It is these complexities however, that will guide the next generation of drug tests and ultimately the process of drug discovery. Even the most ardent adherents to genomic profiling must ultimately recognize that genotype does not equal phenotype. Yet, it is the tumor phenotype that we must study.

I am gratified that the editors of so august a journal as Nature Biotechnology have taken the time to reexamine this important field. Perhaps, if our most scientific colleagues are beginning to recognize the importance of functional analyses, it may be only a matter of time before the clinical oncology community follows suit.

The editor’s final line is poignant, “After years spent on the sidelines, perhaps in-vitro screening methods deserve another look.” We couldn’t agree more.

Cancer Explained – The Role of Cell Death

Following a recent blog, I received an inquiry from one of our readers. The individual asked whether I could better explain my oft repeated statement that “cancer doesn’t grow too much, it dies too little.” The questioner was puzzled by my assertion that chemotherapy drugs acted to stop cells from growing, while she had come to believe that this was synonymous with killing them. This dichotomy is at the crux of our modern understanding of cancer.

In response, I would like to examine the very basis of what is known as carcinogenesis, the process by which cancer comes to exist.

For more than a century, scientists believed that cancer cells were growing more rapidly than normal cells. They based this on serial measurements of patient’s tumors, which revealed that tumor dimensions increased. A small lump in the breast measuring one-half inch in diameter would be found six months later to be one inch in diameter. And six months after that it was two inches in diameter. This was growth, plain and simple, and so it was reasoned that cancer cells must be growing too much. As such, cancer therapies, per force of necessity, would need to stop cancer cells from growing if they were to work at all.

And then, in 1972, a paper was published in the British Journal of Cancer that described the phenomenon of apoptosis, a form of programmed cell death. Although it would be almost a decade before cancer researchers fully grasped the implications of this paper, it represented a sea change in our understanding of human tumor biology.

Let’s use the example of a simple mathematical equation. Every child would recognize the principles of the following formula:
Tumor mass = growth rate – death rate
This simple equation represents the principle of modern cancer biology. Where cancer researchers went wrong was that they mistakenly posited that the only way a tumor mass could increase was through an increase in the growth rate. However, as any child will tell you, a negative of a negative is a positive. That is, at a given growth rate, the tumor mass can also increase if you reduce the death rate. Thus, the “growth” so obvious to earlier investigators did not reflect an increase in proliferation but instead a decrease in cell attrition. Cancer didn’t grow too much it died too little, but the end result was exactly the same.

It should now be abundantly clear exactly why chemotherapy drugs, designed to stop cells from growing, didn’t work. Yes, the drugs stopped cells from growing, and yes any population of “growing cells” would suffer the effect. But they didn’t cure cancers because the cancers weren’t growing particularly fast. Indeed, the fact that chemotherapy works at all is almost an accident. Contrary to our long held belief that we were inhibiting cell proliferation, chemotherapy drugs designed to damage DNA and disrupt mitosis, were actually working (when they did at all) by forcing the cells to take inventory and decide whether they could continue to survive. If the injury were too extreme, the cells would commit suicide through the process of cell death. If the cells were not severely damaged or could repair the damage, then they carried on to fight another day. None of this, however, had anything to do with cell growth.

Chemosensitivity Testing: Lessons Learned

Like all physicians and scientists engaged in the study of cancer biology and cancer treatment, I had accepted that cancer was a disease of abnormal cell growth. I remember reading the lead article in the New England Journal of Medicine (NEJM) that described the clonogenic assay (Salmon, S. E., Hamburger, A. W., Soehnlen, B. S., et al. 1978. Quantitation of differential sensitivity of human tumor stem cells to anticancer drugs. N Engl J Med 298:1321–1327).

I sat in a laboratory at Georgetown University reading about a lab test that could accurately predict the outcome of cancer patients, without first having to give patients toxic drugs. It seemed so logical, so elegant, so inherently attractive. Sitting there as a medical student, far removed from my formal cancer training, I thought to myself, this is a direction that I would like to pursue.

But I was only a first year student and there were miles to go before I would treat cancer patients. Nonetheless, selecting drugs based on a laboratory assay was something I definitely wanted to do. At the time I had no idea just how difficult that could prove to be.

After medical school I found myself in California. There I met an investigator from the National Cancer Institute who had recently joined the faculty at the University of California, Irvine. He too had read the NEJM paper. Being several years ahead of me in training he had applied the clonogenic technique at his laboratory at the National Cancer Institute. Upon his arrival in California, he had continued his work with the clonogenic assay.

All was going along swimmingly until the NEJM published their report documenting the results of five years experience with the clonogenic assay.  It wasn’t a good report card. In fact the clonogenic assay got an “F.”

Despite the enthusiastic reception that the assay had previously enjoyed, the hundreds of investigators around the world who had adopted it and the indefatigable defense of its merits by leading scientists, it seemed that something was very wrong with the clonogenic assay and I desperately needed to know what that was.

It so happens that in parallel to clonogenic assays, my colleague was working on a simpler, faster way to measure drug effects. Using the appearance of cells under the microscope and their staining characteristics, one could skip the weeks of growth in tissue culture and jump right to the finish line. The simple question to be answered was: Did the drugs and combinations kill cancer cells in the test tube? And if they did kill cancer cells in the test tube, would those drugs work in the patient? The answer was, “YES!”

Despite the clonogenic assay’s supporters, it turned out that killing cancer cells outright in the test tube was a much, much better way to predict patient’s outcomes. It would be years before I understood the depth of this seemingly simple observation and the historical implications it would have for cancer therapy.

In Chapter 7 of my soon-to-be-released book, Outliving Cancer I examine the impact of programmed cell death on human biology.