Background and purpose: Explainable models of long-term risk of biochemical failure (BF) after post-prostatectomy salvage radiotherapy (SRT) are lacking. A previously introduced radiobiology-based formula was adapted to incorporate the impact of pelvic nodes irradiation (PNI).Materials and methods: The risk of post-SRT BF may be expressed by a Poisson-based equation including pre-SRT PSA, the radiosensitivity a, the clonogen density C, the prescribed dose (in terms of EQD2, a/b = 1. 5 Gy) and a factor (1-BxkxPSA) accounting for clonogens outside the irradiated volume, being k the recovery due to PNI. Data of 795 pT2-pT3, pN0/pN1/pNx (n = 627/94/74) patients with follow-up >= 5 ye ars and pre-RT PSA <= 2 ng/mL were randomly split into training (n = 528) and validation (n = 267) cohorts; the training cohort data were fitted by the least square method. Separate fits were performed for different risk groups. Model performances were assessed by calibration plots and tested in the validation group.Results: The median follow-up was 8.5y, median pre-SRT PSA and EQD2 were 0.43 ng/mL and 71.3 Gy respectively; 331/795 pts received PNI. The most clinically significant prognostic grouping was pT3b and/or ISUP4-5 versus pT2/3a and ISUP1-3. Best-fit parameters were aeff = 0.26/0.23 Gy-1, C = 107/107, B = 0.40/0.97, k = 0.87/0.41 for low/high-risk group. Performances were confirmed in the validation group (slope = 0.89,R2 = 0.85). Results suggested optimal SRT dose at 70-74 Gy. The estimated reduction of postSRT BF due to PNI at these dose values was > 5 % for PSA > 1/>0.15 ng/mL for low/high-risk patients, being > 10 % for high-risk patients with pre-SRT PSA > 0.25 ng/mL.Conclusion: An explainable one-size-fits-all equation satisfactorily predicts long-term risk of post-SRT BF. The model was independently validated. A calculator tool was made available.(c) 2022 Elsevier B.V. All rights reserved. Radiotherapy and Oncology 175 (2022) 26-32
Accurate prediction of long-term risk of biochemical failure after salvage radiotherapy including the impact of pelvic node irradiation / Cozzarini, Cesare; Olivieri, Michela; Magli, Alessandro; Cante, Domenico; Noris Chiorda, Barbara; Munoz, Fernando; Faiella, Adriana; Olivetta, Elisa; Deantoni, Chiara; Fodor, Andrei; Signor, Marco Andrea; Petrucci, Edoardo; Avuzzi, Barbara; Ferella, Letizia; Pastorino, Alice; Garibaldi, Elisabetta; Gatti, Marco; Rago, Luciana; Statuto, Teodora; Rancati, Tiziana; Briganti, Alberto; Montorsi, Francesco; Valdagni, Riccardo; Sanguineti, Giuseppe; Di Muzio, Nadia Gisella; Fiorino, Claudio. - In: RADIOTHERAPY AND ONCOLOGY. - ISSN 0167-8140. - 175:(2022), pp. 26-32. [10.1016/j.radonc.2022.08.001]
Accurate prediction of long-term risk of biochemical failure after salvage radiotherapy including the impact of pelvic node irradiation
Briganti, Alberto;Montorsi, Francesco;Di Muzio, Nadia Gisella;
2022-01-01
Abstract
Background and purpose: Explainable models of long-term risk of biochemical failure (BF) after post-prostatectomy salvage radiotherapy (SRT) are lacking. A previously introduced radiobiology-based formula was adapted to incorporate the impact of pelvic nodes irradiation (PNI).Materials and methods: The risk of post-SRT BF may be expressed by a Poisson-based equation including pre-SRT PSA, the radiosensitivity a, the clonogen density C, the prescribed dose (in terms of EQD2, a/b = 1. 5 Gy) and a factor (1-BxkxPSA) accounting for clonogens outside the irradiated volume, being k the recovery due to PNI. Data of 795 pT2-pT3, pN0/pN1/pNx (n = 627/94/74) patients with follow-up >= 5 ye ars and pre-RT PSA <= 2 ng/mL were randomly split into training (n = 528) and validation (n = 267) cohorts; the training cohort data were fitted by the least square method. Separate fits were performed for different risk groups. Model performances were assessed by calibration plots and tested in the validation group.Results: The median follow-up was 8.5y, median pre-SRT PSA and EQD2 were 0.43 ng/mL and 71.3 Gy respectively; 331/795 pts received PNI. The most clinically significant prognostic grouping was pT3b and/or ISUP4-5 versus pT2/3a and ISUP1-3. Best-fit parameters were aeff = 0.26/0.23 Gy-1, C = 107/107, B = 0.40/0.97, k = 0.87/0.41 for low/high-risk group. Performances were confirmed in the validation group (slope = 0.89,R2 = 0.85). Results suggested optimal SRT dose at 70-74 Gy. The estimated reduction of postSRT BF due to PNI at these dose values was > 5 % for PSA > 1/>0.15 ng/mL for low/high-risk patients, being > 10 % for high-risk patients with pre-SRT PSA > 0.25 ng/mL.Conclusion: An explainable one-size-fits-all equation satisfactorily predicts long-term risk of post-SRT BF. The model was independently validated. A calculator tool was made available.(c) 2022 Elsevier B.V. All rights reserved. Radiotherapy and Oncology 175 (2022) 26-32I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
