Variations in SUV and textural indices in breast tissue satellite to breast cancer compared to normal breast tissue in FDG-PET.

Objectives: Breast cancer (BC) is the most common cancer in women in western countries. Previous studies have shown a significant correlation between histological data and SUV or textural indices (TI) measured from PET images. However to the best of our knowledge, satellite breast tissue to BC has not been fully explored in terms of SUV and TI. The purpose of this study was to assess SUV and TI in breast tissue satellite to the breast cancer in comparison to normal breast tissue (NBT) to point out differences that might assist patient treatment planning.

Methods: BC group was defined from a population of women who underwent a F18-FDG-PET/CT for initial staging of BC. SUV (max, mean and peak), TLG (total lesion glycolysis, mL) and TI (homogeneity, entropy, LRE, SRE, LGZE and HGZE) were measured in a tumor volume of interest (T-VOI) and in a satellite VOI (S-VOI) drawn next to the T-VOI but outside any tumor border or any suspicious foci especially in multifocal BC. The same S-VOI was mirrored to the contralateral breast (CL-VOI). NBT group was defined from a population of 307 women who underwent a F18-FDG-PET/CT for initial staging of various cancers (with no previous history of BC, local therapy, endometrial, or ovarian cancers) and a B-VOI was drawn in both breasts for comparison. Mann-Whitney (M-W) tests were used to compare SUV and TI between groups: S-VOI vs T-VOI, CL-VOI, B-VOI and CL-VOI vs B-VOI.

Results: One hundred and fifty seven T-VOI, 129 S-VOI and 111 CL-VOI were drawn in the BC group. A total of 95 B-VOI (14.4mL+/-6) drawn in the NBT group were matched according to VOI size to CL-VOI and used for all M-W tests. The SUV and TI measured in the T-VOI significantly differed from those measured in S-VOI (p<0.0001, table 1). There were significant differences in SUV, TLG and TI between S-VOI and CL-VOI (p<0.05, table 1) and between S-VOI and the 95 B-VOI of the NBT group (p<0.0001, table 1). There was no significant difference between CL-VOI and the 95B-VOI except for TLG (p=0.004). The only difference in VOI size was between T-VOI and S-VOI groups while S-VOI, CL-VOI and B-VOI had non significantly different volumes (Anova test: p=0.9). Some values measured in S-VOI were significantly different in patients with breast conservative surgery vs radical mastectomy (TLG: p=0.02), but also as a function of the tumor grade: I and II vs III (LRE: p=0.027), and when in situ carcinoma was diagnosed (homogeneity: p=0.04; SRE: p=0.049; HGZE: p=0.046). There was no difference in S-VOI as a function of the histological type CCI vs CLI, molecular subtype or presence of an inflammatory stroma.

Table 1: Average value and standard deviation for the different index and in the different VOI, [asterisk] p value <0.05 of the M-W tests between S-VOI and T-VOI, S-VOI and CL-VOI, S-VOI and B-VOI (95 VOI).

Conclusion: Significant differences were found between breast tissue satellite to breast tumor and contralateral breast in BC patients with a strong correlation to presence of in situ carcinoma for some textural indices. Those results showed that variations in breast tissue satellite to breast tumor is not random and should be further investigated to help with treatment planning.