Purpose

To study the dosimetric differences of various channel combinations of the Capri vaginal applicator.

Methods and materials

The Capri consists of a single central channel (R1), an inner array of 6 channels (R2), and an outer array of 6 channels (R3). Three-dimensional plans were simulated for 6 channel arrangements (R1, R2, R12, R13, R23, and R123). Treatment plans were optimized to the applicator surface or 5-mm depth while minimizing dose to organs at risk (OARs: bladder, rectum, sigmoid, and urethra). The clinical target volume (CTV) was defined as a 5-mm circumferential shell extending 4 cm in length around the applicator. Clinical target volume coverage (Dmean, D90, V100, and V150) and OAR doses (D0.1 cm3, D1 cm3, D2 cm3, and Dmean) were compared. A comparison between the Capri (R123) and a conventional single-channel applicator was also done. Statistical significance (P value<.05) was evaluated with a 2-tailed t test.

Results

When prescribing to 5-mm depth, CTV coverage using all 13 channels (R123) versus a single channel (R1) was similar; however, when prescribing to the surface there were differences (P<.0001) in all CTV metrics except for the V150. The R1 plans had higher doses to all OARs compared with R123 plans (P<.007). Doses to OARs were not significantly different between R23 and R123 plans (P=.05-.95), and CTV coverage differences were on the order of 1%. Capri R123 plans provided slightly lower CTV D90 and Dmean but equivalent OAR doses with smaller standard deviations compared with conventional cylinder plans for both prescriptions.

Conclusions

The Capri multichannel applicator provides equivalent target coverage at 5-mm depth, with significantly reduced dose to OARs relative to using a single channel. Optimal plans can be achieved using R12 (lowest V150) or R123 or R23 (lowest OAR doses).

Purpose

To determine predictors of distant metastases (DM) in prostate cancer patients treated with high dose rate brachytherapy boost (HDR-B) and external beam radiation therapy (EBRT).

Material and methods

From 1991 to 2002, 768 men with localized prostate cancer were treated with HDR-B and EBRT. The mean EBRT dose was 37.5 Gy (range: 30.6-45 Gy), and the HDR-B was 22 or 24 Gy delivered in 4 fractions. Univariate and multivariate analyses using a Cox proportional hazards model including age at diagnosis, T stage, Gleason score (GS), pretreatment PSA, biologically equivalent dose (BED), and use of androgen deprivation therapy (ADT) was used to determine predictors of developing distant metastases.

Results

The median follow-up time for the entire patient population was 4.2 years (range: 1-11.2 years). Distant metastases were identified in 22/768 (3%) of patients at a median of 4.1 years. PSA failure according to the Phoenix definition developed in 3%, 5%, and 14% of men with low, intermediate, and high risk disease with a median time to failure of 3.8 years. Prostate cancer specific mortality was observed in 2% of cases. T stage, GS, and use of ADT were significantly associated with developing DM on univariate analysis. GS, and use of ADT were the only factors significantly associated with developing DM on multivariate analysis (p < 0.01). Patients who received ADT had significantly higher risk features suggesting patient selection bias for higher DM in this group of patients rather than a negative interaction between HDR-B and EBRT.

Conclusions

In men treated with HDR-B and EBRT, GS is a significant factor on multivariate analysis for developing distant metastasis.

Background

Peripheral blood leucocyte telomere length (PBL-TL) is associated with outcomes in patients with idiopathic pulmonary fibrosis. Whether PBL-TL is associated with progression of systemic sclerosis-associated interstitial lung disease (SSc-ILD) is unknown.

Methods

A retrospective observational cohort study was performed using prospectively collected data from 213 patients with SSc followed at the University of California San Francisco (UCSF) Scleroderma Center. PBL-TL was measured by quantitative PCR of DNA isolated from peripheral blood. Associations between PBL-TL and pulmonary function test trends in patients with SSc-ILD were assessed by longitudinal analysis using Generalised Linear Mixed Models. Findings were validated in a cohort of 61 patients with SSc-ILD enrolled in the Stanford University Scleroderma Center database.

Results

Patients with UCSF SSc with ILD were found to have shorter PBL-TL compared with those without ILD (6554±671 base pairs (bp) vs 6782±698 bp, p=0.01). Shorter PBL-TL was associated with the presence of ILD (adjusted OR 2.1 per 1000 bp TL decrease, 95% CI [1.25 to 3.70], p=0.006). PBL-TL was shorter in patients with SSc-ILD lacking SSc-specific autoantibodies compared with seropositive subjects (6237±647 bp vs 6651±653 bp, p=0.004). Shorter PBL-TL was associated with increased risk for lung function deterioration with an average of 67 mL greater loss in per year for every 1000 bp decrease in PBL-TL in the combined SSc-ILD cohorts (longitudinal analysis, adjusted model: 95% CI -104 mL to -33 mL, p<0.001).

Conclusions

These findings suggest that telomere dysfunction may be associated with SSc-ILD progression and that PBL-TL measurement may be useful for stratifying risk for SSc-ILD progression.

Rationale and objectives

A novel ventilation imaging method based on four-dimensional (4D) computed tomography (CT) has been applied to the field of radiation oncology. Understanding its reproducibility is a prerequisite for clinical applications. The purpose of this study was to quantify the reproducibility of 4D CT ventilation imaging over different days and the same session.

Materials and methods

Two ventilation images were created from repeat 4D CT scans acquired over the average time frames of 15 days for 6 lung cancer patients and 5 minutes for another 6 patients. The reproducibility was quantified using the voxel-based Spearman rank correlation coefficients for all lung voxels and Dice similarity coefficients (DSC) for the spatial overlap of segmented high-, moderate-, and low-functional lung volumes. Furthermore, the relationship between the variation in abdominal motion range as a measure of the depth of breathing and variation in ventilation was evaluated using linear regression.

Results

The voxel-based correlation between the two ventilation images was moderate on average (0.50 ± 0.15). The DSCs were also moderate for the high- (0.60 ± 0.08), moderate- (0.46 ± 0.06), and low-functional lung (0.58 ± 0.09). No patients demonstrated strong correlations. The relationship between the motion range variation and ventilation variation was found to be moderate and significant.

Conclusions

We investigated the reproducibility of 4D CT ventilation imaging over the time frames of 15 days and 5 minutes and found that it was only moderately reproducible. Respiratory variation during 4D CT scans was found to deteriorate the reproducibility. Improvement of 4D CT imaging is necessary to increase the reproducibility of 4D CT ventilation imaging.

Purpose: 4-dimensional computed tomography (4D-CT)-based pulmonary ventilation imaging is an emerging functional imaging modality. The purpose of this study was to investigate the physiological significance of 4D-CT ventilation imaging by comparison with pulmonary function test (PFT) measurements and single-photon emission CT (SPECT) ventilation images, which are the clinical references for global and regional lung function, respectively. Methods and Materials: In an institutional review board-approved prospective clinical trial, 4D-CT imaging and PFT and/or SPECT ventilation imaging were performed in thoracic cancer patients. Regional ventilation (V 4DCT) was calculated by deformable image registration of 4D-CT images and quantitative analysis for regional volume change. V 4DCT defect parameters were compared with the PFT measurements (forced expiratory volume in 1second (FEV1; % predicted) and FEV1/forced vital capacity (FVC; %). V 4DCT was also compared with SPECT ventilation (V SPECT) to (1) test whether V 4DCT in V SPECT defect regions is significantly lower than in nondefect regions by using the 2-tailed t test; (2) to quantify the spatial overlap between V 4DCT and V SPECT defect regions with Dice similarity coefficient (DSC); and (3) to test ventral-to-dorsal gradients by using the 2-tailed t test. Results: Of 21 patients enrolled in the study, 18 patients for whom 4D-CT and either PFT or SPECT were acquired were included in the analysis. V 4DCT defect parameters were found to have significant, moderate correlations with PFT measurements. For example, V4DCTHU defect volume increased significantly with decreasing FEV1/FVC (R=-0.65, P<.01). V 4DCT in V SPECT defect regions was significantly lower than in nondefect regions (mean V4DCTHU 0.049 vs 0.076, P<.01). The average DSCs for the spatial overlap with SPECT ventilation defect regions were only moderate (V4DCTHU0.39±0.11). Furthermore, ventral-to-dorsal gradients of V 4DCT were strong (V4DCTHU R2=0.69, P =.08), which was similar to V SPECT (R2=0.96, P<.01). Conclusions: An 18-patient study demonstrated significant correlations between 4D-CT ventilation and PFT measurements as well as SPECT ventilation, providing evidence toward the validation of 4D-CT ventilation imaging. © 2014 Elsevier Inc.

Purpose

To determine the utility of focal high-dose-rate brachytherapy for localized prostate cancer, we investigated the impact on target coverage and dose to organs at risk (OARs) with hemigland (HG) compared with whole-gland (WG) treatment.

Methods and materials

A total of 10 WG implants were used to generate 10 WG and 20 HG (left and right) treatment plans optimized with the inverse planning simulation annealing algorithm using Oncentra MasterPlan (Nucletron B.V., Veenendaal, The Netherlands). The standard distribution of 17-18 catheters designed for WG was used to generate HG plans. The same OARs namely bladder, rectum, and urethra contours and dose constraints were applied for HG and WG plans. The HG contour was a modification of the WG contour whereby the urethra divided the prostate into HGs. The prescription dose was 7.25 Gy×6. Evaluated dose parameters were target dose D90, V100, and V150 and D0.1 cc, D1 cc, and D2 cc to OARs.

Results

The HG plans had a D90, V100, and V150 to the HG target of 112%, 97.6%, and 33.8%, respectively. The WG plans had a D90, V100, and V150 to the WG target of 108%, 98.8%, and 26.5%, respectively. The OAR D2 cc doses were significantly lower in HG vs. WG plans: rectum (53.1% vs. 64.1%, p<0.0001), bladder (55.9% vs. 67.5%, p<0.0001), and urethra (69.3% vs. 95.2%, p<0.0001).

Conclusions

In the present model, HG plans yielded a statistically significant decreased radiation dose to OARs and provided complete target coverage with a catheter array designed for WG coverage. The good dosimetry results obtained in this study support the feasibility of HG brachytherapy by using a subset of the WG catheter array. Catheter distribution and dosimetry refinements tailored to subtotal prostate brachytherapy should be explored to see if further improvements in dosimetry can be achieved.