Differences between colon and rectal cancers

This study analyzed data from the national cancer surveillance program in order to compare between the characteristics and outcomes of patients with colon and rectal cancer.

Colon and Rectal cancer are the third most common causes of cancer in the United States. The clinical presentation, diagnosis and treatment of the two types of cancer are usually very similar.

Early stage colon cancer, without involvement of the surrounding lymph nodes, is usually treated only with surgical resection of the tumor. On the other hand, advanced colon cancer, that has invaded the surrounding lymph nodes or spread to other organs, is often treated with additional chemotherapy following surgery. 

Rectal cancer is known to have a higher rate of local tumor recurrence following surgery compared to colon cancer, mainly because of the difficulty in excising the entire tumor without leaving behind residual cancer cells. Therefore, the combination of chemotherapy and radiation therapy delivered after surgery is the standard of care in most cases of rectal cancer, regardless of lymph-node invasion.

With the understanding that colon and rectal cancer are similar in some features but different in others, this study analyzed the differences between the two cancers in an attempt to further understand both diseases and improve future treatment guidelines.

In order to compare between colon and rectal cancer patients, this study analyzed data from the SEER (Surveillance, Epidemiology, and End Results) Program database, the largest public cancer database in the United States. Data was analyzed from a total of 372,130 colorectal cancer patients, with an average follow-up of 32 months.  261,523 patients (70.3%) were diagnosed with colon cancer, and 110,607 (29.7%) with rectal cancer.

Among early stage cancer patients, no significant difference was observed in survival between colon and rectal cancer. Among stage IIB patients (indicating that the tumor has grown through the wall of the colon or rectum), colon cancer was associated with a 4-month increase in survival compared to rectal cancer.  Among advanced stage patients (stage III and IV), rectal cancer was associated with a 3-month increase in survival compared to colon cancer.  Surprisingly, among both colon and rectal cancer patients, stage IIB cancer was associated with decreased survival compared to stage III cancer. These results indicate that stage IIB cancer may require more aggressive therapy than is currently provided.

This study concluded that patient survival is similar for both colon and rectal cancer when current treatment guidelines are employed.

Results of this study are limited due to missing data regarding cancer staging and surgical outcomes in many of the patient records included.