A Case of Hemi-ablation with High-intensity Focused Ultrasound for a Localized Reducted Solitary Lesion in the Prostate.

Recently, effectiveness of local treatment for oncological outcomes for patients with metastatic prostate cancer (PC) has been reported. We performed hemi-ablation with high-intensity focused ultrasound (HIFU) for a patient with a localized reducted solitary lesion in the prostate, which was diagnosed with magnetic resonance imaging (MRI)-transrectal ultrasound fusion image-guided target biopsy with PSA level of 0.24 ng/mL, after androgen receptor signaling inhibitors (ARSIs) and chemotherapy for metastatic PC. Prostate specific antigen levels decreased to 0.01ng/mL at 1 month after the treatment, and cancer suspicious lesion disappeared on MRI. During the follow-up of 24 months, there was no elevation of PSA level with no severe complication related to the treatment. HIFU has possibility to be an effective and minimally invasive treatment as a local treatment for the localized reducted solitary lesion in the prostate after ARSIs and chemotherapy for metastatic PC.

Computed diffusion-weighted imaging with a low-apparent diffusion coefficient-pixel cut-off technique for breast cancer detection.

OBJECTIVE: This study aimed to compare the image quality and diagnostic performance of computed diffusion-weighted imaging (DWI) with low-apparent diffusion coefficient (ADC)-pixel cut-off technique (cDWI cut-off) and actual measured DWI (mDWI). METHODS: Eighty-seven consecutive patients with malignant breast lesions and 72 with negative breast lesions who underwent breast MRI were retrospectively evaluated. Computed DWI with high b-values of 800, 1200, and 1500 s/mm2 and ADC cut-off thresholds of none, 0, 0.3, and 0.6 (×10-3 mm2/s) were generated from DWI with two b-values (0 and 800 s/mm2). To identify the optimal conditions, two radiologists evaluated the fat suppression and lesion reduction failure using a cut-off technique. The contrast between breast cancer and glandular tissue was evaluated using region of interest analysis. Three other board-certified radiologists independently assessed the optimised cDWI cut-off and mDWI data sets. Diagnostic performance was evaluated using receiver operating characteristic (ROC) analysis. RESULTS: When an ADC cut-off threshold of 0.3 or 0.6 (× 10-3 mm2/s) was applied, fat suppression improved significantly (p < .05). The contrast of the cDWI cut-off with a b-value of 1200 or 1500 s/mm2 was better than the mDWI (p < .01). The ROC area under the curve for breast cancer detection was 0.837 for the mDWI and 0.909 for the cDWI cut-off (p < .01). CONCLUSION: The cDWI cut-off provided better diagnostic performance than mDWI for breast cancer detection. ADVANCES IN KNOWLEDGE: Using the low-ADC-pixel cut-off technique, computed DWI can improve diagnostic performance by increasing contrast and eliminating un-suppressed fat signals.

A phase II randomized trial of metastasis-directed therapy with alpha emitter radium-223 in men with oligometastatic castration-resistant prostate cancer (MEDAL).

BACKGROUND: The significance of metastasis-directed therapy for oligometastatic prostate cancer has been widely discussed, and targeted therapy for progressive sites is a feasible option as a multidisciplinary treatment for castration-resistant prostate cancer (CRPC). When oligometastatic CRPC with only bone metastases progresses after targeted therapy, it tends to progress as multiple bone metastases. The progression of oligometastatic CRPC after targeted therapy may be due in part to the presence of micrometastatic lesions that, though undetected on imaging, were present prior to targeted therapy. Thus the systemic treatment of micrometastases in combination with targeted therapy for progressive sites is expected to enhance the therapeutic effect. Radium-223 dichloride (radium-223) is a radiopharmaceutical that selectively binds to sites of increased bone turnover and inhibits the growth of adjacent tumor cells by emitting alpha rays. Therefore, for oligometastatic CRPC with only bone metastases, radium-223 may enhance the therapeutic effect of radiotherapy for active metastases. METHODS: This phase II, randomized trial of Metastasis-Directed therapy with ALpha emitter radium-223 in men with oligometastatic CRPC (MEDAL) is designed to assess the utility of radium-223 in combination with metastasis-directed radiotherapy in patients with oligometastatic CRPC confined to bone. In this trial, patients with oligometastatic CRPC with three or fewer bone metastases on whole-body MRI with diffusion-weighted MRI (WB-DWI) will be randomized in a 1:1 ratio to receive radiotherapy for active metastases plus radium-223 or radiotherapy for active metastases alone. The prior use of androgen receptor axis-targeted therapy and prostate-specific antigen doubling time will be used as allocation factors. The primary endpoint will be radiological progression-free survival against progression of bone metastases on WB-DWI. DISCUSSION: This will be the first randomized trial to evaluate the effect of radium-223 in combination with targeted therapy in oligometastatic CRPC patients. The combination of targeted therapy for macroscopic metastases with radiopharmaceuticals targeting micrometastasis is expected to be a promising new therapeutic strategy for patients with oligometastatic CRPC confined to bone. Trial registration Japan Registry of Clinical Trials (jRCT) (jRCTs031200358); Registered on March 1, 2021, https://jrct.niph.go.jp/latest-detail/jRCTs031200358.

Prostate and metastasis diffusion volume based on apparent diffusion coefficient as a prognostic factor in Hormone-naïve prostate Cancer.

In this study, to assess the utility of whole-body DWI (WB-DWI) as an imaging biomarker for metastatic hormone-naïve prostate cancer (mHNPC), we evaluated tumor diffusion volume based on apparent diffusion coefficient (ADC) values. WB-DWI results obtained from 62 mHNPC patients were evaluated in this retrospective analysis. The association with castration resistant-free survival (CFS) was evaluated for both prostate and metastatic tumor diffusion volume (pDV and mDV, respectively) based on WB-DWI. The usefulness of pDV and mDV based on ADC values to predict CFS was also examined. During the follow-up period, 22 patients progressed to castration-resistant prostate cancer, and the median CFS was 42.6 months. The median mDV and pDV were 6.7 and 12.6 mL, respectively. mDV was a significant predictor of CFS (hazard ratio [HR]: 2.75; p = 0.022), while pDV was not significant. When DV was divided into groups by ADC values (× 10- 3 mm2/s) of 0.4-1.0 and 1.0-1.8 (× 10- 3 mm2/s), mDV with ADC values (× 10- 3 mm2/s) of 0.4-1.0 (mDV0.4-1.0) showed a more favorable association with CFS compared to total mDV. On multivariate analysis, mDV0.4-1.0 and Gleason grade group had a statistically significant association with CFS (HR: 4.0; p = 0.004, and HR: 3.4; p = 0.006, respectively), while pDV with ADC values (× 10- 3 mm2/s) of 0.4-1.0 did not have a significant association. mDV is useful for predicting CFS in mHNPC patients. mDV may be a better imaging biomarker when based on ADC values.

Patterns of recurrence in genuine and induced oligometastatic castration-resistant prostate cancer treated with progressive site-directed therapy.

OBJECTIVES: To describe oncological outcomes after progressive site-directed therapy (PSDT) in genuine and induced oligometasatic (OM)-castration-resistant prostate cancer (CRPC). METHODS: Thirty-seven patients with OM-CRPC treated with PSDT were retrospectively analyzed, and oncological outcomes and recurrence patterns on whole-body diffusion-weighted MRI (WB-DWI) were evaluated. RESULTS: Twenty-two (59%) were classified as genuine OM-CRPC and 15 (41%) as induced OM-CRPC. A 50% decline in PSA after PSDT was observed in 21 (95%) genuine OM-CRPCs and 7 (47%) induced OM-CRPCs (p = 0.0005). At a median observation period of 7.3 months, median PSA progression-free survival were 10.9 months in the genuine OM-CRPCs and 4.8 months in the induced OM-CRPCs (p = 0.015). Among the patients who developed PSA progression after PSDT, 11 of 15 in the genuine OM-CRPCs (73%) and 11 of 14 in the induced OM-CRPCs (79%) underwent WB-DWI at PSA progression. The median numbers of newly detected metastases were 2 (range: 1-5) in the genuine OM-CRPCs and 4 (range: 1-40) in the induced OM-CRPCs (p = 0.049). Only one new metastasis appeared in 5 patients from the genuine OM-CRPCs (46%) and 1 from the induced OM-CRPCs (9.1%, p = 0.048). In 7 of 9 patients from the genuine OM-CRPCs (78%) and 7 of 8 patients from the induced OM-CRPCs (88%) who had bone metastases alone, the newly detected metastasis limited to the bone. CONCLUSIONS: Genuine OM-CRPC had better oncological outcomes after PSDT than induced OM-CRPC, and the number of lesions detected at recurrence was limited. Induced OM-CRPC might be a disseminated condition with micrometastases at OM diagnosis.

Quantitative Values from Synthetic MRI Correlate with Breast Cancer Subtypes.

The purpose of this study is to correlate quantitative T1, T2, and proton density (PD) values with breast cancer subtypes. Twenty-eight breast cancer patients underwent MRI of the breast including synthetic MRI. T1, T2, and PD values were correlated with Ki-67 and were compared between ER-positive and ER-negative cancers, and between Luminal A and Luminal B cancers. The effectiveness of T1, T2, and PD in differentiating the ER-negative from the ER-positive group and Luminal A from Luminal B cancers was evaluated using receiver operating characteristic analysis. Mean T2 relaxation of ER-negative cancers was significantly higher than that of ER-positive cancers (p < 0.05). The T1, T2, and PD values exhibited a strong positive correlation with Ki-67 (Pearson's r = 0.75, 0.69, and 0.60 respectively; p < 0.001). Among ER-positive cancers, T1, T2, and PD values of Luminal A cancers were significantly lower than those of Luminal B cancers (p < 0.05). The area under the curve (AUC) of T2 for discriminating ER-negative from ER-positive cancers was 0.87 (95% CI: 0.69−0.97). The AUC of T1 for discriminating Luminal A from Luminal B cancers was 0.83 (95% CI: 0.61−0.95). In conclusion, quantitative values derived from synthetic MRI show potential for subtyping of invasive breast cancers.

Breast Cancer Subtypes and Quantitative Magnetic Resonance Imaging: A Systemic Review.

Magnetic resonance imaging (MRI) is the most sensitive imaging modality for breast cancer detection. This systematic review investigated the role of quantitative MRI features in classifying molecular subtypes of breast cancer. We performed a literature search of articles published on the application of quantitative MRI features in invasive breast cancer molecular subtype classification in PubMed from 1 January 2002 to 30 September 2021. Of the 1275 studies identified, 106 studies with a total of 12,989 patients fulfilled the inclusion criteria. Bias was assessed based using the Quality Assessment of Diagnostic Studies. All studies were case-controlled and research-based. Most studies assessed quantitative MRI features using dynamic contrast-enhanced (DCE) kinetic features and apparent diffusion coefficient (ADC) values. We present a summary of the quantitative MRI features and their correlations with breast cancer subtypes. In DCE studies, conflicting results have been reported; therefore, we performed a meta-analysis. Significant differences in the time intensity curve patterns were observed between receptor statuses. In 10 studies, including a total of 1276 lesions, the pooled difference in proportions of type Ⅲ curves (wash-out) between oestrogen receptor-positive and -negative cancers was not significant (95% confidence interval (CI): [-0.10, 0.03]). In nine studies, including a total of 1070 lesions, the pooled difference in proportions of type 3 curves between human epidermal growth factor receptor 2-positive and -negative cancers was significant (95% CI: [0.01, 0.14]). In six studies including a total of 622 lesions, the pooled difference in proportions of type 3 curves between the high and low Ki-67 groups was significant (95% CI: [0.17, 0.44]). However, the type 3 curve itself is a nonspecific finding in breast cancer. Many studies have examined the relationship between mean ADC and breast cancer subtypes; however, the ADC values overlapped significantly between subtypes. The heterogeneity of ADC using kurtosis or difference, diffusion tensor imaging parameters, and relaxation time was reported recently with promising results; however, current evidence is limited, and further studies are required to explore these potential applications.

Impact of Progressive Site-Directed Therapy in Oligometastatic Castration-Resistant Prostate Cancer on Subsequent Treatment Response.

The purpose of this study was to evaluate the impact of progressive site-directed therapy (PSDT) for oligometastatic castration-resistant prostate cancer (OM-CRPC) on the efficacy of subsequent androgen receptor axis-targeted (ARAT) drugs, and to demonstrate the possibility of prolonging overall survival (OS). We performed a retrospective analysis of 15 OM-CRPC patients who underwent PSDT and subsequently received first-line ARAT drugs (PSDT group) and 13 OM-CRPC patients who were treated with first-line ARAT drugs without PSDT (non-PSDT group). PSDT was performed with the intention of treating all progressing sites detected by whole-body diffusion-weighted MRI with radiotherapy. Thirteen patients (86.7%) treated with PSDT had a decrease in PSA levels, which was at least 50% in 10 (66.7%) patients. The median PSA progression-free survival (PFS) for PSDT was 7.4 months. The median PSA-PFS for ARAT was 27.2 months in patients in the PSDT group and 11.7 months in the non-PSDT group, with a significant difference between the two groups (hazard ratio [HR], 0.28; p = 0.010). The median OS was not reached in the PSDT group and was significantly longer than 44.5 months in the non-PSDT group (HR, 0.11; p = 0.014). In OM-CRPC, PSDT may improve the efficacy of subsequent ARAT and OS.

Metastatic Diffusion Volume Based on Apparent Diffusion Coefficient as a Prognostic Factor in Castration-Resistant Prostate Cancer.

BACKGROUND: Whole-body diffusion-weighted MRI (WB-DWI) is useful for assessing disease activity in castration-resistant prostate cancer (CRPC). MET-RADS-P is a subjective assessment-based reporting system proposed to standardize the interpretation of WB-DWI. However, a quantitative evaluation of WB-DWI has not been fully investigated. PURPOSE: To investigate the validity, and analyze the prognostic value, of quantitative evaluation of WB-DWI based on apparent diffusion coefficient (ADC) values for CRPC. STUDY TYPE: Retrospective. POPULATION: Sixty-six patients with CRPC. The median age was 75 years. During the median follow-up period of 25.2 months, 23 of 66 patients (34.8%) died of prostate cancer. FIELD STRENGTH/SEQUENCE: A 1.5 T WB-DWI was used with two b-values (0 s/mm2 -1000 s/mm2 ). A single-shot echo-planar imaging sequence was used. ASSESSMENT: WB-DWI were evaluated by three readers according to MET-RADS-P scoring system. Using imaging software, Attractive BDScore, tumor diffusion volume (mDV) and ADC value of metastatic lesion (mADC) was calculated by two readers. The mDV was calculated with ADC values (×10-3  mm2 /sec) of 0.4-0.9 (mDV0.4-0.9 ), 0.9-1.4 (mDV0.9-1.4 ), and 1.4-1.8 (mDV1.4-1.8 ), respectively. STATISTICAL TESTS: Spearman's rank correlation coefficient was used to assess the correlation. The relationships between the variables with cancer-specific survival (CSS) were evaluated. Multivariate analysis was performed using the Cox proportional hazards model. RESULTS: mDVs showed a strong positive correlation with MET-RADS-P scores (r = 0.90/0.87, P < 0.05 for both). mDV showed a statistically significant association with CSS (hazard ratio [HR]: 1.01, P < 0.05). When the mDVs calculated based on the ADC values were included, mDV0.4-0.9 (HR: 1.02, P < 0.05) and the number of therapeutic lines (HR: 1.35, P < 0.05) were significant independent indicators of CSS shortening. CONCLUSION: Assessment of metastatic tumor volume based on ADC values can be used in the prognostic evaluation of patients with CRPC. WB-DWI might be a potential prognostic imaging biomarker for CRPC. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: Stage 2.

Whole-body diffusion-weighted magnetic resonance imaging: Diagnosis and follow up of prostate cancer and beyond.

The diffusion-weighted imaging signal is derived from the motion of water molecules. It represents the physiological characteristics of tissue and is an essential imaging sequence for prostate cancer. Whole-body diffusion-weighted imaging facilitates the assessment of pathological conditions throughout the body. The concept of diffusion-weighted whole-body imaging with background body signal suppression and technological advances has led to routine clinical deployment of whole-body diffusion-weighted imaging as a one-step staging tool for prostate cancer. Furthermore, whole-body diffusion-weighted imaging has the potential to reveal the state of osseous lesions, for which conventional imaging techniques are suboptimal for monitoring the response to therapy, and extraosseous lesions, and holds promise as a new imaging-based therapeutic approach. This article reviews the basics of whole-body diffusion-weighted imaging, and focuses on application of whole-body diffusion-weighted imaging in the clinical management of prostate cancer at various stages in the course of the disease.

Potential of Perfusion Magnetic Resonance Imaging to Predict Residual Renal Function after Radical Nephroureterectomy.

INTRODUCTION: The diffusion-weighted imaging (DWI) technique with intravoxel incoherent motion model enables the estimation of capillary blood volume as a perfusion-related parameter- (PP-) value. Therefore, the PP-value of the kidney theoretically reflects renal capillary blood volume. We analyzed the usefulness of the PP-value in estimating postoperative renal function in upper-tract urothelial carcinoma (UTUC) patients. METHODS: Forty-eight consecutive patients who underwent magnetic resonance imaging before radical nephroureterectomy from 2011 to 2018 were analyzed. A PP-map displaying PP-values on a pixel-by-pixel basis was created from DWI signals (b-values of 0, 500, and 1,000 s/mm2). Two readers independently analyzed the renal PP-value. DWI-based split renal function (SRF) of the intact kidney was calculated by splitting serum Cr-based preoperative estimated glomerular filtration rates (eGFRs). The predictive accuracy of the method was evaluated using renography as the reference standard. RESULTS: Interobserver analysis revealed an excellent correlation value of 0.97. The SRF value showed a good linear correlation with the observed postoperative eGFR (r = 0.76, p < 0.001). The predictive accuracy of the DWI-based method was similar to that of the nuclear-based method. CONCLUSION: This DWI-based evaluation of capillary blood volume provides a noninvasive tool for predicting the postoperative renal function, thereby facilitating the management of UTUC patients.

Diagnostic value of computed high b-value whole-body diffusion-weighted imaging for primary prostate cancer.

PURPOSE: To investigate the utility of post-acquisition computed diffusion-weighted imaging (cDWI) for primary prostate cancer (PCa) evaluation in biparametric whole-body MRI (bpWB-MRI). METHODS: Patients who underwent pelvic MRI for PCa screening and subsequent bpWB-MRI for staging were included. Two radiologists assessed the diagnostic performance of the following datasets for clinically significant PCa diagnosis (grade group ≥2 according to the Prostate Imaging-Reporting and Data System, version 2.1): bpMRI2000 (axial DWI scans with a b-value of 2,000 s/mm2 + axial T2WI scans from pre-biopsy pelvic MRI), computed bpWB-MRI2000 (computed WB-DWI scans with a b-value of 2,000 s/mm2 + axial WB-T2WI scans), and native bpWB-MRI1000 (native axial WB-DWI scans with a b-value of 1,000 s/mm2 + axial WB-T2WI scans). Systemic biopsy was used as reference standard. RESULTS: Fifty-one patients with PCa were included. The areas under the curve (AUCs) of bpMRI2000 (0.89 for reader 1 and 0.86 for reader 2) and computed bpWB-MRI2000 (0.86 for reader 1 and 0.83 for reader 2) were significantly higher (p < 0.001) than those of native bpWB-MRI1000 (0.67 for both readers). No significant difference was observed between the AUCs of bpMRI2000 and computed bpWB-MRI2000 (p = 0.10 for reader 1 and p = 0.25 for reader 2). CONCLUSIONS: The diagnostic performance of computed bpWB-MRI2000 was similar to that of dedicated pelvic bpMRI2000 for primary PCa evaluation. cDWI can be recommended for implementation in standard WB-MRI protocols to facilitate a one-step evaluation for concurrent detection of primary and metastatic PCa.

Genuine- and induced-oligometastatic castration-resistant prostate cancer: clinical features and clinical outcomes after progressive site-directed therapy.

PURPOSE: To evaluate the clinical characteristics of genuine- and induced-oligometastatic castration-resistant prostate cancer (OM-CRPC) and assess the therapeutic effect of progressive-site directed therapy (PSDT). METHODS: We performed a retrospective analysis of 45 patients with OM-CRPC. Whole-body diffusion-weighted MRI (WB-DWI) was used to diagnose oligo-progressive disease. Based on the clinical and radiological findings, the OM-CRPCs were classified as genuine or induced. PSDT was performed with the intent to ablate all the progressive sites detected on WB-DWI with radiotherapy. Systemic therapy remained unchanged during and after PSDT. RESULTS: A total of 31 (69%) and 14 (31%) patients were diagnosed with genuine- and induced-OM-CRPC, respectively. The genuine-OM-CRPC group had significantly fewer patients treated with taxane-based chemotherapy and new hormonal drugs than the induced-OM-CRPC group. Of these, 26 OM-CRPC patients were treated with PSDT, and a 50% PSA decline was observed in 14 (93%) of 15 patients with genuine-OM-CRPC and 4 (36%) of 11 patients with induced-OM-CRPC (P = 0.033). Further, the duration of PSA-progression-free survival was significantly longer in the genuine-OM-CRPC group than in the induced-OM-CRPC group (8.7 vs. 5.8 months, P = 0.040). CONCLUSIONS: PSDT can be a promising treatment option for genuine-OM-CRPC. The procedure might also be considered effective for induced-OM-CRPC, although there was less therapeutic benefit of PSDT in patients with induced-OM-CRPC than in patients with genuine-OM-CRPC.

Two cases of oligometastatic castration-resistant prostate cancer detected by diffusion-weighted whole-body imaging with background body signal suppression.

INTRODUCTION: Treatment for oligometastasis in prostate cancer has changed from systemic therapy to metastatic lesion-targeted therapy. Early detection of metastatic lesions and assessment of the treatment response have become very important. Therefore, we started to perfume assessments with whole-body magnetic resonance imaging, especially diffusion-weighted imaging with background body signal suppression, as a modality to detect metastasis in patients with prostate cancer. CASE PRESENTATION: We encountered two cases of castration-resistant prostate cancer in which oligometastasis was detected by diffusion-weighted imaging with background body signal suppression. Metastasis-directed therapy was initiated for to treat the lesions in each case. The treatment was effective for disease control and symptom relief. Diffusion-weighted imaging with background body signal suppression could detect new lesions at an early phase and delineate changes in lesions immediately after therapy. CONCLUSION: Diffusion-weighted imaging with background body signal suppression enables early decision-making for metastasis-directed therapy compared with conventional imaging modalities. Further, metastasis-directed therapy targeting oligometastatic lesions detected by diffusion-weighted imaging with background body signal suppression may improve patients' overall survival and quality of life.

METastasis Reporting and Data System for Prostate Cancer as a Prognostic Imaging Marker in Castration-resistant Prostate Cancer.

BACKGROUND: METastasis Reporting and Data System for Prostate Cancer (MET-RADS-P) has been proposed as a standard of data acquisition and interpretation for whole-body diffusion-weighted magnetic resonance imaging (WB-DWI) performed in men with advanced prostate cancer. The aim of this study is to demonstrate the clinical significance of the scores in castration-resistant prostate cancer (CRPC). MATERIALS AND METHODS: We retrospectively evaluated WB-DWI obtained from 72 patients with CRPC between 2014 and 2017, when disease progression was suspected at the time of starting a new line of anticancer therapy. Twenty-five (35%) and 30 (42%) patients had a treatment history that included taxane-based chemotherapy and new hormonal drugs, respectively. RESULTS: Active bone metastases were identified in 60 patients (83%; number of bone metastasis = 0, 1-2, 3-5, 6-10, and > 10: n = 12 [17%], 20 [28%], 11 [15%], 1 [1%], and 28 [39%], respectively). Progressive lymph node and visceral metastases were identified in 10 (14%) and 4 (6%), respectively. During the median follow-up period of 24 months, 36 (50%) died of prostate cancer. Cancer-specific survival (CSS) was significantly stratified according to the MET-RADS-P scores of osseous metastatic burden and the presence of visceral metastasis (P < .0001). Multivariate analysis revealed that high osseous metastatic burden (> 10) and the presence of visceral metastasis were significant indicators of shorter CSS (P = .0036 and P = .0017, respectively). CONCLUSIONS: The extent of bone metastasis and the presence of visceral metastasis on WB-DWI were associated with a shorter CSS in CRPC. MET-RADS-P score can be a prognostic imaging biomarker for CRPC.

Effects of data count and image scaling on Deep Learning training.

BACKGROUND: Deep learning using convolutional neural networks (CNN) has achieved significant results in various fields that use images. Deep learning can automatically extract features from data, and CNN extracts image features by convolution processing. We assumed that increasing the image size using interpolation methods would result in an effective feature extraction. To investigate how interpolation methods change as the number of data increases, we examined and compared the effectiveness of data augmentation by inversion or rotation with image augmentation by interpolation when the image data for training were small. Further, we clarified whether image augmentation by interpolation was useful for CNN training. To examine the usefulness of interpolation methods in medical images, we used a Gender01 data set, which is a sex classification data set, on chest radiographs. For comparison of image enlargement using an interpolation method with data augmentation by inversion and rotation, we examined the results of two- and four-fold enlargement using a Bilinear method. RESULTS: The average classification accuracy improved by expanding the image size using the interpolation method. The biggest improvement was noted when the number of training data was 100, and the average classification accuracy of the training model with the original data was 0.563. However, upon increasing the image size by four times using the interpolation method, the average classification accuracy significantly improved to 0.715. Compared with the data augmentation by inversion and rotation, the model trained using the Bilinear method showed an improvement in the average classification accuracy by 0.095 with 100 training data and 0.015 with 50,000 training data. Comparisons of the average classification accuracy of the chest X-ray images showed a stable and high-average classification accuracy using the interpolation method. CONCLUSION: Training the CNN by increasing the image size using the interpolation method is a useful method. In the future, we aim to conduct additional verifications using various medical images to further clarify the reason why image size is important.

Progressive Site-Directed Therapy for Castration-Resistant Prostate Cancer: Localization of the Progressive Site as a Prognostic Factor.

PURPOSE: Locoregional therapy for oligometastatic prostate cancer has generated great interest. However, its benefit for castration-resistant prostate cancer (CRPC) has not been fully demonstrated. Our objective was to evaluate the treatment outcome of progressive site-directed therapy (PSDT) for oligoprogressive CRPC (OP-CRPC). METHODS AND MATERIALS: This study cohort consisted of 101 patients with CRPC who underwent whole-body diffusion-weighted magnetic resonance imaging between 2014 and 2018, when a new line of anticancer therapy was being considered. For OP-CRPC, PSDT with radiation therapy and unchanged continuation of systemic therapy were recommended. RESULTS: Thirty-eight patients received a diagnosis of OP-CRPC, and 23 (61%) underwent PSDT at a median prostate-specific antigen (PSA) level of 7.8 ng/mL. The regional radiation therapy targets were the prostate/pelvic lymph nodes (n = 7), bone (n = 15), or both (n = 1). A decrease in PSA levels of at least 50% in response to PSDT (50% PSA decline) was observed in 16 cases (70%); the median time to PSA progression was 8.7 months. Intrapelvic localization of progressive lesions was a significant predictor of time to PSA progression (hazard ratio, 6.6; P = .007) as well as volumes of abnormal signal intensity on whole-body diffusion-weighted magnetic resonance imaging (hazard ratio, 0.5; P = .045). A 50% PSA decline was achieved in 16 of the 18 patients with intrapelvic OP-CRPC (89%) and in none of the 5 patients with non-intrapelvic OP-CRPC (P < .001). Intrapelvic OP-CRPC had a significantly longer time to PSA progression than non-intrapelvic OP-CRPC (10.1 vs 4.8 months, P = .0014). CONCLUSIONS: PSDT can be an effective treatment option for OP-CRPC. Progressive site localization was an important factor in good PSA response.