Clinical Pearls & Morning Reports
Published October 17, 2018
Sporadic colorectal cancer in a young person can be associated with a delay in diagnosis, since the index of suspicion is low. Read the latest NEJM Case Records of the Massachusetts General Hospital here.
Q: What are the most common cancers to occur during pregnancy?
A: The most common cancers to occur during pregnancy are melanoma and breast, cervical, and hematologic cancers, which together account for 70% of all cases.
Q: Describe some aspects of the changing epidemiology of colon cancer.
A: Historically, colorectal cancer has been uncommon among younger people, with a median age at diagnosis of 67 years. Screening with colonoscopy has lowered the overall incidence of colorectal cancer. However, the incidence among younger people has increased at a pronounced rate. As compared with people born around 1950, among whom rates of colorectal cancer are the lowest, people born in 1990 have twice the risk of colon cancer (predominantly cancer involving the left side of the colon) and more than 4 times the risk of rectal cancer. Data show that 11% of colon cancers and 18% of rectal cancers occur in patients 20 to 49 years of age and are considered to be young-onset cases.
A: Young-onset colorectal cancer encompasses a heterogeneous group of diseases associated with unique molecular mechanisms, clinical presentations, and prognoses. In a greater proportion of young-onset cases than of older-onset cases, the underlying cause is a known genetic syndrome, such as the Lynch syndrome and familial adenomatous polyposis. The risk of young-onset colorectal cancer is up to 4 times as high among people who have a family history of colorectal cancer, particularly in a first-degree relative, as among those who do not have a family history. This suggests that the disease is associated with complex trait genetics and epigenetic modifiers of risk. However, in the majority of young patients with colorectal cancer, the disease is sporadic. Sporadic cancers involving the left side of the colon in young patients represent a unique subset of the disease. Such cancers tend to be aggressive and poorly differentiated, often with signet-ring cell differentiation. In general, they are associated with a poor prognosis.
A: Historically, colorectal cancer in pregnancy has been rare, occurring in 1 in 13,000 pregnancies. However, the convergence of two trends — the increased incidence of young-onset colorectal cancer and the increase in delayed childbearing — may place more women at risk. Some symptoms of pregnancy (e.g., anemia, bloating, and a change in bowel habits) overlap with symptoms of colorectal cancer, and thus the cancer diagnosis can be delayed. However, in studies involving patients with colorectal cancer, survival did not differ significantly between pregnant women and age- and stage-matched controls; this finding suggests that poor outcomes are more likely to be related to the aggressive features of sporadic, early-onset disease than to pregnancy. Maternal cancer is an important indication for placental examination, because malignant tumors can metastasize to the placenta. In very rare cases, the tumor crosses the placenta and spreads to the fetus. The most common primary placental cancer is choriocarcinoma in situ, and the most common cancer with metastasis to the placenta is melanoma.