Tumour regression pattern according to tumour shape after brachyther‐apy for 330 uveal melanomas

AbstractPurpose To describe regression patterns and their relationship with tumour shape of uveal melanoma by thickness and cross‐sectional area.Methods A retrospective study of 330 consecutive ciliochoroidal melanomas treated with I or Ru plaques in 2000‐2008 and imaged with Innovative Imaging I3‐ultrasound. Tumours were measured with Olympus DP‐Soft from original digital images. The COMS shape groups were partially collapsed: group 1: flat and crescent; group 2: oval and dome; group 3: mushroom; group 4: lobulated; and group 5: other or undetermined. Regression patterns were adapted from Abramson et al. (1990) into 4 main types: D (net decrease), S (stable), I (net increase), and M (for miscellaneous). We further subdivided M into 5 subtypes: DI (D>I), DS (D>S), ID (I>D), SD (S>D), and Z (zigzag; no trend).Results The regression pattern D was always the most common (31‐63% of tumors by thickness and 33‐72% by cross‐sectional area, for shape groups 1‐4); and the DS pattern was the second most common one (22‐24% and 16‐26%, respectively), except for group 2. Of the DI and Z patterns with later tumor increase, the former was fairly evenly spread across groups (5‐6% and 8‐10%, respectively) whereas the latter was observed mainly in shape groups 1 and 2 (15% and 17‐22%, respectively). The SD and ID patterns later tumor decrease were most common in shape groups 1 and 2, respectively, and most tumors representing the S pattern were shape group 1.Conclusion Heterogeneity in regression patterns and tumour shapes must be taken into account when using regression as a statistical variable in outcome analysis. Until now, all tumours have been pooled together despite significant differences in regression patterns, except in the study by Abramson et al. (1990).