V. Sacco

Dose–volume effects for pelvic bone marrow in predicting hematological toxicity in prostate cancer radiotherapy with pelvic node irradiation

PURPOSE To prospectively identify clinical/dosimetric predictors of acute/late hematologic toxicity (HT) in chemo-naÏve patients treated with whole-pelvis radiotherapy (WPRT) for prostate cancer. MATERIAL AND METHODS Data of 121 patients treated with adjuvant/salvage WPRT were analyzed (static-field IMRT n=19; VMAT/Rapidarc n=57; Tomotherapy n=45). Pelvic bone marrow (BM) was delineated as ilium (IL), lumbosacral, lower and whole pelvis (WP), and the relative DVHs were calculated. HT was graded both according to CTCAE v4.03 and as variation in percentage relative to baseline. Logistic regression was used to analyze association between HT and clinical/DVHs factors. RESULTS Significant differences (p<0.005) in the DVH of BM volumes between different techniques were found: Tomotherapy was associated with larger volumes receiving low doses (3-20 Gy) and smaller receiving 40-50 Gy. Lower baseline absolute values of WBC, neutrophils and lymphocytes (ALC) predicted acute/late HT (p ⩽ 0.001). Higher BM V40 was associated with higher risk of acute Grade3 (OR=1.018) or late Grade2 lymphopenia (OR=1.005). Two models predicting lymphopenia were developed, both including baseline ALC, and BM WP-V40 (AUC=0.73) and IL-V40+smoking (AUC=0.904) for acute/late respectively. CONCLUSIONS Specific regions of pelvic BM predicting acute/late lymphopenia, a risk factor for viral infections, were identified. The 2-variable models including specific constraints to BM may help reduce HT.

Patient-reported intestinal toxicity from whole pelvis intensity-modulated radiotherapy: First quantification of bowel dose–volume effects

BACKGROUND AND PURPOSE Intestinal toxicity is commonly experienced during whole-pelvis intensity-modulated radiotherapy (WPRT) for prostate cancer. The aim of the current study was to assess bowel dose-volume relationships for acute patient-reported intestinal symptoms of patients treated with WPRT for prostate cancer. MATERIALS AND METHODS Complete data of 206 patients were available; the median dose to pelvic nodes was 51.8Gy (range 50.4-54.4, 1.7-2Gy/fr). Intestinal symptoms were assessed as changes in the Inflammatory Bowel Disease Questionnaire scores relative to the Bowel Domain (IBDQ-B) between baseline and radiotherapy mid-point/end. The 25th percentiles of the most severe worsening from baseline (ΔIBDQ-B) were set as end-points. The impact of bowel loops and sigmoid colon dose-volume/surface parameters as well as selected clinical parameters were investigated using multivariate logistic regression. RESULTS Analyses were focused on the four questions showing a median ΔIBDQ-B>0. No dose volume/surface parameters were predictive, other than ΔIBDQ5≥3 (loose stools): when grouping patients according to bowel DVHs (high risk: V20>470cc, V30>245cc, V42>110cc; low risk: all the remaining patients), a two-variable model including high-risk DVH-shape (OR: 9.3) and age (protective, OR: 0.94) was assessed. The model showed good calibration (slope: 1.003, R2=0.92) and was found to be robust after bootstrap-based internal validation. CONCLUSIONS Constraining the bowel loops may reduce the risk of loose stools. The risk is higher for younger patients.

EP-1725: Predictors of diarrhea after whole-pelvis post-prostatectomy radiotherapy

S807 ________________________________________________________________________________ was maintained as long as the effect metric used for Cox regression had a linear correlation with the true effect metric of at least 0.50. The conclusions held if the trial cohort consisted of an expected high benefit population (22% reduced sample size), but the effect was even stronger if the cohort was a population with modest expected benefit (31% reduced sample size).

EP-2053: In-vivo imaging of rat leukocytes redistribution after pelvic irradiation

Purpose or Objective: The standard treatment regimen of patients with primary glioblastoma multiforme (PGBM) consists of neurosurgery, radioand chemotherapy. Despite this multimodal treatment the overall survival of patients with PGBM is still approximately 15 months. The stress-inducible heat shock protein 70 (Hsp70) contributes to tumor cell survival and is associated with poor prognosis, metastasis and therapy resistance. Therefore, the aim of this study is to analyze Hsp70 in PGBM tumor samples as a future prognostic biomarker and possible therapy target.

EP-2106: Structuring a database to evaluate haematological toxcicity in post-prostatectomy IMRT patients

Purpose or Objective: Haematological toxicity (HT) in postprostatectomy patients (WPRT) treated with whole pelvis radiotherapy represents a problem due to the irradiation of a large fraction of the bone marrow (BM). HT is under evaluation in our Institute according to an observational prospective study aiming to explore a dose-effect correlation. Therefore, clinical and dosimetric data have to be collected. This study reports (quantify) the complexity and workload of the clinical data collection were to evaluate its feasibility in the routine clinical practice.