A medical oncologist is a physician who uses medicines to treat cancer. Because the medical therapy of cancer is still a relatively modern occurrence, the field of medical oncology is a relatively new subspecialty of internal medicine. With increasing treatment options and increased complexity of care, the treatment of solid tumor malignancies has evolved into a team approach involving surgical, radiation, and medical oncologists, as well as diagnostic colleagues in radiology and pathology. Often, the medical oncologist will be responsible for the coordination of this care. In this chapter, the role of medical oncology as it pertains to gastrointestinal (GI) malignancies is reviewed.

Before the mid-20th century, the curative treatment of cancer was primarily carried out by the surgeon and the radiation oncologist. Indeed, the first cancer operations were performed several hundred years ago and expanded greatly with the development of ether anesthesia in the 19th century. However, following World War II, the therapeutic options expanded when two pharmacists (Goodman and Gilman) commissioned by the U.S. Department of Defense identified potential antineoplastic uses of nitrogen mustard (1). Specifically, from autopsies of people exposed to mustard gas during the First World War, physicians noted severe myeloid and lymphoid suppression. This led to their initial hypothesis that this chemical class may be active to treat myeloid and lymphoid malignancies, which they then tested in a mouse model of lymphoma. This ultimately led to the first treatment of a patient with non-Hodgkin lymphoma in 1946, where they observed a dramatic but transient reduction in size of the patient’s tumor masses (1). This proof-of-principal clinical experiment introduced the concept of the pharmacologic therapy of malignancy. In 1958, the seminal publication by Hertz et al. first described the curative benefit of chemotherapy in the treatment of trophoblastic tumors in women (2). Even in this early report, the tenets that define medical oncology today were readily apparent. Specifically, these first medical oncologists were required to balance the potential benefits of medical therapy with its toxic side effects. They concluded that the curative effects of cytotoxic chemotherapy in solid tumors outweighed the risks, stating that “although the chemotherapeutic regimen is somewhat hazardous, the morbidity and mortality may be regarded as acceptable” (2). This publication marks the inauguration of the field of medical oncology. Over the past several decades, in parallel to the improvements in understanding the biology of malignancy, there has been an explosion in the discovery of new chemotherapy, hormonal, and targeted therapies, and an expansion of the role of the medical oncologist in the medical therapy of malignancy.

In 1972, medical oncology was designated as a specialty by the American Board of Internal Medicine, 7 years after the formation of the American Society of Clinical Oncology (ASCO) (3). The creation of medical oncology as a specialty largely resulted from the efforts of the society, which first coined the term “medical oncologist.” Many credit the leadership of Arnoldus Goudsmit, MD, PhD, whose vision and leadership mobilized internists to take an active role in the treatment of cancer. Dr. Goudsmit and his colleagues sought to create an organization dedicated to expanding the knowledge of ways to improve survival with cancer chemotherapy, educating physicians in the safe uses of chemotherapy, and improving access of patients to quality cancer care. At the time of its creation in 1965, ASCO was comprised of 7 founding members (4). The society has since grown into an international organization of more than 20,000 members devoted to all aspects of cancer care.

Medical oncology is a subspecialty of internal medicine. Physicians who are pursuing a career in medical oncology first train and certify in internal medicine (5). On completion of an internal medicine residency, an aspiring medical oncologist will then complete a 2- to 3-year fellowship (6). In the early 1970 s, the scope of medical oncology, as defined by the American Board of Internal Medicine, included several areas of cancer: etiology, diagnosis, prevention, patient management, epidemiology, host effects, tumor biology, investigation, orientation, detection, and gerontology (7). Even a cursory glance of this list reveals that the medical oncologist is concerned with the total management of the cancer patient. Over the past several decades, there has been a rapid increase in the armamentarium of treatments that medical oncologists have in their arsenal. This unprecedented upsurge in new therapies and the increased complexity of multidisciplinary care has necessitated the further subspecialization of medical oncology to several disease types. This chapter focuses on the implications of the total management of the cancer patient in the modern era of subspecialized care focusing on the role of medical oncology for GI malignancies.

GI malignancies include a wide variety of cancers throughout the GI tract, with varying epidemiology, tumor biology, and treatments. Together, these cancers are the most common group of cancers worldwide, accounting for more than 30% of the global burden of cancer, surpassing lung, prostate, and breast cancer (8). Table 7.1 provides summary statistics of the common GI malignancies. In terms of new cancer diagnoses,
4 of the top 10 cancers worldwide are GI malignancies (8). As discussed later in this book, the epidemiologies of these cancers vary greatly. For example, liver cancer is associated with a significant male predominance of almost 3:1, whereas for colorectal and pancreatic cancers, females are almost as likely to develop the disease as males (1.16:1). Two-thirds of new cases of stomach cancer occur in developing countries, although the incidence is among the highest in an industrialized nation—Japan (8). GI malignancies affect people without regard to age, gender, race, or health status and together, unfortunately, have the highest case mortality. Except for colorectal cancer and squamous cell carcinoma of the anus, median survival for advanced disease for most GI malignancies is <1 year. Thus, the treatment of GI malignancies poses several challenges: They are prevalent, aggressive, and nondiscriminatory. The unique challenge of GI medical oncology is that the physician must become familiar with a wide range of malignant disease processes, each with its own unique epidemiology, biology, and treatment.

The medical oncologist must confirm and document whether a patient has a cancer, define the organ/tissue of origin, determine the extent of spread of the disease (staging), and assess the patient’s therapeutic options. A patient will meet with a medical oncologist as a result of a referral: (a) for a cancer documented by biopsy or surgical procedure, (b) for the suspicion of malignant disease given clinical or laboratory abnormalities, and (c) because the patient has an increased risk of developing a specific neoplasm as a result of genetic or familial factors. In all three scenarios, the medical oncologist must decide whether he or she has sufficient information to adequately assign stage, determine an estimate of curability or ability to palliate, assess the patient’s fitness to tolerate therapy, and design the optimal course of therapy.