The majority of cancers occurs at an advanced age when fertility (and pregnancy chances) is clearly decreased.

I am sorry to disagree. Cancer is not a regulator of human population.

I also disagree with the concept that cancer is incurable. The world is full of people who had cancer and with the adequate treatment they were cured. There are also many who are not cured but the diasease is in a stable condition. Many patients who have a non metastatic cancer of prostate will die from something that is not related with their cancer.

I agree with Domenico, the majority of cancers arise in an age that is beyond fertility.

So, in this sense, WWII, or famine are  major regulators of human population, because mortality between young people exceeds those of elderly individuals, and this means that fertile lifes are lost.

I do not see that we can include cancer in the Malthusian concept of population regulators.

This is a philosophical rather than scientific question, isn't it?

"regulators of populations" impact birth rates & death rates. Unless cancers are causing more/earlier deaths, they do not really regulate the population. In fact, a higher incidence of many cancers have resulted from an ageing population which resulted from other factors impacting death rates/longevity. For example, antibiotics have reduced rates of people dying of infections and cardiac stents etc have reduced the risk of dying from heart disease. As humans live longer, the processes that cause cancer accumulate and thus we see more cancers - some we can cure, others not. 

I am not sure I have answered your question - then again I am not sure I can!

Thank you all for very insightful answers. Maybe this is just one of those questions I could've put more thought into and phrased a little better, but yes, I appreciate the time you spent voicing out your opinion about my statement.