Cancers That Increase Colorectal Cancer Risk

Greater awareness of colorectal cancer risk factors, along with the rise of early-onset disease in individuals below 50, has brought into focus the urgent need for early detection and more accessible screening methods.

Colorectal cancer treatment has a higher chance of success the earlier it is detected and will prove beneficial to younger at-risk individuals. However, another at-risk group can also benefit from better colorectal cancer surveillance — survivors of other cancers.

In the United States, the number of cancer survivors is expected to rise to 20 million, in part thanks to improved diagnosis and treatment plans. However, cancer survivors are often at higher risk of developing another cancer as a second primary malignancy (SPM). This means that these individuals may be diagnosed with cancer again after their first cancer has been treated or gone into remission, and the second cancer does not develop as a result of the primary cancer metastasizing. In many cases, the second primary malignancy is lethal and cancer survivors carry an overall 33% risk.

If you are a cancer survivor, you may be disheartened to hear that you are still at risk of cancer despite all the difficulties you’ve been through. You may feel like the disease has never truly left you and continues to haunt you. While you might feel trapped in a hopeless situation, there are still ways to help you overcome your second encounter with cancer, and the first step is being aware of what you are at risk of developing.

In the case of colorectal cancer, the risk of developing it as a second primary malignancy is higher if you have previously been diagnosed with certain cancers. What are these cancers, and what do we know about them?

While there are several cancers that uterine and ovarian cancer survivors are at risk of developing, colorectal cancer has a higher incidence rate compared to others. The precise mechanism through which colorectal cancer develops as an SPM following uterine and ovarian cancer is still unclear. However, studies have found strong associations between hereditary risk factors and treatment methods that exacerbate second primary colorectal cancer risk.

Genetic and hereditary factors include a Lynch syndrome or hereditary non-polyposis colorectal cancer (HNPCC) diagnosis. This germline mutation carries an associated risk of endometrial (cancer of the uterine lining), ovarian and colorectal cancer, and women with Lynch syndrome diagnosed with endometrial cancer are at higher risk of colorectal cancer and other abdominal cancers.

In addition, uterine and ovarian cancer treatment may also potentially contribute to the development of colorectal cancer several years after initial treatment. Particularly in cases where radiation therapy is used, cancerous lesions have a higher chance of forming in organs located near the irradiation site, with onset varying based on the dose, exposure and the amount of time passed since radiation exposure (latency).

While breast cancer survivors are at higher risk of developing second primary colorectal cancer for similar Lynch syndrome-related reasons, other factors such as obesity and hormonal changes have also been attributed as potential conditions that drive colorectal cancer development.

Where high estrogen levels have been linked with an increased risk of breast cancer, the hormone has also been implicated in colorectal cancer pathogenesis. Obesity, which also drives up estrogen levels, exacerbates the development of colorectal cancer through other altered biological pathways, including the Wnt signaling pathway that induces mutations in colon epithelial cells such that they progressively grow into tumors.

While improved diagnosis and treatment regimes have helped lower cancer-related mortality by about 1.5% annually, the growing population of cancer survivors faced with a host of risk factors often draws a poor conclusion — that second primary malignancies are often lethal, with survival times averaging one year.

Many of the associated causes of SPM cannot be managed — genetics and treatment of the first cancer cannot be changed. However, better defining high-risk groups and developing more strategic targeted interventions and clinical interventions can improve the chances of survival for these already battle-worn individuals.

If you have battled uterine, ovarian and breast cancer before, and are concerned about your potential risk of developing colorectal cancer, speak with your doctors about regular surveillance colonoscopies following your initial treatment. Hope is not lost, but the first step towards victory against cancer again starts with detecting it early.