Cancer screening tests may not extend life expectancy; however, they still are valuable for public health.
Oncology nurses are intimately familiar with the complexities and uncertainties surrounding cancer screening tests—including the limitations of these tests.
For example, we meet patients who may have had a normal mammogram last year but are now facing a diagnosis of metastatic breast cancer. We also see patients who are much younger than the recommended age for a screening colonoscopy yet have been diagnosed with colorectal cancer.
Additionally, we encounter many patients with a cancer diagnosis for which there is currently no reliable screening test available.
On the other hand, there are many patients who we do not frequently come across. We rarely encounter patients who had an early-stage breast cancer detected through routine mammography and received curative treatment. Seldom do we encounter young women with abnormal Papanicolaou (Pap) tests who received local therapy to their cervix and subsequently had normal test results. The reason for our infrequent encounters with these patients is not their nonexistence, but, instead, the fact that they do not require frequent follow-up appointments because they are generally in good health. They are not visiting our clinics regularly for treatment-related appointments or being admitted to the hospital for symptoms of anti-cancer therapy or disease progression.
A recent meta-analysis, published in JAMA Internal Medicine, examined 6 common cancer screening methods to determine whether they improve life expectancy.1
The study authors evaluated both meta-analyses of randomized clinical trials as well as individual randomized clinical trials that reported cause-specific and all-cause mortality outcomes for widely used cancer screening tests. They included clinical trials that compared the outcomes of patients who underwent screening against those who did not undergo screening. The screening methods included were mammography for breast cancer, the fecal occult blood test (FOBT), sigmoidoscopy or colonoscopy for colorectal cancer, prostate-specific antigen (PSA) for prostate cancer, chest computed tomography (CT) scan for lung cancer in current and former smokers, and the Pap test for cervical cancer. They incorporated trials with a follow-up period of 10 to 15 years, as this timeframe is widely accepted for observing the benefits of screening.
The evidentiary body included 4 clinical trials assessing sigmoidoscopy, 4 assessing FOBT, 4 assessing PSA, 3 assessing chest CT, 2 assessing mammography, and 1 assessing colonoscopy. Additionally, 1 study reported on multiple screening tests—including PSA, chest imaging, sigmoidoscopy, and cancer antigen 125 (CA-125)—to identify ovarian cancer. The analysis ultimately did not include results for cervical cancer screening because no randomized clinical trials with cancer-specific or all-cause mortality endpoints and long-term follow-up were identified for this type of screening. In total, approximately 2.1 million individual patients were enrolled in these clinical trials.
The results of this study demonstrated that the only screening test that significantly extended a patient's lifespan was sigmoidoscopy, which increased longevity by 110 days (95% CI, 0-274). There were no statistically significant impacts on longevity with mammography (0 days; 95% CI, -190 to 237) or FOBT screening (0 days; 95% CI, -70.7 to 70.7).
Colonoscopy screening (37 days; 95% CI, -146 to 146), PSA screening (37 days; 95% CI, -37 to 73 days), and chest CT screening (107 days; 95% CI, -286 to 430 days) showed a potential association with increased longevity. The clinical trial, which included multiple cancer screening tests, demonstrated a mean increase in longevity of 123 days (95% CI, 6-227).
Patients may want to discuss with their nursing care team members about the findings of this study and how it might influence screening recommendations.
It's important for patients to understand that the objective of cancer screening is not necessarily to increase overall life expectancy, but rather to prevent premature death from specific types of cancer, as outlined by Dr. William Dahut, the chief scientific officer for the American Cancer Society.2 For example, if an individual’s life expectancy was 80 years at birth, regular cancer screenings may prevent them from dying prematurely at 63 or 74, but it does not necessarily help them reach 81 or 82 years old.
Further, nurses can emphasize that ongoing research in cancer prevention aims to improve cancer screening tests. For instance, as artificial intelligence (AI) advances and becomes more prevalent, it may be employed to enhance cancer screening. AI has already shown promise in improving the accuracy of colorectal cancer screening3 and breast cancer screening.4
The authors of the meta-analysis discussed here have pointed out the associated risks with cancer screening tests. Nurses are used to discussing these benefit and risk profiles with their patients. The most invasive routine cancer screening test is a colonoscopy, and there is a risk of colon perforation during the procedure. However, it's important to note that this is an exceedingly rare adverse event, with estimates suggesting it occurs in 0.005% to 0.085% of colonoscopies performed.5 When considering this statistic, it's also essential to acknowledge that colonoscopies serve various diagnostic purposes beyond cancer screening alone. For example, patients who present with rectal bleeding may undergo a colonoscopy for diagnostic purposes, and individuals undergoing cancer treatment who develop diarrhea may also undergo a colonoscopy to determine the cause of the diarrhea. The risk of post-colonoscopy complications is higher among older patients and those with inflammatory bowel disease.5
In conclusion, the insights provided by the recent meta-analysis discussed in this article raises important questions about the complex world of cancer screening. We live in a world where we do not have all the answers and screening tests are not perfect, but without these tests, we would not have remarkable success stories of early detection and curative treatments. This recent meta-analysis reinforces the need for open and informed discussions with patients, personalized decision-making, and a commitment to advancing cancer screening technology.