For six of eight types of cancer studied in new research, death rates remain stable or falling, despite the explosion in diagnosed cases. What it means? Should we change something?
The number of cancer diagnoses in people under 50 has increased markedly in recent decades, in Portugal and in many other parts of the world.
But there are medical experts who have been asking: do all these cancers really need to be found and even treated? How many of these tumors, if they had never been discovered, would have ever caused problems?
Not all cancer kills
Research has shown for decades that not all cancers are aggressive or lethal. Some tumors shrink on their own, others stop growing or remain so small that they never cause symptoms or spread. Several autopsies reveal that many people die with small cancers that they never knew they had.
In the case of prostate cancer, for example, autopsies cited by the show that the disease can appear in men in their 20s. By age 70, about a third of white men and half of black men had microscopic, undetected prostate cancer during their lifetime. In thyroid cancer, a study in Finland found hidden malignant nodules in at least a third of adults, although less than 1% of people with this type of cancer die from the disease.
The problem is that, in each individual, it is practically impossible to know in advance whether a cancer will be deadly or not. And, once treated, you will never know if that tumor really needed to be fought.
Incidence and mortality
To the doctor H. Gilbert Welchfrom Brigham and Women’s Hospital at Harvard Medical School, there is a simple way to understand, at a population level, whether we are facing a “false alarm” or a true sign of danger: compare the diagnosis curve with the death curve.
If we are detecting more really dangerous cancers, mortality should go up; But if diagnoses soar but deaths remain stable or decline, many tumors found would never have been fatal.
This is what happened with thyroid cancer in South Korea. The widespread use of neck ultrasounds led to an increase in diagnoses, but the number of deaths did not increase. Subsequent estimates suggest that around 90% of tumors identified and treated in women never need to have been found.
Aware of this history, Welch and two colleagues analyzed data from the last 30 years for the eight cancers that have increased most in people under 50. They wanted to know if only the number of diagnoses is rising or also the number of deaths.
For six of the eight types of cancer, death rates remain stable or fallingdespite the explosion of diagnosed cases. The exceptions are endometrial cancer.
In colorectal cancer, deaths increase by around 0.5% per year, while the incidence grows four times faster, around 2% per year. In the case of endometrium, mortality practically follows the pace of new cases, also in the order of 2% annually. In these two tumors, experts say, the alarm seems to be really necessary.
Obsessed with exams?
For some oncologists, an important part of the explanation for the “epidemic” of cancer in young people lies in the way any health complaint is investigated today. Tomography (CT), ultrasound and magnetic resonance imaging are increasingly sensitive and used. Many cancerous lesions that would otherwise never be discovered appear in tests ordered for other reasons.
Furthermore, the “” speech can fuel pressure to do more tests and thus find more anomalies, the authors warn the NYT.
The big problem is the consequences of treating cancers that would never need treatment: infertility, organ damage, after-effects of surgery and chemotherapy, years of intensive surveillance. Not to mention the financial burden.
For these reasons, the authors advocate two key changes: fewer routine exams in people without symptoms and more restraint in the aggressive investigation of small anomalies detected by chance.
But this reading differs from that of experts who see the rise in diagnoses as a concrete and very real threat. These point to several explanatory hypotheses: environmental toxins, the obesity epidemic, changes in the intestinal microbiome and diets rich in ultra-processed foods. The speed at which cases are rising in recent decades, they argue, forces us to look at rapid changes in lifestyle and the environment. In endometrial cancer, much of the increase in cases is attributed to obesity.
What to actually treat
A possible way out of this impasse is to adjust the strategy depending on the type of cancer. Tumors that tend to be indolent, such as many prostate and thyroid cancers, may be monitored closely rather than treated immediately. This model, known as “active surveillance”gained strength especially after the experience with the prostate specific antigen (PSA) test in the United States.
When PSA began to be used on a large scale, between the late 1980s and early 1990s, prostate cancer diagnoses tripled in a few years. Many men have undergone aggressive surgery and radiation therapy for small tumors that would never have shown signs. However, global prostate cancer mortality has not exploded, suggesting an “outbreak” of detection rather than disease.
Today, many prostate specialists argue that, in more than half of cases considered “low risk”, it is reasonable to postpone treatment and opt for surveillance with periodic analyzes and imaging exams. Treatment is reserved for signs of progression.
