Metronomic Chemotherapy-An Arsenal!
(Image source: Pixabay.com)
“We have assisted
with all plausible prevalent medical facilities to the cancer patient. There is
nothing more we can do. We are sorry.”
Some of us have heard these frightful
words from able bodied, world-class oncologists who hand over our loved ones
into the hands of the Almighty and pray for a least pained exit. Terminally ill
cancer patients (adults or children) have little choice of medicines which can aid
to prolong their lifetime as they become resistant to the treatment engaged.
We spend billions of money to
safe guard fragile boundaries of our countries; fund domestic and international
acts of terror; lobby for the acceptance of genetically modified food and
finance trips to Mars. However, we need a lot more of financial investments to
attain victory in our war against cancer. Cancer is a disease of unregulated
mass of cells wherein the natural cycle of cell death is compromised leading to
the formation of tumour. A neoplastic growth may be benign, premalignant or
malignant. An identified tumour may be removed through surgery followed by
various rounds of radiation and chemotherapy to eradicate remaining tumour
cells. On the other hand in numerous cases on successive rounds of therapy the
tumour aggressively metastasize into other organs ultimately causing demise.
The bygone decades has seen many
scientists who have challenged their scientific acumen to comprehend biological
mechanisms undertaken by cancerous cells in evading cell death and promote
multi drug resistance. Cancer patients often need an amendment of chemo drugs
due to the phenomena of acquired chemo resistance. Present treatment modalities
used often act upon the non-cancerous cells and actively dividing tumour cells
alike. However, due to an inefficient removal of circulating tumour cells most
often it results in reappearance of tumour and relapse of the disease. Hence,
the need of the hour is a combinatorial method to prolong life span of the
patient.
The traditional chemotherapy treatment
regimens use chemotherapeutic drugs which act against epithelial growth factor
receptors and vascular epidermal growth factor receptors in order to prevent
proliferation of circulating cancer cells and metastasis via inactivation of
cellular signalling pathways. Both healthy cells and tumour cells are killed
indiscriminately. In this mode of chemotherapy clinicians administer high doses
of chemo drugs for a limited number of cycles onto patients: to hinder acquired
chemo resistance against the drug and harming the organs. Patients’ are
subjected to a drug-free interval between successive cycles of chemotherapy
which results in revival of healthy and cancer cells equally. Numerous
retrospective analyses have revealed that chemotherapy medicines may limit growth
of tumour volume but it may also promote the assembly of endothelial cells to
form blood vessels in the tumour (angiogenesis) and metastasis. Thus, these
regimens haven’t been fool proof and the
need of the hour is for an alternative
therapeutic regimen.
A prominent alternative therapy which
is gaining recognition to mitigate chemo resistance is metronomic chemotherapy. The concept of metronomic strategy was
first tested by Dr. Timothy Browder in Harvard Medical School, USA. Hanahan and his colleagues from the University
of California, San Francisco has defined metronomic chemotherapy: “chronic
administration of chemo therapeutic agents at relatively low, minimally toxic
doses, and with no prolonged drug-free breaks”. This method uses the same drugs
as in the traditional chemotherapy but in different combinations and in low
doses on a regular basis. Therefore, consistent short exposures of the medicine
hamper growth of endothelial cells: new blood vessels are not formed in the
tumour. Consequently angiogenesis is hampered. In turn this strategy induces hypoxia
and starves tumour cells off nutrients. Metronomic chemotherapy is a multi
targeted therapy: negates migration and proliferation of cancerous cells,
induces apoptosis, increases endogenous level of anti-angiogenic factors and enhances
anticancer immune response in the human body.
The propensity for critical scrutiny
of this strategy is underway through numerous retrospective analyses of clinical
trials which have revealed a mixed reaction. For instance, research has
revealed that adults prescribed to palliative care that are pre-treated with
chemotherapy and are at an advanced stage of colorectal cancer, gastric cancer,
vascular tumours have responded to metronomic chemotherapy successfully. Also,
children suffering from medulloblastoma have shown a good response to
metronomic regimen of temozolomide with radiotherapy. Nonetheless, metronomic
chemotherapy in some glioblastoma and advanced stage renal cancer patients’ did
not significantly enhance their chances of survival.
The high dose of medicines when
injected into patients causes numerous grave side effects due to loss of
healthy cells. Repetitive low dose of chemotherapy may cause side effects like nausea,
anaemia, neutropenia, fatigue and leucopoenia to dwindle. Metronomic chemotherapy
is usually given to patients who cannot bear high doses of chemotherapy. It may
be an alternative mode of treatment for patients who have acquired chemo
resistance and are prescribed to palliative care. Metronomic chemotherapy may
grant that each cancer victim desires: TIME.
Numerous hospitals like the Oasis
of Hope Hospital and Northridge Hospital Medical Centre in the United States of
America are trying to prolong the lives of cancer victims by administering
metronomic chemotherapy. In India, team lead by Dr. S. D. Banavali at Tata
Memorial Hospital, Department of Medical Oncology has assessed the feasibility
of using metronomic chemotherapy for palliation in oral cancer. Their research
indicates a clinical benefit rate of 66.67% and larger clinical trials are
needed to substantiate further in other cancers.
Metronomic chemotherapy is a less
traversed route to combat cancer. Consequently, ample clinical trials in
different ethnic populations are warranted before it may be globally claimed as
a gold standard parapet against cancer. Nevertheless, for those friends and
families who are in a dire-famine like situation looking for alternative modes
of treatment to keep their loved one alive- metronomic chemotherapy may be an option
worth exploring.