Health Letter, October 2019
By Meena Aladdin, M.S., Ph.D.
Pancreatic cancer is relatively uncommon, accounting for only 3% of all cases of cancer in the United States. However, it is a deadly disease that leads to about 7% of all cancer deaths, making it the third-leading cause of cancer-related deaths.
Patients with pancreatic cancer have a five-year survival rate of only 9%, but this rate can vary depending on the stage at which it is detected. Treatments, which include surgery, radiation and chemotherapy, also depend on cancer stage. For instance, surgery may not be beneficial if the cancer is detected at an advanced stage.
Like most other cancer types, pancreatic cancer is largely asymptomatic in its early stages, making it difficult to detect and diagnose. Later into the progression of the disease, however, nonspecific symptoms (which resemble those for many other diseases, such as stomach and back pain, weight loss, appetite loss, nausea and vomiting) may begin to appear as the cancer spreads to other parts of the body.
The U.S. Preventive Services Task Force (USPSTF), a volunteer panel of national experts in disease prevention and evidence-based medicine working independently of the drug and medical device industry, does recommend regular screening for early detection and treatment of some types of cancer, such as breast and colon cancer, in certain populations.
However, the USPSTF in 2004 recommended against routine screening for pancreatic cancer in asymptomatic adults after concluding based on evidence available at that time that the harms from screening exceeded any potential benefit. In August, the USPSTF reaffirmed this recommendation based on a careful review of new evidence published since 2002 regarding screening tests for pancreatic cancer.
The new USPSTF review
To reassess its 2004 recommendation, the USPSTF commissioned a systematic review of research studies published from 2002 to April 2018 that evaluated screening tests for pancreatic cancer. The review was restricted to studies related to any image-based screening technique (such as CT or MRI scans) and excluded other screening tools.
The review was limited to studies with subject populations consisting of adults aged 18 years and older with and without risk factors for pancreatic cancer, such as new-onset diabetes and a family history of pancreatic cancer, and those with screening-detected asymptomatic or incidentally detected pancreatic cancer. The review excluded studies of populations that were exclusively comprised of individuals with genetic conditions that predispose them to pancreatic cancer and those who have had clinically or symptomatically detected pancreatic cancer.
The study outcomes of most interest to the authors of the USPSTF systematic review were effects of screening on pancreatic cancer-related illness and mortality and all-cause mortality (death rate due to any cause). Other outcomes of interest included accuracy of screening tests for detecting pancreatic cancer, harms associated with screening, effects of treatment on screening-detected pancreatic cancer-related illness and mortality and any harms associated with treatment of screening-detected pancreatic cancer.
The USPSTF review found 13 uncontrolled observational studies that assessed screening for pancreatic cancer, all of which were deemed to be of only fair quality. These studies include a total of 1,317 subjects, and all studies, except for one, included subjects who were at high risk for pancreatic cancer based on family history, with or without confirmed genetic mutations or conditions.
Importantly, no studies reported on the effects of screening on pancreatic cancer-related illness or mortality or all-cause mortality, which are the most important outcomes for assessing the benefits of screening tests.
All 13 studies reported on the number of patients diagnosed with pancreatic cancer following the screening tests, but none evaluated the diagnostic accuracy of the screening tests used.
In the eight studies that assessed harms related to the screening procedures, no serious harms were reported. No psychological harms related to screening were identified in the two studies that reported data on this outcome.
In considering the harms of screening, the USPSTF noted that surgery to remove the pancreas carries significant risk of complications and death.
USPSTF’s updated conclusions and recommendations
Based on the new systematic review, the USPSTF reached the same conclusion that it had made in 2004: the potential benefits of screening for pancreatic cancer in asymptomatic adults at average risk for the disease do not outweigh the potential harms.
As a result, the USPSTF in August again recommended against screening for pancreatic cancer in asymptomatic adults who are not known to be at high risk for the disease. The USPSTF emphasized that this recommendation does not apply to individuals who come from families with an abnormally high rate of pancreatic cancer or who have inherited genetic conditions associated with a high risk of pancreatic cancer.