Prevalence study of intermittent hormonal therapy of Prostate Cancer patients in Spain

Abbreviations

ADT: Androgen Deprivation Therapy

ATC: Anatomic Therapeutic Code

CAD: Continuous Androgen Deprivation therapy

ELD: Effect duration of the Last Dose

GPC: Clinical Practice Guideline

IAD: Intermittent Androgen Deprivation therapy

%IAD: Percentage of time off treatment

IntT: Interval Time

LHRH analogue: Luteinizing Hormone-Releasing Hormone analogue

PCa: Prostate Cancer

P_IAD: Prevalence of Intermittent Androgen Deprivation therapy

PIIT: Potentially Intermittent Interval Time

PSA: Prostate Specific Antigen

Introduction

Androgen deprivation therapy (ADT) is the main indication for Prostate Cancer (PCa) patients with metastatic disease and the most used therapeutic approach to treat patients who experience a biochemical relapse after radical prostatectomy. Reduction of circulating levels of androgen hormones can be achieved either with drugs, such as luteinizing hormone-releasing hormone analogues (LHRH) or with orchiectomy, which is irreversible. Nevertheless, ADT is associated with a wide array of adverse effects¹ ranging from the well-known hot flushes, loss of libido, gynecomastia, or erectile dysfunction up to midterm consequences such as bone fractures, depression, diabetes, and hematologic² and cardiovascular events.^3,4 Importantly, all of these undesirable effects increase with the duration of ADT.⁵

In the 1990s, as a response to minimise these negative outcomes, intermittent androgen deprivation therapy (IAD) emerged as an alternative to continuous androgen deprivation therapy (CAD) but not without controversy regarding its feasibility.⁶ Over the years, it has been shown that IAD can improve patients’ quality of life by reducing toxicity,⁷ reduce costs⁸ and potentially delay the onset of resistance to chemical castration.⁹ Recent strong evidence from randomized clinical trials^10–14 and systematic reviews,¹⁵ as well as favourable recommendations included in recently updated clinical guidelines,^16–18 highlight the potential benefits of IAD, supporting its use as an alternative treatment.

Despite the potential advantages of IAD, in a previous study we detected a low use of this approach in Catalonia (Spain)¹⁹ compared to recent evidence of IAD utilization in Canada.²⁰ We conducted the current study with the same methodology but covering a much bigger area of Spain (17 million inhabitants from four autonomous communities) to assess the prevalence of IAD with real-world data.

Methods

Exposure parameters

To distinguish between the CAD and IAD regimens, we identified all the periods during which patients received no LHRH analogue or Potentially Intermittent Interval Times (PIIT). We first identified all interval times (IntT), defined as the period between any two consecutive dispensations for each patient, together with the effect of the last dose (ELD), identified as the time period during which the patient was covered by the medication, as shown in Figure 1. Further details about the methods followed can be consulted in our previous publication.¹⁹ Table 1 summarizes the type of LHRH analogue used, the total dose of the commercially available formulation, and the corresponding total duration of action of each dose. Although an intermittency gap usually starts after a minimum of six months of continuous hormonal treatment to reconfirm patient castration (PSA < 4 ng/mL), in our study, we considered three months as the minimum potential gap in order to have a conservative approach in IAD estimation.

Figure 1. Representation of the parameters needed to identify the intermittent periods in a 36-month scenario.

Table 1. LHRH analogue sustained-release formulations used, including dose and expected duration of action.

	Dose, mg
	≤2	3.30	3.60	3.75	6.60	7.50	9.90	10.80	11.25	22.5	30	45	50
Busereline	1 d*	1 m*	-	-	2 m	-	3 m	-	-	-	-	-	-
Gosereline	-	-	-	-	-	-	-	3 m	-	-	-	-	-
Histreline	-	-	1 m	-	-	-	-	-	-	-	-	-	12 m
Leuproreline	1 d	-	-	1 m	-	2 m	-	-	3 m	6 m	6 m	6 m	-
Triptorelin	1 d	-	-	1 m	-	-	-	-	3 m	6 m	-	-	-
Nafarelin	1 d	-	-	-	-	-	-	-	-	-	-	-	-

* Exposition measure: d = day/s, m = month/s.

Results

For the full study period (2011-2016), a total of 863,005 dispensations corresponding to a total of 65,752 men, including either LHRH analogues administered alone (353,162) or in combination with anti-androgens (509,843), were made in Catalonia, Madrid, Basque Country and Navarra. Previously, 309 males under the age 18 were excluded together with 7,731 subjects that were dispensed only with antiandrogens, because complete castration was not guaranteed. Additionally, 2012 data from the Basque Country were considered inconsistent (likely incomplete electronic system introduction in this area) and were also excluded from the analysis. Finally, a total of 44,264 PCa patients were included in the study, as summarized in Figure 2. Overall, the mean (±SD) age of the patients was 76.9 (±10.4) years, although 81% were older than 70 years and 47% older than 80 years.

Figure 2. Patient distribution flowchart.

Of the total men (44,264) finally included in the study and taking LHRH analogues alone, 36,775 (83%) were under CAD therapy and 7,489 (17%) under IAD therapy, considering the full five-year period of the study. However, this value of global prevalence represents an overestimation of the actual annual prevalence of IAD, as can be observed in Figure 3. For example, among the ten patient profiles simulated, only five profiles (6 to 10) fulfilled IAD requirements at least once (5/10 cases where “Potential IAD = Yes”), when considering the six years globally. Then, the global IAD prevalence was of 50%. However, when considering each year separately, the annual prevalence varied from 0 to 50%, with a mean annual prevalence of 24%. The age distribution of the patients according to the treatment regimen (IAD vs CAD) is shown in Figure 4. Patients on the IAD regimen were somewhat older compared to the total patients under continuous hormonal therapy. The proportion of octogenarians and older patients under IAD therapy (56.7%) was higher compared to those under CAD (45.1%).

Figure 3. Simulation of 10 putative subject profiles in terms of CAD or IAD.

Figure 4. Age distribution of prostate cancer patients under IAD or under CAD.

The five-year prevalence (P_IAD) of patients under an IAD regimen was 6.6% in the total population studied. The global prevalence of intermittency slightly increased from 8.2% in 2012 to 8.4% in 2013, but later decreased to 3.6% in 2016. We also calculated the %IAD during the five-year study period with a total %IAD value of 5.6%, which is rather consistent with the P_IAD figure reported earlier.

Statistically significant differences (P < 0.0001) were observed in prevalence of intermittency among the four Spanish regions and among the five years of study (2012-2016). The P_IAD shows that in 2012 Madrid had the highest prevalence of IAD therapy (10.7%), followed by Navarra (8.2%) and Catalonia (5.8%). Peak values obtained were up to 14.2% [2014] in Madrid, 8.5% [2013] in Navarra, 8.4% [2013] in Catalonia, and 3.8% [2015] in the Basque Country; thereafter, the use of intermittent treatment decreased to 4.3% by 2016 in Madrid, 4.0% in Catalonia, 3.4% in Navarra and 2.5% in the Basque Country. Table 2 shows the total P_IAD distributed per community per year, as well as %IAD for each community.

We found that the most representative non-treatment period lasted for a median of six months (ranging from 3 to 58 months) considering all four areas. In Madrid and Catalonia, the median of the PIIT intervals was 6.2 months with an IQR of 7.1 and 9.2 months respectively, while in the Navarra and Basque Country the PIIT intervals were shorter and less variable: 5.1 months (IQR 4 months) and 4.0 months (IQR 3.1 months), respectively. In the four areas the global tendency was to increase the duration of the “off” period from four (2012) up to six months (2016).

The most prescribed drug in all four communities during the five-year study period was leuprorelin, followed by triptorelin and goserelin (representing globally a 51.72%, 34.72%, and 12.33%, respectively) of the total LHRH analogues dispensed.

The global mean cost of hormonal therapy per year was 25 million euros for LHRH analogues and 6.3 million euros for anti-androgens for the four regions. Along the study period, the total expenditure in Catalonia, Madrid and Navarra decreased from 34.7 million euros [2011] down to 25.3 million euros [2016]. Figure 5 plots the changes in total cost for each specific LHRH analogue per year. The global mean (±SD) cost per dispensation was 214.6 ± 33.5 euros in 2011, then decreased to 201.7 ± 31.9 euros in 2014, and increased again up to 213.9 ± 26.3 euros in 2016.

Figure 5. Total cost of LHRH analogues per year from 2011 to 2016 in Spain.

Discussion

Our results show that, taking either the mean P_IAD (6.6%) or the %IAD (5.6%) as reference, IAD use was in the range of 6% in Spain. These results are in agreement with our previous estimations from Catalonia (2008-2012): P_IAD = 4.2% and %IAD = 1.7%¹⁹ and confirm a low global utilisation of IAD in Spain. Even worse, the IAD utilisation rate has evolved in a progressively decreasing manner along the current study period, ranging from 8.4% (2013) to 3.6% (2016). Among the four Spanish regions, the %IAD showed that Madrid had the highest prevalence of intermittency (11.4%), followed by Catalonia (5.2%), Navarra (4.3%) and the Basque Country (1.7%). The P_IAD showed a decreasing trend along the study period until 2016 in Madrid (4.3%), Catalonia (4.0%), Navarra (3.4%) and the Basque Country (2.5%). Based on the obtained data, we interpret that the well-known role of intermittent treatment in hormonal therapy, based on sound evidence from randomised controlled trails^10–14 and systematic reviews,^15,16 does not appear to be influencing actual clinical practice in a significant proportion of cases. It seems that the necessary trade-off between benefits and adverse effects could be much improved in those situations where IAD is as effective as CAD, since adverse effects of IAD should be lower for a broad range of morbidities.^{4,13,15,21–23} An international survey conducted in 19 countries asking 441 physicians currently treating PCa patients, showed that 23% of non-metastatic patients treated with gonadotropin-releasing hormone analogues were using IAD. Additionally, the same authors agree with our results that the CAD and IAD use in Spain among men with non-metastatic prostate cancer, was of 35.7% and 6.9%, respectively.²⁴ Reference countries like France, Italy or Germany showed higher IAD use than Spain (9.1, 13.9 and 14.3%, respectively), still based on physicians opinions. This fact could be explained by the relatively higher healthcare pressure of physicians in Spain than in France, Italy or Germany (3.8 vs. >4.1 per 1000 people in 2015, respectively). Further evidence suggesting that the use of IAD is low in Spain, comes from data collected in Manitoba (Canada), where 74% (447/601 nonmetastatic hormone-sensitive PCa patients) were using IAD for the management of their relapse.²⁰

When analysing the data related to the duration of the “off” periods, or halted medication periods, we observed that the median duration varied between 4 and 6,2 months in all four regions (ranging from 3 to 13 months). These off-treatment periods are concordant with the corresponding values reported by Crook et al., that ranged from approximately 20 months in the first non-treatment interval, down to three months in the 6^th interval.¹³ Globally, there was also a tendency to increase the median duration of the pause period between 2012 (three to four months) and 2016 (five to six months). This may suggest that prescribers using IAD are progressively more confident with the risk/benefit balance of this therapeutic strategy. This is in agreement with the fact that patient-reported outcomes were significantly better in IAD versus CAD at 20 and 38 months of treatment, based on validated quality of life questionnaires in Japan.²⁵

We calculated that the total cost of hormonal therapy in the four autonomous communities was 31.3 million euros per year (25 million corresponding to LHRH analogues and 6.3 to anti-androgens), which represents a mean of 214 euros per dispensation. The fact that the mean cost per dispensation declined from 214.6 euros in 2011 to 201.7 euros in 2014 could be related to the fact that in 2012, the Spanish health authorities introduced restrictive measures for the sustainability of the National Health System (Royal Decree 16/2012)²⁶ and all kind medication were reduced in the whole country by as much as 12 million per month.²⁷ However, thereafter the cost increased again up to 213.9 euros per dispensation in 2016. Obviously, the efforts to enhance the use of IAD would produce important cost savings due to the reduction in expensive drug consumption, which some authors estimate in the range of one-third of CAD.¹² In the population studied, we would be talking of around half a million savings per million inhabitants per year.

If PCa patients are to be actively involved in their decision process related to hormonal therapy medications, as current clinical guidelines suggest, they should know the existing sound evidence that shows similar overall survival of both CAD and IAD users, but the broader span of morbidities associated to CAD. From the physicians’ point of view, the PSA levels (54%), patient request (48%), desire to maintain sexual function (40%), patient age and comorbidities (38%) were reported as the most frequent reasons for IAD use.²⁴

The main strength of our study is the capacity to analyse all public health systems electronic dispensations data from the selected Spanish regions, which eliminates any potential selection bias. They constitute a very large sample size, which favours the representativeness of the whole Spanish population. Also, the reliability of the database reduces information bias and missing data problems as previously observed by other authors.²⁸

Due to the administrative nature of our data sources, our study is not able to estimate whether patients identified under IAD are clinically appropriate or not. However, taking into account the conservative approach that we used and compared to the real-world utilization in Canada²⁰ and 19 other countries,²⁴ we could say that the use of IAD in Spain could be significantly increased, leading to the consequent improvement in patients’ quality of life²⁵ and significant savings for the National Health Service.¹⁰ We plan to conduct an audit in a sample of the electronic records of PCa patients who were potential IAD candidates, to assess if they fulfilled the clinical criteria for having eventually stopped the hormonal therapy.

Conclusions

We conclude that the IAD use in Spain was relatively low during the study period, although enough time has passed since the related international recommendations were published. As a consequence, an important proportion of hormone-sensitive prostate cancer patients could be currently missing the chance to reduce avoidable adverse effects and to improve their quality of life, apart from the important repercussion that this expense has on the health budget in times of crisis. The population-based method to estimate the IAD prevalence seems to be a quite consistent approach and opens the door to comparable international data to set up reference standards on adequate IAD utilisation.

Data availability