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Рак на панкреаса

Рак на панкреаса

STAGING PANCREATIC CANCERStaging of cancer started over a hundred years ago. The efforts were focused on specific anatomic sites of cancer. The system advocated by Dukes for rectal cancer is an example. The first effort to develop a staging system whose principles and codes could be applied to all cancer sites was that of the French surgeon Pierre Denoix, who between 1943 and 1952 developed the tumor-node-metastasis (TNM) classification. In 1958, the first international TNM recommendations were published by the International Union Against Cancer (UICC) for the clinical stage classification of cancers of the breast and larynx. Between 1960 and 1967, 9 UICC brochures were published describing proposals for the classification of tumors at 23 body sites.

The importance of staging cannot be over-emphasized in the management of patients. A primary role for staging is to stratify patients into groups that are prognostically and therapeutically similar, i.e. a strategy for the individuals as well as for groups of patients. With this framework it allows for comparison across large populations either within geopolitical borders or between disparate countries. Staging in fact is the accepted "language of to describe cancer," and it is necessary for that language to be learned early in medical education to allow clinicians to become facile with the dialect and vernacular of staging strategies. Staging provides a format for the uniform exchange of information among clinicians regarding extent of disease and a basis for their selection of initial therapeutic approaches and consideration of the possible need for adjuvant treatment. For clinical investigators, staging allows the stratification of patients in observational and interventional therapeutic studies and facilitates the exchange of information through data sets and peer-reviewed communication. As a general rule, the earlier the stage and the lower the grade of a cancer, the better the outlook (prognosis). The stage of a cancer is a descriptor (usually numbers I to IV) of how much the cancer has spread. The stage often takes into account the size of a tumor, how deep it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to (if any), and whether it has spread to distant organs. Staging of cancer is important because the stage at diagnosis is the most powerful predictor of survival, and treatments are often changed based on the stage.

Clinical stage is based on all of the available information obtained before a surgery to remove the tumor. Thus, it may include information about the tumor obtained by physical examination, radiologic examination, and endoscopy.  Pathologic stage adds additional information gained by examination of the tumor microscopically by a pathologist. Because they use different information, clinical stage and pathologic stage are often different. Pathologic staging is usually considered the "better" or "truer" stage because it allows direct examination of the tumor and its spread, contrasted with clinical staging which is limited by the fact that the information is obtained by making indirect observations at a tumor which is still in the body. However, clinical staging and pathologic staging should complement each other. Not every tumor is treated surgically, so sometimes pathologic staging is not available. Also, sometimes surgery is preceded by other treatments such as chemotherapy and radiation therapy which shrink the tumor, so the pathologic stage may underestimate the true stage.

The most important challenge facing staging is how to interface with the great numbers of nonanatomic prognostic factors that are currently in use or under study. As nonanatomic prognostic factors become widely used, there is a risk that staging will be overwhelmed by such a variety of prognostic data. An anatomic extent of disease classification is needed to select the initial therapeutic approach, stratify patients for therapeutic studies, evaluate nonanatomic prognostic factors at specific anatomic stages, compare the weight of nonanatomic factors with extent of disease, and communicate extent of disease data in a uniform manner. Some cancers are also graded by looking at certain features of the cancer cells using a microscope or other tests.

Staging can also be used to measure early detection efforts (e.g. to see what impact screening could have on the stage distribution of disease at the time of diagnosis).

A special problem refers to stage migration which is due to our collection of knowledge and experience, i.e. the problem arises when we as a medical community gets better. It describes changes in the distribution of stage in a particular cancer population induced by either a change in the staging system itself or else a change in technology which allows more sensitive detection of tumor spread and therefore more sensitivity in detecting spread of disease (e.g. the use of MRI scan). Stage migration can lead to curious statistical phenomena (for example, the Will Rogers phenomenon). The Will Rogers phenomenon is obtained when moving an element from one set to another set raises the average values of both sets. It is based on the following quote, attributed to comedian Will Rogers: “When the Okies left Oklahoma and moved to California, they raised the average intelligence level in both states”. This means that the element being moved is below average for its current set. Removing it will, by definition, raise the average of the remaining elements. On the other hand, the element being moved is above the current average of the set it is entering. Adding it to the new set will, by definition, raise the average. All of this of course also works the other way around. In medical stage migration, improved detection of illness leads to the movement of people from the set of healthy people to the set of unhealthy people. Because these people are not healthy, removing them from the set of healthy people increases the average lifespan of the healthy group. Likewise, the migrated people are healthier than the people already in the unhealthy set, so adding them raises the average lifespan of that group as well.

Pancreatic surgery is a very challenging field and the management of pancreatic diseases continues to evolve. Although surgery is considered the only treatment to offer patients with localized pancreatic adenocarcinoma a chance of cure, resection alone is rarely sufficient for long-term survival. High rates of postoperative recurrence and subsequent disease-related mortality have, over the past two decades, encouraged the study and use of multimodality strategies that include adjuvant systemic chemotherapy and radiation. These modalities have been utilized both preoperatively and postoperatively with encouraging results. Moreover, their use has led increasingly to the development of institutional multidisciplinary groups with a focused interest in the care of patients with pancreatic malignancy, which have become responsible for the diagnosis, staging, treatment, follow-up and study of these patients. Today the rationale for the use of our knowledge and experience may be achieved through the use of a multidisciplinary approach to patients with resectable adenocarcinoma of the pancreas – and then again a staging procedure is essential.

Startlingly, it appears that in many places up to a third of patients with resectable pancreatic cancer do not receive an operation, but for those who do receive surgery new emphasis on adequate lymph node staging has been reported. Extended pancreatic resections with vascular resection appear safe and with reasonable survival outcomes. The use of laparoscopic techniques for the pancreas continues to advance. Thus, pancreatic surgery is a fascinating field as we learn more about the biology of the conditions that afflict this gland and the best practices to address these diseases.

This book summarizes what we know of staging of pancreatic cancer. The impressive work has been gathered to the benefit of the patients of today and the patients to come, which we acknowledge. The author has made an important work that will help us for the future.

Åke Andrén-Sandberg
Professor of Surgery
Karolinska University Hospital
Stockholm, Sweden


Автор: Десислав Врачански
Редактори: проф. Оке Андрен-Сандберг и проф. Дамян Дамянов
Академично издателсво проф. Марин Дринов
Година: 2007
Език: английски
ISSN: 978-954-332-360-2

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