The journey of curing the most dreaded of all diseases in children spanning over five decades encompasses the greatest achievement in the field of medical research. Acute Lymphoblastic Leukemia (ALL) is the most common cancer in children and was associated with 100 per cent mortality till the 1970s. However, a group of German researchers formed a consortium in the early seventies which was later known as the Berlin-Frankfurt-Munster (BFM) trials. They first introduced the concept of using several anti-cancer agents in different combinations at short and repeated intervals. Due to this consorted effort from this dedicated group of clinical researchers, about 40 per cent of those treated in these trials in the mid-70s were alive for five more years — an achievement which was unfathomable in those times. The achievement occured owing to profound attempts and a deeper understanding of the factors which can predict the outcome.

Blood cancer cannot be staged like solid organ cancers. They already exist in every nook and corner of the body where the blood flows. Whilst being omnipresent, it is also associated with invariable and rapid death, the same property led in due course for blood cancers, particularly ALL, to be the most curable of all cancers. Another three decades of clinical trials have now made ALL curable in 80-90 per cent of all affected children.

Why should some children with ALL be cured with simple combination of drugs, whereas others remain incurable with repeated assaults on leukemia with high doses of the best drugs known to date? This led the researchers to study each cell from these children and discover a whole gamut of genetic changes inside these leukemia cells. Some of these changes have made some of these leukemia susceptible to certain drugs and others resistant. This also allowed the doctors to target the key genetic events with tailored molecules which could stop the uncontrolled growth of cancer cells. It’s worth noting that these path-breaking discoveries in the field of medicine have been carried out mostly by chemists, biochemists, biotechnologists and engineers. While clinicians execute and assess the efficacy of these findings, the brain behind these achievements often remain unnoticed in the public eye.

Yet, the fact remains that the last cancer cell cannot be eliminated by any number of drugs, chemicals or radiation without complete destruction of the human body. The question remains is how then so many children are cured with drugs alone. Human body is taught to fight against any cell that is not its own. The body produces and trains these soldiers from birth — they are called lymphocytes. This training comes useful in fighting against infections since birth. When any of our own cells turn rogue or cancerous, they lose their ‘own-ness’ and the lymphocytes destroy them. It is only when the lymphocytes fail, leukemia develops. And similarly, when the leukemia is reduced to its final shreds (a million cells still), it is up to the body’s own soldier lymphocytes to exterminate them forever. Failure to do so results in the return of the leukemia, often in a deadlier avatar. When we do not have something, we must borrow. So, we borrow lymphocytes from someone close to destroy the cancer.

To take some, one must forego some as well. If we want to borrow a new bunch of lymphocytes to fight leukemia, we must let go our own lymphocytes and the cells that produce them. These cells are blood stem cells. With drugs or radiation, the existing blood stem cells and the lymphocytes are destroyed in part and replaced by blood stem cells and lymphocytes from healthy donors. This process is called Blood and Marrow Cell transplantation (BMT).