oa Editorial [Hot topic: Developing New Anti-Cancer Drugs (Guest Editor: Ricardo De Souza Pereira)]

Cancer is a class of diseases with an uncontrolled growth of cells (usually derived from a single cell) beyond the normal limits. The growths often invade adjacent tissues and, sometimes, migrate to other locations of the body (metastasis) via lymph or blood, and promote the growth of new blood vessels from which the cells derive nutrients. Cancerous (malignant) cells can develop from any tissue within the body. These malignant properties of cancers differentiate them from benign tumors, which are self-limited, and do not invade or metastasize [1, 2]. TYPES OF CANCER Cancerous tissues (malignancies) can be divided into those of the blood and blood-forming tissues and cells of the immune system (leukemias and lymphomas) and “solid” tumors, often termed cancer. Cancers can be carcinomas (tumor derived from epithelial tissue) or sarcomas (tumor arising from cells that form muscles and connective tissue) [2]. COSTS OF CANCER The National Institutes of Health in United States estimated overall costs of cancer in 2010 at $263.8 billion: $102.8 billion for direct medical costs (total of all health expenditures); $20.9 billion for indirect morbidity costs (cost of lost productivity due to illness); and $140.1 billion for indirect mortality costs (cost of lost productivity due to premature death) [3, 4]. STATISTICS One in eight deaths worldwide are due to cancer, it is the second and third leading cause of death in economically developed and developing countries, respectively. Cancer affects 1 in 3 of us in our lifetime. It also affects people at all ages with the risk for most types increasing with age. Over 70% of cancers happen to people who are over the age of 60 [5]. Lung cancer, the most common cause of cancer-related death in men and women, is responsible for 1.3 million deaths worldwide annually [1]. In 2007, cancer caused about 13% of all human deaths (7.6 million) in the world. In 2010, according to National Institutes of Health, about 569,490 Americans were expected to die of cancer, more than 1,500 people a day. Cancer is the second most common cause of death in the US, exceeded only by heart disease. In the US, cancer accounts for nearly 1 of every 4 deaths [1, 3, 4, 6-9]. CAUSES OF CANCER Cancer is caused by both external and internal factors. It is primarily an environmental disease with 90-95% of cases due to lifestyle and environmental factors and 5-10% due to genetics [10]. Common environmental factors leading to cancer death include: tobacco (25-30%), diet and obesity (30-35%), infections (15-20%), radiation, stress, lack of physical activity, environmental pollutants [10]. These environmental factors cause abnormalities in the genetic material of cells [11]. May be another important cause for this disease is the post-traumatic stress disorder (PTSD) which is an anxiety disorder associated with serious traumatic events (death of a beloved person, robbery, bankruptcy, financial lost, rape, assault, kidnapping, fighting in war, imprisonment, natural catastrophes and car, bus, train, airplane accidents, etc.) and is characterized by symptoms such as survivor guilt, reliving the trauma in dreams, numbness, lack of involvement with reality or recurrent thoughts and images, absence of optimism, and higher neuroticism [12, 13]. Studies demonstrated that patients with higher scores on the neuroticism test tended to have lower immune system responses [14, 15]. When the immune mechanism is slowed down or made ineffective, the malignant cells develop [16, 17]. Some studies of cancer survival have found significant associations between lower optimism and higher neuroticism with shorter survival. More mental distress and fatigue and poorer quality of life is significantly associated with higher neuroticism and lower optimism at cancer screening, diagnosis and primary treatment, short- and long-term follow-up and towards the end of life. Neuroticism is a strong predictor of PTSD triggered by cancer as a life-threatening experience eventually leading to negative personality changes [18, 19]. Recently, a study was conducted to determine the prevalence of PTSD in parents of children with cancer. The prevalence of PTSD was 34.6%. The statistically significant tendency to develop PTSD were found in the female gender, better educational status, death of a loved one, previous history of psychiatric disorder, having a child with poorer prognosis, and the presence of radiotherapy in child's treatment [20, 21]. . . . . .