Japanese Journal of Clinical Oncology Advance Access published online on October 22, 2007
Japanese Journal of Clinical Oncology, doi:10.1093/jjco/hym105
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© 2007 Foundation for Promotion of Cancer Research
Decision Analyses in Consideration of Treatment Strategies for Patients with Biochemical Failure After Curative Therapy on Clinically Localized Prostate Cancer in the Prostate-Specific Antigen Era
1 Department of Urology, Juntendo University, Tokyo
2 Department of Drug Policy and Management, University of Tokyo
3 Juntendo Urayasu Hospital, Chiba
4 Department of Urology, International Medical Center, Tokyo
5 Department of Biostatistics/Epidemiology and Preventive Health Sciences, University of Tokyo, Tokyo, Japan
For reprints and all correspondence: Fumitaka Shimizu, Department of Urology, Juntendo University, 2-1-1Hongo, Bunkyo-ku, Tokyo 113-0033, Japan. E-mail: fshimizu-jua{at}umin.ac.jp
Received April 21, 2007; accepted June 8, 2007
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Abstract |
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 TOP Abstract INTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONReferences |
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Background: The introduction of prostate-specific antigen (PSA) testing has not only shortened the time required to make diagnosis but changed the treatment strategies of localized prostate cancer. We conducted the decision analysis on its treatment focusing on patients with biochemical failure.
Methods: We developed a Markov model to calculate life expectancy (LE) and quality-adjusted life expectancy (QALE) stratified by age, comorbidity and tumor characteristics in patients with newly diagnosed prostate cancer or biochemical failure after curative therapy. For newly diagnosed patients, three treatment strategies were considered as primary managements: radial prostatectomy (RP), external beam radiotherapy (EBRT) and watchful waiting (WW). Managements considered for biochemical failure were: after RP, salvage radiotherapy (SRT), salvage hormonal therapy (SHT) and WW; and after EBRT, SHT and WW. Transition probabilities in the Markov model were derived from published studies. Quality of life (QOL) data to estimate QALE score were derived from 323 patients with prostate cancer.
Results: For patients with Gleason 2–6 cancer at diagnosis, WW yielded the greatest number of QALE. For patients with Gleason 7 cancer, it was controversial whether curative therapy was the preferred strategy. For patients with Gleason 8–10 cancer, curative therapy yielded the greatest number of QALE in younger patients without severe comorbidity. Patients' benefit from salvage therapy for biochemical failure after curative therapy depended on age, comorbidities, tumor characteristics and QOL effect.
Conclusions: Our findings support the need for various treatment options, taking into consideration the patient's age, comorbidity and the QOL effect in the aging society.
Key Words: prostatic neoplasms • recurrence • decision support techniques • life expectancy
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INTRODUCTION |
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TOPAbstractINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONReferences |
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Prostate-specific antigen (PSA) screening has brought about an increased number of detected cases, and also changed the treatment strategy for prostate cancer (1,2). Patients with localized prostate cancer have many treatment alternatives such as radical prostatectomy (RP), external beam radiotherapy (EBRT), prostate brachytherapy (PB), primary hormonal therapy (PHT), watchful waiting (WW) and active surveillance. While local therapy yields long-term survival probability, all available treatments impact patients' health-related quality of life (HRQOL) (3). To compare treatment alternatives taking HRQOL into account in addition to survival, several decision analyses for patients with localized prostate cancer have been published (4–7). However, several points need to be modified. First, to calculate quality-adjusted life expectancy (QALE), which is based on value judgments, ‘quality of life (QOL) weights’ in decision analysis should be derived from patients with prostate cancer, not from clinicians or the general public as previously reported (8). Second, we should consider available treatment strategies for patients with biochemical failure after curative therapy. Some aspects of the decision analyses in the previous studies are outdated in the current PSA era. On the other hand, for patients with biochemical failure after RP, the value of salvage radiotherapy (SRT) is still unclear. The decision-analytic model may enable us to estimate the benefits of various salvage therapies. Third, in addition to the patient's age, considerations of comorbidities are essential in making treatment decisions, since comorbidities were reported to be highly significant predictors of mortality in these patients (9,10).
No published study satisfies all of the above requirements. Therefore, we developed a decision-analytic model which takes into considerations the patient's age, comorbidities, tumor characteristics and treatment strategies in patients with localized prostate cancer and those with biochemical failure after curative therapy.
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PATIENTS AND METHODS |
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Model Design
We developed a Markov model to compare life expectancy (LE) and QALE (Fig. 1). This model simulates the natural history of a hypothetical cohort of patients with localized prostate cancer and patients with biochemical failure after primary management. The QALE score was obtained by multiplying LE by QOL weight. Three treatment strategies were considered primarily in the management of these patients: RP, EBRT and WW. After undergoing curative therapy, patients enter the health state of ‘No recurrence’. Patients who opted for WW directly enter ‘Watchful waiting’. In any health state, patients have a probability of remaining stable or transitioning to the other states. The Markov cycle represents a 1-year cycle of the model.
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For patients with biochemical failure after RP, available managements include SRT, salvage hormonal therapy (SHT) and WW. Patients managed by SRT, SHT and WW enter the health states of ‘Radio responsive’, ‘Hormone responsive’, and ‘Watchful waiting’, respectively. If patients managed by SRT or WW following postoperative biochemical failure developed metastasis, they received SHT and then transitioned to the health state of ‘Hormone responsive’. In patients with biochemical failure after EBRT, SHT and WW were considered. If patients managed by WW following postirradiation biochemical failure developed metastasis, these patients also received SHT, and transitioned to the health state of ‘Hormone responsive’.
For the simulation scenarios, patients aged 60, 70 and 80 years were considered. The model was run until all the patients died or were aged 100 years. The model was developed and analyzed using TreeAge Pro 2006 + Healthcare software package.
Transition Probabilities
Transition probabilities mean the probabilities of moving from one health state to another. In all patients, hazards were converted to transition probabilities for use in the Markov model by the following equation: transition probability = 1 – e–ratextime, where e is the base of natural logarithms, rate expresses the annual incidence of an event in a population, and time is the interval over which the event might occur. These probabilities were derived from published studies through a PubMed search in the post-PSA era (11–24) (Table 1). However, the only probability of metastasis in WW patients was derived from the study in the pre-PSA era (13). Accordingly, time to the diagnosis of localized prostate cancer was adjusted for lead time by the age of the patients and Gleason score (14–16).
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For patients with clinically localized prostate cancer, we obtained progression rates after primary managements stratified by Gleason score. In RP patients, we estimated the biochemical relapse rate by 1 year (11). In this study, all patients received radical retropubic prostatectomy (RRP). Most patients in the EBRT group were treated using the three-dimensional conformal technique with median total doses of 70.5 Gy (12). To estimate the progression rate by Gleason score among WW patients, we converted grades 1, 2 and 3 of the WHO classification into Gleason scores of 2–6, 7 and 8–10, respectively (13).
For patients with biochemical failure after curative therapy, we obtained the progression rate stratified by the prostate-specific antigen doubling time (PSADT). We chose the PSADT as a stratified factor because Eisenberger et al. (26) suggested PSADT has replaced both the Gleason score and the time to biochemical failure in predicting time to bone metastases after biochemical failure following RP. Also, Zhou et al. (27) reported that the PSADT in patients with biochemical failure after RP or EBRT was the most significant prognostic factor.
We substituted the mortality rate of HRPC patients with metastatic disease at diagnosis for the mortality rate of patients with biochemical failure following SHT, since the median survivals of both groups were similar (28). Life tables for men were used to estimate the age-specific annual probabilities of dying from other causes (25).
QOL Weights
QOL weights in each health state are shown in Table 1. We separated QOL weights of the patients within 6 months after primary management to consider acute complications in decision analytic model. A total of 323 prostate cancer patients were interviewed with the time trade-off technique (TTO) using props, which were specially designed boards (29) between October 2004 and September 2005. TTO, whose scale is 0 for death and 1 for perfect health, is the most widely used among the methods to derive directly QOL weights (30). The characteristics of 323 prostate cancer patients are shown in Table 2. In this population, most patients undergoing RRP did not receive nerve sparing. Patients undergoing EBRT were treated using three-dimensional conformal techniques. Total doses of EBRT were 72 Gy as primary management and 64 Gy as SRT. Patients receiving HT were treated with the use of a luteinizing hormone-releasing hormone agonist or combined androgen blockade. To assess the relations between QOL weights and covariates, which are age, ICED (Index of Coexistent Disease) and disease-specific functions, we applied the general linear model by the least-squares means method. The disease-specific functions were obtained from the UCLA Prostate Cancer Index (PCI) version 1.2 (31), the items for hormonal functions in the Expanded Prostate cancer Index Composite (EPIC) (32) and the International Prostate Symptom Score (IPSS) (33). Because age and ICED were not related to the QOL weights (Table 3), we calculated those stratified only by managements administered to patients (Table 1).
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Adjustment for Comorbidities
We estimated mortality rates of other causes stratified by ICED including two subscales: (1) the severity of each set of categories of coexistent medical conditions (Index of Disease Severity, IDS), and (2) the degree of physical impairment (Index of Physical Impairment, IPI) (9). The two subscales were then condensed into a single composite index by ranking patients according to increasing severity of coexistent disease and physical impairment. The final index is an ordinal scale in which the two subscales are combined to form four levels of severity (0 = no disease or asymptomatic disease, 3 = severely disabling or life-threatening disease) (34). The hazard ratio for each comorbidity level, relative to no comorbidity, was multiplied by age-specific annual probability of dying from other causes.
Outcome Measure
We calculated LE and QALE stratified by age, comorbidities and Gleason score on three primary managements. It depended on the Gleason score whether a patient who was destined to experience biochemical failure after curative therapy entered the shorter or longer PSADT group (35,36). If patients with Gleason scores of 2–4, 5–6, 7 and 8–10 had experienced biochemical failure after RP, their proportions to enter the shorter PSADT group were defined as 0, 10, 20 and 40%, respectively. On the other hand, if patients with Gleason scores of 2–4, 5–6, 7 and 8–10 had experienced biochemical failure after EBRT, their proportions to enter the shorter PSADT group were defined as 0, 15, 30 and 45% (36). LE and QALE for each primary management were averaged by weighting the proportion to enter the shorter or longer PSADT group. Probabilities of choosing managements after biochemical failure following RP or EBRT were defined as equal. We summarized QALE gain from curative therapy.
Next, we calculated LE and QALE stratified by age, comorbidities and PSADT on biochemical failure after curative therapy. We also summarized QALE gain from salvage therapy.
Threshold Analyses
We performed threshold analyses to examine the stability of results of our model in the base-case estimates. We chose men aged 70 years with one of the ICED levels for base-case. We searched the threshold by moving the value in the expected plausible range for treatment efficacy, lead time and QOL weight.
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RESULTS |
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LE and QALE for Primary Management
For Gleason 2–4 and 5–6 patients, younger patients with milder comorbidities had small LE gains from RP, but WW was superior to curative therapy in QALE (Tables 4 and 5 and Fig. 2). For Gleason 7 patients, greater LE gains were observed for younger patients with milder comorbidities, but patients aged 60 years with ICED level 0 only had a small QALE gains from RP (Tables 4 and 5 and Fig. 2). In comparison with WW, Gleason 8–10 patients aged 60 years with ICED level 0 had a 3.3 LE gain from RP, and a 2.3 LE gain from EBRT (Table 4). Curative therapies yielded the greatest number of QALE in younger patients with milder comorbidities in this group (Table 5 and Fig. 2).
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LE and QALE for Biochemical Failure Following Curative Therapy
Patients with Biochemical Failure After RP
In the longer PSADT group (longer than 12 months), younger patients with milder comorbidities had LE gains from salvage therapy (Table 6). Only patients aged 60 years with milder comorbidities had QALE gains from salvage therapy (Table 7 and Fig. 3).
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For those with shorter PSADT, the salvage therapy might yield the greatest number of LE for those patients aged up to 80 years without severe comorbidities (Table 6). Younger patients with milder comorbidities had a larger QALE gain from salvage therapy than those in the longer PSADT group (Table 7 and Fig. 3). In two salvage therapies, SRT yielded slight larger LE and QALE gains than SHT (Tables 6 and 7).
Patients with Biochemical Failure After EBRT
Younger patients with milder comorbidities had LE gains from salvage therapy (Table 6), and the gains were larger in patients with shorter PSADT. However, the LE gains were offset by QOL effects due to complications in longer PSADT group (Table 7 and Fig. 3), but the shorter PSADT patients had QOL gains from salvage therapy.
Threshold Analyses
Patients for Primary Managements
Thresholds for variables related to treatment were examined in patients receiving primary managements at aged 70 years with ICED level 1 (Table 8). Although transition probabilities for progression after primary managements moved in the expected plausible range, no threshold was found for these variables. Although lead times for WW patients at diagnosis moved in the expected plausible range, no threshold was found for this variable.
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The preferred strategy did not depend on QOL weights for the short term after curative therapy, whereas those for the long term after curative therapy were influenced by the preferred strategy. WW was preferred in the base-case analyses for patients with Gleason scores of 2–7 (Table 5). However, if the QOL weight of WW was less than 0.92 with Gleason scores of 2–6, or 0.95 with a Gleason score of 7, RP became the preferred strategy. If the QOL weight for the long term after RP was greater than 0.98 with a Gleason score of 7, RP also became the preferred strategy. RP was preferred in the base-case analyses for patients with Gleason scores of 8–10 (Table 5). If the QOL weight for the long term after RP was less than 0.85 with Gleason scores of 8–10, EBRT became the preferred strategy. If the QOL weight for the long term after EBRT was greater than 0.98 with Gleason scores of 8–10, EBRT became the preferred strategy.
Patients with Biochemical Failure After RP
Thresholds for variables related to treatment were examined in patients aged 70 years with biochemical failure following RP with ICED level 1 (Table 8). The preferred strategy was influenced by moving the probabilities of metastases after each management in the expected plausible range. If the QOL weight of WW after RP was greater than 0.93, then WW became the preferred strategy in the longer PSADT group. On the other hand, WW after RP could not become the preferred strategy in the shorter PSADT group. In both PSADT groups, the preferred strategy depended on the QOL weight of SRT after RP or of SHT after RP.
Patients with Biochemical Failure After EBRT
Thresholds for variables related to treatment were examined in patients aged 70 years with biochemical failure after EBRT with ICED level 1 (Table 8). In both PSADT groups, the preferred strategy depended on the probability of metastasis after each management and also depended on the QOL weight of SHT after EBRT or of WW after EBRT.
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DISCUSSION |
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TOPAbstractINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONReferences |
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We found no randomized control trial on the treatment strategies for patients with biochemical failure after curative therapy of localized prostate cancer in the literature. By synthesizing available data within the Markov model, we conducted decision analyses, which allowed us to gain insight into the factors that determine the outcomes of various treatment decisions.
Patients for Primary Managements
Older patients with a lower Gleason score and more severe comorbidities hardly benefited from curative therapy, and the results are similar to the published reports (4,5,7). Gleason score 2–6 patients with QOL weight of WW smaller than the value of threshold preferred RP in our study (Table 8). Steineck et al. (37) reported that psychological function scores were inferior in patients receiving RP compared with the patients on WW, although the difference was not significant. For patients who are anxious about not receiving treatment, curative therapy may be an alternative even if their Gleason score is low.
Patients receiving RP often experience sexual dysfunction and urinary incontinence. These dysfunctions were not related to decreasing QOL weights in our studied patients (Table 3). Stanford et al. (38) reported that, while only a few patients regarded urinary incontinence as a moderate to severe problem, many patients regarded sexual dysfunction as a moderate to severe problem. Each patient should weigh treatment complications to make a decision on treatment because the value judgments for treatment complications differ individually.
In patients receiving EBRT, we calculated LE and QALE using the data derived from patients who were treated with three-dimensional conformal techniques (median dose 70.5 Gy). LE and QALE scores in patients receiving EBRT were inferior to those for RP. Zietman et al. (39) reported that patients with localized prostate cancer benefited from dose escalation with three-dimensional conformal techniques. Using intensity-modulated radiotherapy therapy (IMRT), we can escalate the dose without increasing complications (40,41). Although bowel problems caused by EBRT were related to decreasing QOL weights (Table 3), LE and QALE in EBRT may surpass those in RP by improving the technique.
Our results were estimated by the average QOL effect derived from patients who received treatment. The preferred strategy depended on the QOL weight in some patients; however, patients who have to make treatment decisions may score a QOL weight for unknown treatment complications differently from patients receiving treatment. In fact, the QOL weight derived from patients who were inexperienced with treatment complications tended to be lower (5,7).
Patients with Biochemical Failure After Curative Therapy
In our model, patients with biochemical failure after SRT are not treated until they develop metastasis. If they are treated for biochemical failure after SRT, LE for SRT may lengthen. The transition probability of metastases after SRT was estimated from a published study in which some patients with higher PSA levels were treated with SRT (17), although the recommended PSA level by the American Society for Therapeutic Radiology and Oncology (ASTRO) is less than 1.5 ng/ml for an SRT candidate (42).
For the shorter PSADT group with biochemical failure after RP, SRT yielded larger LE gains than SHT (Table 6). However, SRT is not beneficial for patients with microscopic distant metastasis after RP. In the phase of biochemical failure after RP, we cannot differentiate between microscopic distant metastasis and local recurrence at the present time. Patients with biochemical failure without microscopic distant metastasis in the shorter PSADT group may be candidates for SRT.
WW after biochemical failure following RP or EBRT may be suitable for patients who are older or have more severe comorbidities with shorter PSADT, or for most patients with longer PSADT. Pound et al. (21) reported that the median actual time to metastases was 8 years from the time of biochemical failure after RP without salvage therapy. More specific detection for these patients is needed to avoid unnecessary salvage therapies.
We examined the instability of these transition probabilities or QOL weights by threshold analyses. The preferred strategy changes by different transition probabilities associated with treatment efficacy or QOL weights for patients with biochemical failure following curative therapy (Table 8). Randomized controlled trials or registrations for a large database for such a condition are essential.
Limitations of the Study
There was no randomized controlled trial to derive the transition probability by tumor characteristics. Recently, a new paradigm for localized prostate cancer called active surveillance has emerged (43), and this method may be beneficial not only in HRQOL but also in cost-effectiveness. However, without any long-term follow-up data, we could not introduce it to our decision-analytic model. No long-term follow-up data was available for patients with biochemical failure following PB. Although PHT has been increased in patients with localized prostate cancer (44,45), the studied population was unsuitable for curative therapy (46,47). For patients with biochemical failure after curative therapy, SHT was defined as continuous administration in our model. We also could not set PSA value and clinical T stage in the model as a stratified factor.
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CONCLUSION |
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TOPAbstractINTRODUCTIONPATIENTS AND METHODSRESULTSDISCUSSIONCONCLUSIONReferences |
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From the decision-analytic model, WW is a reasonable option for patients with Gleason scores of 2–6. For patients with a Gleason score of 7, it was uncertain whether the curative therapy was the preferred strategy, whereas WW was not a beneficial option for patients with Gleason scores of 8–10. Patients with biochemical failure after curative therapy, especially in the shorter PSADT group, benefited from salvage therapy. Although there is uncertainty in transition probabilities and QOL weights, our findings support the treatment selections which take into considerations the patient's age, comorbid conditions and QOL effects in the aging society.
Conflict of interest
None declared.
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References |
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