It is one of the striking findings of a study into male-female differences in a large number of cancer types, which the Integrated Cancer Center of the Netherlands (IKNL) is releasing today. The knowledge center studied, among other things, the treatments that patients receive, the occurrence of cancer types, survival rates and quality of life.
The knowledge center calculated that 48 percent of women with metastatic colorectal cancer do not receive tumor-targeted treatment, compared to 40 percent of men; for advanced gastric cancer this difference is 7 percentage points.
Another difference: last year, more than 65 thousand men in our country were told that they had cancer, compared to more than 58 thousand women. Adjusted for age differences, men have a 10 percent greater risk of the disease. Women have the greatest risk of breast cancer, men of prostate cancer. This is followed by skin, lung and colon cancer respectively. The prognosis is slightly better for women: five years after diagnosis, 71 percent of women are still alive, compared to 65 percent of men.
It is striking that most cancer types examined increasingly occur equally in both sexes. For example, while in 1990 men were almost six times more likely to develop lung cancer than women, the ratio is now almost equal. An important cause of this is that women have started smoking more over the last thirty years, and men less. Smoking causes about 85 percent of all lung cancer cases.
“An important report,” responds Toine Lagro-Janssen, emeritus professor of women’s studies and medical sciences at Radboud UMC. ‘Such a broad overview has never been made for cancer before. In cardiovascular diseases, for example, it was already known that there are large male-female differences, for example in symptoms. But in many other conditions this is not taken into account enough.’
For their analysis, the researchers studied various sources, including the Dutch Cancer Registry. In this database, the IKNL has kept data on all cancer cases in the Netherlands since 1989, such as diagnoses and treatments.
By listing all the figures, IKNL wants to create more awareness, says research leader and epidemiologist Melinda Schuurman. ‘Not only among practitioners and patients, but also among policy makers and trainers. In addition, we call on researchers to more often look at men and women separately in clinical studies,” says Schuurman.
Bladder cancer (7 thousand cases per year) appears to be discovered on average at a later disease stage in women than in men. A possible explanation for this, Schuurman and her colleagues write, is that women would be less likely to worry about typical symptoms such as blood in the urine; GPs may also be more likely to think of a more harmless bladder infection in this case. Men are diagnosed later with thyroid cancer.
It is unknown why women are less likely to receive treatment that targets the tumor, such as in advanced stomach cancer. Schuurman: ‘We therefore argue for more research, for example into what happens in the decision-making process surrounding treatments.’
Truuske de Bock, professor of cancer epidemiology at the UMC Groningen and not involved in the study, also emphasizes the need to further investigate these differences. ‘Which treatment is used is a decision made by the doctor, in consultation with the patient and his environment. Do healthcare providers offer women other treatments? Or are women less likely to opt for drastic tumor-targeted treatments because they want to burden their environment less with care tasks?’ What may also play a role, Schuurman adds, is that women may suffer more from the side effects of chemotherapy.