Prognostic and Predictive Significance of Tumor Immune Microenvironment in Breast Ductal Carcinoma In Situ

PURPOSE/OBJECTIVE(S)

This study aims to identify the role of different subtypes of tumor infiltrating lymphocytes (TILs) in ductal carcinoma in situ (DCIS) in predicting risk of recurrence and benefit of whole breast irradiation (WBI).

MATERIALS/METHODS

Immunohistochemical stain for CD3, CD4, CD8, FOXP3 and CD20 were carried in a well characterized DCIS cohort who received breast-conserving surgery (BCS) from Jan 2009 to Dec 2018. All the TILs subtypes were evaluated by the average numbers of touching-TILs which defined as TILs touching or within one lymphocyte cell thickness from the malignant ducts' basement membrane. The optimal cut-off values of TILs subtypes were selected by the X-tile.

RESULTS

In total, 167 patients were enrolled in this analysis with 114 patients received WBI. After a median follow-up of 67 months, 15 IBTR events occurred with 6 invasive-IBTRs. Nine out of 15 IBTRs occurred outside of the original quadrant (elsewhere failure event, EFE). CD3+ lymphocytes were the predominant cell subtype while Treg showed the lowest levels. High abundance of TILs subtypes was associated with high tumor grade, presence of microinvasion, high Ki67 index, ER negativity and HER2 positivity. For various TILs subtypes, the multivariate analyses showed that dense CD4+ TILs (HR = 9.84, 95% CI 2.43-39.91, p<0.01) and dense Treg (HR = 4.22, 95% CI 1.24-14.36, p = 0.02) were independent prognostic factors for higher IBTR. As the infiltration of TIL subsets was correlated with one another, we also analyzed the relationship between IBTR and the ratios of different TILs subtypes. By adjusted by clinicopathological parameters, high ratios of CD4+/CD8+, Treg/CD4+ and Treg/CD8+ were found to be independent prognostic factors for higher IBTR (HR = 11.31, 95% CI 3.14-40.76, p<0.01; HR = 3.09, 95% CI 1.05-9.11, p = 0.04; HR = 7.14, 95% CI 1.98-25.73, p<0.01). Consistent with the results of IBTR, the 5-y rate of invasive-IBTR and EFE was both significantly associated with the high CD4+/CD8+, Treg/CD4+ and Treg/CD8+ TILs ratios (all p<0.01). WBI reduced the rate of 5y-IBTR risk from 8.4% to 1.3% (p = 0.02) in the low Treg/CD8+ group, but there was no benefit of WBI in the high group. With respect to EFE, WBI significantly reduced the rate from 2.8% to 0.0% (p = 0.03) in the low Treg/CD8+ group while not in the high group. The benefits of WBI in reducing IBTR and EFE were not significant difference between different CD4+/CD8+ and Treg/CD4+ groups.

CONCLUSION

Assessment of overall TILs provides a tool for comprehensive evaluation of the DCIS immune microenvironment. Patients with pro-tumoral immune infiltrate (high Treg, high ratios of CD4+/CD8+, Treg/CD4+ and Treg/CD8+) in tumor microenvironment show an increased risk of IBTR and less benefit from breast radiotherapy.

Evaluation of immunogenicity of enterobactin conjugate vaccine for the control of Escherichia coli mastitis in dairy cows

Mastitis is the most common disease of dairy cows that incurs severe economic losses to the dairy industry. Currently, environmental mastitis pathogens are a major problem for most dairy farms. A current commercially available Escherichia coli vaccine does not prevent clinical mastitis and production losses, likely due to antibody accessibility and antigenic variation issues. Therefore, a novel vaccine that prevents clinical disease and production losses is critically needed. Recently a nutritional immunity approach, which restricts bacterial iron uptake by immunologically sequestering conserved iron-binding enterobactin (Ent), has been developed. The objective of this study was to evaluate the immunogenicity of the keyhole limpet hemocyanin-enterobactin (KLH-Ent) conjugate vaccine in dairy cows. Twelve pregnant Holstein dairy cows in their first through third lactations were randomized to the control or vaccine group, with 6 cows per group. The vaccine group received 3 subcutaneous vaccinations of KLH-Ent with adjuvants at drying off (D0), 20 (D21), and 40 (D42) days after drying off. The control group was injected with phosphate-buffered saline (pH 7.4) mixed with the same adjuvants at the same time points. Vaccination effects were assessed over the study period until the end of the first month of lactation. The KLH-Ent vaccine did not cause any systemic adverse reactions or reduction in milk production. Compared with the control group, the vaccine elicited significantly higher levels of serum Ent-specific IgG at calving (C0) and 30 d postcalving (C30), mainly its IgG2 fraction, which was significantly higher at D42, C0, C14, and C30 d, with no significant change in IgG1 levels. Milk Ent-specific IgG and IgG2 levels in the vaccine group were significantly higher on C30. Fecal microbial community structures were similar for both control and vaccine groups on the same day and shifted directionally along the sampling days. In conclusion, the KLH-Ent vaccine successfully triggered strong Ent-specific immune responses in dairy cows without significantly affecting the gut microbiota diversity and health. The results show that Ent conjugate vaccine is a promising nutritional immunity approach in control of E. coli mastitis in dairy cows.

A Cascaded Deep Learning-Based Cardiac Substructures Segmentation Frame and on Non-Gated Non-Enhanced Planning CT Scans in Breast Cancer Patients

PURPOSE/OBJECTIVE(S)

To develop a deep learning-based segmentation frame for cardiac substructures especially coronary arteries (CAs) on non-gated non-enhanced planning computed tomography (CT) scans in breast cancer (BC) patients.

MATERIALS/METHODS

Non-gated non-enhanced CT scans of 39 BC patients receiving adjuvant radiotherapy (RT) were collected. Cardiac substructures were manually labelled, including four chambers, left main (LM), left anterior descending (LAD), left circumflex (LCX) and right coronary artery (RCA). The training, validation, and test sample is 28, 7 and 4, respectively. A cascaded network, using nnUNet as the backbone, is proposed to use chambers as prior information to constrain the segmentation of CAs. The mean Dice similarity coefficient (DSC), 95th percentile Hausdorff distance (HD95) and average symmetrical surface distance (ASSD) were used as geometric metrics. Dosimetric parameters of cardiac substructures was calculated based on the segmentation frame and manually labeled contouring, respectively. The data of cardiac examination including ultrasonography, electrocardiogram before and during the follow-up after RT were retrospectively collected. The cardiac event was any symptomatic heart disease or new-onset abnormality in the cardiac examination after RT.

RESULTS

The mean DSC of heart, atriums and ventricles of the proposed frame was 0.93, 0.90, and 0.93, respectively. As shown in Table 1, compared with direct segmentation (as baseline), the proposed frame had a better performance in terms of HD95, ASSD, and the mean dose (Dmean) absolute error for all CAs. Compared to the dosimetric parameters of the heart collected based on the manual labelled contours, the relative errors of D5, D95, and V15Gy for LAD was 4.3±7.8%, 11.7±5.9%, and 14.6±13.0% collected based on the direct segmentation contours and 2.4±4.4%, 3.9±3.1%, 8.5±6.9% collected based on the auto-segmented contours, respectively. Multivariate analysis showed that increased V15Gy of LAD was an independent cardiac toxicity risk factor ([HR] = 1.07, 95% CI 1-1.15, p = 0.0387).

CONCLUSION

We developed a cascaded network for cardiac substructures segmentation with dosimetric validation on non-enhanced CT scans in breast cancer radiotherapy. This is the first attempt to use chambers as prior information for CAs' segmentation and had a superior stable performance. Accurate segmentation will help radiation oncologists to better evaluate DVHs based on substructures and thus to estimate cardiovascular risk. An optimized cardiac substructure-based dosimetric constrain may be proposed accordingly.

Identification and Dosimetric Analysis of Axillary Substructures Associated with Breast Cancer Related Lymphedema

PURPOSE/OBJECTIVE(S)

It has been hypothesized that substructures in the axillary region may be involved in the development of upper limb lymphedema in breast cancer patients. We aimed to compare dosimetric parameters of different substructures to identify risk regions and dose indicators related to the development of lymphedema.

MATERIALS/METHODS

A total of 486 patients with breast cancer treated with axillary node dissection (ALND) and regional node irradiation (RNI) between 2017 and 2020 were analyzed. Ten axillary substructures were retrospectively contoured, and dose-volume histogram (DVH) parameters (maximum dose [Dmax], Dmean, Dmin, V5 Gy, V10 Gy, V15 Gy, V20 Gy, V25 Gy, V30 Gy, V35 Gy, V40 Gy, V45 Gy and V50 Gy) were evaluated. EQD2 using α/β = 3 was applied for hypofractionation.

RESULTS

The cumulative incidence of lymphedema was 32.5% during the median follow-up of 25 month (IQR 15-35). Higher BMI (≥21.77 kg/m2, hazard ratio [HR]1.6, 95% CI 1.1-2.3, p = 0.019) and higher number of dissected lymph nodes (≥13, HR 1.8, 95% CI 1.1-3.0, p = 0.026) were baseline risk factors associated with breast cancer related lymphedema (BCRL). A cohort of 196 patients was obtained by 1:1 propensity score matching based on the above two factors (154 treated with 50 Gy/25 fractions [Fx] and 42 with 40.05 Gy/15Fx). The optimal metric was axillary-lateral thoracic vessel juncture (ALTJ) Dmean ≥36.84 Gy (HR 3.7, 95% CI 1.6-8.6, p = 0.002). Other significant risk factors are Medial of Axillary Nodes level I(ALN-I-M) Dmin <9.19 Gy (HR 2.3, 95% CI 1.4-3.7, p = 0.001) and Posterior of Axillary Nodes level II(ALN-II-P) Dmax <52.75 Gy (HR 2.0, 95% CI 1.2-3.5, p = 0.015). A nomogram incorporated the above three parameters was created to predict the risk of lymphedema with reasonable accuracy confirmed by both self-training (area under curve [AUC], 0.76; 95% CI, 0.67-0.84) and internal validation (AUC 0.66; 95% CI, 0.50-0.80).

CONCLUSION

A mean dose of 36.84 Gy of ALTJ may be a suggested dose limit for patients indicated RNI after ALND, especially when patients with higher BMI and higher dissected nodes. Ideally, avoidance of ALTJ may be realized without compromising dose coverage to high-risk nodal region. Confirmation of this finding in future prospective studies is needed.

Does Dual Anti-HER2 Therapy Increase Early Cardiac Toxicity in Comparison with Trastuzumab Alone in Breast Cancer Patients Receiving Adjuvant Radiotherapy? A Multicenter Retrospective Study

PURPOSE/OBJECTIVE(S)

Adjuvant trastuzumab in combination with RT has proved its safety in terms of cardiac events. Dual anti-HER2 therapy with pertuzumab is currently standard adjuvant therapy in N+ and high-risk N0 early breast cancer (BC) patients. Our study aims to find if it increases early cardiac toxicity compared with trastuzumab alone in BC patients receiving adjuvant radiotherapy.

MATERIALS/METHODS

Operable BC patients who received adjuvant radiotherapy (RT) and trastuzumab with or without pertuzumab between January 2017 and September 2020 in 7 Chinese centers were retrospectively reviewed. The cardiac examination included ultrasonography, electrocardiogram (ECG), NT-proBNP, and cTnI before RT and during follow-up. The cardiac event was any new-onset symptomatic heart disease or abnormality in the cardiac examination after RT.

RESULTS

In total, 711 patients with a median age of 52 years were included, of whom 567 (79.7%) patients were treated with trastuzumab-only and 144 (20.3%) patients received dual anti-HER2 therapy. Adjuvant RT was given concurrently in 140/144 (97.2%) of dual anti-HER2 therapy and 562/567 (99.1%) of trastuzumab alone, respectively. With a median follow-up of 11 months, no patients developed symptomatic heart diseases. Among patients with normal baseline, 17 (2.4%), 86 (12.1%), 18 (2.5%) and 14 (7.3%) developed new-onset diastolic dysfunction, left ventricular ejection fraction (LVEF) decline, abnormal ECG, and abnormal NT-proBNP, respectively. No significant difference was found between the trastuzumab-only and dual anti-HER2 cohort in the incidence of all kinds of new-onset cardiac events (all p > 0.1). Multivariate analysis showed that left-sided (vs right-sided) RT significantly increased the risk of ECG abnormality (HR = 2.32, 95% CI 1.62-3.32, p<0.001). Increased age was an independent risk factor for diastolic dysfunction (HR = 1.1, 95% CI 1.02-1.18, p = 0.0098). Dosimetric analysis showed that patients who developed any cardiac events had increased mean heart dose (397.67±251.08 vs 344.87±236.75 cGy, p = 0.032). A significant increase in risk of cardiac events was found in patients with mean heart dose > 450 cGy (HR = 1.55, 95% CI 1.17-2.05, p = 0.0024), V5 > 26% (HR = 1.51, 95% CI 1.09-2.09, p = 0.013), and V30 > 5.5% (HR = 1.49, 95% CI 1.09-2.04, p = 0.0117), respectively. Further analysis was done in the subgroup of patients treated with left-sided RT, internal mammary nodes RT, or anthracyclines, no difference in risk of cardiac events was found between trastuzumab alone and dual anti-HER2 therapy in concurrent with RT (all p > 0.05).

CONCLUSION

Compared with trastuzumab-only, dual anti-HER2 therapy does not increase early cardiac toxicity in combination with adjuvant RT in BC patients. Cardiac radiation exposure remains the primary risk factor associated with early cardiac toxicity.

Convolution Neural Network-Based Automatic Scoring of Coronary Artery Calcification and Its Value to Identify the Risk of Radiation-Induced Cardiac Toxicity on Radiotherapy Planning CT Scans in Breast Cancer Patients

PURPOSE/OBJECTIVE(S)

To develop an automatic scoring of coronary artery calcification (CAC) on breast cancer radiotherapy (RT) planning computed tomography (CT) scans, and to explore its predictive value of CAC for radiation-induced cardiac toxicity.

MATERIALS/METHODS

Planning CT scans of 668 breast cancer patients from two prospective clinical trials (NCT02942615, NCT03829553) were retrospectively reviewed. In total, 34 CTs containing CAC were identified. The training and test samples were 29 and 5, respectively. We proposed a two-stage model for CAC segmentation task with nnU-Net as backbone. The segmentation results were processed by threshold extraction and region growth algorithm. We also employed transfer learning to automatically identify calcification of left anterior descending artery (LAD), right coronary artery (RCA), left circumflex artery (LCX), and left main coronary artery (LM) based on a public dataset of 430 cases from Stanford University. The data of cardiac examination of these 34 patients before and during the follow-up after RT were collected. The cardiac event was any symptomatic heart disease or new-onset abnormality in the cardiac examination after RT.

RESULTS

The mean dice coefficients (DSC) and 95% Harsdorf distance (95HD) of test samples were 0.992 and 0.599 mm, respectively. The mean absolute error (MAE) of CAC Angaston score between ground truth (GT) and predictions was 0.532. The detailed consistency parameters of 5 test samples were shown in Table 1. After 1:2 propensity score matching (PSM), 21 patients had CAC and 42 patients had no CAC were selected. The number of patients with CAC scores of 1 to 10, 11 to 100, and greater than 100 was 10, 9 and 2, respectively. During median follow-up of 9.2 months (range, 1-42.7), 90.5% and 38.1% of patients in CAC cohort and no CAC cohort developed cardiac event (p<0.001). Patients with CAC had significantly increased cardiac events (HR = 2.4; 95% CI, 1.22-4.75; p = 0.0117). The risk of cardiac events increased with CAC scores ([HR]1-10 = 2.1, 95% CI 0.9-4.9; [HR]11-100 = 2.5, 95% CI 1.0-5.9; [HR]>100 = 4.0, 95% CI 0.9-17.4).

CONCLUSION

Our primary results showed that this two-stage segmentation model is capable of achieving automatic CAC scoring which might assist to predict the risk of post-RT cardiac events in breast cancer patients.

Dosimetry Comparison of Incidental Irradiation to the Low Axilla in Whole Breast Irradiation Using IMRT and IMPT Therapy

PURPOSE/OBJECTIVE(S)

It has been hypothesized that incidental dose to low axilla contributes to regional control in patients receiving whole breast irradiation (WBI), especially in patients with limited metastatic sentinel nodes who were spared from subsequent axillary dissection. We aimed to compare axillary dose between intensity-modulated radiotherapy (IMRT) and intensity-modulated proton radiotherapy (IMPT).

MATERIALS/METHODS

Dosimetric comparisons between IMRT and IMPT were conducted in 15 patients treated with WBI without planned regional node irradiation (RNI). The prescribed dose was 40.05 Gy (RBE)/15 Fx. Axillary lymph nodes levels I, II (ALN I, ALN II) and rotter's lymph nodes (RN) were contoured and evaluated.

RESULTS

The dose to the axilla was generally low for IMPT, with mean dose to ALN I, ALN II, and RN of 896.31, 194.64, and 2111.58 cGy (RBE), respectively. The mean V90% and V50% of ALN I was higher for IMRT (11.5 cm3, 22.9% of structure volume, p < 0.0001; 36.1 cm3, 66.6%, p < 0.0001) compared to IMPT (1.1 cm3, 2.0%; 8.1cm3, 15.9%). Similar finding was found in other low axilla. Mean dose to total ALN caudal to axillary vein was 936.6 cGy (RBE) in IMPT compared to 2407.3 cGy in IMRT (p < 0.0001). Within all substructures of axilla, mean dose to RN was the highest, but it remains lower in IMPT than in IMRT [2111.58 cGy (RBE) versus 3510.88 cGy, p < 0.0001].

CONCLUSION

WBI treated with IMPT leads to a significant reduction of axilla dose compared to IMRT. In clinical scenarios like Z0011 or likewise requiring incidental irradiation to the low axilla without additional RNI, contouring should be modified based on individual risk.

Mesenchymal stromal cells confer breast cancer doxorubicin resistance by producing hyaluronan

Chemotherapy resistance represents a major cause of therapeutic failure and mortality in cancer patients. Mesenchymal stromal cells (MSCs), an integral component of tumor microenvironment, are known to promote drug resistance. However, the detailed mechanisms remain to be elucidated. Here, we found that MSCs confer breast cancer resistance to doxorubicin by diminishing its intratumoral accumulation. Hyaluronan (HA), a major extracellular matrix (ECM) product of MSCs, was found to mediate the chemoresistant effect. The chemoresistant effect of MSCs was abrogated when hyaluronic acid synthase 2 (HAS2) was depleted or inhibited. Exogenous HA also protected tumor grafts from doxorubicin. Molecular dynamics simulation analysis indicates that HA can bind with doxorubicin, mainly via hydrophobic and hydrogen bonds, and thus reduce its entry into breast cancer cells. This mechanism is distinct from the reported chemoresistant effect of HA via its receptor on cell surface. High HA serum levels were also found to be positively associated with chemoresistance in breast cancer patients. Our findings indicate that the HA-doxorubicin binding dynamics can confer cancer cells chemoresistance. Reducing HA may enhance chemotherapy efficacy.

A Modified Robust Nomogram for Predicting the Probability of Pelvic Lymph Node Invasion in Localized Prostate Cancer

PURPOSE/OBJECTIVE(S)

Improved predictive models for the risk of pelvic lymph node invasion (LNI) in localized prostate cancer (PCa) is important in decision making of pelvic lymph node dissection (PLND) or whole pelvic RT (WPRT). We aimed to establish a nomogram with improved robustness (Ruijin model) based on pre-treatment information.

MATERIALS/METHODS

Continuous localized PCa patients with detailed prostate tumor biopsy information, treated with laparoscopic radical prostatectomy and PLND between 2013 and 2022 in single institution were retrospectively reviewed. A multivariable logistic regression model was fitted and represented the basis for a coefficient-based nomogram of predicting LNI. Comparisons between the Ruijin model and the Roach formula were conducted using the receiver operating characteristic-derived area under the curve (AUC), calibration plot, and decision-curve analyses (DCAs).

RESULTS

In total, 624 patients with median age (69.5 year) were included in this analysis. The median number of pelvis lymph nodes removed was 6 (range: 2-30). LNI was found in 35 (5.6%) patients. In the multivariable logistic regression model, total prostate-specific antigen (OR = 1.008, P = 0.025), percentage of cores with the highest-grade PCa (OR = 14.822, P<0.001), clinical stage (III vs. I-II: OR = 7.733, P = 0.008), and biopsy Gleason Grading Group (G3 vs G1-2: OR = 3.152, P = 0.082; G4 vs G1-2: OR = 3.065, P = 0.083; G5 vs G1-2: OR = 5.262, P = 0.008;) were included and formed the basis for the nomogram. The predictive accuracy of Ruijin nomogram in our cohort was 87.7%. Using a cutoff of 4% based on Ruijin nomogram, 395 (63%) PLND would be spared and LNI would be missed in only two (0.5%) patients. The sensitivity, specificity, and negative predictive value associated with the 4% cutoff were 94.3%, 66.7%, and 99.5%, respectively. As compared with the Roach formula, the Ruijin model showed higher AUC (87.7% vs 80.9%, Z = -2.013, P = 0.044), better calibration characteristics, and a higher net benefit at DCA.

CONCLUSION

We developed a novel nomogram for predicting the LNI in localized PCa patients with detailed biopsy information. PLND or WPRT could be avoided in patients with a risk of LNI <4%, so as to spare more than 60% of unnecessary pelvic nodal treatment with a cost of missing only 0.5% LNIs.

Quality Assurance of Protocol Compliance in a Multicenter Randomized Trial Investigating the Role of Hypofractionated Comprehensive Reginal Nodal Irradiation in Node-Positive Breast Cancer (HARVEST)

PURPOSE/OBJECTIVE(S)

The HARVEST trial (NCT03829553) is a phase III, multicenter, randomized clinical trial to explore efficacy and safety of hypofractionated irradiation (HFI) involving regional nodal irradiation (RNI, including internal mammary nodes, IMN) in N+ breast cancer patients treated with mastectomy or breast conserving surgery (BCS). Current study aims to analyze the dosimetric quality assurance so as to evaluate the compliance to the trial protocol.

MATERIALS/METHODS

Eligible patients were randomly assigned (1:1) to receive conventional fractionated irradiation (CFI: 50 Gy/25Fx) or HFI (40.05 Gy/15Fx), which is delivered to ipsilateral chest wall or whole breast (CW/WB) with tumor bed boost (HFI: 10.68 Gy/4Fx; CFI: 10 Gy/5Fx) and comprehensive RNI (supra/infraclavicular nodes and IMN in each patient, lower axilla if indicated) by using IMRT technique. The plan quality was evaluated based on dose distribution, dose volume histogram (DVH) and field parameters. The target coverage, including planning target volume of CW/WB (PTV1) and tumor bed (PTV2) and doses of the organs at risk (OARs) were evaluated. The LQ model was used to convert doses of OARs in HFI group using α/β = 3 Gy (EQD23) for comparison.

RESULTS

Between Feb 21, 2019 and Feb 14, 2022, 801 patients were enrolled at 8 centers with 401 and 400 in CFI and HFI group, respectively. There were 182 patients received BCS and 387 patients were with more than three positive lymph nodes. In the CFI group, the D90 and V45 of PTV1 reached the prescribed dose in 70.6% and 96.0% of the patients, respectively. In the HFI group, the D90 and V36 of PTV1 reached the prescribed dose in 87.8% and 95.5% of the patients, respectively. When the tumor bed was irradiated, the D90 of PTV2 reached the prescribed dose in 95.6% in the CFI group and 100% in the HFI group, respectively. The mean D90 of PTV1 and PTV2 were 50.09±0.65 Gy and 60.63±0.91 Gy in CFI group while 40.11±0.56 Gy and 50.79±2.03 Gy in HFI group. For OARs constraints, protocol compliance was all above 95% (heart: 95.3%; ipsilateral lung: 95.5%; contralateral lung: 97.1%; humeral head: 98.2% and spinal cord: 100%) with no significant difference between CFI and HFI groups. For patients with left-sided breast cancer, the Dmean of the heart was 5.10±1.75 Gy vs. 4.59±1.86 Gy (EQD23) in CFI and HFI groups (p = 0.51), respectively. No significant differences in Dmean of the heart (1.45±0.71 Gy vs. 1.33±0.77 Gy (EQD23), p = 0.40) was found either between two groups in right-sided patients. The differences were significant in the Dmean of the ipsilateral lung (13.37±1.99 Gy vs. 11.17±3.50 Gy (EQD23), p<0.01), contralateral lung (0.88±0.73 Gy vs. 0.74±0.61 Gy (EQD23), p<0.01) and the ipsilateral humeral head (15.27±7.62 Gy vs. 13.05±6.19 Gy (EQD23), p<0.01) and the Dmax of spinal cord (21.40±8.82 Gy vs. 19.47±7.99 Gy (EQD23), p = 0.05) between CFI and HFI groups.

CONCLUSION

A high degree of compliance with protocol dose constraints was found for treatment plans in the HARVEST trial and doses to the most of OARs decreased in HFI group.

Establishing a Risk Stratification Model to Identify Clinically High-Risk N0 Breast Cancer Who Could Benefit from Regional Nodal Irradiation: A Single Institute Analysis

PURPOSE/OBJECTIVE(S)

The adverse clinical features for pN0 BC patients significantly varies and there is no established clinical risk stratification system to identify those "high-risk" pN0 BC patients who might benefit from RNI. The purpose of this real-world study was to investigate the risk factors for developing recurrence among patients with pathological T1-3N0 breast cancer (BC) treated with breast-conserving surgery (BCS) followed by whole breast irradiation alone (WBI) and identify those clinically high-risk BCs who could benefit from regional nodal irradiation (RNI).

MATERIALS/METHODS

Female BC patients treated from 2009 to 2016 were retrospectively reviewed. The disease-free survival (DFS) and overall survival (OS) were estimated by the Kaplan-Meier method, and survival differences were compared with the log-rank test. Univariate and multivariate analysis was performed using Cox logistic regression analysis. An external validation was conducted by using SEER database.

RESULTS

A total of 622 BC patients treated with BCS+WBI alone were included. With a median follow-up of 82 months, the 7-year OS and DFS for the entire cohort was 97% and 91%, respectively. Multivariable Cox analysis indicated that tumor size (p = 0.006), tumor location (p = 0.033), lymphovascular invasion (LVI) status (p = 0.0028) and Ki-67 index (p = 0.051) were independent risk factors for DFS, while only tumor size was the only independent risk factors for OS (p = 0.029). A scoring system was developed using these four factors and the 7-year DFS and OS were 97% and 96% for patients with 0-1 risk factors, 95% and 82% for patients with ≥2 risk factors (p<0.0001 for DFS, and p = 0.0063 for OS). Based on tumor size and tumor location, an external validation by demonstrated that the 7-year OS was 90% and 88% for patients with 0-1 risk factor, which was significantly better than those defined as high-risk BC patients (82%, p<0.0001).

CONCLUSION

By using our institute database, we establish a risk stratification system for identifying sub-group of pN0 BC patients, who are at high risk for developing recurrence. The results of our study support tailored RT decision-making according to individual risks, which needed to be confirmed in further studies.

Treatment Outcomes and Prognostic Factors of Chemotherapy Combined with Radiotherapy for Patients with Stage I-II Nasal-Type Natural Killer/T-Cell Lymphoma

PURPOSE/OBJECTIVE(S)

The purpose of this study was to assess the treatment outcome and the potential prognostic factors for patients with stage I-II nasal ENKTL treated with radiotherapy (RT) combined chemotherapy (CT).

MATERIALS/METHODS

From July, 2005 to January, 2019, 118 eligible patients were retrospective included in the study. Among the 118 patients, 84 were male and 34 were female. The median age was 45 years (range: 14-77 years). According to the Ann Arbor staging system, 66 patients had stage I disease (Primary tumor invasion (PTI) was present in 29 patients), and 52 patients had stage II disease. B symptoms were observed in 61 patients. The Eastern Cooperative Oncology Group (ECOG) performance score was 0 to 1 in 88 patients. Cervical lymph node involvement was observed in 51 patients. The primary lesions were located in the nasal cavity in 92 cases and in the Waldeyer ring in 26 cases. Five patients had received RT followed by CT (RT + CT), 20 patients had received CT followed by RT (CT + RT), 90 patients had received CT followed by RT, again followed by CT (CT+RT+CT), and 3 patients had received concurrent chemoradiotherapy (CRT) (1 patient received CRT + CT, other 2 patients received CT+CRT+CT). Patients were irradiated with a median dose of 50 Gy (range, 24-61.2). All patients received chemotherapy, 91 received non-anthracycline-based chemotherapy, whereas 27 patients received anthracycline-based chemotherapy. The median number of courses of chemotherapy was four (range: 1-10). Patients were scored as having low-risk disease (n = 50), intermediate-risk disease (n = 60) or high-risk disease (n = 8) according to the prognostic index of natural killer cell lymphoma (PINK).

RESULTS

Among the 118 patients, after initial therapy, the complete response (CR) rate was 82.2% (n = 97), and the partial response (PR) rate was 11.0% (n = 13). The stable disease (SD) rate was 2.5% (n = 3), and the progressive disease (PD) rate was 4.2% (n = 5). With a median follow-up of 43 months (range, 4-201) after irradiation, the 3-year PFS and OS were 76.9% and 82.9%, respectively. The 3-year OS rate was 75.0% for RT + CT, 70.0% for CT + RT, 87.1% for CT + RT+ CT, and 50.0% for CRT (P = 0.052). Three-year OS and PFS were 88.6% and 83.4%, respectively, for non-anthracycline-based chemotherapy regimen compared to 61.6% (P = 0.001) and 58.4% (P = 0.003), respectively, for the anthracycline-based chemotherapy regimen. Three-year OS and PFS were 84.0% and 79.0%, respectively, for patients receiving high-dose RT (≥50 Gy, n = 111) compared to 71.4% (P = 0.076) and 71.4% (P = 0.228), respectively, for low-dose RT (<50 Gy, n = 7). In multivariate analysis, adverse factors associated with OS in our study were chemotherapy regimen and response to RT and CT (P = 0.047, <0.001).

CONCLUSION

Radiotherapy combined with chemotherapy reported promising response rate and a favorable survival for patients with stage I-II nasal ENKTL. Anthracycline-based chemotherapy regimen and no remission after RT and CT were adverse factors of OS.

Improving Interfraction Robustness for IMPT Treatment Planning for Lung Cancer Using Multiple-CT Incorporated Robust Optimization

PURPOSE/OBJECTIVE(S)

Dose deterioration due to motion-induced density variation is a major concern in intensity-modulated proton therapy (IMPT) for lung cancer. Robust optimization is capable to address the intrafraction motion issue but not the interfraction variation. This study aims to investigate the potential of a new robust optimization technique of IMPT in mitigating the interfraction variation of lung cancer patients.

MATERIALS/METHODS

Two optimization techniques were used to create an IMPT plan for a lung cancer case, one was conventional robust optimization (ROcon) considering the perturbation of 3 mm setup uncertainty and 3.5% range uncertainty, and the other was multiple-CT incorporated robust optimization (ROmul) considering one more perturbation quantified using the end-of-inhalation-phase (T0) and end-of-exhalation-phase (T50) CTs. The ROcon plan was optimized on the average-intensity-projection (AIP) planning CT (pCT), and the ROmul plan was optimized on the AIP, T0, and T50 pCTs. The dose prescription was 40 Gy (RBE) in 5 fractions. The patient underwent a verification 4DCT (vCT) scan on six successive days. Both plans were recalculated on the T0 pCT, T50 pCT, and AIP vCT. The dose to the target and organ at risk of the ROcon and ROmul plans on pCT and vCT were compared.

RESULTS

Compared with the ROcon plan, the ROmul plan reduced the deviation of target coverage by greater than 50% in presence of intrafraction motion (ROmul:0.38-0.88%, ROcon:1.90-2.23%) and interfraction variation (ROmul: 0.62-1.63% vs ROcon:0.50-2.75%) while meeting the dose criteria on the planning AIP CT. As for the dose to the organ at risk, the ROmul plan had a slightly high lung V20 (0.3%) than did the ROcon plan on the AIP pCT. The deviations in lung V20 of the ROmul plan (mean 0.15%) on the vCTs were similar to that of the ROcon plan (mean 0.17%).

CONCLUSION

This study indicates that dose variation of an IMPT plan can be reduced in presence of interfraction variation along the treatment course by combining conventional robust optimization and novel multiple-CT optimization using only the planning CT.

Nodal Response to Neo-Adjuvant Systemic Therapy Predicts Prognosis of cN3c Breast Cancer Patients Receiving Multidisciplinary Therapy

PURPOSE/OBJECTIVE(S)

cN3c breast cancer with ipsilateral supraclavicular (SCV) lymph nodal (SCLN) metastasis has a dismal prognosis. We investigated the survival outcomes, patterns and risks of recurrence in those patients after multidisciplinary therapy, as well as the predictors of candidates for SCV area boosting.

MATERIALS/METHODS

Consecutive cN3c breast cancer patients without distant metastases from January 2009 to December 2020 in our institution were retrospectively reviewed. Based on nodal response to neoadjuvant therapy (NAT), patients were categorized into three groups: clinical complete response (cCR) not achieved in SCLN (Group A, n = 66), SCLN cCR but axillary node (ALN) did not achieve pathological complete response (pCR, Group B, n = 34), cCR in SCLN and pCR in ALN (Group C, n = 13).

RESULTS

The median follow-up time was 32.7 months (range, 21.9-53.3months). The 5-year overall survival (OS) and recurrence-free survival (RFS) rates were 64.6% and 43.7% respectively. Multivariate analysis showed cumulative SCV dose and ypT stage, ALN response and SCV response to NAT were significantly associated with OS and RFS respectively. The 3-year for patients receiving the cumulative SCV dose of ≥60 Gy versus <60 Gy was 81.3% versus 69.0% (P = 0.042). Compared with Group A or B, Group C showed significantly improved RFS (3y-RFS: 53.8% vs 73.6% vs 100%, p = 0.003) and a numerically longer OS (3y-OS: 73.4% vs 86.7% vs 100%, p = 0.089). Meanwhile, Group C showed the lowest rate of DM as first failure (37.9 % vs 23.5% vs 0 in group A, B and C, respectively, p = 0.010). In patients of Group A, the 3-year OS rates for patients receiving the cumulative SCV dose of ≥60 Gy versus <60 Gy was 78.0% versus 57.3% (p = 0.029).

CONCLUSION

Nodal response to NAT is an independent prognostic factor for survival and pattern of failure. cN3c breast cancer patients with SCLN cCR and ALN pCR after NAT are potentially curable. A cumulative SCV dose of ≥60 Gy is positively associated with improved OS, especially in patients of SCLN without achieving cCR. Our data supports the perspective of optimizing radiotherapeutic strategy based on nodal response.

Search for a τ^{+}τ^{-} Resonance in e^{+}e^{-}→μ^{+}μ^{-}τ^{+}τ^{-} Events with the Belle II Experiment

We report the first search for a nonstandard-model resonance decaying into τ pairs in e^{+}e^{-}→μ^{+}μ^{-}τ^{+}τ^{-} events in the 3.6-10  GeV/c^{2} mass range. We use a 62.8  fb^{-1} sample of e^{+}e^{-} collisions collected at a center-of-mass energy of 10.58 GeV by the Belle II experiment at the SuperKEKB collider. The analysis probes three different models predicting a spin-1 particle coupling only to the heavier lepton families, a Higgs-like spin-0 particle that couples preferentially to charged leptons (leptophilic scalar), and an axionlike particle, respectively. We observe no evidence for a signal and set exclusion limits at 90% confidence level on the product of cross section and branching fraction into τ pairs, ranging from 0.7 to 24 fb, and on the couplings of these processes. We obtain world-leading constraints on the couplings for the leptophilic scalar model for masses above 6.5  GeV/c^{2} and for the axionlike particle model over the entire mass range.

Nitric oxide-dependent immunosuppressive function of thymus-derived mesenchymal stromal/stem cells

BACKGROUND

The thymus is required for T cell development and the formation of the adaptive immunity. Stromal cells, which include thymic epithelial cells (TECs) and mesenchymal stromal cells (MSCs), are essential for thymic function. However, the immunomodulatory function of thymus-derived MSCs (T-MSCs) has not been fully explored.

METHODS

MSCs were isolated from mouse thymus and their general characteristics including surface markers and multi-differentiation potential were characterized. The immunomodulatory function of T-MSCs stimulated by IFN-γ and TNF-α was evaluated in vitro and in vivo. Furthermore, the spatial distribution of MSCs in the thymus was interrogated by using tdTomato-flox mice corssed to various MSC lineage Cre recombinase lines.

RESULTS

A subset of T-MSCs express Nestin, and are mainly distributed in the thymic medulla region and cortical-medulla junction, but not in the capsule. The Nestin-positive T-MSCs exhibit typical immunophenotypic characteristics and differentiation potential. Additionally, when stimulated with IFN-γ and TNF-α, they can inhibit activated T lymphocytes as efficiently as BM-MSCs, and this function is dependent on the production of nitric oxide (NO). Additionally, the T-MSCs exhibit a remarkable therapeutic efficacy in acute liver injury and inflammatory bowel disease (IBD).

CONCLUSIONS

Nestin-positive MSCs are mainly distributed in medulla and cortical-medulla junction in thymus and possess immunosuppressive ability upon stimulation by inflammatory cytokines. The findings have implications in understanding the physiological function of MSCs in thymus.

Measurement of CP Violation in B^{0}→K_{S}^{0}π^{0} Decays at Belle II

We report a measurement of the CP-violating parameters C and S in B^{0}→K_{S}^{0}π^{0} decays at Belle II using a sample of 387×10^{6}  BB[over ¯] events recorded in e^{+}e^{-} collisions at a center-of-mass energy corresponding to the ϒ(4S) resonance. These parameters are determined by fitting the proper decay-time distribution of a sample of 415 signal events. We obtain C=-0.04_{-0.15}^{+0.14}±0.05 and S=0.75_{-0.23}^{+0.20}±0.04, where the first uncertainties are statistical and the second are systematic.

Orchestration of Mesenchymal Stem/Stromal Cells and Inflammation During Wound Healing

Wound healing is a complex process and encompasses a number of overlapping phases, during which coordinated inflammatory responses following tissue injury play dominant roles in triggering evolutionarily highly conserved principals governing tissue repair and regeneration. Among all nonimmune cells involved in the process, mesenchymal stem/stromal cells (MSCs) are most intensely investigated and have been shown to play fundamental roles in orchestrating wound healing and regeneration through interaction with the ordered inflammatory processes. Despite recent progress and encouraging results, an informed view of the scope of this evolutionarily conserved biological process requires a clear understanding of the dynamic interplay between MSCs and the immune systems in the process of wound healing. In this review, we outline current insights into the ways in which MSCs sense and modulate inflammation undergoing the process of wound healing, highlighting the central role of neutrophils, macrophages, and T cells during the interaction. We also draw attention to the specific effects of MSC-based therapy on different pathological wound healing. Finally, we discuss how ongoing scientific advances in MSCs could be efficiently translated into clinical strategies, focusing on the current limitations and gaps that remain to be overcome for achieving preferred functional tissue regeneration.

Test of Light-Lepton Universality in the Rates of Inclusive Semileptonic B-Meson Decays at Belle II

We present the first measurement of the ratio of branching fractions of inclusive semileptonic B-meson decays, R(X_{e/μ})=B(B→Xeν)/B(B→Xμν), a precision test of electron-muon universality, using data corresponding to 189  fb^{-1} from electron-positron collisions collected with the Belle II detector. In events where the partner B meson is fully reconstructed, we use fits to the lepton momentum spectra above 1.3  GeV/c to obtain R(X_{e/μ})=1.007±0.009(stat)±0.019(syst), which is the most precise lepton-universality test of its kind and agrees with the standard-model expectation.

IL4I1-catalyzed tryptophan metabolites mediate the anti-inflammatory function of cytokine-primed human muscle stem cells

Muscle stem cells (MuSCs) have been demonstrated to exert impressive therapeutic efficacy in disease settings through orchestrating inflammatory microenvironments. Nevertheless, the mechanisms underlying the immunoregulatory property of MuSCs remain largely uncharacterized. Here, we showed that interleukin-4-induced-1 (IL4I1), an essential enzyme that catalyzes indole metabolism in humans, was highly expressed in human MuSCs exposed to IFN-γ and TNF-α. Functionally, the MuSCs were found to inhibit the infiltration of neutrophils into sites of inflammation in a IL4I1-dependent manner and thus ameliorate acute lung injury in mice. Mechanistically, the indole metabolites, including indole-3-pyruvic acid (I3P) and indole-3-aldehyde (I3A), produced by IL4I1, acted as ligands to activate aryl hydrocarbon receptor (AHR), leading to augmented expression of TNF-stimulated gene 6 (TSG-6) in inflammatory cytokine-primed MuSCs. Furthermore, I3P administration alone suppressed neutrophil infiltration into damaged lungs. I3P could also reduce the level of reactive oxygen species in neutrophils. Therefore, our study has uncovered a novel mechanism by which MuSCs acquire their immunoregulatory property and may help to develop or optimize MuSC-based therapies for inflammatory diseases.

[Protective effect and mechanism of AKAP1 on myocardial injury induced by highland hypobaric hypoxia]

Objective: To investigate the protective effect and its possible mechanism of A-kinase anchored protein 1 (AKAP1) on the myocardial injury induced by highland hypobaric hypoxia. Methods: From January 2021 to May 2022, male C57BL/6 SPF grade mice were divided into wild type control (WT) group and highland hypobaric hypoxia (HH) group with 6 mice in each group. HH group simulated 6000 m altitude with low pressure oxygen chamber for 4 weeks to build the model. Primary myocardial cells of SD rats were divided into normoxia control group and hypoxia experimental group (n=3). Cell models were constructed in a three-gas hypoxia incubator with 1% oxygen concentration for 24 h. AKAP1 protein and mRNA expression in myocardial tissue and cells were detected by western blotting, immunohistochemistry and quantitative real-time polymerase chain reaction (qPCR). After myocardial point injection of the AKAP1 or the control adenovirus, the mice were divided into 3 groups (n=6) : WT group, highland hypobaric hypoxia overexpression control group (HH+Ad-Ctrl group) and highland hypobaric hypoxia overexpression experimental group (HH+Ad-AKAP1 group). The cardiac function of mice was detected by noninvasive M-type ultrasonic cardiomotive, myocardial fibrosis was detected by Masson and Sirius Red staining, and cardiomyocyte hypertrophy was detected by wheat germ agglutinin. After the expression of AKAP1 in primary cardiomyocytes was downregulated by siRNA and upregulated by adenovirus, the cells were divided into three groups (n=3) : normoxia control group, hypoxia interference control group (hypoxia+siCtrl group), hypoxia AKAP1 knockdown group (hypoxia+siAKAP1 group) ; normoxia control group, hypoxia overexpression control group (hypoxia+Ad-Ctrl group), hypoxia AKAP1 overexpression group (hypoxia+Ad-AKAP1 group). Apoptosis was detected by flow cytometry, AKAP1, apoptosis-related protein and mRNA expression levels were detected by western blotting and qPCR, mitochondrial membrane potential was detected by JC-1 staining, and mitochondrial reactive oxygen specie (ROS) level was detected by MitoSOX. Results: The expression of AKAP1 in cardiac muscle of HH group was lower than that in the WT group, and the expression of AKAP1 in hypoxia experimental group was lower than that in normoxia control group (P<0.01). Compared with WT group, the left ventricular ejection fraction and fraction shortening of left ventricle in HH+Ad-Ctrl group were decreased (P<0.01), myocardial fibrosis and hypertrophy were aggravated (P<0.01), and the expression of B-cell lymphoma-2 (BCL-2) was decreased, the expressions of BCL-2-associated X protein (BAX), Caspase 3 and Caspase 9 were increased (P<0.01). After AKAP1 overexpression, compared with HH+Ad-Ctrl group, the left ventricular ejection fraction and left ventricular fraction shortening were increased in HH+Ad-AKAP1 group (P<0.01), myocardial fibrosis and hypertrophy were reduced (P<0.01), and the expression of BCL-2 was increased, the expressions of BAX, Caspase 3 and Caspase 9 were decreased (P<0.01). Compared with normoxia control group, the expression of BCL-2 in hypoxia+siCtrl group was decreased, the expressions of BAX, Caspase 3, Caspase 9 were increased, the apoptosis level was increased (P<0.01), the mitochondrial membrane potential was decreased and the production of ROS was increased (P<0.01). After AKAP1 knockdown, compared with hypoxia+siCtrl group, the expression of BCL-2 in hypoxia+siAKAP1 group was decreased, the expressions of BAX, Caspase 3, Caspase 9 were increased, the apoptosis level was increased (P<0.01), mitochondrial membrane potential was decreased, and the production of ROS was increased (P<0.01). After AKAP1 overexpression, compared with hypoxia+Ad-Ctrl group, the expression of BCL-2 in hypoxia+Ad-AKAP1 group was increased, the expressions of BAX, Caspase 3 and Caspase 9 were decreased (P<0.05), the apoptosis level was decreased (P<0.01), and the mitochondrial membrane potential was enhanced, and the production of ROS was decreased (P<0.01) . Conclusion: The downregulation of AKAP1 in cardiomyocytes under highland hypobaric hypoxia may lead to the decrease of mitochondrial membrane potential and the increase of ROS generation, leading to the apoptosis of cardiomyocytes, and thus aggravating the myocardial injury at highland hypobaric hypoxia.

Search for the Lepton Flavor Violating Decays B^{+}→K^{+}τ^{±}ℓ^{∓} (ℓ=e, μ) at Belle

We present a search for the lepton flavor violating decays B^{+}→K^{+}τ^{±}ℓ^{∓}, with ℓ=(e,μ), using the full data sample of 772×10^{6}  BB[over ¯] pairs recorded by the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. We use events in which one B meson is fully reconstructed in a hadronic decay mode. We find no evidence for B^{±}→K^{±}τℓ decays and set upper limits on their branching fractions at the 90% confidence level in the (1-3)×10^{-5} range. The obtained limits are the world's best results.

Search for an Invisible Z^{'} in a Final State with Two Muons and Missing Energy at Belle II

The L_{μ}-L_{τ} extension of the standard model predicts the existence of a lepton-flavor-universality-violating Z^{'} boson that couples only to the heavier lepton families. We search for such a Z^{'} through its invisible decay in the process e^{+}e^{-}→μ^{+}μ^{-}Z^{'}. We use a sample of electron-positron collisions at a center-of-mass energy of 10.58 GeV collected by the Belle II experiment in 2019-2020, corresponding to an integrated luminosity of 79.7  fb^{-1}. We find no excess over the expected standard-model background. We set 90%-confidence-level upper limits on the cross section for this process as well as on the coupling of the model, which ranges from 3×10^{-3} at low Z^{'} masses to 1 at Z^{'} masses of 8  GeV/c^{2}.

[A region-level contrastive learning-based deep model for glomerular ultrastructure segmentation on electron microscope images]

OBJECTIVE

We propose a novel region- level self-supervised contrastive learning method USRegCon (ultrastructural region contrast) based on the semantic similarity of ultrastructures to improve the performance of the model for glomerular ultrastructure segmentation on electron microscope images.

METHODS

USRegCon used a large amount of unlabeled data for pre- training of the model in 3 steps: (1) The model encoded and decoded the ultrastructural information in the image and adaptively divided the image into multiple regions based on the semantic similarity of the ultrastructures; (2) Based on the divided regions, the first-order grayscale region representations and deep semantic region representations of each region were extracted by region pooling operation; (3) For the first-order grayscale region representations, a grayscale loss function was proposed to minimize the grayscale difference within regions and maximize the difference between regions. For deep semantic region representations, a semantic loss function was introduced to maximize the similarity of positive region pairs and the difference of negative region pairs in the representation space. These two loss functions were jointly used for pre-training of the model.

RESULTS

In the segmentation task for 3 ultrastructures of the glomerular filtration barrier based on the private dataset GlomEM, USRegCon achieved promising segmentation results for basement membrane, endothelial cells, and podocytes, with Dice coefficients of (85.69 ± 0.13)%, (74.59 ± 0.13)%, and (78.57 ± 0.16)%, respectively, demonstrating a good performance of the model superior to many existing image-level, pixel-level, and region-level self-supervised contrastive learning methods and close to the fully- supervised pre-training method based on the large- scale labeled dataset ImageNet.

CONCLUSION

USRegCon facilitates the model to learn beneficial region representations from large amounts of unlabeled data to overcome the scarcity of labeled data and improves the deep model performance for glomerular ultrastructure recognition and boundary segmentation.

Search for Lepton-Flavor-Violating τ Decays to a Lepton and an Invisible Boson at Belle II

We search for lepton-flavor-violating τ^{-}→e^{-}α and τ^{-}→μ^{-}α decays, where α is an invisible spin-0 boson. The search uses electron-positron collisions at 10.58 GeV center-of-mass energy with an integrated luminosity of 62.8  fb^{-1}, produced by the SuperKEKB collider and collected with the Belle II detector. We search for an excess in the lepton-energy spectrum of the known τ^{-}→e^{-}ν[over ¯]_{e}ν_{τ} and τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ} decays. We report 95% confidence-level upper limits on the branching-fraction ratio B(τ^{-}→e^{-}α)/B(τ^{-}→e^{-}ν[over ¯]_{e}ν_{τ}) in the range (1.1-9.7)×10^{-3} and on B(τ^{-}→μ^{-}α)/B(τ^{-}→μ^{-}ν[over ¯]_{μ}ν_{τ}) in the range (0.7-12.2)×10^{-3} for α masses between 0 and 1.6  GeV/c^{2}. These results provide the most stringent bounds on invisible boson production from τ decays.