# Which cancer has the worst survival rate

### What is the difference between absolute and relative survival rates?

The results of the survival time analyzes describe the average chances of survival of adult patients after a certain cancer diagnosis. For this, absolute and relative survival rates were calculated.

Absolute survival rates represent the proportion of patients who are still alive at a certain point in time after their diagnosis. For example, an absolute 5-year survival of 80 percent means that 80 out of 100 people with a certain type of cancer survived the first five years after their diagnosis.

The relative survival takes into account the fact that only a fraction of the deaths among cancer patients are due to the cancer. For this purpose, the official mortality tables of the Federal Statistical Office are used, which show the probability of survival in the general population in Germany according to age, gender and calendar year. Relative survival rates depict cancer-related mortality by calculating the quotient of the absolute survival of cancer patients and survival in the general population of the same age and sex (= expected survival).

A relative 5-year survival of 80 percent, for example, means that five years after a cancer diagnosis, the proportion of survivors is 80 percent of the proportion observed in the total population of the same age and sex over the same period. The relative survival is always higher than the corresponding absolute survival. The higher the mean age at diagnosis for the respective cancer, the greater the difference. The expected survival was calculated using the so-called Ederer II method.

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### What does the 'period method' mean?

In order to estimate the most recent survival prospects possible, the so-called period method according to Brenner was used. This takes into account all information on the survival of people who lived during a certain period of time (e.g. 2015-2016). The calculation of the 5-year survival for the period 2015 to 2016 therefore includes data from all people who fell ill between 2010 and 2016 and who had not yet died before the beginning of 2015. The result can be interpreted as an estimate of the survival rates of people diagnosed with cancer between 2015 and 2016. Naturally, the 5-year survival for these individuals can only be determined directly in 2021. Assuming a continuous improvement in survival rates over time, this method would, however, lead to a slight underestimation of the chances of survival.

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### Why was only the data from certain registers used?

Because the accuracy of survival time analyzes depends very much on the quality of the underlying data, registers were included for the current calculations that meet two criteria. On the one hand, the percentage of all malignant cancers (C00-C97 without C44) should not exceed 15% in the period under consideration. The diagnosis date of a case, which is unknown by definition, i.e. a case of illness that is only known through the death certificate, inevitably leads to the exclusion of this case from the survival time analysis. This leads to a potential overestimation of the survival rates, since, according to the results of many studies, cases tend to represent a selection of patients with shorter survival times.

The second criterion evaluates the quality of the determination of the vital status of patients who were recorded by a registry during their lifetime. International studies show that people diagnosed with pancreatic or lung cancer with metastases have a very poor prognosis. In addition, the average chance of survival with these diagnoses has not changed significantly over a long period of time. Therefore, a high proportion of surviving patients with these types of cancer determined by the cancer registry can be an indication of deficiencies in data quality or a relevant proportion of 'missed' deaths. Therefore, only those registries were included in the analysis in which patients with the diagnosis of pancreatic cancer or metastatic lung cancer had a relative 5-year survival of a maximum of 8 percent on average.

According to the two criteria mentioned above, the cancer registries in Hamburg, Lower Saxony, North Rhine-Westphalia (only Münster district) and Saarland as well as the data from Brandenburg, Mecklenburg-Western Pomerania, Saxony and Thuringia from the joint cancer registry were included in the current evaluations.

Status: December 17, 2019