Cancer: treating and understanding the disease. Clinical Nutrition 365 Rachel Crawford

Transcription

1 Cancer: treating and understanding the disease Clinical Nutrition 365 Rachel Crawford 0

2 INTRODUCTION Cancer has been a source of much research and concern for many years. Over time, researchers have come to know a great deal more about the disease itself, including the incidence and prevalence, etiology and risk factors, pathophysiology, how to medically diagnose it, current medical therapies, nutrition assessment, medical nutrition therapy, long term prognosis, and alternative therapies. DISEASE DESCRIPTION Cancer is defined as a group of diseases characterized by uncontrolled growth and the spread of abnormal cells (1). In the United States, it is the second most common cause of death behind heart disease with approximately 580,350 American deaths and 1,660,290 new cancer diagnoses expected in 2013 (2). Lifetime risks of developing cancer are about 1 in 2 for men and 1 in 3 for women (1). However, 13.7 million Americans with a history of cancer were alive in January 1, 2012 and the current 5-year survival rate for all cancers is about 67%, giving some hope (2). ETIOLOGY AND RISK FACTORS Cancer is caused by a combination of both external and internal factors that act together to initiate or promote the growth and development of cancer. External factors include tobacco and cigarette use, alcohol consumption, excess energy consumption, infectious organisms, radiation and UV ray exposure, limited fruit, vegetable and fiber consumption, and exposure to certain chemicals and carcinogens. Tobacco and cigarette is responsible for at least 30% of all cancer deaths and 80% of lung cancer deaths (1). Alcohol use is associated with increased mouth, pharynx, larynx, esophagus, lung, colon, rectum, liver, and breast cancer. In addition to 1

3 this, chronic alcohol use is also associated with malnutrition, a factor that likely increases the risk for certain cancers. Excess energy intake leads to several problems, including increased BMI, obesity, and insulin resistance. All of these factors are associated with an increased risk of cancer and in the case of insulin, increased cancerous growth once cancer develops due to increased glucose levels in the bloodstream (3). Infectious organisms such as Hepatitis B, HPV, HIV, and H. pylori are other external risk factors. Radiation and UV ray exposure are yet another risk factor to be considered (1). Finally, there are many chemicals and carcinogens that have been linked to increased cancer risk. N-nitroso compounds, polycyclic aromatic hydrocarbons, and Bisphenol A are all known carcinogens. Internal risk factors include inherited mutations, hormones, immune conditions, and mutations in metabolism. Finally, other risk factors for cancer include race, with African Americans being at greatest risk for developing cancer, and age, with a sharp increase in cancer risk with age (4). PATHOPHYSIOLOGY AND COURSE OF CANCER The pathophysiology of cancer is extremely diverse but includes initiation, promotion, and progression. In the phase of initiation, cells change in response to carcinogenic agents (3). It can take ten or more years for the exposure of the cells to external risk factors to lead to detectable cancer (1). Due to a combination of exposure to external and internal risk factors, cells begin to experience minor mutations such as self-sufficiency in growth signals due to autocrine stimulation, increased growth factor receptors, limitless replicative potential, and hundreds of other mutations that can combine to form a cancerous cell. During the promotion phase, neoplasms form through the failure of protective mechanisms. The final step in the process is progression. In this phase, angiogenesis occurs, a tumor is formed, and metastasis may occur. Metastasis, or the point where neoplasms have the capacity for tissue invasion, occurs as cancer 2

4 cells mutate to experience a decrease in fibronectin, allowing tumor cells to dissociate from their surrounding cells, and an increase in laminin, allowing tumor cells to latch onto cells throughout the body. Once attachment occurs, cancer cells produce proteases and collagenases that dissolve or degrade the matrix and allow for the cancer cells to move into the matrix through a process called invadopia (5). The progression of the disease can be measured through an intricate staging system. Staging is used to identify the severity of the cancer based on how far it has spread and is a strong predictor for survival (3). The TNM system is the most commonly used of all staging systems. In this system, T stands for extent of the tumor and is based on the size or extent of the primary tumor, N stands for the extent of spreading to lymph nodes, and M stands for metastasis and is measured if it is present (6). These factors are combined together to give a final stage of 0, I, IIA, IIb, IIIA, IIIB, and IV with 0 being the least serious and IV being the most serious (3). METHODS OF MEDICAL DIAGNOSIS Early warning signs that lead doctors to suspect cancer are be described with the acronym CAUTION. The acronym CAUTION summarizes many warning signs of cancer and stands for change in bowel or bladder habits, a sore that does not heal, unusual bleeding or discharge, thickening or lumping in the breast or elsewhere, indigestion or difficulty in swallowing or chewing, obvious change in a wart or mole, and a nagging cough or hoarseness. These and other early warning signs such as anorexia, fatigue, weight loss, fever, sweating, anemia, pain, enlarged lymph nodes or body organs, bone pain, and neurological symptoms are red flags to physicians that cancer might be present (3). 3

5 After medical doctors see early warning signs of cancer, they can arrive at a diagnosis through the use of laboratory tests, physical examination, imaging procedures, and tissue biopsy. Laboratory tests of blood, urine, and other body fluids are used as a method of diagnosis once cancer is suspected. Specifically, medical doctors look for tumor-specific markers such as hormones, enzymes, genes, antigens, and antibodies that are found on cell membranes, in the blood, in the cerebral spinal fluid, and urine that are released by cancerous cells in their explosive growth (5). Doctors also look for other things such as cancer antigen, α-fibronectin, and carcinoembryonic antigen that can be elevated in cancer (3). Physical examination is another way physicians can detect cancer. Some ectopically present cancers, such as skin cancer can be detected this way. In addition to this, physical palpation can lead to diagnosis of certain cancers, such as breast cancer and prostate cancer (5). Imaging procedures that can lead to a diagnosis include CT scans, MRI scans, and PET scans. CT scans are radiographic procedures which take pictures at multiple angles and evaluate for abnormalities in areas such as the head, chest, abdomen, or pelvis. MRI scans use radio waves and a magnet linked to a computer to produce images that show differences in normal and cancerous tissue. This method is used mainly in the brain, spinal cord, and liver. Finally, PET scans follow radioactive glucose and look for spots of tissue that utilize the glucose. Cancer cells preferentially utilize glucose and so appear as hot spots in PET scans (3). Finally, tissue biopsy can be used by doctors to diagnose patients as the cells are viewed under a microscope. Although this method is invasive, it also provides images of the actual tissues and the degree of differentiation can easily be seen (5). 4

6 CURRENT MEDICAL THERAPIES Current treatment for cancer consists of chemotherapy, radiation therapy, surgery, and bone marrow transplant. Although there are many other forms of treatment, none are as commonly used as these (5). Chemotherapy is a wide array of chemical agents or medications used to treat cancer (3). Each chemotherapy drug works to attack some aspect of rapidly growing cells and hopefully kills more cancer cells than body cells. Because the mutations of cancer are so varied, several chemotherapy drugs are usually combined and even compounded with surgery and radiation treatments (7). Unfortunately, recent evidence suggests that chemotherapy might not significantly help in the fight against cancer. A comprehensive literature search done on 5- year survival in adult malignancies revealed an increase in survival rate attributed to chemotherapy of only % (8). Another commonly used method of treatment is radiation therapy. Radiation therapy uses high-energy radiation to kill cancer cells by damaging the cell s DNA. As with chemotherapy, radiation can damage health body cells as well and so must be carefully monitored to ensure as little damage is done to healthy body cells as possible. Radiation therapy can come from a machine outside of the body or from radioactive material, such as radioactive isotopes, placed in the body or injected into the bloodstream (9). This treatment appears to be promising; for example, radiation appears to be very helpful in managing primary cutaneous follicle-center lymphoma and primary cutaneous marginal zone lymphoma with solitary or relatively few skin lesions (10). However, researchers are still actively trying to research new methods of radiation treatment (9). 5

7 Surgery is another form of medical treatment for cancer. This method is often the greatest chance for cure if the cancer has not spread to the whole body. Surgery is divided into several categories including debulking surgery where only partial removal is possible, palliative surgery to treat symptoms but not cure, and curative surgery where the entirety of the cancer is removed. These methods are often combined with chemotherapy and radiation to improve effectiveness and keep cancer in remission (5). Finally, bone marrow transplant, or hematopoietic cell transplant, is a common medical therapy used to treat cancer. Bone marrow transplant involves the complete destruction of all existing bone marrow in a preparative phase through cytotoxic chemotherapy and sometimes total-body irradiation. Next, an intravenous infusion of hematopoietic cells is conducted using cells from the individual or from a histocompatible related or unrelated individual (3). This treatment has been proven to be beneficial. In a 2012 Cochrane review, strong evidence was found for progression-free survival rates in patients with follicular lymphoma when a high dose therapy was combined with autologous stem cell transplantation as compared with chemotherapy or immuno-chemotherapy in previously untreated patients with no evidence of secondary cancers (11). Schaaf et. al (11) asserted that more research needs to be done to determine overall survival but that this treatment appears promising. NUTRITION ASSESSMENT Nutrition assessment, particularly subjective global assessment, is of utmost importance in treating cancer. A subjective global assessment can be conducted that reviews weight history, food intake, symptoms, and functioning. This is used to analyze weight loss, disease, metabolic stress, and includes a nutrition-focused physical exam. In this exam, a general survey of the body 6

8 is conducted as well as a review of vital signs, anthropometrics, fat stores, muscle mass, and fluid status. Additional tools for nutrition assessment are the Activities of Daily Living tool that assesses a patient s ability to complete routine tasks such as walking, feeding, and dressing, the Common Toxicity Criteria that compares acute toxicities of cancer treatment, and the Karnofsky Performance Scale which associates a patient s functioning status with disease status and survival (3). MEDICAL NUTRITION THERAPY Status of key nutrients such as energy, protein, and fluids must be monitored in cancer as well as symptoms of cancer treatments that may affect a patient s nutrient intake. In measuring energy requirements, indirect calorimetry is always preferred but energy needs can also be calculated based on the Harris Benedict equation or body weight. However, energy intake must be sufficient or the body will begin to catabolize lean body tissue, leading to cancer cachexia and weight loss (3). Protein needs are increased in cancer as additional protein is required to repair the body tissues destroyed in treatment and maintain a healthy immune system, particularly when cachexia is present. Protein needs should be based on the progression of disease, the extent of malnutrition, and degree of stress. In general, protein needs for cancer patients are well above the normal 0.8 g/kg and into the g/kg range (3). Fluid needs in cancer patients change when ascites, edema, fistulas, profuse vomiting or diarrhea, multiple concurrent intravenous therapies, impaired renal function, or medications that act as diuretics are present. Clinicians must also be on the watch for signs and symptoms of dehydration, such as fatigue, acute weight loss, hypernatremia, poor skin turgor, dry oral 7

9 mucosa, dark or strong smelling urine, and decreased urine output. Labs to watch in relation to fluid status are serum electrolytes, blood urea nitrogen, and blood creatinine (3). Symptoms of cancer treatment to be managed through medical nutrition therapy are nausea and vomiting, alterations in taste and smell, diarrhea and constipation, xerostoma, sore throat, trouble swallowing, appetite loss, and weight loss. Nausea and vomiting are common side effects of cancer treatments and must be managed to promote adequate calorie and nutrient intake. Ideas to manage this include eating small meals, never skipping a meal, graduating from clear liquids to non-irritating foods, and eating small meals throughout the day (12). Alterations in taste and smell happen as a result of cancer treatment, the cancer itself, or dental problems. Ideas to manage this are helping the patient to choose foods that still look and smell good to the patient, marinating foods, trying tart foods and drinks, eating with plastic utensils, and adding extra flavors to meals (12). Diarrhea and constipation can also occur and can be treated with drinking plenty of fluids and drinking hot liquids. Constipation can be treated by eating foods high in fiber. Diarrhea can be treated by drinking fluids, drinking less carbonated drinks, eating small meals throughout the day, eating foods low in fiber, and consuming foods and liquids high in sodium and potassium to replace daily losses (12). Xerostoma, or dry mouth, a sore throat, and difficulty swallowing are also frequent sideeffects of chemotherapy and radiation. These symptoms can be managed through sipping water throughout the day, having sweet or tart foods, chewing gum or ice chips, eating foods that are easy to swallow, moistening foods with gravies and sauces, and avoiding foods that hurt the mouth such as sharp foods and alcohol (12). 8

10 Finally, appetite loss can happen as a result of treatment, the patient s mental status, pain, nausea and vomiting, and changes in taste and smell. Ways to manage this and prevent subsequent cachexia and weight loss are consuming meal replacements, eating small meals throughout the day, keeping snacks nearby, eating smoothies and shakes and other soft, cool foods, and sipping only a small amount of liquids during meals to save room for solid food (12). PROGNOSIS Medical personnel often base the prognosis of a patient on information researchers have collected throughout the years on cancer-specific survival, relative survival, overall survival, and disease-free survival. Cancer-specific survival is the calculated percentage of patients with a specific type and stage of cancer who have survived. Relative survival is a statistic that compares the survival of patients diagnosed with cancer with the survival of people in the general population who belong to the same demographic category. Overall survival is the percentage of patients who have been diagnosed with the same stage and type of cancer that are still living. Finally, disease-free survival is the percentage of patients who have no evidence of cancer after a certain amount of time. All of these can be used to give a tentative prognosis (13). ALTERNATIVE AND COMPLIMENTARY THERAPIES Because the methods of cancer treatment can be so invasive and do not work all of the time, patients sometimes turn to alternative and complimentary therapies such as behavioral and psychological approaches, dietary treatments, and herbal treatments. Guided imagery, meditation, psychological counseling, support groups, and other approaches are frequently used to help patients manage their emotions and hopefully build an environment where healing can 9

11 occur. Although the effectiveness of these type of treatments is still uncertain, they are increasingly becoming a routine part of cancer treatment (14). Dietary therapies are another area patients often turn to during treatment and are subdivided into two groups: metabolic therapies and macrobiotic diets. Metabolic therapies are based on the idea that cancer produces toxins that the body must be cleansed of. This cleansing is supposedly achieved by consumption of coffee and wheat grass followed by a special diet and vitamin and mineral supplementation (3). Followers of this diet hope to boost the immune system through wheatgrass consumption (14). The Macrobiotic diet advocates a high consumption of 40-60% of calories from whole grains, 20-30% of calories from vegetables, and the remainder from beans, sea vegetables, fruit, seeds, nuts, and occasionally meats. Unfortunately, this diet has not been found to treat or cure cancer and is deficient in calcium and vitamin B 12 (3). Dietary supplements are used very commonly in alternative and integrative medicine today. In fact, dietary supplements are the most commonly used form of complementary therapy in the United States. These are mostly used for symptom management but can be dangerous if patients choose to seek these methods of disease management over the opinions of their doctors, particularly with the rampant practice of nondisclosure in herbal supplements (3). CONCLUSION Cancer is a very complex disease with many risk factors that contribute to the initiation, promotion, and progression of cancer. It can be diagnosed through several methods and treated in various ways. However, the effects of the disease and treatment must be assessed and addressed to increase quality of life and likelihood for survival. 10

12 REFERENCES 1. American Cancer Society. Cancer Facts & Figures Atlanta, GA; American Cancer Society. Cancer Facts & Figures Atlanta, GA; Grant B, Hamilton KK. Medical nutrition therapy for cancer. In: Mahan LK, Escott- Stump S, ed. Krause s Food, Nutrition, & Diet Therapy. 13 th ed. St. Louis, MO: Elsevier; 2012: Agency for Toxic Substances & Disease Registry. The nature of cancer. Available at: Accessed February 12, Bikman B. Lecture notes. Pathophysiology, Brigham Young University, September 11, National Cancer Institute. Cancer staging. Available at: Accessed February 20, American Cancer Society. Understanding chemotherapy: A guide for patients and families. Available at: Accessed February 20, Morgan G, Ward R, Barton M. The contribution of cytotoxic chemotherapy to 5-years survival in adult malignancies. Clin Oncol. 2004;16(8): National Cancer Institute. Radiation therapy for cancer. Available at: Accessed February 21, Wilcox RA. Cutaneous B-cell lymphomas: 2013 update on diagnosis, risk-stratification, and management. Am J Hematol. 2013;88(1): Schaaf M, Reiser M, Borchmann P, Engert A, Skoetz N. High-dose therapy with autologous stem cell transplantation versus chemotherapy or immune-chemotherapy for follicular lymphoma in adults. Cochrane Database Syst Rev. 2012; published online. Available at: Accessed February 21, National Cancer Institute. Eating Habits Before, During, and After Cancer Treatment

13 13. National Cancer Institute. Understanding cancer prognosis. Available at: Accessed February 20, U.S. Congress, Office of Technology Assessment. Unconventional Cancer Treatments, OTA-H-405. Washington, DC: U.S. Government Printing Office;