The ProCaSP Study

Quality of Life Outcomes of Prostate Cancer Patients After Radiotherapy or Radical Prostatectomy in a Cohort Study

Nora Eisemann; Sandra Nolte; Maike Schnoor; Alexander Katalinic; Volker Rohde; Annika Waldmann

Disclosures

BMC Urol. 2015;15(28) 

In This Article

Methods

The ProCaSP Study

The Prostate Cancer, Sexuality, and Partnership (ProCaSP) Study was a German prospective multicenter study. ProCaSP was aimed at evaluating HRQOL outcomes of patients with localised prostate cancer treated with either radical prostatectomy or radiotherapy. Furthermore, the data included patients' perceptions on sexuality and partnership (data not reported) and their partners' HRQOL.[19] Inclusion criteria were stages T1a to T3b according to the TNM-classification 5th edition,[20] no transurethral prostate resection within the last six months, and prostate volume ≤50 ml. Exclusion criteria were positive skeletal scintigraphy, synchronic or metachronic secondary tumours, participation in another study, and insufficient capacity to contract. Patients were classified into different risk groups.[21]

The choice of treatment was based on a shared decision between patient and urologist. The decision regarding nerve-sparing versus non-nerve-sparing procedure was made by the hospital surgeon during surgery.

Data Collection

From 2002 to 2006, patients were recruited in ten German study locations. Follow-up was completed in 2008. Data were collected before (baseline), three, six, twelve, and twenty-four months after the start of treatment. Patients were asked to provide information on sociodemographic characteristics, treatment, sexual functioning, and HRQOL.

Cancer-specific HRQOL, prostate-specific HRQOL, and sexual functioning were measured by validated questionnaires (see below). Urinary functioning, which is of interest as it is often compromised after RT, was measured by the best available instrument in German language at that time, the Prostate Specific Module (PSM).[22] However, in our study cohort the PSM was found to have insufficient psychometric properties for some of the PSM scales and the data was, therefore, not considered in this analysis.

European Organisation of Research and Treatment in Cancer Quality of Life Questionnaire, Core Module (EORTC QLQ-C30)

The QLQ-C30 is a cancer-specific HRQOL measure. Version 3.0 comprises 30 items covering five functioning scales, three symptom scales, six symptom items, and two items on global HRQOL. Raw scores can be transformed to a range between 0 and 100, with higher functioning scores representing better functioning and higher scores for symptoms/problems representing worse conditions, respectively.[23] The minimal clinically important difference (MCID) was set at ten points.[24]

Patient-oriented Prostate Utility Scale (PORPUS)

The PORPUS questionnaire is a prostate-specific HRQOL instrument. The single HRQOL score, the PORPUS-P,[25,26] ranges from 0 to 100, with higher values representing higher HRQOL. Differences of five points were interpreted as the MCID.[25]

International Index of Erectile Function (IIEF)

The IIEF-15 measures sexual functioning. The 15 items were summed up to a total score ranging between 5 and 75. Higher values correspond to higher functioning.

Ethics and Consent

The study protocol was approved by the ethics committee of the Giessen University Hospital, Germany. All patients provided written informed consent.

Statistical Analysis

Analyses were performed using R 3.0.2.[27] First, patients' sociodemographic characteristics and their tumor-specific data were described with means (standard deviations), absolute and relative frequencies. Differences in patients' characteristics between the three main groups (nnsRP, nsRP, RT) were tested with Chi-square and F-tests, respectively. Statistical significance was defined as p< =0.05.

Second, time trends of mean HRQOL were presented graphically by main treatment groups (nnsRP, nsRP, RT) and by RT subgroups (brachyRT, externRT, and combRT). Although we did not consider sexual functioning as a main outcome, changes over time are shown to illustrate the different trends of the treatment group.

Third, the relationship between treatment (nnsRP, nsRP, RT) and HRQOL was analysed using generalised estimating equations (GEE) that account for the correlation between repeated HRQOL observations. The HRQOL observations of the follow-up period were modeled depending on respective treatment option, while adjusting for baseline characteristics (baseline HRQOL, age, having a partner (yes/no), highest education level (no graduation, 8–9 years ('Hauptschulabschluss'), 10–11 years ('Realschulabschluss'), >= 12 years high school ('(Fach-)Abitur'), working (yes/no), residence (rural/urban), tumour stage (T-category of the TNM-classification), pre-therapeutic Gleason score, pre-therapeutic PSA score, and sexual functioning at baseline (IIEF total scale)). Regression coefficients of treatment options with their confidence intervals and Wald tests for testing the effect of treatment option are reported. The analysis was repeated after splitting the RT group into the three subgroups brachyRT, externRT, and combRT.

Most HRQOL domains and some patient characteristics were affected by missing values ranging from 0% to 41.1%, with 22.7% of all observations missing. Multiple imputation is known to be a statistically sound method for handling incomplete data.[28] Hence, missing values were imputed ten times depending on all patient characteristics and on those observation times of HRQOL domains with a correlation of at least 0.5. Results were pooled according to Rubin's Rule.[28]

Fourth, the HRQOL scores at baseline and twenty-four months after treatment of the three main treatment groups as well as the three RT subgroups were compared to German norm values for the EORTC QLQ-C30[29] by calculating the reference score in a population with a similar age distribution and presenting the difference between the treatment groups' score and the reference value.

Post Hoc Statistical Power Analysis

A post hoc power analysis was conducted using the software package G*Power3[30] with α = 0.05, two-tailed. The calculation was based on a repeated measure MANOVA for the two groups with the highest and the lowest HRQOL, which had also the lowest sample sizes: nsRP (n = 127) and RP (n = 133). The expected treatment difference was the MCID, namely 10 for HRQOL and 5 for PORPUS-P. The standard deviation (SD) (between 10 and 20 for the different outcomes) and the correlation between the four repeated measures of the individuals (between 0.5 and 0.8) were estimated from the data. Power was generally far above 95%.

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