Magali Quivrin

Multiparametric MRI and post implant CT-based dosimetry after prostate brachytherapy with iodine seeds: The higher the dose to the dominant index lesion, the lower the PSA bounce

PURPOSE To determine whether post-implant MRI-based dosimetry of the Dominant Intra-prostatic Lesion (DIL) could best predict the occurrence of PSA bounce after prostate brachytherapy. METHODS AND MATERIALS We selected 66 patients with a low risk prostate cancer treated with (125)I prostate brachytherapy as monotherapy. Post-implant dosimetry based on day 30 CT-scan and multiparametric MRI co-registration was generated: planned D90, D95, V100, V150 values were calculated for each DIL. Bounce was defined as a PSA elevation ⩾ 0.2 ng/mL from the previous baseline value followed by a decrease to or below the prior nadir with no additional treatment. RESULTS After a median follow-up of 35.5 months (range 13.2-72.5), a PSA bounce occurred in 24 (36.4%) patients. The mean planned D90 of the DIL was significantly lower in bouncers: 196 ± 61 Gy vs. 234 ± 62 Gy, p = 0.018. The mean planned V150 of the DIL was 56 ± 32% for bouncers while it was 75 ± 30% for non-bouncers, p = 0.026. CONCLUSION A lower planned D90 or V150 in the DIL were predictive of PSA bounce after prostate brachytherapy. PSA bounce could be caused by delayed cell death related to sublethal damage accumulation in the tumor.

Mapping of failures after radiochemotherapy in patients with non-metastatic esophageal cancer: A posteriori analysis of the dose distribution in the sites of loco-regional relapse

BACKGROUND AND PURPOSE We aimed to evaluate the patterns of loco-regional failure (LRF) after exclusive chemoradiotherapy (eCRT) for esophageal cancer with respect to planned dose and/or the incidental (unplanned) dose outside target volumes. MATERIALS AND METHODS Co-image registration of CT or (18)F-FDG PET-CT at the time of failure (tf) and at the time of CRT (t0) was performed in 34 patients with LRF. Dosimetric parameters with regard to local failure (LF), nodal failure (NF) and involved nodal stations (NS) were derived. RESULTS Twenty-two patients (64.7%) had LF, the majority of which (95.5%) were located at the epicenter of the GTV of the primary tumor. The mean doses recalculated to the NS at tf were more likely to be lower than the planned dose delivered to the PTV at t0: Dmean=33.9 ± 20.8 Gy vs 52.2 ± 8.5 Gy (p=0.0009), D95%=27.5 ± 21 Gy vs 46.1 ± 4.8 Gy (p=0.004). Among the 12 patients with NF outside the elective nodal irradiation (ENI) volume, Dmean of NS outside the ENI was significantly lower (19.4 ± 21.4 Gy) than the Dmean of NS with failure within the ENI (45.1 ± 6.1 Gy, p=0.01). CONCLUSION Loco-regional failure after exclusive chemoradiotherapy for esophageal cancer may be due to an inadequately low dose.

EP-1786: Rectal distension impact on prostate CBCT-based positioning assessed with 6 degrees of freedom couch

Purpose or Objective: The prostate requires a daily correction of its position in relation with rectal distension. With 6 degrees of freedom (DOF) couch, it is possible to correct the pitch and the roll. In this study, we sought to determine whether rectal distension might have an impact on any of these prostate translations and/or rotations during a protracted course of external beam radiation therapy for a localized prostate cancer

Impact of waiting time on nodal staging in head and neck squamous-cell carcinoma treated with radical intensity modulated radiotherapy

Background and purpose To evaluate the influence of delays for radiotherapy on survival, recurrence and upstaging for head and neck squamous-cell carcinoma (HNSCC) with no nodal involvement treated with intensity modulated radiotherapy (IMRT). Material and methods This retrospective study included 63 consecutive patients with HNSCC located in the pharynx and larynx and treated with exclusive IMRT with or without chemotherapy. Survival, loco-regional or distant failure and upstaging were analyzed according to the waiting time. Results Mean waiting time for treatment was 62.5 days for the hypopharynx subgroup (range = 37–102), 63 days for the larynx subgroup (range = 19–128) and 58.5 days for the oropharynx subgroup (range = 29–99) (p = 0.725). Nine patients (14%) experienced upstaging. Loco-regional or distant failure occurred in 18 patients. Beyond a delay of 50 days, 19% of patients had local failure, 17% nodal recurrence and 11% distant failure. Within a delay of 50 days, no nodal or distant failure was observed and only 1 patient experienced local recurrence. Upstaging and overall survival were not significantly affected by an increased waiting time. Conclusion For N0 patients treated with IMRT for HNSCC, waiting time around 50 days after the diagnosis was not significantly associated with an excessive risk of upstaging or recurrence.

Multiparametric MRI-based Dosimetric Parameters Best Predict Short-term Time Course of PSA After Iodine 125 Permanent Prostate Implantation for Localized Prostate Cancer

D90% and V150% of the entire prostate are recognized as the best dosimetric predictors of outcome after 125 I permanent prostate implantation (PPI). The purpose of this study was 2-fold: 1) to determine the relationship between dose-volume parameters of the Dominant Intraprostatic Lesion (DIL) when compared to the prostate and early biochemical outcome after PPI; 2) to define if dose-volume parameters of the central gland (CG), the peripheral zone (PZ) and the DIL could best predict PSA bounce occurrence. The time course of PSA and mechanisms of bounces still remain unclear after PPI. Patients who had a higher dose in the DIL had a worse PSA level at 1 year which is in keeping with previous reports with a longer follow-up suggesting that patients who will achieve a very low PSA are more likely to require a protracted time after PPI. A strong relationship was found between V150% in the CG and PSA bounce. These pioneering results require further investigations.