Table of ContentI. Introduction |
Normal cells only proliferate when stimulated by an appropriate growth factor and regulated by inhibitory signals. Cancer cells become increasingly independent of the start and stop signals. The net result is characteristic uncontrolled growth of cancer cells which behave as autonomous individuals rather than as integrated components of the body. They are also characterized by their ability to invade surrounding tissues and metastasize throughout the body. The movement of cancer cells are not inhibited by contact with other cells. By now 200 forms of cancer are known including leukemias and lymphomas and among them, some are common, such as breast, bowel, prostate and lung cancer, some types are uncommon and some are rare. Rare cancer starts in an unusual place in the body or an unusual type and needs special treatment. According to a recent analysis by European Medicines Agency (EMA) rare cancers are identified as those with an incidence of less than six per 100 000 persons per year. Less common cancers have between six and 12 incidences per year per 100 000 population. According to the Radboud Institute for Molecular Life Sciences (RIMLS), rare cancers represent 22% of all cancers cases.
Till now following seven types of rare cancers have been identified –
- Head and neck cancer – They usually begin in the squamous cells that line the mucosal surfaces inside the head and neck (e.g. mouth, the nose and throat) and categorized by the area where they begin, e.g. the oral cavity, pharynx, larynx, paranasal sinuses and nasal cavity and salivary glands.
- Sarcoma – It arises in the connective tissue of the body, i.e. fat, blood vessels, nerves, bones, muscles, deep skin tissues, and cartilage.
- Thyroid cancer – It affects the thyroid gland, a small gland at the base of the neck that produces hormones. Symptoms include a painless lump or swelling in the front of the neck, swollen glands in the neck, unexplained hoarseness, a lingering sore throat and difficulty swallowing.
- Neuroendocrine cancer – This cancer begins in the neuroendocrine system, which is the hormone-producing cells of the body. Neuroendocrine cells are found in organs like the lungs and gastrointestinal tract, including the stomach and intestines.
- Brain tumors – These are high-grade tumors that either primary or secondary depending on the location. Tumors starting in the brain are primary tumours whereas spread into the brain from elsewhere are secondary tumors. Symptoms include severe, persistent headaches, seizures, persistent nausea, vomiting and drowsiness, mental or behavioral changes, vision or speech problems, progressive weakness or paralysis on one side of the body.
- Lymphoma – It occurs when lymphocytes (white blood cells) divide in an abnormal way or don’t die when they should. Abnormal lymphocytes can collect in lymph nodes, often in armpits, neck or groin, almost any part of the body. Symptoms will depend on where the lymphoma starts and what parts of the body is affected.
- Pediatric (childhood) cancer – The most common cancers in children include leukemia, lymphoma, and brain cancer. Things that cause cancer in adults (e.g. smoking or exposure to environmental toxins) are usually not the same as in children. In most cases, childhood cancers come from random mutations in the genes of growing cells, which means that there’s often no effective way to prevent them.
Patients with rare cancer have a 15% poorer overall survival rate than patients with common cancer. This can be attributed to the fact that the level of prognosis achieved for common cancer has not been achieved in rare cancers. Numerous reasons can be cited for the same. Late or incorrect diagnosis due to limited awareness by patients and general practitioners, Lack of access to appropriate therapies and clinical expertise, Relatively small number of clinical trials due to the small number of patients, Market limitations, Few available registries, and tissue banks and lastly low on the political agenda of the international community.
However, we can learn a lot from research on rare diseases and rare cancers. For example, Fanconi anemia research in 2010 has provided insights into disease mechanisms of bone marrow failure, cancer, and the resistance to chemotherapy 1. A rare pediatric cancer, Wilms’ tumor, a has been referred to as a “model” for understanding the genetics, epigenetics, and molecular biology of pediatric cancers and cancers generally 2. IMATINIB for the treatment of chronic myeloid leukemia (CML), seminoma, and gastrointestinal stromal tumor (GIST) has set “a new paradigm for the treatment of cancer with molecularly targeted therapies” 3. It has also prompted a lot of additional research on tyrosine kinase inhibitors 4. Researchers at the U.S. National Institutes of Health (NIH), who analysed the tissue of patients affected by paraganglioma, a rare endocrine tumor, recently discovered a genetic mutation that appears to increase the production of red blood cells in tumors. Such type of findings may have an impact on the understanding and treatment of several other cancers. A large share of research funding goes into the most common cancers (breast, colon, lung, and prostate) and also more patients are represented in a clinical trial for them. It would, therefore, be rational to anticipate that the most significant therapeutic advances are made in common cancers. However, a recent study reports that novel cancer treatments have their most striking effects in rare cancers, suggesting that “only by stratifying the common tumors, especially when using targeted agents, into the molecular subsets of diseases that compose them are we likely to achieve a substantial effect in these disorders.” 5 To improve diagnosis, treatment and, outcome of rare cancers, translational research, clinical studies, and population-based research are essential. This can be achieved only by collaboration between (inter) national partners and patient advocacy groups.
References
- D’Andrea AD. Susceptibility pathways in Fanconi’s anemia and breast cancer. N Engl J Med.2010 May 20;362(20):1909-19. doi: 10.1056/NEJMra0809889.
- Feinberg AP1, Williams BR. Wilms’ tumor as a model for cancer biology. Methods Mol Biol.2003;222:239-48.
- Eck MJ1, Manley PW. The interplay of structural information and functional studies in kinase drug design: insights from BCR-Abl. Curr Opin Cell Biol.2009 Apr;21(2):288-95.
- Müller BA Imatinib and its successors–how modern chemistry has changed drug development. Curr Pharm Des.2009;15(2):120-33.
- Braiteh F, Kurzrock R. Uncommon tumors and exceptional therapies: paradox or paradigm? Mol Cancer Ther.2007 Apr;6(4):1175-9.