Clinical practice guidelines for molecular tumor marker, 2nd edition review part 2.

In recent years, rapid advancement in gene/protein analysis technology has resulted in target molecule identification that may be useful in cancer treatment. Therefore, "Clinical Practice Guidelines for Molecular Tumor Marker, Second Edition" was published in Japan in September 2021. These guidelines were established to align the clinical usefulness of external diagnostic products with the evaluation criteria of the Pharmaceuticals and Medical Devices Agency. The guidelines were scoped for each tumor, and a clinical questionnaire was developed based on a serious clinical problem. This guideline was based on a careful review of the evidence obtained through a literature search, and recommendations were identified following the recommended grades of the Medical Information Network Distribution Services (Minds). Therefore, this guideline can be a tool for cancer treatment in clinical practice. We have already reported the review portion of "Clinical Practice Guidelines for Molecular Tumor Marker, Second Edition" as Part 1. Here, we present the English version of each part of the Clinical Practice Guidelines for Molecular Tumor Marker, Second Edition.

Testosterone bounce predicts favorable prognoses for prostate cancer patients treated with degarelix.

BACKGROUND: To clarify the clinical roles of changes in testosterone (T) levels with a cut-off level of 20 ng/dL as predictive factors for prostate cancer patients treated with degarelix acetate. METHODS: A total of 120 prostate cancer patients who received hormone therapies with gonadotropin-releasing hormone antagonist degarelix acetate were retrospectively analyzed. The predictive values of nadir T levels, max T levels, T bounce, and other clinical factors were evaluated for overall survival (OS), cancer-specific survival (CSS), and progression-free survival (PFS). T bounce was defined as satisfying both nadir serum T levels of <20 ng/dL and max serum T levels of ≥20 ng/dL during hormone therapies. RESULTS: In 120 prostate cancer patients, 16 (13%) patients did not achieve nadir T < 20 ng/dL, and 76 (63%) patients had max T ≥ 20 ng/dL. The median times to nadir T and max T are 108 and 312 days, respectively. T bounce was shown in 60 (50%) patients and is associated with favorable prognoses both for OS (p = 0.0019) and CSS (p = 0.0013) but not for PFS (p = 0.92). While in the subgroup analyses of the patients with the progression of the first-line hormone therapies, T bounce predicts favorable OS (p = 0.0015) and CSS (p = 0.0013) after biochemical recurrence. CONCLUSIONS: The present study revealed that T bounce with cut-off levels of 20 ng/dL is a promising biomarker that predicts OS and CSS for prostate cancer patients treated with degarelix acetate.

Copy Number Gain in Androgen Receptors Predicts the Poor Prognosis in Japanese Castration-resistant Prostate Cancer.

BACKGROUND/AIM: The prognostic significance of androgen receptor amplification (AR amp) in cell-free DNA (cfDNA) was studied in Japanese patients with castration-resistant prostate cancer (CRPC). PATIENTS AND METHODS: A total of 120 serum samples were obtained from 38 patients with CRPC. Serum cfDNA was purified and the AR copy number was determined. Factors associated with progression-free survival (PFS) and overall survival (OS) were statistically investigated. RESULTS: The number of patients administered enzalutamide (Enza)/abiraterone (Abi)/docetaxel (DTX) was 33/25/11, respectively. The median PSA was 16.5 ng/ml. Thirty patients (79%) had bone metastases and three patients (7.9%) had lung metastases. The median follow-up was 655 days. The median initial AR copy number was 1.27 (1.10-11.50); an AR copy number of 1.27 or higher was defined as an AR-amp. Regarding PFS, the presence of AR-amp, Gleason score (GS), and ALP were significant factors in univariate analysis. In multivariate analysis, AR amplification was an independent prognostic factor (hazard ratio=7.7, p=0.0035). For OS, PSA and AR-amp were significant factors. In multivariate analysis, AR-amp (hazard ratio=4.65, p=0.0188) was the only independent prognostic factor. CONCLUSION: AR-amp was associated with high nadir PSA and low iPSA/PSA ratio. AR-amp was significantly associated with poor prognosis in Japanese patients with CRPC.

Metastatic castration resistant prostate cancer patients' experience with Radium-223 treatment in Japan.

Aim: We aimed to determine Japanese metastatic castration resistant prostate cancer (CRPC) patients' Ra-223 treatment experience. Patients & methods: Patients answered the Cancer Therapy Satisfaction Questionnaire (CTSQ domains: Satisfaction with Therapy [SWT], Expectations of Therapy [ET], Feelings about Side Effects [FSE]), the Memorial Anxiety Scale for Prostate Cancer (MAX-PC) and the FACT-Bone Pain (FACT-BP) Questionnaire at baseline, during (vists 3 and 5) and after treatment (end of observation; EOO). Results: Data from 72 patients were included. Baseline median CTSQ scores SWT: 66.1 (IQR19.7), ET: 75.0 (IQR45), and FSE 68.8 (IQR 34.4) were unchanged during vists 3 and 5, but the SWT (-3.57 [IQR17.9]) and ET (-5.0 [IQR30]) decreased while FSE was unchanged (0.0 [IQR31.25]) at EOO. The median MAX-PC (18.0 [IQR 49]) score was unchanged (0.0, IQR 6) while the median FACT BP (54.0 [IQR13]) score decreased by -1.0 (IQR 8) at EOO. Conclusion: Japanese metastatic castration resistant prostate cancer patients' experience is stable during Ra-223 treatment.

What is this study about? We wanted to know the treatment experience with Radium-223 (Ra-223) among Japanese prostate cancer patients. Ra-223 is a radioactive molecule used for the treatment of metastatic castration resistant prostate cancer. We asked patients to answer different questionnaires on treatment satisfaction, anxiety and quality of life before, during, and after treatment with Ra-223. What were the results? Based on the patients' answers to our questionnaires, treatment satisfaction, anxiety and quality of life remain stable while the patients undergo treatment with Ra-223, but in some aspects may decline after treatment. What do the results mean? The results mean that patients' experience during Ra-223 treatment is stable but patients should share any concerns they have about their treatment with their doctors.

Identification of Early Biochemical Recurrence Predictors in High-Risk Prostate Cancer Patients Treated with Carbon-Ion Radiotherapy and Androgen Deprivation Therapy.

The aim of this retrospective study was to identify clinical predictors of early biochemical recurrence (BCR) in patients with high-risk prostate cancer (PCa) treated with carbon-ion radiotherapy (CIRT) and androgen deprivation therapy (ADT). A total of 670 high-risk PCa patients treated with CIRT and ADT were included in the study. Early BCR was defined as recurrence occurring during adjuvant ADT after CIRT or within 2 years after completion of ADT. Univariate and multivariate analyses were performed to identify clinical predictors of early BCR. Patients were also classified according to the Systemic Therapy in Advancing or Metastatic Prostate cancer (STAMPEDE) PCa classification. Early BCR was observed in 5.4% of the patients. Multivariate analysis identified clinical T3b stage and ≥75% positive biopsy cores as clinical predictors of early BCR after CIRT and ADT. The STAMPEDE PCa classification was also significantly associated with early BCR based on univariate analysis. These predictors can help clinicians identify patients who are at risk of early BCR. In the future, combination therapy of ADT with abiraterone may be an option for high-risk PCa patients who are at risk of early BCR, based on the results of the STAMPEDE study.

Detection of intraductal carcinoma in prostate cancer patients with small tumor volume.

OBJECTIVES: The purpose of this study was to investigate intraductal carcinoma of the prostate (intraductal carcinoma) and significant cancer (SC) in patients with small tumor volume (<0.5 cm3 ) in prostatectomy specimens. METHODS: Data from 639 patients undergoing radical prostatectomy between April 2006 and December 2017 at Chiba University Hospital and 2 affiliated institutions were retrospectively reviewed. Tumor volume in prostatectomy specimens was measured, and with a tumor volume of less than 0.5 cm3 , the presence of intraductal carcinoma and SC was examined. SC was defined as one that did not meet the definition of pathological insignificant cancer (organ-confined cancer, Grade Group 1, tumor volume < 0.5 cm3 ). The number of patients who met four active surveillance (AS) protocols was also examined. RESULTS: A total of 83 patients with tumor volume < 0.5 cm3 were identified in this study population (SC: 43 patients [52%], intraductal carcinoma: 5 patients [6%]). The median follow-up was 34.6 months (range: 18-57 months). Four (5%) developed biochemical recurrence. The number of positive biopsy cores ≥ 2 was an independent predictor of SC in patients with tumor volume < 0.5 cm3 (hazard ratio: 4.39; 95% confidence interval: 1.67-11.56; p = 0.003). In tumor volume < 0.5 cm3 , tumor volume was significantly correlated with the International Society of Urological Pathology Grade Group (1 vs. 4-5, p = 0.002) and the presence of intraductal carcinoma (p = 0.004). In intraductal carcinoma-positive cases, four of five patients (80%) had the predictor of SC, which was two or more positive biopsy cores. Of the four AS protocols, the criteria for Prostate Cancer Research International: Active Surveillance were met most frequently in 46 cases (55%) of tumor volume less than 0.5 cm3 if targeted biopsy by magnetic resonance imaging was available. CONCLUSION: The results of the present study suggest that intraductal carcinoma was present even in cases with small tumor volumes. Grade Group and intraductal carcinoma showed a positive correlation with tumor volume.

Tumor Location and a Tumor Volume over 2.8 cc Predict the Prognosis for Japanese Localized Prostate Cancer.

(1) Objective: Our study investigated the prognostic value of tumor volume and location in prostate cancer patients who received radical prostatectomy (RP). (2) Methods: The prognostic significance of tumor volume and location, together with other clinical factors, was studied using 557 patients who received RP. (3) Results: The receiver operating characteristic (ROC) curve identified the optimal cutoff value of tumor volume as 2.8 cc for predicting biochemical recurrence (BCR). Cox regression analysis revealed that a tumor in the posterior area (p = 0.031), peripheral zone (p = 0.0472), and tumor volume ≥ 2.8 cc (p < 0.0001) were predictive factors in univariate analysis. After multivariate analysis, tumor volume ≥ 2.8 cc (p = 0.0225) was an independent predictive factor for BCR. Among them, a novel risk model was established using tumor volume and location in the posterior area and peripheral zone. The progression-free survival (PFS) of patients who met the three criteria (unfavorable group) was significantly worse than other groups (p ≤ 0.001). Furthermore, multivariate analysis showed that the unfavorable risk was an independent prognostic factor for BCR. The prognostic significance of our risk model was observed in low- to intermediate-risk patients, although it was not observed in high-risk patients. (4) Conclusion: Tumor volume (≥2.8 cc) and localization (posterior/peripheral zone) may be a novel prognostic factor in patients undergoing RP.

Successful radiofrequency ablation of liver metastases from prostate cancer.

Introduction: Patients with liver metastases from prostate cancer show poor prognosis. We performed metastases-directed therapy using radiofrequency ablation of liver metastases in an attempt to improve the prognosis in a patient with metastatic prostate cancer. Case presentation: We present the case of a 66-year-old man who was treated for metastatic castration-resistant prostate cancer. Evaluation showed isolated liver metastases together with elevated serum prostate-specific antigen levels. We performed metastases-directed therapy using radiofrequency ablation of the liver tumor. The patient showed no recurrent liver metastases for 42 months and survived for 66 months after diagnosis of metastatic prostate cancer. Conclusion: To our knowledge, this is the first report that describes radiofrequency ablation of liver metastases from prostate cancer. This procedure may be a useful therapeutic option for metastases-directed therapy in patients with liver metastases from prostate cancer.

Safety and Efficacy of Carbon-Ion Radiotherapy for Elderly Patients with High-Risk Prostate Cancer.

Carbon-ion radiotherapy (CIRT) is a high-dose intensive treatment, whose safety and efficacy have been proven for prostate cancer. This study aims to evaluate the outcomes of CIRT in elderly patients with prostate cancer. Patients aged 75 years or above at the initiation of CIRT were designated as the elderly group, and younger than 75 years as the young group. The overall survival (OS), disease-specific survival (DSS), biochemical control rate (BCR), biochemical relapse-free survival (BRFS), and adverse events were compared between the elderly and young patients with high-risk prostate cancer treated with CIRT. The elderly group comprised 173 of 927 patients treated for high-risk prostate cancer between April 2000 and May 2018. The overall median age was 69 (range: 45−92) years. The median follow-up period was 91.9 (range: 12.6−232.3) months. The 10-year OS, DSS, BCR, and BRFS rates in the young and elderly groups were 86.9%/71.5%, 96.6%/96.8%, 76.8%/88.1%, and 68.6%/64.3%, respectively. The OS (p < 0.001) was longer in the younger group and the BCR was better in the elderly group (p = 0.008). The DSS and BRFS did not differ significantly between the two groups. The rates of adverse events between the two groups did not differ significantly and no patient had an adverse event of Grade 4 or higher during the study period. CIRT may be as effective and safe in elderly patients as the treatment for high-risk prostate cancer.

Comparison of the medical costs between active surveillance and other treatments for early prostate cancer in Japan using data from the PRIAS-JAPAN study.

OBJECTIVES: To compare the medical costs of active surveillance with those of robot-assisted laparoscopic prostatectomy, brachytherapy, intensity-modulated radiation therapy, and hormone therapy for low-risk prostate cancer. METHODS: The costs of protocol biopsies performed in the first year of surveillance (between January 2010 and June 2020) and those of brachytherapy and radiation therapy performed between May 2019 and June 2020 at the Kagawa University Hospital were analyzed. Hormone therapy costs were assumed to be the costs of luteinizing hormone-releasing hormone analogs for over 5 years. Active surveillance-eligible patients were defined based on the following: age <74 years, ≤T2, Gleason score ≤6, prostate-specific antigen level ≤10 ng/ml, and 1-2 positive cores. We estimated the total number of active surveillance-eligible patients in Japan based on the Japan Study Group of Prostate Cancer (J-CAP) study and the 2017 cancer statistical data. We then calculated the 5-year treatment costs of active surveillance-eligible patients using the J-CAP and PRIAS-JAPAN study data. RESULTS: In 2017, number of active surveillance-eligible patients in Japan was estimated to be 2808. The 5-year total costs of surveillance, prostatectomy, brachytherapy, radiation therapy, and hormone therapy were 1.65, 14.0, 4.61, 4.04, and 5.87 million United States dollar (USD), respectively. If 50% and 100% of the patients in each treatment group had opted for active surveillance as the initial treatment, the total treatment cost would have been reduced by USD 6.89 million (JPY 889 million) and USD 13.8 million (JPY 1.78 billion), respectively. CONCLUSION: Expanding active surveillance to eligible patients with prostate cancer helps save medical costs.

Carbon-ion radiotherapy for urological cancers.

Carbon-ions are charged particles with a high linear energy transfer, and therefore, they make a better dose distribution with greater biological effects on the tumors compared with photons and protons. Since prostate cancer, renal cell carcinoma, and retroperitoneal sarcomas such as liposarcoma and leiomyosarcoma are known to be radioresistant tumors, carbon-ion radiotherapy, which provides the advantageous radiobiological properties such as an increasing relative biological effectiveness toward the Bragg peak, a reduced oxygen enhancement ratio, and a reduced dependence on fractionation and cell-cycle stage, has been tested for these urological tumors at the National Institute for Radiological Sciences since 1994. To promote carbon-ion radiotherapy as a standard cancer therapy, the Japan Carbon-ion Radiation Oncology Study Group was established in 2015 to create a registry of all treated patients and conduct multi-institutional prospective studies in cooperation with all the Japanese institutes. Based on accumulating evidence of the efficacy and feasibility of carbon-ion therapy for prostate cancer and retroperitoneal sarcoma, it is now covered by the Japanese health insurance system. On the other hand, carbon-ion radiotherapy for renal cell cancer is not still covered by the insurance system, although the two previous studies showed the efficacy. In this review, we introduce the characteristics, clinical outcomes, and perspectives of carbon-ion radiotherapy and our efforts to disseminate the use of this new technology worldwide.

External validation of the Candiolo nomogram for high-risk prostate cancer patients treated with carbon ion radiotherapy plus androgen deprivation therapy: a retrospective cohort study.

The aim of this study was to reclassify high-risk prostate cancer patients treated with carbon-ion radiotherapy and androgen deprivation therapy using the Candiolo nomogram and evaluate usefulness to predict the following 10-year biochemical recurrence. Six hundred seventy-two high-risk prostate cancer patients were reclassified according to the Candiolo nomogram. The cumulative incidence curves for biochemical recurrence were compared by Gray's test. Furthermore, five predictors of the Candiolo nomogram in our patients were evaluated by Fine and Gray regression hazards model. The higher the Candiolo risk, the worse the biochemical recurrence, especially in high- and very high-risk patients. Out of five predictors, age ≥70 years, cT3 stage, biopsy Gleason score ≥9 or the percentage of positive biopsy cores ≥50% had significant impacts on 10-year biochemical recurrence in our patients. The Candiolo nomogram can reclassify our high-risk prostate cancer patients treated with carbon-ion radiotherapy and androgen deprivation therapy and evaluate the biochemical recurrence preciously.

A qualitative research study in Japan investigating patients' experience with metastatic castration-resistant prostate cancer: from diagnosis to decision for Ra-223 treatment.

Aim: This qualitative study aimed to reveal symptoms and impacts among bone metastatic castration-resistant prostate cancer (or mCRPC) Japanese patients, prior to Radium-223 (Ra-223) treatment. Materials & Methods: Twenty-three mCRPC patients designated to receive Ra-223 and three treating physicians (Ra-223 prescribers) in Japan, were interviewed. All interview data were assessed for concept frequency, themes and saturation. Results: Forty-five percent of the patients (mean age: 75.8 years) were symptomatic at the time of enrollment. Interviews with all patients revealed 47 mCRPC symptoms, including back pain and bone-specific pain, and 45 life impacts, including worry about disease progression and the impact on daily, physical activities. Conclusion: The symptoms and impacts of living with mCRPC and the associated burden of bone metastasis and skeletal-related symptoms are varied and are important considerations for treatment.

Lay abstract Aim: This study looked at symptoms and impacts among patients with a type of prostate cancer called metastatic castration-resistant prostate cancer. This cancer has spread to other parts of the body including patients' bones. Patients' prostate-specific antigen levels continue to rise despite surgical or medical treatment and their doctors decided the next best treatment is Radium-223 (Ra-223), a radiopharmaceutical therapy. Materials & methods: Twenty-three metastatic castration-resistant prostate cancer patients designated to receive Ra-223 and three treating physicians (Ra-223 prescribers) in Japan, were interviewed. All interview data were assessed for the number of times some words or themes are mentioned by the patients. Results: Ten of the 23 patients (average age of 76 years) had symptoms when the study started. Interviewed patients talked about symptoms including back pain and pain in their bones, and how their cancer caused them to worry about their physical activities and disease progression. Conclusion: The symptoms impact on patients' daily living and the burden of bone metastasis and bone-related symptoms are varied and are important considerations for treatment.

Patients' poor performance status is an independent risk factor for urosepsis induced by kidney and ureteral stones.

This study was aimed to identify the risk factors for urosepsis caused by kidney and ureteral stones. One hundred and nine patients who had kidney or ureteral stones and who were treated with trans-ureteral lithotripsy (TUL) at our institution from 2016 to 2020 were included. We investigated the risk factors for urosepsis caused by kidney or ureteral stones that occurred prior to TUL. Thirty patients (28%) had urosepsis prior to TUL. Patients were divided into a urosepsis group (n = 30, 28%) and a non-urosepsis group (n = 79, 72%). Patients' characteristics (gender, age, performance status [PS] score, presence of diabetes mellitus, and skeletal muscle mass), as well as their stone and urine characteristics (stone size, presence of obstructive ureteral stones, stone composition, and urine and stone cultures), were compared between the two groups. When compared to the non-urosepsis group, patients with urosepsis were more likely to be older (p < 0.001), female (p < 0.001), with lower skeletal muscle mass (p < 0.001) and with poor PSs (p < 0.001). For stone and urine characteristics, infection stones (p = 0.01), positive urine (p < 0.001) and stone culture (p = 0.007) were more often detected in patients with urosepsis. A multivariate analysis showed patients' poor PS to be an independent risk factor for urosepsis due to kidney and ureteral stones (OR = 15.7; 95% CI = 2.2-115, p = 0.007). Our study revealed that the most significant risk factor for urosepsis caused by kidney and ureteral stones was the patients' poor PS.

Pretreatment PSA levels affects the completion rate of Ra-223 treatment.

The aim of this study was to review our initial experience of using radium 223 (Ra-223) for metastatic castration-resistant prostate cancer (CRPC) and to evaluate whether pretreatment PSA levels correlate with completion of Ra-223 treatment. In addition, we examined change ratios of PSA, ALP and BAP after the third administration to evaluate the correlation of these change ratios with completion of the subsequent Ra-223 treatment. Forty patients were enrolled in this retrospective study. Ra-223 treatment was considered completed in patients who received five or six administrations. Patient backgrounds and changes in biomarkers were compared between patient groups (complete vs. incomplete Ra-223 treatment). PSA levels before treatment were significantly lower in the complete compared with the incomplete group (cutoff value; 21.7). ALP and BAP levels had decreased after the third administration in the complete group, compared with baseline levels, while levels in the incomplete group had increased. Significant difference was seen in ALP levels, while was not seen in BAP levels between the two groups. Ra-223 treatment should be considered for CRPC with low PSA levels. Changes in PSA and ALP during Ra-223 treatment might provide markers to identify patients likely to complete Ra-223 treatment, with implications for prognosis.

Revision of CHAARTED and LATITUDE criteria among Japanese de novo metastatic prostate cancer patients.

BACKGROUND: To identify the real high-risk group among Japanese de novo metastatic prostate cancer patients who fit CHAARTED or LATITUDE criteria. METHODS: We retrospectively studied patients who fitted CHAARTED (292 patients) and LATITUDE (294 patients) criteria from Japanese multi-institutions. All patients received androgen deprivation therapy with bicalutamide as an initial treatment. Factors related to overall survival (OS) and progression-free survival were statistically analyzed. RESULTS: The median OS was 55.5 months and 60.0 months in patients who met the CHAARTED and the LATITUDE criteria, respectively. In patients who met CHAARTED criteria, lactate dehydrogenase (LDH) (hazard ratio (HR) 2.63, P < 0.0001) and C-reactive protein (CRP) (HR 1.65, P = 0.042) were independent risk factors for OS. In patients who met the LATITUDE criteria, Gleason score (GS) ≥9 (HR 1.77, P = 0.0326) and LDH (HR 2.62, P < 0.0001) were independent risk factors for OS. Modified CHAARTED criteria by adding LDH and CRP showed a significant difference in OS (HR 2.55, P < 0.0001) with a comparative median OS (31.8 months) to placebo of CHAARTED trial (32.2 months). Modified LATITUDE criteria by adding GS ≥9 and LDH showed a significant difference in OS (HR 2.66, P < 0.0001) with a comparative median OS (32.7 months) to placebo of LATITUDE trial (34.7 months). CONCLUSION: Modified criteria may potentially elucidate the true "high volume" and "high risk" patients in the Japanese cohort who require early intensive therapy.

Not all prostate cancer is the same - patient perceptions: an Asia-Pacific region study.

OBJECTIVE: To explore the perceptions of patients living with different stages of prostate cancer across the Asia-Pacific (APAC) region, as while extensive quantitative research has been undertaken into outcomes of treatments for prostate cancer, little in the way of qualitative research has been performed looking at subjective perceptions of patients in regard to their perceived deficits in the treatment of this condition and such research is particularly lacking in reference to the APAC region. PATIENTS AND METHODS: Initial 45-min qualitative research interrogatory interviews were conducted with 12 patients from Australia, China and Japan to identify themes that were significant to patients in the management of prostate cancer. Thereafter, 150 patients with different stages of prostate cancer underwent 30-min online (Australia) or computer-assisted/personal interviews categorised on the five key themes identified, in order to more fully clarify the nature of patient perceptions of how their prostate cancer had been treated and the issues they felt could be more fully addressed in order to improve the management of this condition. RESULTS: Interviews indicated common challenges and unmet needs among patients, including: (i) patients' feelings and emotional state change during their disease journey, (ii) patients lack of knowledge about prostate cancer and disease progression prior to diagnosis, (iii) patients felt shared decision-making was uncommon, (iv) patients have misperceptions about surgery, and (v) patients have unmet needs for greater information and support to manage their condition. CONCLUSIONS: These patient perceptions of unmet needs in prostate cancer management stand in contrast to patient awareness of other common diseases such as heart failure and diabetes. Such unmet needs vary across disease stages and between different nationalities. Patients with prostate cancer in the APAC region appear to have gaps in knowledge about their disease and wish for greater information, support and public awareness about prostate cancer.

Prognostic factors influencing overall survival in de novo oligometastatic prostate cancer patients.

BACKGROUND: Oligometastatic cancer has been suggested as an intermediate state between localized disease and wide-ranging metastases. The clinical significance of local treatment in oligometastatic prostate cancer (PCa) has been a recent topic of interest. However, standard definitions of oligometastasis are lacking. Here we studied risk factors among Japanese de novo oligometastatic patients with PCa. METHODS: We retrospectively assessed clinical data from 264 patients, including locally advanced (T3 or T4N0M0) cancer, lymph-node-positive cancer (Tany N1M0), and cancer with ≤10 bone metastases. All patients received androgen deprivation therapy only. The number of bone metastases and clinical factors were evaluated in association with overall survival (OS) and progression-free survival (PFS). The Mann-Whitney U test, Cox proportional hazard models, and Kaplan-Meier methods were used as statistical analyses. RESULTS: Median age, PSA at baseline and OS were 74 years, 55.2 ng/mL, and 129.0 months, respectively. The cutoff for the number of bone metastases having the greatest impact on OS was ≥3 (hazard ratio [HR]: 2.67; P = .0001). In multivariate analysis, non-regional lymph node (LN) metastases (HR: 2.15; P = .0222), ISUP grade group (GG) 5 (HR: 2.04; P = .0186) and ≥3 bone metastases (HR: 1.82; P = .0390) were independent predictors of OS. In risk classification based on these factors, OS and PFS were significantly classifiable into poor (2-3 factors), intermediate (1 factor), and good (no factors) risk groups (P < .0001). CONCLUSION: Not only the number of bone metastases, but also non-regional LN metastases predict OS in patients with de novo oligometastatic PCa.