The current role of precision surgery in oligometastatic prostate cancer

Oligometastatic prostate cancer (omPCa) is a novel intermediate disease state characterized by a limited volume of metastatic cells and specific locations. Accurate staging is paramount to unmask oligometastatic disease, as provided by prostate-specific membrane antigen-positron emission tomography. Driven by the results of prospective trials employing conventional and/or modern staging modalities, the treatment landscape of omPCa has rapidly evolved over the last years. Several treatment-related questions comprising the concept of precision strikes are under development. For example, beyond systemic therapy, cohort studies have found that cytoreductive radical prostatectomy (CRP) can confer a survival benefit in select patients with omPCa. More importantly, CRP has been consistently shown to improve long-term local symptoms when the tumor progresses across disease states due to resistance to systemic therapies. Metastasis-directed treatments have also emerged as a promising treatment option due to the visibility of oligometastatic disease and new technologies as well as treatment strategies to target the novel PCa colonies. Whether metastases are present at primary cancer diagnosis or detected upon biochemical recurrence after treatment with curative intent, targeted yet decisive elimination of disseminated tumor cell hotspots is thought to improve survival outcomes. One such strategy is salvage lymph node dissection in oligorecurrent PCa which can alter the natural history of progressive PCa. In this review, we will highlight how refinements in modern staging modalities change the classification and treatment of (oligo-)metastatic PCa. Further, we will also discuss the current role and future directions of precision surgery in omPCa.

Electric Quadrupolar Contributions in the Magnetic Phases of UNi_{4}B

We present acoustic signatures of the electric quadrupolar degrees of freedom in the honeycomb-layer compound UNi_{4}B. The transverse ultrasonic mode C_{66} shows softening below 30 K both in the paramagnetic phase and antiferromagnetic phases down to ∼0.33  K. Furthermore, we traced magnetic field-temperature phase diagrams up to 30 T and observed a highly anisotropic elastic response within the honeycomb layer. These observations strongly suggest that Γ_{6}(E_{2g}) electric quadrupolar degrees of freedom in localized 5f^{2} (J=4) states are playing an important role in the magnetic toroidal dipole order and magnetic-field-induced phases of UNi_{4}B, and evidence some of the U ions remain in the paramagnetic state even if the system undergoes magnetic toroidal ordering.

Impact of frailty on super elderly patients with peripheral artery disease from the I-PAD 3 year registry

Background

Unlike age, frailty is often not taken into account in treatment indications of Endovascular treatment (EVT). One of the reason is that there was little known the relationship between frailty and the outcome of EVT for super elderly patients with peripheral artery disease (PAD). We investigate impacts of frailty on the super elderly patient prognosis who underwent EVT.

Purpose

To investigate impacts of frailty on the super elderly patient prognosis who underwent EVT.

Methods

From August 2015 to July 2016, 335 consecutive patients who underwent EVT were enrolled in the I-PAD registry from 7 institutes in Nagano prefecture. Among them, we selected and analyzed 91 super elderly PAD patients (≥80 years-old) and divided them into two groups:those with moderate or higher frailty (Clinical Frailty Scale (CFS) ≥6, n=28) and those without (CFS ≤5, n=63). The primary endpoints were cardiovascular death and major adverse cardiovascular and limb events (MACLE), defined as a composite of cardiovascular death, myocardial infarction, stroke, admission for heart failure, major amputation and revascularization.

Results

The median follow-up period was 2.7 years. Freedom rate from cardiovascular death and MACLE were significantly lower among patients with moderate or higher frailty than among those without (47.0% vs. 58.0%, P=0.03; 39.1% vs. 68.5%, P<0.01).

Conclusion

The prognosis of super elderly patients with moderate or higher frailty is worse than those without.

Funding Acknowledgement

Type of funding source: None

Impact of hinge motion on stent edge restenosis after new generation drug-eluting-stent implantation in RCA

Background

Edge restenosis still occurs after stent implantation, even by using new generation drug-eluting stents (DES) considered to have favorable biomechanical properties. Mechanical stress imposed on the stent edge are thought to be aggravated by hinge motion at a point between the stented and unstented segments, inducing chronic local inflammation and neointimal overgrowth.

Purpose

The aim of this study was to investigate the association between the development of edge restenosis and hinge motion in right coronary artery (RCA) where the excessive vessel movement is commonly observed.

Methods

Among consecutive 650 lesions in RCA where new generation DESs were implanted between 2009 and 2019, 427 serial lesions with sets of angiographies at baseline and follow-up (6–18 month) were included. In addition to conventional quantitative angiography analysis, hinge angle at stent edges was measured (Fig. 1). All the appropriate data for intravascular imaging were analyzed for both stent edges and reference segments.

Results

Binary restenosis occurred in 43 lesions, and 39 of them were referred to re-intervention. Fifty five percent of them were related to stent edges (15 at proximal and 9 at distal edges). Classical risk factors including diabetes and hemodialysis were more prevalent in the restenosis group (p<0.05). Hinge angle was statistically larger in edge restenosis group than body restenosis or no restenosis group (17.3° vs 11.6° vs 10.6°, p<0.001, Fig. 2). In per-edge analysis, hinge angle, dissection and residual plaque ratio were the independent predictors for binary restenosis (Table 1) with the optimal cut-off value of hinge angle 11.5°. The coexistence of excessive hinge angle and residual plaque burden had an amplified effect on the angiographic stenotic progression at stent edge (p for interaction <0.001) and the incidents of binary restenosis (16.7% vs 1.7% p<0.01, Figs. 3,4).

Conclusion

Substantial stress determined by angulation at the stent edge and its interaction with residual plaque can be considered as one of the plausible mechanisms for edge restenosis. For tortuous RCA lesions, it would be important to decide the stent-landing zone for minimizing hinge motion and optimize the future stent design.

Funding Acknowledgement

Type of funding source: None

P942Impact of left ventricular ejection fraction in patients with critical limb ischemia: from I-PAD registry

Introduction

In patients with critical limb ischemia (CLI) it is known that malnutrition, low BMI, inflammation and so on are prognostic factors. But, it is unclear whether left ventricular ejection fraction (LVEF) affects prognosis of CLI patients. So we investigated that LVEF affects prognosis of CLI patients.

Methods

From July 2015 to July 2016, 371 consecutive peripheral artery disease patients who performed endovascular treatment (EVT) were enrolled in I-PAD registry. 179 of them were patients with CLI. We could conduct follow up survey about 126 (age 75.5±11.1, men 63.5%) and divided two groups according to their LVEF (group with LVEF≤40%, n=13, group without LVEF≤40%, n=113). The primary end point was major adverse limb events (MALE: TLR, TVR, major amputations) and secondary end point was all-cause death.

Results

The median follow-up period was 11.5±6.7 months. The 18 months MALE rate was significant higher in the group with low LVEF than group without low LVEF (76.9% vs 37.2% p<0.05). The 18months all-cause death tended to be higher in the group with low LVEF, however there was not statistical significance in the two groups (53.8% vs 24.8% p=0.09).

Conclusion

LVEF was associated with MALE in patients with CLI.

P1788The outcome of TAVI in patients with small annulus and the comparison between intra-annular and supra-annular devices in small anulus: From the analysis of the Japanese nationwide registry

Background

Transcatheter aortic valve implantation (TAVI) has been widely accepted strategy of the treatment for aortic stenosis in patients at intermediate to high or prohibitive surgical risk. The Asian people are of smaller body size compared to Western people. As the result, Asian people have smaller aortic annulus size, which accommodate only smaller transcatheter heart valves (THVs), however, the details and consequences of small aortic annulus size in TAVI is uncertain.

Purpose

The purposes of this study were to clarify the short-term outcomes of TAVI in patients with small annulus and the differences of intra-annular and supra-annular THVs in small annulus using Japanese national TAVI registry.

Methods

Multi-detector computed tomography (MDCT) was performed before TAVI and the annulus area was registered. We compared the 30-day clinical outcomes between patients with and without small annulus (annulus area 3.14cm2). Further investigation to compare intra-annular and supra-annular THVs in patients with small annulus was conducted.

Results

The total of 5,870 patients (103 sites in Japan) who underwent TAVI between August 2013 to December 2017 were enrolled in this study. Out of 5,870 patients, 647 had small annulus.

Thirty-day mortality, new pacemaker implantation and stroke rate were comparable between patients with and without small annulus. Echocardiography within 30 days after TAVI revealed that patients with small annulus had significantly smaller indexed effective orifice area (iEOA, 1.10.cm2/m2 [0.92–1.35] vs. 1.16 cm2/m2 [0.96–1.39], p<0.001), higher mean pressure gradient (10.0 mmHg [6.9–14.2] vs. 8.5 mmHg [6.0–11.5], p<0.001) and lower frequency of paravalvular leakage moderate (17.3% vs. 24.4%, p<0.001). Patient-prosthesis mismatch (PPM) were more frequent in patients with small annulus (p=0.002). Logistic regression analysis revealed that small annulus (OR: 1.82; 95% CI: 1.45–2.30, p<0.001), female gender (OR: 0.54; 95% CI: 0.42–0.70, p<0.001), weight (OR: 1.03; 95% CI: 1.02–1.04, p<0.001), height (OR: 1.04; 95% CI: 1.02–1.05, p<0.001), hyperlipidemia (OR: 1.25; 95% CI: 1.07–1.47, p=0.006), femoral access (OR: 0.80; 95% CI: 0.66–0.97, p=0.026) were significantly associated with the PPM after TAVI.

The use of SAPIEN 3 20mm THV in patients with small annulus was associated with the smaller iEOA (0.94 cm2/m2 [0.78–1.06] vs. 1.07 cm2/m2 [0.84–1.24], p=0.001) and higher mean pressure gradient (14.0 mmHg [10.0–18.5] vs. 11.0 [7.0–14.0], p<0.001) compared to the usage of Evolut R 23 mm THV. The rate of paravalvular leakage more than moderate was similar in both THVs (14.4% vs. 16.5%, p=0.69).

Conclusions

Small annulus did not affect clinical 30-day outcomes, however, small annulus was associated with smaller iEOA and higher mean pressure gradient. Supra-annular device might contribute the better hemodynamical improvement in patients with small annulus without increase of paravalvular leakage.

Acknowledgement/Funding

None

P936Impact of left ventricular ejection fraction in patients with peripheral artery disease: from I-PAD registry

Introduction

In patients with peripheral artery disease (PAD) it is known that CVD is one of prognostic factors. But, it is unclear whether left ventricular ejection fraction (LVEF) affects prognosis of PAD patients. So we investigated that LVEF affects prognosis of PAD patients.

Methods

From July 2015 to July 2016, 371 consecutive PAD patients who performed endovascular treatment (EVT) were enrolled in I-PAD registry. We could conduct follow up survey about 337 (age 73.8±9.6, men 72.4%) patients and divided two groups according to their LVEF (group with LVEF≤40%, n=18, group without LVEF≤40%, n=319). The primary end point was major adverse limb events (MALE: TLR, TVR, major amputations) and secondary end point was all-cause death.

Results

The median follow-up period was 13.6±5.7 months. The 18 months MALE and all-cause death rate were significantly higher in the group with low LVEF than group without low LVEF (61.1% vs 21.6% p<0.001, 44.4% vs 11.6% p<0.001).

Conclusion

LVEF was significantly associated with MALE and all-cause death in patients with PAD.

P1809Impact of mitral regurgitation on clinical outcome in patients with cardiac sarcoidosis

Background

Mitral regurgitation (MR) is sometimes observed in cardiac sarcoidosis (CS), and might be related to worsening heart failure. However, mechanism and clinical significance of MR associated with CS remains undetermined.

Methods

We retrospectively analyzed consecutive 51 CS patients, and identified 16 patients with moderate to severe MR evaluated by quantitative echocardiography. According to the assessment of coaptation point and tenting height, main mechanisms of the 16 patients with MR were classified into prolapse (P) in 5, and tethering in 11 (T). Prednisolone was started from 30 mg/day, gradually tapered over a period of 6 months to a maintenance dose of 5 to 10 mg/day and continued a lifetime.

Results

At the first visit, patients with MR showed higher incidence of NYHA class IV heart failure as compared to those without MR (56 vs. 9%, p<0.001). Abnormal uptake of fluorine-18 fluorodeoxyglucose in the papillary muscle was more frequent in patients with MR than those without MR (63% vs. 23%, p<0.05). Patients with tethering MR showed higher incidence of complete atrioventricular block (T: 74% vs. P: 40% vs. without MR: 31%, p<0.05), significantly reduced left ventricular (LV) ejection fraction (T: 33±7% vs. P: 52±9% vs. without MR: 52±16%, p<0.001) and increased LV end-diastolic volume index (T: 100±52ml/m2 vs. P: 66±23ml vs. without MR: 62±21ml, p<0.001). During the mean follow-up of 108 months, cardiac-event free survival was significantly worse in patients with tethering MR as compared to the other patients (log-rank; 11.7, p<0.001). Six of the 11 patients with tethering MR received cardiac resynchronization therapy, and then did not experience further hospitalization due to decompensated heart failure for at least 2 years. Multivariate analysis identified tethering MR as an independent predictor of cardiac event (HR: 6.7, p<0.05).

Conclusions

MR associated with CS has variety of mechanisms including prolapse, tethering and inflammation of the LV papillary muscle, and may be related to ventricular remodeling and poor clinical outcome.

P2696Clinical characteristics of late catch-up phenomenon after implantation of 2nd generation drug eluting stent

Introduction

Late catch-up phenomenon (LCU) of 1st generation drug eluting stent (DES) has been increasing yearly despite the rate of restenosis in 1 year has reduced compared with bare metal stent (BMS). 2nd generation DES was more improved than 1st generation DES and suggested more benefits about clinical outcome.

Purpose

To investigate the incidence and predictor of LCU after implantation of 2nd generation DES and to evaluate the association between LCU phenomenon and adverse events.

Methods

Between August 2012 and July 2013, a total of 1665 consecutive patients (1956 lesions with elective/urgent PCI) were enrolled in SHINANO 5 years Registry (a prospective observational multicenter cohort study) from 13 institutions in Nagano, Japan. 711 patients that were treated with 2nd generation DES and 576 patients with BMS were selected. Exclusion criterias were cases of 1st DES, only POBA, only aspiration and chronic total occulusion.

Results

There were significant difference about patients background between BMS and 2nd generation DES groups. Those groups were matched with propensity score. After matching, 822 patients (BMS group 411 patients, 2nd generation group 411 patients) were analyzed. The rates of 2nd DES and BMS restenosis 5 years after initial PCI were 9.2% and 8.5% (p=0.572), those of LCU were 2.6% and 5.6% (p=0.043) by 1 year landmark analysis. Cox proportional hazards analysis revealed that the DES in-stent restenosis (ISR) lesion and higher HbA1c were independent predictors for LCU from 1year to 5year (HR 5.304, p=0.009, HR 1.254, p=0.015), but 2nd generation DES was not. Kaplan Meier curve showed no association between LCU phenomenon and all cause death (p=0.446). Cox regression analysis showed LCU was not independent predictor for all cause death (p=0.414).

Conclusions

Implantation to DES-ISR lesion with 2nd generation DES was associated with higher LCU. Despite of more complex lesions with 2nd generation DES, there were no differences of LCU incidence between 2nd generation DES and BMS.

Acknowledgement/Funding

None

Evidence for the Single-Site Quadrupolar Kondo Effect in the Dilute Non-Kramers System Y_{1-x}Pr_{x}Ir_{2}Zn_{20}

Acoustic signatures of the single-site quadrupolar Kondo effect in Y_{0.966}Pr_{0.034}Ir_{2}Zn_{20} are presented. The elastic constant (C_{11}-C_{12})/2, corresponding to the Γ_{3}(E)-symmetry electric-quadrupolar response, reveals a logarithmic temperature dependence of the quadrupolar susceptibility in the low-magnetic-field region below ∼0.3  K. Furthermore, the Curie-type divergence of the elastic constant down to ∼1  K indicates that the Pr ions in this diluted system have a non-Kramers ground-state doublet. These observations evidence the single-site quadrupolar Kondo effect, as previously suggested based on specific-heat and electrical-resistivity data.

Intratumoural immune cell landscape in germinoma reveals multipotent lineages and exhibits prognostic significance

AIMS

Alterations in microenvironments are a hallmark of cancer, and these alterations in germinomas are of particular significance. Germinoma, the most common subtype of central nervous system germ cell tumours, often exhibits massive immune cell infiltration intermingled with tumour cells. The role of these immune cells in germinoma, however, remains unknown.

METHODS

We investigated the cellular constituents of immune microenvironments and their clinical impacts on prognosis in 100 germinoma cases.

RESULTS

Patients with germinomas lower in tumour cell content (i.e. higher immune cell infiltration) had a significantly longer progression-free survival time than those with higher tumour cell contents (P = 0.03). Transcriptome analyses and RNA in-situ hybridization indicated that infiltrating immune cells comprised a wide variety of cell types, including lymphocytes and myelocyte-lineage cells. High expression of CD4 was significantly associated with good prognosis, whereas elevated nitric oxide synthase 2 was associated with poor prognosis. PD1 (PDCD1) was expressed by immune cells present in most germinomas (93.8%), and PD-L1 (CD274) expression was found in tumour cells in the majority of germinomas examined (73.5%).

CONCLUSIONS

The collective data strongly suggest that infiltrating immune cells play an important role in predicting treatment response. Further investigation should lead to additional categorization of germinoma to safely reduce treatment intensity depending on tumour/immune cell balance and to develop possible future immunotherapies.

Possibility of Flat-Band Ferromagnetism in Hole-Doped Pyrochlore Oxides Sn_{2}Nb_{2}O_{7} and Sn_{2}Ta_{2}O_{7}

Quantum mechanics tells us that the hopping integral between local orbitals makes the energy band dispersive. In a lattice with geometric frustration, however, dispersionless flat bands may appear due to quantum interference. Several models possessing flat bands have been proposed theoretically, and many attracting magnetic and electronic properties are predicted. However, despite many attempts to realize these models experimentally, compounds that are appropriately described by this model have not been found so far. Here we show that pyrochlore oxides Sn_{2}Nb_{2}O_{7} and Sn_{2}Ta_{2}O_{7} are such examples, by performing first-principles band calculation and several tight-binding analyses. Moreover, spin-polarized band calculation shows that the hole-doped systems Sn_{2}Nb_{2}O_{6}N and Sn_{2}Ta_{2}O_{6}N have complete spin polarization, and their magnetic moments are mostly carried by Sn-s and N-p orbitals, which are usually nonmagnetic. These compounds are not only candidates for ferromagnets without a magnetic element, but also will provide an experimental platform for a flat-band model which shows a wide range of physical properties.

Computational Design of Flat-Band Material

Quantum mechanics states that hopping integral between local orbitals makes the energy band dispersive. However, in some special cases, there are bands with no dispersion due to quantum interference. These bands are called as flat band. Many models having flat band have been proposed, and many interesting physical properties are predicted. However, no real compound having flat band has been found yet despite the 25 years of vigorous researches. We have found that some pyrochlore oxides have quasi-flat band just below the Fermi level by first principles calculation. Moreover, their valence bands are well described by a tight-binding model of pyrochlore lattice with isotropic nearest neighbor hopping integral. This model belongs to a class of Mielke model, whose ground state is known to be ferromagnetic with appropriate carrier doping and on-site repulsive Coulomb interaction. We have also performed a spin-polarized band calculation for the hole-doped system from first principles and found that the ground state is ferromagnetic for some doping region. Interestingly, these compounds do not include magnetic element, such as transition metal and rare-earth elements.

One Way to Design a Valence-Skip Compound

Valence-skip compound is a good candidate with high T _c and low anisotropy because it has a large attractive interaction at the site of valence-skip atom. However, it is not easy to synthesize such compound because of (i) the instability of the skipping valence state, (ii) the competing charge order, and (iii) that formal valence may not be true in some compounds. In the present study, we show several examples of the valence-skip compounds and discuss how we can design them by first principles calculations. Furthermore, we calculated the electronic structure of a promising candidate of valence skipping compound RbTlCl₃ from first principles. We confirmed that the charge-density wave (CDW) is formed in this compound, and the Tl atoms in two crystallographic different sites take the valence Tl¹⁺ and Tl³⁺. Structure optimization study reveals that this CDW is stable at the ambient pressure, while this CDW gap can be collapsed when we apply pressure with several gigapascals. In this metallic phase, we can expect a large charge fluctuation and a large electron-phonon interaction.

Abstract P2-01-37: Technical feasibility and validity of sentinel lymph node biopsy in patients with ipsilateral breast tumor recurrence

Background: The incidence of ipsilateral breast tumor recurrence (IBTR) was reported to be approximately 5-10% of breast cancer patients who had breast-conserving surgery. However, the role of sentinel lymph node biopsy (SLNB) in patients with IBTR still remains to be elucidated. The aim of this study wasto evaluate feasibility and validity of sentinel lymph node biopsy for ipsilateral breast tumor recurrence (second SLNB).

Patients and methods: A prospective database of 1607 patients with clinically node-negative breast cancer who underwent SLNB from January 2005 to May 2015 was analyzed and 46 patients with IBTR underwent SLNB. Lymphatic mapping was performed using a combined method of blue dye and radioisotope. ICG fluorescence imaging was performed in cases with failure of identification by blue dye and radioisotope.

Results: The median age was 52 (range: 36-82) years at the time of second SLNB and the mean size of recurrent tumor was 1.39 ± 0.63 cm. Thirty-one (67.4%) and 10 (21.7%) patients had a history of previous SLNB and axillary lymph node dissection (ALND), respectively. Another five (10.9%) patients had no previous axillary surgery for primary tumors. Preoperative lymphatic mapping by lymphoscintigraphy was successfully performed in 24 of 36 patients (66.7%). The identification rate by lymphoscintigraphy among patients with previous SLNB, ALND, and no axillary surgery was 64.0% (16/25), 66.6% (6/9) and 100% (2/2), respectively (P= 0.583). Overall, sentinel lymph nodes (SLNs) were successfully identified in 37 (80.4%) of 46 patients during surgery. The identification rate in patients with previous SLNB, ALND and no axillary surgery was 80.6% (25/31), 80.0% (8/10) and 80.0% (4/5), respectively (P=0.990). The aberrant lymphatic drainage to extra-ipsilateral axilla was found more frequently in patients with previous ALND compared with previous SLNB and no axillary surgery (40.0% vs. 6.5% vs. 0%, P=0.015).Among three (6.5%) patients with SLN metastases, one patient with previous SLNB had macrometastasis at the ipsilateral axilla and ALND found a positive non-SLN (1/21). The remaining two patients with previous SLNB and ALND had micrometastases at ipsilateral and contralateral axilla, respectively and both patients underwent no further axillary treatment. After second SLNB, systemic treatment including chemotherapy, endocrine therapy and trastuzumab was performed in 17 (37.0%), 36 (78.3%) and seven (15.2%) patients, respectively. No axillary recurrence was observed after a median follow-up time of 37.2 months from surgery for IBTR.

Conclusions: Second SLNB is technically feasible regardless of types of previous axillary surgery and may avoid complications from unnecessary ALND for IBTR. Furthermore, it could improve risk prediction for IBTR and provide valid information for deciding adjuvant therapy.

Citation Format: Matsumoto A, Jinno H, Yanagisawa T, Yoshikawa M, Takahashi Y, Seki T, Takahashi M, Hayashida T, Ikeda T, Kitagawa Y. Technical feasibility and validity of sentinel lymph node biopsy in patients with ipsilateral breast tumor recurrence [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P2-01-37.

Expression of Mn-SOD, iNOS and eNOS mRNAs in osteoblasts from the maxilla of osteopetrotic mice

Active oxygens and free radicals are involved in the metabolism and clinical conditions of tissues; however, little is known about the localisation and expression levels of associated enzymes. The expressions of active oxygens, free radicals and associated enzymes are reported to be site-specific; therefore, the expression states of free radical enzymes differ between sites, even within the same cell. In particular, there has been no report concerning the catabolic enzymes of active oxygens in osteoblasts of the maxilla, other than normal osteoblasts that were weakly positive by immunohistochemical staining. We conducted this study to elucidate the relationship between osteodystrophy and radical-associated enzymes by investigating mRNAs of enzymes associated with active oxygens and free radicals using osteoblasts from the maxilla of normal and osteopetrotic model (op/op) mice. In op/op mouse maxilla osteoblasts, mRNAs of Mn-SOD, i-NOS and e-NOS were strongly positive. Mn-SOD and iNOS enzymes were considered to be highly expressed in osteoblasts of the narrowed medullary cavity of this bone.

Ultrastructural immunolocalization of dentin matrix protein 1 on Sharpey's fibers in monkey tooth cementum

Despite the importance of dentin matrix protein 1 (DMP1) in the formation of mineralized tissue, including dentinogenesis and osteogenesis, its precise role in cementogenesis remains to be clarified fully. The purpose of our study was to demonstrate the ultrastructural immunolocalization of DMP1 in monkey molar tooth cementum. Japanese Macaca fuscata monkeys were fixed by perfusion. The upper molar teeth and accompanying periodontium then were dissected and demineralized with EDTA. Cryosections were obtained, incubated in anti-DMP1 polyclonal antibody, and processed by immunoperoxidase and immunogold labeling. Intense immunoperoxidase staining for DMP1 was observed in acellular extrinsic fiber cementum, particularly in Sharpey's fibers. Cementocyte lacunae with canaliculi showed DMP1 staining in the apical region of the tooth root. Electron immunomicroscopy revealed the close proximity of DMP1 to collagen fibrils in Sharpey's fibers at the mineralization front. Intense immunogold labeling was localized on the walls of the cementocyte lacunae in cellular cementum. These results should contribute to better understanding of the role of DMP1, not only in Sharpey's fiber biomineralization, but also in the maintenance of the cementocyte lacunar space in cementum.