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A gamble with bacteria
Radical attempt: Shyamal Sarkar (left) and Chandan Dasgupta (Picture by Sanat K Sinha)

It was a gamble for the patient, his hopes for survival seemed to be hinging on a vial containing about 50 million bacteria. The man was in his mid-50s, a former smoker, now ravaged by cancer in his mouth, throat and lymph nodes. He was about to receive the standard chemotherapy and radiotherapy when his doctors in Calcutta asked him whether he’d like to gamble with a bacterium.

It’s called Mycobacterium w, an organism known to boost the immune system against leprosy and, as some scientists believe, even against tuberculosis. The doctors, Shyamal Sarkar and Chandan Dasgupta, at the Calcutta Medical College asked him whether he would agree to accept a weekly injection of Mycobacterium w, in addition to the standard anti-cancer treatment.

The Calcutta doctors wanted to pit the bacteria as extra therapy against advanced cancer. In all, 30 patients with cancers in the head and neck agreed to take the injections. Over the past year, doctors in Ahmedabad and Lucknow have also offered Mycobacterium w to patients with advanced cancer, including some in the terminal stages of the disease. Now, all three medical teams have reported that the bacteria did indeed make a difference. Their findings were accepted as abstracts at the annual meeting of the American Society of Clinical Oncology (ASCO) in the US last month. “It is too early to say whether the bacteria will influence survival in cancer, but it does improve the quality of life of the patients,” said Dr Sarkar, professor of radiotherapy at the Calcutta Medical College.

Mycobacterium w was developed as a candidate vaccine against leprosy by scientists at the National Institute of Immunology (NII) in New Delhi during the 1980s. The organism belongs to the family of Mycobacteria that also contain the germs that cause leprosy and tuberculosis. Studies at the NII showed that killed Mycobacterium w could lead to a faster cure of leprosy when added to the conventional anti-leprosy treatment. Laboratory experiments on its likely mechanisms of action showed that Mycobacterium w functioned as an immunomodular ' a substance that could strengthen the human immune system.

The NII transferred the technology for Mycobacterium w to Cadila Pharmaceuticals in 1998 which has been investigating its potential for immunomodulation in other diseases. Researchers have known for long that the development of cancer is preceded by malfunctions in the immune system. The human immune system has cells trained to recognise and kill renegade cells that threaten to seed tumours. The formation of cancer implies that this natural defence system has broken down. The use of Mycobacterium w in cancer patients is an attempt to explore whether the immunomodulation by the bacteria can influence the progress of cancer.

“The results so far are encouraging,” says Dr Arun Maseeh, vice-president, medical, Cadila Pharmaceuticals, the company that produces Mycobacterium w. In Calcutta, Sarkar and Dasgupta divided 60 patients into two groups ' 30 who got the standard chemotherapy and radiotherapy, and the rest who received the bacteria as additional therapy with standard treatment. “A major concern during radiotherapy is the severe toxic reaction on the skin and throat inflammation,” says Dasgupta, now a resident medical officer at the Institute of Postgraduate Medical Education and Research in Calcutta. The inflammation prevents people from even swallowing food. The skin reactions sometimes force researchers to temporarily stop the radiotherapy until the toxicity subsides.

In their paper published in a supplement of this month’s issue of the Journal of Clinical Oncology, the Calcutta doctors have reported that all the 30 patients who received the weekly injections of Mycobacterium w were able to complete treatment. However, 12 out of the other 30 patients who received only standard treatment developed such high levels of toxicity that their treatment had to be interrupted. This led to a longer treatment time. “The addition of the bacteria to treatment allowed the patients to tolerate chemotherapy and radiotherapy better,” says Sarkar, who concedes that how exactly the bacteria brings about that effect is unknown.

The study in Ahmedabad investigated the effect of Mycobacterium w on a group of 100 patients with cancers so advanced that their doctors had given them less than two months to live. All available standard treatment had been exhausted and the disease had been declared as incurable when the doctors at the Gujarat Cancer Research Institute offered them Mycobacterium w. Among the 100 patients, doctors could follow up only 77. In their abstract, the GCRI doctors said that 27 out of the 77 patients had improvement in symptoms. They had less pain and could do with reduced doses of opioid analgesics which are traditionally used to combat the intense pain in cancer.

The researchers in Lucknow also offered Mycobacterium w as additional therapy to 61 patients with head and neck cancers and compared their response to treatment with 30 patients who received only standard treatment. The patients who received the bacteria reported lower side effects than those who received conventional therapy.

The abstracts from India have attracted the attention of doctors in the US. If the research is authenticated through larger studies, Mycobacterium w could be India’s contribution to efforts to combat cancer with immunomodulation.

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