Types of Cancer based on Location - Traditional Thinking

Traditionally, cancer is a disease classified by organ site. There are many examples of how this idea is ingrained into oncology culture. Oncologists specialize to treat cancers based on the anatomical location of the cancer in the body, not on the molecular features of the tumor, which can be vastly more informative in terms of how to successfully treat the patient. A patient is diagnosed with colon cancer, breast cancer, or prostate cancer, rather than EGFR-positive cancer first and foremost, with the location as the secondary classification. This phenomenon is seen in the laboratory setting as well, with researchers focusing on a type of cancer based on its location, and in granting agencies and foundations that release funding announcements based on disease site.

Not All Cancers Share the Same Molecular and Genetic Characteristics

Up until now, classification of cancer by disease site made sense; it simplified and categorized a complex disease in the absence of molecular or genetic characterization techniques. As a result, treatments were – and still are – largely based on the location of the tumor, with some patients responding well while others not. As molecular techniques are developed and applied to cancer, researchers and clinicians are realizing that not all cancers at a particular organ site share the same molecular and genetic characteristics, and thus, the beginnings of an explanation for why some patients respond to treatment while others do not.

Breast Cancer - Different Molecular and Genetic Sub-Types

Breast cancer is a sub-field of oncology that has led the way in classification of the disease at the molecular level, most notably based on estrogen and progesterone receptor and HER2 status. While this is a step in the right direction, we are finding that classification of breast cancer based on these three markers may still be an oversimplification. At a recent American Society for Clinical Oncology (ASCO) meeting, one of the discussions on breast cancer amongst the participants centered on how the disease may have at least 40 or 50 different molecular and genetic sub-types.

Cancer; A Truly Complex Disease

The more we look, the more we realize that cancer is truly a complex and heterogeneous disease, and there is still a long way to go in understanding its molecular and genetic nature. For example, not all EGFR-positive tumors are the same. Scientists have discovered that the mutation status of an unrelated protein, KRAS, influences the response of colorectal cancer patients to EGFR inhibitors. And recently, some colon cancers have been identified as HER2 positive, making patients with advanced gastric and gastroesophageal cancers candidates for trastuzumab treatment. For certain, many more discoveries similar to this one are yet to be identified.

Researchers and Clinicians Still Think of Cancer as a Disease of an Organ!

Perhaps, the first step is to change the way we think about cancer. More specifically, why don’t patients get a diagnosis of cancer that is EGFR mutated and KRAS mutated at codon 13 (p.G13D) that happens to be in the colon instead of a diagnosis of colon cancer? We need to change the way we think about cancer in order to be able to translate important genetic and molecular findings into the clinic. There is a lot of great research delving into the sub-anatomical characteristics of tumors, but patients are not seeing as much of a benefit as they could be. Part of the reason is that researchers and clinicians still think of cancer as a disease of an organ.

Written by Dr Melissa H. Kuchm PhD.The President and Chief Operating Officer of Pandora Genomics.Assistant Professor and Research Scientist of Oncology at the Cancer Research Institute of MD Anderson Cancer This email address is being protected from spambots. You need JavaScript enabled to view it.