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Strahlentherapie und Onkologie

, Volume 190, Issue 8, pp 732–738 | Cite as

Biologically effective dose and definitive radiation treatment for localized prostate cancer

Treatment gaps do affect the risk of biochemical failure
  • P. SanpaoloEmail author
  • V. Barbieri
  • D. Genovesi
Original article

Abstract

Background and purpose

It is not clear if prolongation of definitive external radiation therapy for prostate cancer has an effect on biochemical failure. The aim of this work was to evaluate whether the biologically effective dose (BED), and in particular the duration of radiotherapy, intended as overall treatment time, has an effect on biochemical failure rates and to develop a nomogram useful to predict the 6-year probability of biochemical failure.

Patients and methods

A total of 670 patients with T1–3 N0 prostate cancer were treated with external beam definitive radiotherapy, to a total dose of 72–79.2 Gy in 40–44 fractions. The computed BED values were treated with restricted cubic splines. Variables were checked for colinearity using Spearman’s test. The Kaplan–Meier method was used to calculate freedom from biochemical relapse (FFBR) rates. The Cox regression analysis was used to identify prognostic factors of biochemical relapse in the final most performing model and to create a nomogram. Concordance probability estimate and calibration methods were used to validate the nomogram.

Results

Neoadjuvant and concomitant androgen deprivation was administered to 475 patients (70 %). The median follow-up was 80 months (range 20–129 months). Overall, the 6-year FFBR rate was 88.3 %. BED values were associated with higher biochemical failure risk. Age, iPSA, risk category, and days of radiotherapy treatment were independent variables of biochemical failure.

Conclusion

A prolongation of RT (lower BED values) is associated with an increased risk of biochemical failure. The nomogram may be helpful in decision making for the individual patient.

Keywords

Prostate cancer External beam radiotherapy Biologically effective dose Linear-quadratic model Nomogram 

Biologisch effektive Dosis und definitiven Strahlentherapie des lokalisierten Prostatakarzinoms

Behandlungslücken beeinflussen das Risiko eines biochemischen Versagens

Zusammenfassung

Hintergrund und Ziele

Es ist nicht geklärt, ob die Verlängerung einer definitiven Strahlentherapie bei der Behandlung von Prostatakarzinompatienten einen Effekt auf das biochemische Versagen hat. Die vorliegende Studie hat das Ziel zu evaluieren, ob biologisch die effektive Dosis und insbesondere die Gesamtdauer der Behandlung eine Wirkung auf das biochemisches Rezidiv haben könnte. Ferner wurde ein Nomogramm zur Vorhersage der 6-Jahres-Wahrscheinlichkeit von biochemischem Versagen entwickelt.

Patienten und Methoden

Insgesamt erhielten 670 Patienten im Tumorstadium T1–3, N0, eine Strahlentherapie mit einer Gesamtdosis von 72–79,2 Gy in 40–44 Fraktionen. Errechnete Werte der biologisch effektiven Dosis (BED) wurden mittels begrenzten kubischen Splines bearbeitet. Variablen wurden mit Spearman-Test hinsichtlich Kollinearität untersucht. Zur Abschätzung der Rate an „freedom from biochemical relapse” (Freiheit von biochemischen Versagen, FFBR) wurde die Kaplan-Meier-Methode angewendet. Mittels Cox-Regression wurden anhand des letzten am besten funktionierenden Models prognostische Faktoren für biochemisches Versagen identifiziert sowie ein Nomogramm etabliert. Durch Schätzung der Konkordanzwahrscheinlichkeit und mithilfe von Kalibrationsmethoden wurde das Nomogramm validiert.

Ergebnisse

Es erhielten 475 Patienten (70 %) neoadjuvant und begleitend eine Androgendeprivation. Der mediane Follow-up betrug 80 Monate (20–129). Insgesamt betrug die 6-Jahres-FFBR-Rate 88,3 %. BED-Werte waren mit höherem Risiko eines biochemischen Versagens assoziiert. Alter, initialer Wert des prostataspezifischen Antigens (PSA), Risikokategorie und Zeitraum der Strahlentherapie erwiesen sich als unabhängige Variable in Bezug auf biochemisches Versagen.

Schlussfolgerungen

Eine Verlängerung der Strahlentherapie (niedrige BED-Werte) ist mit einem steigenden Risiko eines biochemischen Versagen assoziiert. Das Nomogramm kann als Entscheidungshilfe in Bezug auf einzelne Patienten hilfreich sein.

Schlüsselwörter

Prostatakarzinom Strahlentherapie Biologisch effective Dosis Linearquadratisches Modell Nomogramm 

Notes

Acknowledgments

The authors thank Dr. Loreta Sanpaolo for helping us with this manuscript and the editor and reviewers for their helpful comments.

Compliance with ethical guidelines

Conflict of interest

P. Sanpaolo, V. Barbieri, and D. Genovesi state that there are no conflicts of interest.

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Copyright information

© Springer-Verlag Berlin Heidelberg 2014

Authors and Affiliations

  1. 1.Radiation Oncology DepartmentCROBRionero in VultureItaly
  2. 2.Radiation Oncology Department“G. D’Annunzio” UniversityChietiItaly

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