Impact of Complete Surgical Resection of Metastatic Lesions in Patients with Advanced Renal Cell Carcinoma in the Era of Tyrosine Kinase Inhibitors and Immune Checkpoint Inhibitors.

Complete metastasectomy (CM) in metastatic renal cell carcinoma (mRCC) has demonstrated efficacy in the cytokine era, but its effectiveness in the era of tyrosine kinase inhibitors (TKIs) and immune checkpoint inhibitors (ICIs) remains unclear. A multi-institutional database included clinicopathological data of 367 patients with mRCC. Patients were divided into two groups: the CM group and the non-CM group. These two groups were compared before and after propensity score matching (PSM). Cox proportional hazard models were used to detect factors associated with disease-free survival (DFS) and overall survival (OS) from mRCC diagnosis. The CM group showed a significant association with longer overall survival compared to the non-CM group in the PSM-unadjusted cohorts (p < 0.001, hazard ratio 0.49, 95% confidence interval 0.35-0.69), but no superiority was noted in the adjusted cohorts. The median DFS after CM was 24 months, with no significant differences based on relapse timing. Notably, the international metastatic RCC database consortium risk categories and metastatic burden were associated with DFS. This study supports the potential of CM in mRCC management during the TKI/ICI era, although limitations including sample size and selection bias need to be considered.

Impact of nutrition and inflammation indicators on peritoneal dialysis initiation and management.

BACKGROUND: The clinical significance of nutrition and inflammation in dialysis patients is well established. This study aimed to evaluate the association between prognosis and indicators of nutrition and inflammation. METHODS: A total of 253 consecutive patients who underwent peritoneal dialysis (PD) as primary renal replacement therapy at our institute between 2006 and 2021 were included. We retrospectively reviewed the patient's medical charts and obtained their clinical information. Nine nutritional and two inflammatory indicators were assessed. Patient outcomes were investigated, and predictive factors were explored. RESULTS: The median age and follow-up period were 65 years and 54 months, respectively. Most nutritional indicators and C-reactive protein (CRP) levels showed a significant correlation with residual renal function. Multivariate analysis revealed that the survival index, nutritional risk index for Japanese hemodialysis patients, and CRP levels were independent indicators of patient survival (P < 0.001, P = 0.034, and P = 0.005, respectively) and cardiovascular disease-free survival (P = 0.009, P = 0.04, and P = 0.017, respectively). Patients with a survival index < 19 and CRP ≥ 0.5 had a high risk of mortality and cardiovascular death (P < 0.0001 and P = 0.0002, respectively). CONCLUSIONS: Our findings suggest that indicators of nutrition and inflammation play important roles in predicting patient outcomes. Further research is warranted to establish optimal management strategies for patients on PD.

Enfortumab vedotin following platinum-based chemotherapy and immune checkpoint inhibitors for advanced urothelial carcinoma: response, survival and safety analysis from a multicentre real-world Japanese cohort.

OBJECTIVE: Real-world evidence regarding enfortumab vedotin for unresectable or metastatic urothelial carcinoma is scarce, particularly in Japan. We investigated real-world data focusing on patient background, previous treatments, response, survival and adverse events in patients receiving enfortumab vedotin. METHODS: A multicentre database was used to register 556 patients diagnosed with metastatic urothelial carcinoma from 2008 to 2023; 34 patients (6.1%) treated with enfortumab vedotin were included. Best radiographic objective responses were evaluated using the Response Evaluation Criteria in Solid Tumors (v1.1) during treatments. Overall survival and progression-free survival were estimated (Kaplan-Meier method). Toxicities were reported according to the Common Terminology Criteria for Adverse Events, version 5.0. The relative dose intensity, which could impact oncological outcomes, was calculated. RESULTS: The median number of enfortumab vedotin therapy cycles was 5. The best objective response to enfortumab vedotin was partial response, stable disease and progressive disease in 19 (56%), 5 (15%) and 10 (29%) patients, respectively. The median overall survival and progression-free survival after the first enfortumab vedotin dose were 16 and 9 months, respectively. No significant relationship was observed between survival outcomes after enfortumab vedotin initiation and the enfortumab vedotin relative dose intensity. The median overall survival from first-line platinum-based chemotherapy initiation was 42 months. Twenty-six (76%) patients experienced any grade of enfortumab vedotin-related toxicities; eight (24%) experienced Grades 3-4 toxicities, the most common being skin toxicity (any grade, 47%; Grades 3-4, 12%). CONCLUSIONS: Here, we report real-world evidence for enfortumab vedotin therapy in Japan. Tumour responses and safety profiles were comparable with those of clinical trials on this novel treatment.

[Efficacy of Recombinant Thrombomodulin for Sepsis-Associated Disseminated Intravascular Coagulation Caused by Urinary Tract Infections].

Severe urinary tract infections occasionally cause sepsis and disseminated intravascular coagulation (DIC). We examined the efficacy of recombinant thrombomodulin (rTM) for treating DIC caused by urosepsis. We enrolled 40 patients who were diagnosed with DIC caused by urosepsis at our hospital between April 2018 and May 2022. Twenty-six patients were treated with rTM (rTM group), while 14 patients did not receive rTM (non-rTM group). The DIC score before treatment in the rTM group was significantly higher than that in the non-rTM group (P＜0.01). There was no significant difference in disease-specific survival between the two groups. There was a significant improvement in DIC scores on days 1-3 after administering rTM. However, the duration of DIC in the rTM group was significantly longer than that in the non-rTM group (P＝0.038). The administration of rTM may have benefits in patients with DIC caused by urosepsis.

Direct screening for effective shRNA with a single mismatch in human cells without laborious cloning.

We have devised a method for the direct screening of efficient short hairpin (sh)RNA molecules in human cells, eliminating the need for the time-consuming process of cloning in Escherichia coli. Our screening suggested that single mismatches to shRNAs can significantly alter their activity.

[Adrenal Hemangiomatous Endothelial Cyst That was Difficult to Differentiate from Adrenal Malignant Tumor: A Case Report].

A 65-year-old woman was referred to our hospital for fever and diagnosed with pyelonephritis. Abdominal computed tomography showed a right adrenal tumor incidentally, that was 6.5 cm in diameter. We could not rule out malignant disease by magnetic resonance imaging examination and performed resection of the right adrenal tumor. The histopathological examination revealed an adrenal hemangiomatous endothelial cyst, and there was no evidence of malignancy. It was difficult to differentiate between adrenal cyst and adrenal cancer in preoperative diagnostic imaging because the tumor contained hemorrhage and necrotic tissue.

Composite pheochromocytoma associated with neurofibromatosis type 1.

Introduction: Composite pheochromocytoma is a rare tumor, occurring in only 3% of pheochromocytomas. We report a case of composite pheochromocytoma with neurofibromatosis type 1. Case presentation: A 42-year-old man was referred to our department for further evaluation of an incidentally detected right adrenal tumor. He was a patient at another hospital for neurofibromatosis type 1. The serum and urinary catecholamine levels exceeded the normal range. Abdominal computed tomography and magnetic resonance imaging showed a 2.8 cm diameter right adrenal tumor, and 123I-metaiodobenzyguanidine scintigraphy showed radioisotope uptake. He was diagnosed with pheochromocytoma and underwent a right laparoscopic adrenalectomy. Histopathological examination revealed that the tumor consisted of a pheochromocytoma and ganglioneuroma. The final diagnosis was composite pheochromocytoma-ganglioneuroma. Five years after surgery, no recurrence was observed. Conclusion: Preoperative diagnosis of composite pheochromocytoma-ganglioneuroma is difficult; therefore, histopathological examination is necessary for a definitive diagnosis. Pheochromocytoma management requires lifelong follow-up.

Clinical impact of catheter insertion for peritoneal dialysis on patient survival and catheter-related complications.

OBJECTIVES: The stepwise initiation of peritoneal dialysis (PD) using Moncrief and Popovich's technique (SMAP) for catheter insertion is recommended for the systemic introduction of PD and prevention of catheter-related infections. In this study, we investigated patient outcomes in patients who underwent insertion of a PD catheter with a direct method versus the SMAP method. METHODS: We enrolled 295 consecutive patients who underwent PD as a primary renal replacement therapy and underwent insertion of a PD catheter at our institute between 2006 and 2021. We retrospectively reviewed their data and investigated patient outcomes, including mortality and PD catheter-related complications. RESULTS: Median age at PD induction was 65 years in the direct insertion group and 65 years in the SMAP group (P = 0.80). The rate of PD introduction after emergency hemodialysis was significantly higher in the direct insertion group than in the SMAP group (P < 0.001). There was no significant difference in survival between the direct insertion and SMAP groups during the median follow-up period of 54 months (P = 0.12). Additionally, patients who transitioned to hemodialysis or kidney transplantation after PD showed significantly longer survival (P < 0.001). The incidence of PD catheter-related complications was not significantly different between the two groups. A body mass index ≥ 23 kg/m2 was an independent risk factor for peritonitis and exit-site infection (P = 0.006 and P = 0.011, respectively). CONCLUSIONS: Planned sequential renal replacement therapy including hybrid hemodialysis, complete hemodialysis, and kidney transplantation after PD is important for improving patient outcomes. PD catheter insertion by SMAP may not be mandatory in our clinical practice.

Incidence of antiresorptive agent-related osteonecrosis of the jaw: A multicenter retrospective epidemiological study in Hyogo Prefecture, Japan.

Background/purpose: The incidence of medication-related osteonecrosis of the jaw is increasing worldwide, mostly due to the use of antiresorptive agents (ARAs) such as bisphosphonate (BP) and denosumab (Dmab). However, the proportion of BP-related osteonecrosis of the jaw (BRONJ) and Dmab-related osteonecrosis of the jaw (DRONJ) among all ARA-related osteonecrosis of the jaw (ARONJ) cases is not clear; this hinders appropriate treatment, recurrence-prevention planning, and avoidance of unnecessary Dmab withdrawal. Moreover, the causative drug administered at each disease stage remains unknown. Therefore, we conducted a retrospective study of patients with ARONJ who visited oral and maxillofacial surgery departments at hospitals in Hyogo Prefecture, Japan, over 3 years to classify and compare patient characteristics with those having BRONJ and DRONJ. We sought to identify the proportion of DRONJ in ARONJ. Materials and methods: After excluding stage 0 patients, 1021 patients were included (471 high-dose; 560 low-dose). ARA treatment for bone metastases of malignant tumors and multiple myeloma was considered high dose, while that for cancer treatment-induced bone loss and osteoporosis was low dose. Results: Low doses of BP and Dmab accounted for >50% patients; the results differed from those in other countries. DRONJ accounted for 58% and 35% of high-dose and low-dose cases, respectively. Stage 3 ARONJ cases comprised 92 (19.5%) low-dose BRONJ, 39 (20.1%) high-dose BRONJ, 24 (30%) low-dose DRONJ, and 68 (24.5%) high-dose DRONJ. Eighty-nine patients who received switch therapy were divided into BRONJ or DRONJ, but there was no difference in the ratio of each stage compared to the non-switch therapy. Conclusion: To the best of our knowledge, this is the first study to clarify the proportion of BRONJ and DRONJ cases, causative drug, and its doses by disease stages. DRONJ accounted for approximately 30% of the ARONJ, approximately 60% of which was due to high doses.

Is the LRINEC score useful for predicting necrotizing fasciitis as a complication of MRONJ?

INTRODUCTION: Necrotizing fasciitis as a complication of medication-related osteonecrosis of the jaw (MRONJ), which we named "ONJ-NF", has been sometimes reported. This study aimed to investigate the usefulness of the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score for predicting ONJ-NF. MATERIALS AND METHODS: We included patients with acute MRONJ who required hospitalization at a single institution from April 2013 to June 2022. They were divided into two groups: patients with ONJ-NF and those with severe cellulitis as a complication of MRONJ, which we named "ONJ-SC." LRINEC scores were compared between the groups and the cut-off value of the score was set by creating a receiver operating characteristic curve. RESULTS: Eight patients with ONJ-NF and 22 patients with ONJ-SC were included. The LRINEC score was significantly higher in patients with ONJ-NF (median: 8.0 points, range 6-10 points) than in those with ONJ-SC (median: 2.5 points, range 0-6 points). A LRINEC score of ≥ 6 points had a sensitivity of 100.0%, a specificity of 77.3%, and an area under the curve of 0.97. Among 6 parameters of LRINEC score, only C-reactive protein (CRP) and white blood cell count (WBC) had significant differences between two groups. Most of the patients with ONJ-NF were rescued by antibiotic therapy and surgical drainage including debridement of necrotic tissues, but unfortunately, one patient did not survive. CONCLUSION: Our results suggested that the LRINEC score may be a useful diagnostic tool to predict ONJ-NF but valuating only CRP and WBC may be sufficient particularly in patients with osteoporosis.

Relationship between oral health and prognosis in patients with empyema: Single center retrospective study with propensity score matching analysis.

BACKGROUND: Empyema is a life-threatening infection often caused by oral microbiota. To the best of our knowledge, no reports have investigated the association between the objective assessment of oral health and prognosis in patients with empyema. MATERIALS AND METHODS: A total of 63 patients with empyema who required hospitalization at a single institution were included in this retrospective study. We compared non-survivors and survivors to assess risk factors for death at three months, including the Renal, age, pus, infection, diet (RAPID) score, and Oral Health Assessment Tool (OHAT) score. Furthermore, to minimize the background bias of the OHAT high-score and low-score groups determined based on the cut-off value, we also analyzed the association between the OHAT score and death at 3 months using the propensity score matching method. RESULTS: The 3-month mortality rate was 20.6% (13 patients). Multivariate analysis showed that a RAPID score ≥5 points (odds ratio (OR) 8.74) and an OHAT score ≥7 points (OR 13.91) were significantly associated with death at 3 months. In the propensity score analysis, a significant association was found between a high OHAT score (≥7 points) and death at 3 months (P = 0.019). CONCLUSION: Our results indicated that oral health assessed using the OHAT score may be a potential independent prognostic factor in patients with empyema. Similar to the RAPID score, the OHAT score may become an important indicator for the treatment of empyema.

Calorie restriction alters the mechanisms of radiation-induced mouse thymic lymphomagenesis.

Calorie restriction (CR) suppresses not only spontaneous but also chemical- and radiation-induced carcinogenesis. Our previous study revealed that the cancer-preventive effect of CR is tissue dependent and that CR does not effectively prevent the development of thymic lymphoma (TL). We investigated the association between CR and the genomic alterations of resulting TLs to clarify the underlying resistance mechanism. TLs were obtained from previous and new experiments, in which B6C3F1 mice were exposed to radiation at 1 week of age and fed with a CR or standard (non-CR) diet from 7 weeks throughout their lifetimes. All available TLs were used for analysis of genomic DNA. In contrast to the TLs of the non-CR group, those of the CR group displayed suppression of copy-neutral loss of heterozygosity (LOH) involving relevant tumor suppressor genes (Cdkn2a, Ikzf1, Trp53, Pten), an event regarded as cell division-associated. However, CR did not affect interstitial deletions of those genes, which were observed in both groups. In addition, CR affected the mechanism of Ikzf1 inactivation in TLs: the non-CR group exhibited copy-neutral LOH with duplicated inactive alleles, whereas the CR group showed expression of dominant-negative isoforms accompanying a point mutation or an intragenic deletion. These results suggest that, even though CR reduces cell division-related genomic rearrangements by suppressing cell proliferation, tumors arise via diverse carcinogenic pathways including inactivation of tumor suppressors via interstitial deletions and other mutations. These findings provide a molecular basis for improved prevention strategies that overcome the CR resistance of lymphomagenesis.

Switch-maintenance avelumab immunotherapy following first-line chemotherapy for patients with advanced, unresectable or metastatic urothelial carcinoma: the first Japanese real-world evidence from a multicenter study.

OBJECTIVE: To develop the first Japanese real-world evidence of switch-maintenance avelumab in advanced, unresectable or metastatic urothelial carcinoma (aUC). METHODS: A multicenter-derived database registered 505 patients diagnosed with aUC between 2008 and 2021. Of these, 204 patients (40%) were selected and stratified according to the type of therapy used: maintenance avelumab group (27 [5.3%]), second-line (2 L) pembrolizumab group (103 [20%]) and 2 L cytotoxic chemotherapy group (74 [15%]). The progression-free survival and overall survival from the initiation of following therapy were compared. Tumor response was evaluated based on the Response Evaluation Criteria in Solid Tumors guideline v1.1 during the treatment period. A detailed analysis was performed in the maintenance avelumab group to investigate possible factors associated with response to avelumab therapy. RESULTS: The maintenance avelumab group had a longer overall survival, not progression-free survival, compared with the other two treatment groups. The median treatment-free interval between the last dose of first-line (1 L) chemotherapy and the initiation of avelumab therapy was 6 weeks (range, 3-22). Disease control rate of maintenance avelumab therapy in patients with a treatment-free interval of ≤6 weeks was higher than that in patients with a treatment-free interval of >6 weeks (77 vs 40%, P = 0.029). The patients showing objective response to 1 L chemotherapy were less likely to experience tumor relapse (4 of 19) after the initiation of avelumab therapy compared with those showing stable disease (7 of 8). CONCLUSIONS: Objective response to 1 L chemotherapy and early induction of maintenance avelumab therapy may be associated with increased benefit from maintenance avelumab therapy.

Effects on Life Expectancy of Treatment Decisions in Patients With Non-metastatic Prostate Cancer.

BACKGROUND/AIM: Life expectancy is considered in treatment decision-making for non-metastatic prostate cancer (PCa). We explored the factors related to overall survival (OS) and investigated the association between OS and life expectancy in patients with non-metastatic PCa according to various treatment modalities. PATIENTS AND METHODS: This retrospective study included 714 patients with non-metastatic PCa between 2006 and 2010 at our institute. The treatment modalities were classified as follows: radical prostatectomy (RP), androgen deprivation therapy (ADT), brachytherapy (BT) and external beam radiation therapy (EBRT). We defined life expectancy according to an abridged life table published by the Ministry of Health, Labour and Welfare in Japan. RESULTS: The median age and initial prostate-specific antigen levels at treatment were 71 years and 8.8 ng/mL, respectively. Advanced age, Charlson comorbidity index (CCI) ≥1, cT3a stage and ADT were independent poor prognostic factors for OS. OS and life expectancy did not significantly differ in all patients (p=0.32) and in the National Comprehensive Cancer Network (NCCN) high-risk group (p=0.059). In patients with a life expectancy of <10 years, the OS was significantly shorter than life expectancy (p<0.001). CONCLUSION: Patients with non-metastatic PCa may live beyond their life expectancy regardless of the type of therapy and NCCN risk classification, and patients with a life expectancy of <10 years may benefit from BT rather than ADT and EBRT.

Clinical significance of limited and extended pelvic lymph node dissection during robot-assisted radical prostatectomy for patients with localized prostate cancer: A retrospective, propensity score matching analysis.

OBJECTIVES: We investigated the diagnostic and therapeutic benefits of limited or extended pelvic lymph node dissection during a robot-assisted radical prostatectomy for localized prostate cancer. METHODS: Diagnostic and therapeutic benefits were assessed according to the rates of pN1 and biochemical recurrence, respectively. The primary outcome was the biochemical recurrence-free rate, and secondary outcomes included the diagnostic and therapeutic benefits of pelvic lymph node dissection. RESULTS: A total of 534 patients were analyzed. Out of the 534 patients, 207 (38.8%) received limited pelvic lymph node dissection while 134 (25.1%) received extended dissection. There were 297 patients with a Briganti index ≥5%. Extended dissections yielded significantly more resected lymph nodes (p < 0.0001), and 72.2% of cases of pN1 were located outside the obturator. The incidence rate of pN1 was 6.1%, and performance of extended lymph node dissection was an independent predictor for pN1 (odds ratio 9.0, 95% confidence interval 2.5-33.1). The rate of biochemical recurrence was 14.9%, and Cox proportional hazards regression analysis of the propensity score matched population revealed that patients with high or very-high risk tended to benefit from limited lymph node dissection (hazard ratio 8.4, 95% confidence interval 0.8-82.3) while the therapeutic benefit of extended dissection was unclear by comparison. CONCLUSIONS: Extended pelvic lymph node dissection significantly improves diagnostic accuracy; however, the therapeutic benefit of pelvic lymph node dissection was not observed in this study.

Hematologic and inflammatory parameters for determining severity of odontogenic infections at admission: a retrospective study.

BACKGROUND: Severe odontogenic infections in the head and neck region, especially necrotizing soft tissue infection (NSTI) and deep neck abscess, are potentially fatal due to their delayed diagnosis and treatment. Clinically, it is often difficult to distinguish NSTI and deep neck abscess in its early stage from cellulitis, and the decision to perform contrast-enhanced computed tomography imaging for detection is often a challenge. This retrospective case-control study aimed to examine the utility of routine blood tests as an adjunctive diagnostic tool for NSTI in the head and neck region and deep neck abscesses. METHODS: Patients with severe odontogenic infections in the head and neck region that required hospitalization were classified into four groups. At admission, hematologic and inflammatory parameters were calculated according to the blood test results. In addition, a decision tree analysis was performed to detect NSTI and deep neck abscesses. RESULTS: There were 271 patients, 45.4% in Group I (cellulitis), 22.5% in Group II (cellulitis with shallow abscess formation), 27.3% in Group III (deep neck abscess), and 4.8% in Group IV (NSTI). All hematologic and inflammatory parameters were higher in Groups III and IV. The Laboratory Risk Indicator for Necrotizing Fasciitis score, with a cut-off value of 6 and C-reactive protein (CRP) + the neutrophil-to-lymphocyte ratio (NLR), with a cut-off of 27, were remarkably useful for the exclusion diagnosis for Group IV. The decision tree analysis showed that the systemic immune-inflammation index (SII) of ≥ 282 or < 282 but with a CRP + NLR of ≥ 25 suggests Group III + IV and the classification accuracy was 89.3%. CONCLUSIONS: Hematologic and inflammatory parameters calculated using routine blood tests can be helpful as an adjunctive diagnostic tool in the early diagnosis of potentially fatal odontogenic infections. An SII of ≥ 282 or < 282 but with a CRP + NLR of ≥ 25 can be useful in the decision-making for performing contrast-enhanced computed tomography imaging.

Efficacy of pembrolizumab rechallenge for metastatic urothelial carcinoma.

Introduction: Before the approval of enfortumab vedotin, no standard treatment was available as the salvage treatment for patients with metastatic urothelial carcinoma who had failed second-line or later pembrolizumab. Pembrolizumab rechallenge is one of the options for these patients, but there is limited evidence on the effectiveness of pembrolizumab rechallenge. We report three patients with metastatic urothelial carcinoma treated with pembrolizumab rechallenge and discuss rechallenge of immune checkpoint inhibitors in other malignancies. Case presentation: This study included three cases treated with pembrolizumab rechallenge with the age of 54 (Case 1), 78 (Case 2), and 67 (Case 3) years old. A complete response to the prior pembrolizumab was observed only in Case 1. However, no patients responded to the pembrolizumab rechallenge. Conclusion: Pembrolizumab rechallenge is not recommended in the current clinical setting of metastatic urothelial carcinoma, even for patients who showed complete response to the prior pembrolizumab.

Establishing a ready biodegradability test system using OxiTop® to evaluate chemical fate in a realistic environment.

The purpose of this study is to propose the use of OxiTop® for measuring biochemical oxygen demand (BOD) under the Japanese Chemical Substances Control Law in order to properly evaluate chemical fate in a real environment. In our previous study, the biodegradation of test chemicals was accelerated by both adsorbing the chemical to silica gel with chloroform and increasing the medium volume from 300 to 3900 mL in the OECD 301F test using a coulometer. However, the biodegradability of these chemicals could not be evaluated based on BOD due to chloroform residue in the silica gel, or the medium volume could not be increased further due to the oven size of the coulometer. In this study, we established an evaluation system using OxiTop® based on BOD by increasing the medium volume to 9000 mL. Based on triplicate testing, increasing the medium volume accelerated biodegradation and decreased variation in BOD.

Post-Irradiation Thymic Regeneration in B6C3F1 Mice Is Age Dependent and Modulated by Activation of the PI3K-AKT-mTOR Pathway.

The risk of radiation-induced carcinogenesis depends on age at exposure. We previously reported principal causative genes in lymphomas arising after infant or adult exposure to 4-fractionated irradiation as Pten or Ikzf1, respectively, suggesting that cells with mutation in these genes might be the origin of lymphomas arising after irradiation depending on age at exposure. Here, we clarified the age-dependent differences in thymus-cell dynamics in mice during the initial post-irradiation period. The thymocyte number initially decreased, followed by two regeneration phases. During the first regeneration, the proportion of phosphorylated-AKT-positive (p-AKT+) cells in cell-cycle phases S+G2/M of immature CD4-CD8- and CD4+CD8+ thymocytes and in phases G0/G1 of mature CD4+CD8- and CD4-CD8+ thymocytes was significantly greater in irradiated infants than in irradiated adults. During the second regeneration, the proportion of p-AKT+ thymocytes in phases G0/G1 increased in each of the three populations other than CD4-CD8- thymocytes more so than during the first regeneration. Finally, PI3K-AKT-mTOR signaling in infants contributed, at least in part, to biphasic thymic regeneration through the modification of cell proliferation and survival after irradiation, which may be associated with the risk of Pten mutation-associated thymic lymphoma.