1 Introduction
Prostate cancer is the most commonly diagnosed malignancy in the male genitourinary system and is estimated to account for approximately 1.4 million new cases and 375 000 associated deaths worldwide in 2020.[1] [2] [3] [4] [5] statin use on BCR in patients undergoing curative treatment, but the conclusions are inconsistent. Therefore, we performed this systematic review and meta-analysis to investigate the impact of statin use on BCR in patients undergoing RP or RT as a curative treatment for prostate cancer. Our objective was to investigate the difference in BCR risk between patients with statin use and those without such medication to assess whether statin use would reduce recurrence and progression after treatment with curative intent.
2 Methods
2.1 Search strategy and study selection
We promoted our systematic review following the guidelines of Preferred Reporting Items for Systematic reviews and Meta-Analyses and completed the registration of PROSPERO with CRD42020212969.[6] statin use in patients undergoing RP or RT as curative treatment for prostate cancer up to December 31, 2020, in the following online databases: MEDLINE, EMBASE, and the Cochrane Central Search Library. We retrieved citations using combinations of the medical subject heading terms “prostate cancer,” “biochemical recurrence,” “prostatectomy,” “radiotherapy,” “brachytherapy,” “statin ,” and “lipid-lowering drug” for medical subject heading search with the Boolean logic including “((statin ) AND (prostate cancer)) AND (biochemical recurrence),” “((statin ) AND (prostate cancer)) AND (prostatectomy),” “((statin ) AND (prostate cancer)) AND (radiotherapy)” and “((statin ) AND (prostate cancer)) AND (brachytherapy).” We also used these as keywords and text words for the freedom search. We implemented no restriction for the timing or duration of medication and different types of statins, and we also implemented no restriction for surgical approaches (open, laparoscopic, or robot-assisted RP) and radiotherapy (brachytherapy or external beam radiotherapy). Articles in languages other than English were included, whereas case reports, meeting records, and review articles were excluded. All included studies contained original data evaluating BCR associated with statin use, or these could be calculated from the data source. Additionally, we attempted to connect the corresponding authors when the data were incomplete. Independent researchers (Peng Yin and Sheng Han) individually identified candidates for review, and senior investigators (Qingfeng Hu and Shijun Tong) made the final decision to include or exclude this review.
2.2 Quality assessment of included studies
We retrieved no randomized clinical trials (RCTs) investigating this issue in the search and screening and applied the Newcastle-Ottawa Quality Assessment Scale (NOQAS) to assess the quality of the included cohort studies.[7]
2.3 Data extraction and analysis
We aimed to assess the cumulative risk of BCR associated with statin use in patients undergoing curative treatment for prostate cancer. Biochemical recurrence was defined as 2 consecutive PSA measurements >0.2 ng/mL after an undetectable PSA value following the original curative therapy (RP or RT). We analyzed BCR-free survival and calculated the pooled hazard ratio (HR) using time-to-event survival data from the included studies. When HRs could not be collected directly from articles, we tried to calculate the estimated HRs according to the practical methods given by Tierney and colleagues.[8] statin use to patients without statin use, and we performed subgroup analysis for RP and RT individually. Additionally, we performed a pooled analysis for intermediate-and high-risk patients and for patients with new statin use after curative treatment. Intermediate -and high-risk patients were identified according to the D’Amico criteria.[9] χ 2 -test using the I 2 metric, and the random-effects model was employed in pooled analysis considering the intention to generalize our results beyond the included studies, even though heterogeneity among studies was insignificant. It was almost impossible to assume that all studies shared a common therapeutic effect from a clinical perspective and that the random-effects model would provide a more conservative estimation. Egger's linear regression test and funnel plot were used to identify potential publication bias, and meta-analysis was abandoned when the bias was obvious. Statistical analysis was performed using STATA 16.0, and all statistical tests were 2-sided and declared significant when P < .05.
3 Results
We identified 27 studies for this meta-analysis, and the flow chart of the search and selection is shown in Figure 1 .[10–36] statin use and 25937 patients without such medication were included; 18 studies evaluated the impact of statin use in patients undergoing RP and 9 studies evaluated the impact of statin use in patients undergoing RT. In addition, 7 studies investigated BCR risk associated with statin use in intermediate-and high-risk patients, and 5 studies compared BCR differences between patients starting statin use after curative treatment and patients without statin use. All included studies are characterized in Table 1 , and we used the NOQAS to assess the quality of the included cohort studies. The results ranged from 4 to 7, with a higher score indicating a higher quality study; the three dimensions of selection, comparability, and outcome in the NOQAS are shown in Figure 2 in detail.
Figure 1: Flow chart of study selection and inclusion.
Table 1 -
Characteristics of included studies.
Study
Area
Treatment†
Timing‡
Statin Nonstatin
NOS
Prabhu N. 2020
USA
RP
Both
1222
1866
7
Jarimba R. 2020
Portugal
RP
Before
320
382
5
Meijer D. 2019
Netherlands
RP
Before
252
870
5
Wettstein M.S. 2017
Switzerland
RP
Before
54
265
6
Liu X. 2017
USA
RT
Both
158
223
5
Lyon T.D. 2016
USA
RP
Before
824
2218
6
Ohno Y. 2016
Japan
RP
Before
69
493
5
Cattarino S. 2015
France
RP
Before
156
435
7
Song C. 2015
Korea
RP
After
210
1671
5
Bahig H. 2015
Canada
RT
Both
762
1010
4
Cuaron J. 2015
USA
RT
both
273
481
5
Oh D.S. 2015
USA
RT
Both
174
73
4
Ishak-Howard M.B. 2014
USA
RP
Both
258
281
7
Allott E.H. 2014
USA
RP
After
400
746
6
Rieken M. 2013
NA and EU
RP
Before
2275
4567
7
Kontraros M. 2013
Greece
RP
Both
107
481
7
Chao C.(P) 2013
USA
RP
After
654
530
6
Chao C.(R) 2013
USA
RT
Before
401
373
6
Mass A.Y. 2012
USA
RP
Before
437
1009
5
Misrai V. 2012
France
RP
Both
97
280
4
Ritch C.R. 2011
USA
RP
Before
281
980
6
Ku J.H. 2011
Korea
RP
Before
87
600
5
Kollmeier M.A. 2011
USA
RT
Both
382
1299
6
Krane L.S. 2010
USA
RP
Before
1031
2807
5
Gutt R. 2010
USA
RT
Both
189
502
6
Soto D.E. 2009
USA
RT
Both
220
748
4
Moyad M.A. 2006
USA
RT
Both
191
747
6
† RP = radical prostatectomy, RT = radiotherapy, including brachytherapy and external beam radiotherapy.
‡ before = initiating statin use before treatment included, after = initiating statin use after treatment included, both = either statin use before or after treatment included.
Figure 2: Characteristics of NOS for included studies.
We revealed that statin use appeared to be associated with a potential tendency to improve BCR-free survival, although we failed to observe a significant difference (pooled HR = 0.88, 95% CI 0.77 to 1.00, P = .05) (Fig. 3 ), and subgroup analysis of RP (pooled HR = 0.92, 95% CI 0.79–1.07) and RT (pooled HR = 0.78, 95% CI 0.61–1.00) also showed insignificant results. Additionally, only high-risk prostate cancer patients experienced improved BCR-free survival from statin use (pooled HR = 0.51, 95% CI 0.37–0.70, P < .01), while an insignificant difference was observed in the subgroup analysis including both intermediate-and high-risk patients (pooled HR = 0.89, 95% CI 0.78 –1.01, P = .08) (Fig. 4 ). In addition, starting statin use after curative treatment did not improve BCR-free survival (pooled HR = 0.85, 95% CI 0.62–1.18, P = .33) (Fig. 5 ). No publication bias was observed in the funnel plot or Egger test.
Figure 3: Overall and subgroup analysis comparing BCR-free survival in patients with ever statin use compared to those with never statin use using the random-effects model.
Figure 4: Pooled analysis comparing BCR-free survival in intermediate and high risk patients.
Figure 5: Pooled analysis comparing BCR-free survival in patients with statin use after curative treatment compared to those without statin use.
4 Discussion
Although previous studies have evaluated the potential improvement of statin use for progression and mortality in patients with prostate cancer, it is still controversial whether statin use would reduce BCR in patients undergoing RP or RT as curative treatment.[37–39] statin use. We revealed that statin use appeared to be associated with a potential tendency to improve BCR-free survival; however, we failed to find significant differences, and subgroup analysis of RP and RT also showed insignificant results. Moreover, statin use after curative treatment did not improve the BCR-free survival. However, only high-risk patients with prostate cancer experience improved BCR-free survival following statin use. Our results would be valuable for further research to reduce recurrence and improve the survival of prostate cancer patients, especially when more prostate cancer patients can be detected at an early stage and curative treatment strategies are currently possible and effective.
Statins are specific inhibitors of the mevalonate pathway, which is responsible for the de novo synthesis of cholesterol and non-sterol isoprenoids, and have been accepted as the most effective treatment in the clinical management of high lipids and high cholesterol. Moreover, in addition to the association between obesity and cancer, dysregulation of the mevalonate pathway can support tumorigenesis and progression.[40,41] [42] statin use appeared to be only associated with a potential tendency to improve BCR-free survival, although we failed to find a significant difference. In addition, patients who started statin use after curative treatment did not show improved BCR. The only positive outcome was that statin use would improve BCR-free survival in high-risk prostate cancer patients, and such improvement might involve a distinctive molecular or metabolic mechanism for the special subtype. An interesting issue is the potential tendency for statin use to improve BCR-free survival in patients undergoing RT instead of RP. Currently, the combination of RT and ADT has definitively proven its superiority compared with RT alone on recurrence by various RCTs,[43–45] statin use combined with ADT would prolong time to progression, and statin could competitively reduce androgen uptake in vitro.[46]
Finally, the limitations of our meta-analysis should be reviewed and considered before interpreting our results. First, no RCT is available, and baseline imbalances are inevitable, even in well-designed cohort studies. Patients using statins might return to clinics more frequently, and BCR might be detected earlier. Statin use might be related to obesity, diabetes, or other metabolic disorders, which are also risk factors for the incidence and mortality of prostate cancer.[47] P value. However, the insufficient quantity and heterogeneity of studies would still reduce the reliability of statistical inferences. Therefore, it is important to interpret our results critically, and more well-designed studies with larger samples are needed to provide a robust conclusion.
In conclusion, statin use is associated with a potential tendency to improve BCR-free survival in prostate cancer and could reduce BCR in high-risk patients.
Author contributions
Investigation: Peng Yin.
Resources: Peng Yin.
Software: Sheng Han, Qingfeng Hu, Shijun Tong.
Supervision: Qingfeng Hu, Shijun Tong.
Writing – original draft: Peng Yin.
Writing – review & editing: Qingfeng Hu.
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