Abstract
Aim
To assess the predictors of the onset of impotence 1 year after radiotherapy for prostate cancer.
Patients and methods
In a multi-centric prospective study, the International Index of Erectile Function (IIEF) questionnaire-based potency of 91 hormone-naïve and potent patients (IIEF1-5 > 11 before radiotherapy) was assessed. At the time of this analysis, information on potency 1 year after treatment was available for 62 of 91 patients (42 treated with hypofractionation: 2.35–2.65 Gy/fr, 70–74.2 Gy; 20 with conventional fractionation: 74–78 Gy). Prospectively collected individual information and Dmax/Dmean to the penile bulb were available; the corresponding 2 Gy-equivalent values (EQD2_max/EQD2_mean) were also considered. Predictors of 1‑year impotency were assessed through uni- and multi-variable backward logistic regression: The best cut-off values discriminating between potent and impotent patients were assessed by ROC analyses. The discriminative power of the models and goodness-of-fit were measured by AUC analysis and the Hosmer–Lemeshow (H&L) test.
Results
At 1‑year follow-up, 26 of 62 patients (42 %) became impotent. The only predictive variables were baseline IIEF1-5 values (best cut-off baseline IIEF1-5 ≥ 19), Dmax ≥ 68.5 Gy and EQD2_max ≥ 74.2 Gy. The risk of 1‑year impotence may be predicted by a two-variable model including baseline IIEF1-5 (OR: 0.80, p = 0.003) and EQD2_max ≥ 74.2 Gy (OR: 4.1, p = 0.022). The AUC of the model was 0.77 (95% CI: 0.64–0.87, p = 0.0007, H&L: p = 0.62).
The 1‑year risk of impotency after high-dose radiotherapy in potent men depends on the EQD2_max to the penile bulb and on baseline IIEF1-5 values.
Conclusion
A significant reduction in the risk may be expected mainly when sparing the bulb in patients with no/mild baseline impotency (IIEF1-5 > 17).
Zusammenfassung
Ziele
Beurteilung von Prädiktoren für das Auftreten von Impotenz 1 Jahr nach Radiotherapie bei Prostatakrebs.
Patienten und Methoden
In einer multizentrischen prospektiven Studie wurde mithilfe des IIEF(International Index of Erectile Function)-Fragebogens die Potenz von 91 hormonnaiven und potenten Patienten (IIEF1-5 > 11 vor Radiotherapie) bewertet. Zum Zeitpunkt dieser Analyse waren Informationen über die Potenz von 62/91 Patienten ein Jahr nach der Behandlung verfügbar (42 hypofraktioniert behandelt: 2,35–2,65 Gy/fr; 70–74,2 Gy; 20 konventionell: 74–78 Gy). Prospektiv erhobene individuelle Informationen und Dmax/Dmean am Bulbus penis waren verfügbar, ebenfalls berücksichtigt wurden die entsprechenden 2 Gy-äquivalent Werte (EQD2_max/EQD2_mean).
Prädiktoren der 1‑Jahres-Impotenz wurden durch uni- und multivariable rückwärtsgerichtete logistische Regression beurteilt, die besten Cut-off-Werte zur Potent-impotent-Unterscheidung durch ROC-Analysen. Die diskriminative Power der Modelle und die Anpassungsgüte wurden mithilfe der AUC und dem Hosmer–Lemeshow-Test bestimmt.
Ergebnisse
Bei der Kontrolle nach einem Jahr waren 26/62 Patienten (42 %) impotent. Die einzigen Vorhersagevariablen waren Baseline IIEF1-5 (bester Cut-off IIEF1-5 ≥ 19), Dmax ≥ 68,5 Gy und EQD2_max ≥ 74,2 Gy. Das Risiko für das Auftreten von Impotenz nach einem Jahr lässt sich durch ein 2‑Variablen-Modell (Baseline IIEF1-5 [OR: 0,80; p = 0,003] und EQD2_max ≥ 74,2 Gy [OR: 4,1; p = 0,022]) vorhersagen (AUC 0,77 [95%-KI: 0,64–0,87; p = 0,0007, H‑L-Test: p = 0,62]). Das Impotenzrisiko ein Jahr nach hochdosierter Radiotherapie hängt ab von EQD2_max im Bulbus penis und vom Baseline IIEF1-5.
Schlussfolgerung
Eine signifikante Risikoreduktion ist v.a. zu erwarten bei Schonung des Bulbus bei Potenz bzw. nur schwacher Impotenz zu Behandlungsbeginn (IIEF1-5 > 17).
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Acknowledgements
The study was supported by the Associazione Italiana Ricerca sul Cancro (AIRC-IG13090). We acknowledge Cinzia Bianconi for data management and Frank Bagg for the language revision. Tiziana Rancati is supported by a grant from Fondazione Monzino.
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C. Cozzarini, T. Rancati, F. Badenchini, F. Palorini, B. Avuzzi, C. Degli Esposti, G. Girelli, I. Improta, V. Vavassori, R. Valdagni, and C. Fiorino state that there are no conflicts of interest.
All studies on humans described in the present manuscript were carried out with the approval of the responsible ethics committee and in accordance with national law and the Helsinki Declaration of 1975 (in its current, revised form). Informed consent was obtained from all patients included in studies.
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Cozzarini, C., Rancati, T., Badenchini, F. et al. Baseline status and dose to the penile bulb predict impotence 1 year after radiotherapy for prostate cancer. Strahlenther Onkol 192, 297–304 (2016). https://doi.org/10.1007/s00066-016-0964-1
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DOI: https://doi.org/10.1007/s00066-016-0964-1