Introduction

The predictions of the Federal Statistical Office foresee a substantial increase in the population proportion over 60 years of age in the context of demographic change [1]. At the same time, an increase in cancer cases is expected within this development [2]. This results in a rising demand for care and treatment. However, no estimates are currently available regarding the extent of the available resources.

The data of the German Centre for Cancer Registry Data provide excellent information on the incidence rates for most entities throughout Germany. However, more data on different oncologic therapeutic demands radiation therapy (RT), surgical treatment, and systemic therapies in Germany are urgently needed.

Only historical collectives with limited significance for current and future events are available. Information on the required therapies in connection with current trends can help estimate future needs and ensure maintenance of sufficient resources [3]. It is essential to see the demographic change in the German society as a potential driver for a rising rather than a declining demand [4].

Estimates are available for the most common entities in the clinical field [2], but also for rare entities such as thyroid cancer [5]. Some studies deal with the demand for chemotherapy [6]. Still, to our knowledge, no estimates are currently available regarding the demand for RT. Prostate cancer (PC) is among the most common entities with a high societal and individual disease burden [7, 8]. In addition, valid estimates of the expected primary cases in the future are already available, but data on demand for RT are still lacking.

How does demographic change influence the incidence of PC cases, and how does this influence the demand for RT?

Methods

This work estimates the demographic influence on the incidence of PC in Germany. In addition, we estimate the impact of these changing incidences on the requirements for RT.

We captured the incidence values for PC from 1999 to 2019 for the age cohorts 50–54, 55–59, 60–64, 65–69, 70–74, 75–79, 80–84, and +85 years from the German Centre for Cancer Registry Data of the Robert Koch Institute [9]. In addition, we retrieved the demographic survey from 1999 to 2019 and the population projection for 2030 for the respective cohorts via the GENESIS database of the Federal Statistical Office [1]. In the estimate, we assumed a substantial increase in life expectancy. The birth rate and the migration index are negligible because they have little or no influence on the age cohort relevant for RT. Based on the retrospective incidence and population data from 1999 to 2019, we used linear regression to determine the correlation between incidence rate and population size for each age cohort (Eq. 1).

Equation 1: a is defined as the regression line that describes the relationship between population size and the magnitude of the increase in incidence rate. The value b in the linear regression formula describes the baseline incidence rate of the specific age cohort, and x represents the population size for the corresponding age cohort to determine the incidence rate for 2030.

$$a = \frac{\left( N \times \sum (\text{Incidence} \times \text{Population}) - \sum (\text{Incidence}) \times \sum (\text{Population}) \right)}{(N \times \sum (\text{Incidence}^{2}) - (\sum \text{Incidence})^{2})N}$$
(1)
$$b=\sum \left(\text{iPopulation}\right)-a\times \frac{\sum \left(\text{Population}\right)}{N}$$
$$\text{estimated}\,\text{Incidence}\,for2030=ax+b$$

Using the 2030 population projections, we estimated the 2030 incidence value for the defined age cohorts. We calculated the expected cases of disease based on the estimated incidence and, assuming the RT demand of 2016 published in the cancer report 2016 [10], calculated the RT demand for 2030. Finally, we compared our estimation with the historical collective of 2016.

Results

The calculated estimates of incidence values for 2030 in the age cohorts show an increase in most of the age cohorts, with the most pronounced increases in the groups 80–84 and +85 years. However, we also describe a decrease in the age groups 60–64, 70–74, and 75–79 years (Table 1).

Table 1 Comparison of incidences recorded in 2016 with incidences estimated for 2030
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The estimate of the absolute number of cases shows no increase in the number of new cases in the 60–64 and 65–69 years cohorts, despite the falling incidence value of the estimate for 2030. We expect an increase in the absolute number of cases and, specifically, in the demand for RT in all cohorts except for the age cohorts 55–59 and 70–74 years. However, in both cases, this decrease is less than 10%. The absolute strongest increase is calculated for the group 80–84 years, while the relative percentage increase is estimated to be strongest in the +85 years cohort (Table 2). Overall, cohorts, new cases, and the need for radiotherapy are increasing.

Table 2 Comparison of new patients and RT demand from 2016 to 2030. We estimate the largest increase in the age cohorts 75–79 and 80–84 years, and in the group +85, which also shows the largest percentage increase
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Discussion

Within the estimate for 2030, we can describe an increase in incidences in almost all age cohorts. Moreover, the increases are significantly more significant than those in the just two age groups with decreases. This also influences the number of cases and, therefore, we expect an increase in the number of primary disease cases in 2030.

If the indications for RT in the primary situation were to be set according to the baseline situation of the historical collective of 2016, an increase in demand for RT in the primary disease case would also be expected here.

The peculiarity here, however, is that there would be a shift to the right of the curve, and the largest proportion of absolutes would be expected in the 75–79 years age group (Fig. 1) simultaneously. There is only a slight drop in indications in the 60–64 and 65–69 years age groups. In both cases, treatment cases were reduced to below 10%.

Fig. 1
figure 1

Comparison of radiotherapy demand of the historical collective with the estimated demand for 2030. (The increase is particularly noticeable in the age cohort 70–74 years) RT radiation therapy

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Our estimates of total primary cases are comparable to a 2016 paper by Quante et al. The paper predicts a number of 121,335 primary cases of PC in 2030 [2]. However, our estimates are slightly lower, by about 10,000 cases.

Still, within the scope of our estimate, two points have influenced the number of cases. First, we neglect primary cases that occur at an age of younger than 50 years entirely in our estimation. In addition, we consider the excess mortality of the corona pandemic through the current population projection query [11]. Forecasting must adapt dynamically to changes and trends to provide an accurate projection.

A trend-adapted adjustment may also become relevant for further design of the screening strategy in Germany. The expansion of PSA screening affects the incidence of newly diagnosed PC [12]. Starting at the age of 45 years, statutory health insurance funds cover the costs of PSA screening. However, there is no screening call for the relevant age groups, as is the case, for example, with mammography for breast cancer. Recently published data showed the relation between the decreasing risk of cancer-specific death and early diagnoses in younger ages [13]. Therefore, expansion and adaptation of the screening strategy could also lead to a further increase in the number of cases and, thus, further raise the incidence rates in the cohorts.

However, in addition to the screening strategy, there are also difficulties in defining RT strategies in the context of the initial diagnosis. In the context of the query on the therapeutic approach in Germany, the German Centre for Cancer Registry Data was unable to provide us with any more current calculation basis beyond the historical collective of 2016 [10, 14]. Nevertheless, the indication for prostate RT in the primary situation is increasingly expanding, e.g., by including oligometastatic primary situations in the German healthcare reality with a wide range of recommendations from the German Society for Radiotherapy (DEGRO) [15]. This approach is supported by solid evidence from the Stampede study [16]. Furthermore, early initiation of therapy in the patient population of localized primary situations improved disease-free survival and reduced the need for antihormonal therapies [17].

Also, the decision on initial primary therapy needs to be further discussed. The UK ProtecT trial provides long-term data showing that RT is noninferior to surgical therapy for localized primary prostate cancer [17]. A more balanced approach to counseling could increase the trend towards RT in older age groups. The rightward shift of the curves compared to the historical collective shows the trend to irradiate older patients.

The tendency to treat older patients with RT and younger patients with surgery was a trend already evident in a retrospective analysis of treatment data from the Swedish healthcare system between from 1998 and 2012. While in the age cohort 60–64 years, the indication for surgery decreases, in the 70–74 years cohort, only 11% of patients receive surgery, and the indication for RT increases from 60–64 years of age (19.3%). In the 70–74 age cohort, the proportion is still 17.5% [18].

German data on the indication for primary prostatectomy in the same population would be very informative but are only available to a limited extent and insufficient to construct an accurate model. This information could be helpful to plan for care needs more accurately in the healthcare system.

In addition to the planning of healthcare delivery strategies, the late effects associated with treatment also play an essential role in the delivery of healthcare. Modern RT techniques increasingly reduce late complications and create an excellent posttherapeutic quality of life [19, 20]. However, a sufficient follow-up after the treatment remains indispensable for validation of the outcome. Not only must a sufficient number of specialists be available for application of the treatment itself, but structured aftercare must also be available.

A 2019 paper estimated the global demand for chemotherapy considering demographic change. The authors see an increasing demand of up to 51% more. In addition, an estimate was also given that this will also result in a corresponding need for qualified specialists [6]. Corresponding analogies can be derived for RT, indicating a rising demand for qualified specialists to meet the demand for treatment.

The data from the historical collective on the indication of 2016 also do not reflect the type and technique of RT or the indication (curative versus palliative). The collection of data consisted of indications for radiotherapy following initial diagnosis of legally insured persons in Germany [10]. However, it was not recorded whether the radiotherapy was indicated in the primary or metastatic situation. Therefore, a portion of the population may have also been treated with radiotherapy in the palliative setting, which would explain the constant proportion of patients over 80 years of age with indications for initial radiotherapy. Adequate representation of indications can only be achieved through better data transmission to cancer registries.

Furthermore, in addition to the indication, the type of administration of radiotherapy is also not represented. Besides conventional teletherapy, prostate brachytherapy is a very suitable treatment technique within its indication limits in terms of efficacy and toxicity [21]. However, this application is not available everywhere. Furthermore, hypofractionated techniques can also reduce the use of treatment facilities, but this approach does little to change the continuing need for specialists in treatment application, and it also requires adequate technical equipment, such as image guidance systems, to ensure the safety of treatment application [22]. Ultimately, it must also be considered that there is currently no clear German guideline recommendation for hypofractionation of prostate RT [23].

The demand for future treatment is never exactly estimable, but trends in population development and treatment prescriptions can help make estimates to plan resource-oriented care. Therefore, comprehensive reporting to the German cancer registries is essential to create this data basis.