## 3 Results  
In the initial study, we recruited 118 patients with an established histological diagnosis of breast carcinoma, and TRS-based values such as HbO\({}_{2}\), HHb, tHb, and SO\({}_{2}\) of breast tumors were found to be significantly higher than those of the contralateral normal tissue (Figure 3A) [34]. There were no significant differences in average rtHb levels among the various histological types such as ductal carcinoma in situ, invasive ductal carcinoma, invasive lobular carcinoma, or mucinous carcinoma. On the other hand, higher tumor rtHb was significantly and positively correlated with tumor size, nuclear grade, and lymphatic vascular invasion. The overall detection rate for breast tumors using TRS was 62.7%, while its sensitivity according to tumors stratified by T stage was: T0, 31.3%; T1, 44.7%; T2, 78.9%; and T3, 100% (Figure 3B). These results imply that our approach using TRS is not suitable for early detection of breast cancer; however, Hb parameters measured by TRS may be useful for assessing tumor aggressiveness. Regarding neoadjuvant chemotherapy, we found that pCR tumors showed a significantly greater reduction in percentage tHb change after the first course of chemotherapy compared to non-pCR tumors (average, \(-\)23.4% \(\pm\) 4.3 SE vs. \(-\)14.1% \(\pm\) 1.7 SE; \(p\) = 0.02), which increased after the second course of chemotherapy (average, \(-\)33.9% \(\pm\) 3.8 SE vs. \(-\)20.2% \(\pm\) 1.7 SE; \(p\) = 0.001, Figure 4A-1,A-2). Receiver-operating-characteristic (ROC) curve analysis yielded an Area under the curve (AUC) of 0.69 for the first chemotherapy infusion, and of 0.75 for the second chemotherapy infusion. Thus, we considered that tHb measurement alone may be insufficient for monitoring tumor response to NAC and for precisely predicting histological outcome, as many neoadjuvant studies using FDG-PET/CT have reported a diagnostic performance of 75-90% when serial scans of FDG-PET/CT were administered at baseline and during the initial stages of 1-3 courses of chemotherapy. Next, patients were categorized into a hormonal-receptor-dependent sub-group and a hormonal-independent sub-group based on ER status. A total of 47 patients had ER-positive breast cancer, including eight patients with pCR (Figure 4B-1), while 36 patients had ER-negative breast cancer, including seven patients with pCR (Figure 4B-2). When ER-positive tumors and ER-negative tumors were separately evaluated, the ROC curve analysis yielded AUC values of 0.6 (0.15 SE) and 0.5 (0.13 SE)  
Figure 3: **(A)** Tissue concentration of hemoglobin: tumor vs. normal breast. **(B)** Tumor detection rate using the TRS breast imaging system. Tis: in situ carcinoma; T1: tumor size of 2 cm or less; T2: tumor size of 2–5 cm; T3: tumor size of 5 cm or more, or tumor with skin invasion, or tumor with muscle invasion. SD: standard deviation. for ER-positive breast cancer, and 0.81 (0.08 SE) and 0.82 (0.07 SE) for ER-negative breast cancer after the first and the second courses of chemotherapy, respectively. When stratified by intrinsic subtypes, 40 patients had luminal breast cancer, including three with pCR (Figure 4C-1). Importantly, tHb in pCR tumors did not decrease after the first chemotherapy infusion, and showed no difference after the second infusion compared to non-pCR. Among 27 patients with triple-negative breast cancer (TNBC), three patients had pCR. The decrease in tHb in pCR tumors was higher compared to that of non-pCR tumors (Figure 4C-2), and among 19 HER2-positive patients, nine achieved pCR (Figure 4C-3). Thus, it appears that pCR tumors show a trend of greater reduction in tHb than non-pCR tumors, but these differences were smaller than those seen in TNBC patients. Figure 4: **(A)** Hemodynamic monitoring of breast tHb during neoadjuvant chemotherapy. C1, the first cycle of chemotherapy; C2, the second cycle of chemotherapy; pCR, pathological complete response. **(B)** Diagnostic performance of pCR stratified by ER status.