TUTOR ANSWER: What's the difference between incidence rates and mortality rates?

Incidence rates and mortality rates can be confusing. So let's talk a little bit more about them!

The cancer incidence is really based on the number of new cases of cancer per 100,000 people. We then turn the rate (per 100,000) to a percentage (per 100) to make it easier to understand. We will use 100 instead of 100,000 here for simplicity.

Let’s look at the case of lung cancer. So in a group of 100 individuals with cancer, 13 will have been diagnosed with lung cancer. This is where the 13% lung cancer incidence rate comes from.

The method to calculate mortality rate is slightly different. With mortality, the calculation is based on a group of 100 individuals who died from cancer (100 cancer deaths); not just 100 total individuals. In the case of lung cancer this means that in a group of 100 individuals who died from any type of cancer, 19 will die from lung cancer. So 19% of the total cancer deaths is due to lung cancer.

Here is a summary of that information:

% (type) Cancer Incidence = # people who were diagnosed with this particular cancer/100 individuals who were diagnosed with cancer
% (type) Cancer Mortality = # people who died from this particular cancer/100 individuals who died from cancer

[Note: % means percentage, # means number, and / means divided by.]

Let’s look at two more examples: stomach cancer and breast cancer.

In the case of stomach cancer the incidence rate is 7% and the mortality rate is 9%. This means that 7 out of 100 cancer cases will be stomach cancer but 9 out of 100 cancer deaths will be from stomach cancer.

For breast cancer, the incidence rate is 12% and the mortality rate is 6%. Here the incidence rate is higher than then mortality rate. So for breast cancer, 12 out of 100 individuals with cancer will be diagnosed with breast cancer but only 6 out of 100 cancer deaths will be from breast cancer.

Statistics are based on what individuals want to look at.

Let’s look at the incidence rates and mortality rates for all cancers. The above equations will not work in this case.

In this situation, the total cancer incidence rate is # of people diagnosed with cancer/100 total individuals and the total cancer mortality rate is the # people who died from cancer / 100 total deaths.

The rates can also be viewed in additional ways. Sometimes you will read in the news about breast cancer incidence rates based on 100 females and not total individuals (males and females). Or you may see a statistics about the cancer mortality rate in developing countries. In both these cases the population that is being examined is different.

In the Nutrition for Cancer Prevention and Longevity course, we use the equations that are listed above unless other stated. You will learn more cancer statistics for the individual cancer rates in the

BONUS Module 8, so it is important to understand these differences.

Remember to pay attention to the population that is being studied.

For additional information on understanding cancer statistics, Cancer Research UK summarises it well.

For more information regarding cancer statistics visit the GLOBOCAN website. They are an excellent source of all the latest cancer data.

AUTHOR: Written by Dr Michelle, Lead Instructor

Updated on: 29/10/2026