Achievable Dosimetric Constraints in Stereotactic Reirradiation for Recurrent Prostate Cancer - Archive ouverte HAL Accéder directement au contenu
Article Dans Une Revue Practical Radiation Oncology: An official journal of the American Society for Radiation Oncology Année : 2023

Achievable Dosimetric Constraints in Stereotactic Reirradiation for Recurrent Prostate Cancer

Résumé

PURPOSE: Stereotactic body radiation therapy has been proposed as a salvage treatment for recurrent prostate cancer after irradiation. One crucial issue is choosing appropriate dose-volume constraints (DVCs) during planning. The objectives of this study were to (1) quantify the proportion of patients respecting the DVCs according to the Urogenital Tumor Study Group GETUG-31 trial, testing 36 Gy in six fractions, (2) explain geometrically why the DVCs could not be respected, and (3) propose the most suitable DVCs. METHODS AND MATERIALS: This retrospective dosimetric analysis included 141 patients treated for recurrent prostate cancer with Cyberknife (Accuray), according to GETUG-31 DVCs: V(95%) ≥ 95% for the planning target volume (PTV), V(12Gy) < 20% and V(27Gy) < 2 cc for the rectum, and V(12Gy) < 15% and V(27Gy) < 5 cc for the bladder. The percentage of patients not respecting the DVCs was quantified. Correlations between the DVCs and anatomic structures were examined. New DVCs were proposed. RESULTS: Only 19% of patients respected all DVCs, with a mean PTV of 18.5 cc (range, 3-48 cc), although the mean PTV was 40.5 cc (range, 3-174 cc) in the whole series. A total of 98% of the patients with a clinical target volume (CTV)/prostate ratio >0.5 could not respect the DVCs in the organs at risk. The target coverage and organ-at-risk sparing decreased significantly with increase in the values of PTV, CTV, CTV/prostate ratio, the overlapping volume between the PTV and bladder wall and between the PTV and rectal wall. Threshold values of PTV, >20 cc and 40 cc, allowed for the PTV and bladder DVCs, respectively. To improve DVC respect in case of large target volume, we proposed the following new DVCs: V(12Gy) < 25% and 25% and V(27Gy) < 2 cc and 5 cc for the rectum and bladder, respectively. CONCLUSIONS: GETUG-31 DVCs are achievable only for small target volumes (CTV more than half of the prostate). For a larger target volume, new DVCs have been proposed.
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hal-04164898 , version 1 (08-09-2023)

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Manon Baty, David Pasquier, Khemara Gnep, Joël Castelli, Nolewenn Delaby, et al.. Achievable Dosimetric Constraints in Stereotactic Reirradiation for Recurrent Prostate Cancer. Practical Radiation Oncology: An official journal of the American Society for Radiation Oncology, 2023, ⟨10.1016/j.prro.2023.05.007⟩. ⟨hal-04164898⟩
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