The Microvascular Health Status Predicts Radio-Induced Acute Toxicities in Breast, Prostate and Head and Neck Cancer Patients

PURPOSE/OBJECTIVE(S)

investigate the role of healthy/unhealthy microcirculation in predicting acute toxicity (tox) after breast (BC), prostate (PC) and Head & Neck (HNC) cancer RT.

MATERIALS/METHODS

We enrolled BC patients (pts) treated with hypofractionated-RT after conservative surgery (42.4 Gy + 10 Gy boost to tumor bed), PC pts receiving radical-RT (65 Gy / 25 fractions), HNC pts treated with conventional RT (54-70 Gy @ 1.8-2 Gy/fr) or moderately hypofractionation (56.1-69.96 Gy @ 1.7-2.12 Gy/fr). We assessed baseline sublingual-microvasculature (MV) health status before RT using a sidestream dark-field camera coupled to the GlycoCheck™ software. The system records videos showing the live movement of red blood cells (RBCs) in the microvessels. It computes 5 functional parameters: (a) perfused boundary region (PBR) estimating the penetration of RBCs into the permeable part of the endothelial glycocalyx (higher PBR values result from damaged glycocalyx, indicating impaired microcirculation); (b) density of capillaries (1/mm2); (c) blood flow in the recorded area (103 μm3/s/mm2); (d) recruitment capacity (quantifying the ability to recruit additional capillaries); (e) a global MV_HealthScore (MVHS), higher values indicate healthier MV. MVHS is computed by weighting information from the previous parameters. The computation of MVHS needs a prolonged video acquisition not reached by less compliant patients. Endpoint for this analysis was acute tox. We selected a clinically relevant tox endpoint for each cancer site: grade≥2 erythema (G2+E) for BC, any grade≥3 tox (G3Tox) for HNC and persistent grade≥1 tox simultaneously present in gastrointestinal and genitourinary domains (G1+GIGU) for PC. We used logistic regression to assess MV functional parameters' association with toxicity.

RESULTS

We evaluated 63 BC, 38 PC, 39 HNC pts. 77 (55%) had an evaluation for MVHS. 23/63 BC pts presented with G2+E, 12/38 PC pts with G1+GIGU, 12/39 HNC pts with G3Tox. Average MVHS was 3.6, 3.2, 2.7 in BC, HNC and PC, respectively (P>0.15). The MVHS associated with tox: healthy MV protects from tox (continuous, OR = 0.66 for 1 point increase, p = 0.01, AUC 0.69). Categorizing pts as low MVHS (<2.5), average MVHS (2.5-6.5) and high MVHA (>6.5), the observed toxicity rates in the 3 classes were 50%, 26%, 0% (p = 0.02). Also, a 3-variate model including the separated functional parameters predicted tox (AUC 0.67) on the 144 pts: higher PBR is a risk (OR = 7.6), higher capillary density protects (Logarithm, OR 0.002), higher blood flow is a risk (Logarithm, OR = 14.2).

CONCLUSION

These data suggest an interaction of compromised MV with repair mechanisms. The MVHS model predicts acute toxicity in BC/PC/HN pts proving (i) a quantitative relationship between MV state and radio-susceptibility and (ii) in an organ-agnostic way. The systemic functional information derived by the sublingual microscope could boost the personalization of predictive models and tailor them to the single-patient functional status. Funded by AIRC IG 21479.

Modelling late stool frequency and rectal pain after radical radiotherapy in prostate cancer patients: Results from a large pooled population

AIM

To investigate late gastrointestinal toxicity in a large pooled population of prostate cancer patients treated with radical radiotherapy. Normal tissue complication probability models were developed for late stool frequency and late rectal pain.

METHODS AND MATERIALS

Population included 1336 patients, 3-year minimum follow-up, treated with 66-80Gy. Toxicity was scored with LENT-SOMA-scale. Two toxicity endpoints were considered: grade ⩾2 rectal pain and mean grade (average score during follow-up) in stool frequency >1. DVHs of anorectum were reduced to equivalent uniform dose (EUD). The best-value of the volume parameter n was determined through numerical optimization. Association between EUD/clinical factors and the endpoints was investigated by logistic analyses. Likelihood, Brier-score and calibration were used to evaluate models. External calibration was also carried out.

RESULTS

4% of patients (45/1122) reported mean stool frequency grade >1; grade ⩾2 rectal pain was present in the TROG 03.04 RADAR population only (21/677, 3.1%): for this endpoint, the analysis was limited to this population. Analysis of DVHs highlighted the importance of mid-range doses (30-50Gy) for both endpoints. EUDs calculated with n=1 (OR=1.04) and n=0.35 (OR=1.06) were the most suitable dosimetric descriptors for stool frequency and rectal pain respectively. The final models included EUD and cardiovascular diseases (OR=1.78) for stool frequency and EUD and presence of acute gastrointestinal toxicity (OR=4.2) for rectal pain.

CONCLUSION

Best predictors of stool frequency and rectal pain are consistent with findings previously reported for late faecal incontinence, indicating an important role in optimization of mid-range dose region to minimize these symptoms highly impacting the quality-of-life of long surviving patients.

High quality surface reconstruction in radiotherapy: Cross-sectional contours to 3D mesh using wavelets

A novel approach for three-dimensional (3D) surface reconstruction of anatomical structures in radiotherapy (RT) is presented. This is obtained from manual cross-sectional contours by combining both image voxel segmentation processing and implicit surface streaming methods using wavelets. 3D meshes reconstructed with the proposed approach are compared to those obtained from traditional triangulation algorithm. Qualitative and quantitative evaluations are performed in terms of mesh quality metrics. Differences in smoothness, detail and accuracy are observed in the comparison, considering three different anatomical districts and several organs at risk in radiotherapy. Overall best performances were recorded for the proposed approach, regardless the complexity of the anatomical structure. This demonstrates the efficacy of the proposed approach for the 3D surface reconstruction in radiotherapy and allows for further specific image analyses using real biomedical data.