An experimental treatment ‘cures’ leukemia. But, it leaves one crucial question unanswered about cancer treatment

Doug Olson calls himself ‘a lucky man’. In 1996, he was diagnosed with lymphocytic leukemia at the age of 49, and after six years, his survival chances were slim. When rounds of chemo did not help, and his cancer came back aggressively each time, his then oncologist, Dr. David Porter (University of Pennsylvania) suggested something rather radical.

Porter was part of a cancer clinical trial on CAR T Cell therapy at the time and Olsen – whom he had asked to participate – became the 2nd of the three patients to receive this new and innovative treatment in 2010. Twelve years down the line, Olsen is alive and his cancer has been ‘cured’.

The word ‘cure’ isn’t used lightly in cancer research. However, in this particular case it was discovered that the CAR T Cell therapy that Olsen received did just that.


What Is CAR T Cell Therapy?
In simple terms, CAR T Cell therapy involves genetically engineering T cells, white blood cells to fight cancer, outside the patient’s body and then infusing their blood with it so that they can kill the cancerous cells.

In Olsen’s case, the cancer involved the B cells, therefore, the genetically engineered T cells, in order to eradicate cancer had to destroy all B Cells. Unfortunately, B Cells are also body’s antibody-body forming cells and when destroyed, they leave the patient without the required antibodies, so he has to receive immunoglobulin infusions to maintain his antibody level.

The therapy has proven to be useful in several blood cancer cases, and in patients with acute leukemia. However, with chronic lymphocytic leukemia (like Olsen’s), its success rate is lower. Relapses are common in such cancer post CAR T Cell therapy.

Unanswered Question
What happens to the modified T cells in the cured patients is a question that has been repeatedly raised about this study.

A subset of T Cells known as CD8 cells actually do the cancer killing in patients who receive CAR T Cell therapy. To help them, CD4 cells, another type of T Cells, join forces.

Initially, in a patient who has cancer, CD8 is in ‘kill’ mode and can kill from three and a half to seven pounds of cancerous cells, according to a New York Times report.

However, after their killing job is done, they continue to live in the bloodstream of the patient and convert to CD4 cells. Therefore, in the recovery stage of the patient, CD4 cells turn into assassins, and have the capacity to kill B Cells.

While the researchers propound that they stay on as CD4 cells to keep cancer cells at bay, it begs the question, can CD4 cells stay on in the blood if they have no enemy to fight, and cancer is completely gone?

The answer to that question is slightly ambiguous at this point. Dr. Carl June, the principal investigator for the CAR T Cell trial at Pennsylvania told NYT, “Perhaps they (cancerous cells) are still there in tiny quantities and emerging, only to be knocked back by CD4 cells, ‘like whack-a-mole,’ …the leukemia is gone, but they (CD4) stay on the job,” he added.

Shortcomings
According to NYT, the CAR T treatment is likely to cause severe side-effects among patients who receive this therapy, and in some cases it leads to coma, and even death.

Also, the treatment has not shown any effect on solid tumors of breast or prostate.