Cancer in the colon and rectum, i.e. colorectal cancer, is one of the most common cancer forms. Every year about 6500 people are affected in Sweden, and about 1.8 million worldwide. The number of new cases is rising because of increased incidence due to changes in lifestyle among the world populations with transition to a western lifestyle, and because of increasing life expectancy.
When colorectal cancer has been diagnosed, the tumor spread is investigated usually with computed tomography. About three out of four patients do not have any detectable metastases (secondary tumors) in other organs. When curative treatment is considered possible, surgery is performed with a standardized bowel resection including the tumor draining lymph node field. After surgery, chemotherapy is sometimes given, known as adjuvant chemotherapy. When rectal cancer is diagnosed, radiation therapy, which sometimes is given in combination with chemotherapy before or after surgery, may be indicated.
Surgery cures approximately 50% of those affected by colorectal cancer. This is partly due to that there are metastases present already at diagnosis (stage IV). After potentially curative surgery, the resected bowel specimen is examined for determination of the local tumor growth, which may be present only superficially in the bowel wall (stage I), deeper in the bowel wall (stage II), and in the tumor draining lymph node field (stage III). The number of patients surviving five years after surgery is close to 100% in stage I, approximately 80-90% in stage II, and 60-80% in stage III. Usually patients with a stage III tumor is offered adjuvant chemotherapy as tumor growth in the resected tumor draining lymph nodes indicates a risk for that cancer cells may have disseminated beyond these lymph nodes. If the tumor is in stage I, the patient is considered as cured by surgery alone. In stage II the recurrence rate, 12(9-31)%, is considerably lower than in stage III, 33(17-44)%, and adjuvant chemotherapy is then offered only when there are other detected risk factors.
Adjuvant chemotherapy increases the relative 5-year survival rate with up to 40% depending on the selection of adjuvant therapy regime. One problem is that patients receiving adjuvant chemotherapy after stage III-tumor surgery eventually will be treated unnecessary, i.e. overtreated. Some microscopically detected tumor cells in the lymph nodes may lack the capacity to spread and generate metastases. This difference in the ability to disseminate and generate metastases cannot be determined by the microscopic examination. An even greater problem is that the pathologist examines only a single or very few sections of each lymph node which implicates a risk for missing the presence of tumor cells in other parts of the lymph node. In such a case, there is a real risk of inadequate treatment as the tumor will be classified as stage I or II.
Over- and undertreatment means great suffering for the patient and unnecessary costs for society. We have become aware that there is a need for increased efforts for diagnosis and characterization of tumor cell aggressiveness in lymph nodes in the resected cancer specimens. The decision on adjuvant chemotherapy should be made based on a safer tumor staging procedure than only microscopic evaluation.
HiloProbe is focusing on safe examination of the tumor draining lymph nodes in the resected surgical specimen, and ColoNode is a diagnostic product that has been developed for this purpose.