Abstract
As many as 20-70% of patients undergoing breast conserving surgery require repeat surgeries due to a close or positive surgical margin diagnosed post-operatively [1]. Currently there are no widely accepted tools for intra-operative margin assessment which is a significant unmet clinical need. Our group has developed a first-generation optical visible spectral imaging platform to image the molecular composition of breast tumor margins and has tested it clinically in 48 patients in a previously published study [2]. The goal of this paper is to report on the performance metrics of the system and compare it to clinical criteria for intra-operative tumor margin assessment. The system was found to have an average signal to noise ratio (SNR) >100 and <15% error in the extraction of optical properties indicating that there is sufficient SNR to leverage the differences in optical properties between negative and close/positive margins. The probe had a sensing depth of 0.5-2.2 mm over the wavelength range of 450-600 nm which is consistent with the pathologic criterion for clear margins of 0-2 mm. There was <1% cross-talk between adjacent channels of the multi-channel probe which shows that multiple sites can be measured simultaneously with negligible cross-talk between adjacent sites. Lastly, the system and measurement procedure were found to be reproducible when evaluated with repeated measures, with a low coefficient of variation (<0.11). The only aspect of the system not optimized for intra-operative use was the imaging time. The manuscript includes a discussion of how the speed of the system can be improved to work within the time constraints of an intra-operative setting.
Highlights
Breast conserving surgery (BCS) is a recommended treatment for early stage breast cancer and for breast cancers that have been reduced in size by neoadjuvant therapy
The extracted values of total hemoglobin (THb), , β-carotene, THb/, β-carotene/, and βcarotene/THb from all measured sites (n = 854) are shown in the boxplots of Fig. 4. These plots show the empirical distribution of the data for sites on breast tumor margins, regardless
Bender et al [30] tested phantoms with hemoglobin concentrations ranging from 1 to 35 μM and showed that the model can accurately extract absorption and scattering with accuracies of 9.8 ± 8.2% and 7.68 ± 6.3%, respectively [30]. In this phantom study we wanted to look at higher concentrations of hemoglobin since previous studies have characterized the accuracy at lower concentrations
Summary
Breast conserving surgery (BCS) is a recommended treatment for early stage breast cancer and for breast cancers that have been reduced in size by neoadjuvant therapy. Surgeons do not have adequate intra-operative assessment tools to ensure that the cancer has been completely removed at the time of first surgery. The lack of this capability represents a significant unmet clinical need. Touch-prep cytology allows for evaluation of the whole lumpectomy surface, albeit with a wide range of sensitivities (38-100%) and specificities (85-100%) reported in the literature [8,9,10,11,12] This technique is time consuming, requires special expertise by a cytopathologist, and does not detect tumor cells close to the lumpectomy surface. Sensitivity ranges in the literature from 65 to 91% and specificity ranges from 86 to 100% [11,13]
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