Table 1. Sample Size Estimates for Clinical Trials Using the Square Root of Lesion Area to Investigate Treatment Efficacy.

Months Followed	No Treatment		100% reduction in Enlargement Rate with treatment*				75% reduction in Enlargement Rate with treatment*				50% reduction in Enlargement Rate with treatment*				25% reduction in Enlargement Rate with treatment*
	Predicted change in square-root lesion area (mm)		Predicted Change in square-root lesion area (mm)		Sample Size required per group for power of		Predicted Change in square-root lesion area (mm)		Sample Size required per group for power of		Predicted Change in square-root lesion area (mm)		Sample Size required per group for power of		Predicted Change in square-root lesion area (mm)		Sample Size required per group for power of
	Mean†	SD‡	Mean	SD‡	80%	90%	Mean	SD‡	80%	90%	Mean	SD‡	80%	90%	Mean	SD‡	80%	90%
6	0.14	0.10	0.00	0.03	5	6	0.04	0.05	10	14	0.07	0.07	24	32	0.11	0.08	144	192
12	0.28	0.17	0.00	0.03	<5	5	0.07	0.07	7	9	0.14	0.10	16	21	0.21	0.14	78	105
18	0.42	0.24	0.00	0.03	<5	<5	0.11	0.08	6	7	0.21	0.14	14	19	0.32	0.19	74	99
24	0.56	0.32	0.00	0.03	<5	<5	0.14	0.10	6	7	0.28	0.17	14	18	0.42	0.24	65	86

^*The required sample sizes for a clinical trial comparing natural history growth of the square-root area (mm) to 100%, 75%, 50%, and 25% reduction in enlargement rate with treatment. Calculations assume analysis with independent samples t-test with unequal variances

^†Assuming Enlargement Rate of square root lesion area of 0.28 mm/year

^‡Standard deviation (SD) was estimated as a linear function of the mean growth of the square root of the lesion area; SD = (0.509)×(Mean Growth) + 0.030 (see results)