I guess that it is caused by higher rates of identification due to newer technologies, higher survival rate leading to reocurrence or genetic susceptibility being passed on, and an increase in certain pollutants or use of substances that increase risk of certain cancers. Theres also a possibility of one type of cancer which is confused for another type when it metastasizes, which was likely more common in 1930 than today with less accurate detection and identification methods
I guess that it is caused by higher rates of identification due to newer technologies, higher survival rate leading to reocurrence or genetic susceptibility being passed on, and an increase in certain pollutants or use of substances that increase risk of certain cancers. Theres also a possibility of one type of cancer which is confused for another type when it metastasizes, which was likely more common in 1930 than today with less accurate detection and identification methods
If they didn’t correct for these factors, it would make for a very poor scientific article indeed.