Estimating choroidal melanoma volume: comparison of methods

Association of Uveal Melanoma Metastatic Rate With Stochastic Mutation Rate and Type of Mutation

Importance

It is necessary to understand the mechanisms of metastasis of uveal melanoma to advise patients and develop treatments for this tumor.

Objective

To examine the stochastic properties of primary uveal melanoma including the mutation rate as a function of tumor size and metastatic rate relative to the type of mutation.

Design, Setting, and Participants

We computed the mutation rate in different sized uveal melanomas using previously published large data sets. Tumor volume was estimated using the spherical cap method. We also calculated the metastatic rate using an updated data set of patients with uveal melanoma with known mutations in BAP1, SF3B1, and EIF1AX provided by the Rotterdam Ocular Melanoma Study Group. Data were analyzed from 2 studies, one taking place from August 25, 1970, to August 27, 2008, and the other taking place between 1993 and 2013. Data were analyzed between 2016 and 2017.

Main Outcomes and Measures

Mutation rates and metastic rates.

Results

Based on the 5-year metastatic rates, mutation rates ranged from 1.09 × 10-8 to 7.86 × 10-7 per cell division, using our calculation algorithm. A higher mutation rate was found for tumors with smaller thicknesses. EIF1AX mutations were not exclusive of other mutations because 2 cases with EIF1AX mutations and metastasis also had BAP1 mutations. None of the tumors with only an EIF1AX mutation metastasized. After plotting the yearly metastatic rate vs time after treatment, we observed a small peak at 1 year and a large peak at 3.5 years after treatment for BAP1 mutations, with peaks between 2 and 3 years and at 7 years for SF3B1 mutations.

Conclusions and Relevance

We observed a higher mutation rate for smaller tumors, which may be explained by a greater number of cell divisions occurring during the expansion phase of smaller uveal melanomas. Regarding time to clinically detected metastases, the first 2 peaks appear to be associated with BAP1-mutated tumors and the late peak to SF3B1-mutated tumors.

Tumour thickness, diameter, area or volume? The prognostic significance of conventional versus digital image analysis-based size estimation methods in uveal melanoma

PURPOSE

The aim of this study was to compare conventional and novel size estimation methods' ability to predict survival in uveal melanoma (UM).

METHODS

The study was designed as a retrospective consecutive chart review of patients with UM, enucleated between the years 1984 and 1993. Area and volume were estimated based on the largest histopathological cross-section, the second centroid theorem of Pappus and digital image analysis, correlated to overall and relative survival.

RESULTS

Of 168 patients analysed, 20 (12%) of tumours were categorized as T1, 47 (28%) as T2, 67 (40%) as T3 and 19 (11%) as T4 (15 N/a). A total of 91 tumours with complete survival and measurement data were included and recategorized into small, medium and large volume groups. Increased separation of overall survival was seen compared with current American Joint Committee on Cancer T categories. Difference between the large and small volume groups was 8.6 years (p = 0.001), compared to a difference of 5.6 years (p = 0.091) between T1 and T4. Hazard ratio for all-cause mortality in the large versus small volume group was 2.6 compared to 1.9 for T4 versus T1. Relative survival rates for small, medium and large volumes were 62, 44 and 31% at 10 years, versus 50, 45, 56 and 0% for T1, T2, T3 and T4.

CONCLUSION

This study provides evidence that a novel UM volume estimation method might offer a practical and cost-efficient alternative to improve the prognostic value intrinsic to a tumour's size.

Tumor Volumes in Choroidal Melanoma: Agreement Between Three-Dimensional Ultrasound and Two Mathematical Models

PURPOSE

To determine the degree of agreement between 2 mathematical models and 3-dimensional ultrasonography (3DUS) in estimating choroidal melanoma tumor volumes.

DESIGN

Reliability analysis.

METHODS

Tumor measurements estimated by 2 mathematical models (designated Formula 1 and Formula 2) were compared to those obtained by 3DUS in 45 consecutive patients with primary choroidal melanoma to determine the percentage agreement between the models and 3DUS.

RESULTS

Both formulas tended to overestimate the tumor volume. Overall, the mean volume differences between 3DUS and Formula 1 and between 3DUS and Formula 2, respectively, were 51.7 mm(3) (95% confidence interval [CI], 187.6 to 84.3) and 23.8 mm(3) (95% CI, 122.5 to 74.8). Excluding mushroom-shaped tumors, the mean volume differences were 52.0 mm(3) (95% CI, 194.9 to 91.0) and 23.0 mm(3) (95% CI, 127.0 to 81.0), respectively. In mushroom-shaped tumors, mean volume differences were 49.9 mm(3) (95% CI, 135.7 to 35.9) and 29.3 mm(3) (95% CI, 87.6 to 29.0), respectively.

CONCLUSIONS

The agreement between these mathematical models and the measured 3DUS volume was high. The data obtained in this study show that both formulas provide a simple, fast, and accurate method of estimating tumor volumes in the clinical setting, suggesting that these models could be used as a reliable and inexpensive alternative to time-consuming procedures such as 3DUS or magnetic resonance imaging. The accurate tumor volume values provided by these formulas may help to provide more reliable estimates of tumor regression or regrowth following globe-preserving treatment of choroidal melanomas, and may be a valuable prognostic indicator.

Regression rate of posterior uveal melanomas following iodine-125 plaque radiotherapy

AIM

To characterize the regression rate of posterior uveal melanoma following radioactive iodine-125 (I-125) plaque.

MATERIALS AND METHODS

We retrospectively analyzed 95 patients with posterior uveal melanoma who were treated with only radioactive I-125 plaque and had more than 3 years follow-up. All patients were treated with plaque radiotherapy using tumor dose of 85 Gy at the tumor apex, following COMS protocol. Regression rate was assessed with standardized A-scan ultrasonography. Associations with tumor regression were evaluated by means of mixed linear regression modeling.

RESULTS

Mean decrease in the tumor thickness (% original thickness) at 12, 24, and 36 months after radiotherapy for melanomas < 3 mm in thickness was 29%, 38%, and 45%, for melanoma 3-8 mm in thickness was 32%, 44%, and 59%, and for melanoma more than 8 mm in thickness was 52%, 62%, and 68%, respectively. With a doubling of follow-up time (0.5-1 year, or 1-2 years of follow-up from treatment), tumors < 3 mm in thickness at treatment showed a 0.5 mm decrease in tumor thickness, whereas melanomas 3-8 mm showed a 1 mm decrease, and melanomas >8 mm showed a 1.7 mm decrease. Uveal melanomas that developed systemic metastasis showed an additional 0.4 mm decrease with a doubling of follow-up time from treatment, compared with those that did not develop metastasis (P = 0.050).

CONCLUSIONS

Posterior uveal melanomas with higher initial thickness show steeper and more reduction in tumor thickness following radioactive I-125 plaque. After the initial phases, the regression curve became similar for tumors with different thicknesses.

In vivo high-frequency contrast-enhanced ultrasonography of choroidal melanoma in rabbits: imaging features and histopathologic correlations

PURPOSE

To evaluate the use of in vivo imaging of rabbit model of choroidal melanoma using high-frequency contrast-enhanced ultrasound (HF-CE-US) with two-dimensional (2D) or three-dimensional (3D) modes and to correlate the sonographic findings with histopathologic characteristics.

METHODS

Five New Zealand white rabbits, which were immunosuppressed with daily cyclosporin A (CsA), were inoculated into their right eyes with aliquots of 1.5×10(6)/50 μl of 92.1 human uveal melanoma cells cultured in RPMI. At week 4, the tumour-bearing eyes were imaged using high-frequency ultrasound (HF-US) with microbubble contrast agent to determine the 2D tumour size and relative blood volume and by 3D mode to determine tumour volume. Histologic tumour burden was quantified in enucleated eyes by ImageJ software, and mean vascular density (MVD) was determined by counting vascular channels in periodic acid Schiff (PAS) without haematoxylin sections.

RESULTS

Using HF-CE-US, melanomas were visualised as relatively hyperechoic regions in the images. The correlation coefficients of sonographic size and volume compared with histologic area were 0.72 and 0.70, respectively. The sonographic tumour relative blood volume correlated with the histologic tumour vascularity (r(2)=0.92, p=0.04).

CONCLUSIONS

There is a positive correlation between in vivo sonographic tumour volume/size and histologic tumour size in our rabbit choroidal melanoma model. HF-CE-US corresponds to MVD and blood volume.

In vivo high-frequency, contrast-enhanced ultrasonography of uveal melanoma in mice: imaging features and histopathologic correlations

PURPOSE

To evaluate the usefulness of in vivo imaging of uveal melanoma in mice using high-frequency contrast-enhanced ultrasound (HF-CE-US) with 2D or 3D modes and to correlate the sonographic findings with histopathologic characteristics.

METHODS

Fourteen 12-week-old C57BL6 mice were inoculated into their right eyes with aliquots of 5 × 10(5)/2.5 μL B16LS9 melanoma cells and were randomly assigned to either of two groups. At 7 days after inoculation, tumor-bearing eyes in group 1 (n = 8) were imaged using HF-CE-US to determine the 2D tumor size and relative blood volume; eyes in group 2 (n = 6) were imaged by 3D microbubble contrast-enhanced ultrasound, and the tumor volume was determined. Histologic tumor burden was quantified in enucleated eyes by image processing software, and microvascular density was determined by counting von Willebrand factor-positive vascular channels. Ultrasound images were evaluated and compared with histopathologic findings.

RESULTS

Using HF-CE-US, melanomas were visualized as relatively hyperechoic regions. The intraobserver variability of sonographic measurements was 9.65% ± 7.89%, and the coefficient of variation for multiple measurements was 7.33% ± 5.71%. The correlation coefficient of sonographic volume or size and histologic area was 0.71 (P = 0.11) and 0.79 (P = 0.32). The relative blood volume within the tumor demonstrated sonographically correlated significantly with histologic tumor vascularity (r = 0.83; P < 0.001).

CONCLUSIONS

There was a positive linear correlation between sonographic tumor measurements and histologic tumor burden in the mouse ocular melanoma model. Contrast-enhanced intensity corresponded with microvascular density and blood volume. HF-CE-US is a real-time, noninvasive, reliable method for in vivo evaluation of experimental intraocular melanoma tumor area and relative blood volume.