Phase separation in DNA double-strand break response.

DNA double-strand break (DSB) is the most dangerous type of DNA damage, which may lead to cell death or oncogenic mutations. Homologous recombination (HR) and nonhomologous end-joining (NHEJ) are two typical DSB repair mechanisms. Recently, many studies have revealed that liquid-liquid phase separation (LLPS) plays a pivotal role in DSB repair and response. Through LLPS, the crucial biomolecules are quickly recruited to damaged sites with a high concentration to ensure DNA repair is conducted quickly and efficiently, which facilitates DSB repair factors activating downstream proteins or transmitting signals. In addition, the dysregulation of the DSB repair factor's phase separation has been reported to promote the development of a variety of diseases. This review not only provides a comprehensive overview of the emerging roles of LLPS in the repair of DSB but also sheds light on the regulatory patterns of phase separation in relation to the DNA damage response (DDR).

CiRS-7 Enhances the Liquid-liquid Phase Separation of miRISC and Promotes DNA Damage Repair.

Noncoding RNAs have been found to play important roles in DNA damage repair, whereas the participation of circRNA remains undisclosed. Here, we characterized ciRS-7, a circRNA containing over 70 putative miR-7-binding sites, as an enhancer of miRISC condensation and DNA repair. Both in vivo and in vitro experiments confirmed the condensation of TNRC6B and AGO2, two core protein components of human miRISC. Moreover, overexpressing ciRS-7 largely increased the condensate number of TNRC6B and AGO2 in cells, while silencing ciRS-7 reduced it. Additionally, miR-7 overexpression also promoted miRISC condensation. Consistent with the previous report that AGO2 participated in RAD51-mediated DNA damage repair, the overexpression of ciRS-7 significantly promoted irradiation-induced DNA damage repair by enhancing RAD51 recruitment. Our results uncover a new role of circRNA in liquid-liquid phase separation and provide new insight into the regulatory mechanism of ciRS-7 on miRISC function and DNA repair.

Liquid-liquid phase separation in DNA double-strand breaks repair.

DNA double-strand breaks (DSBs) are the fatal type of DNA damage mostly induced by exposure genome to ionizing radiation or genotoxic chemicals. DSBs are mainly repaired by homologous recombination (HR) and nonhomologous end joining (NHEJ). To repair DSBs, a large amount of DNA repair factors was observed to be concentrated at the end of DSBs in a specific spatiotemporal manner to form a repair center. Recently, this repair center was characterized as a condensate derived from liquid-liquid phase separation (LLPS) of key DSBs repair factors. LLPS has been found to be the mechanism of membraneless organelles formation and plays key roles in a variety of biological processes. In this review, the recent advances and mechanisms of LLPS in the formation of DSBs repair-related condensates are summarized.

RAP80 phase separation at DNA double-strand break promotes BRCA1 recruitment.

RAP80 has been characterized as a component of the BRCA1-A complex and is responsible for the recruitment of BRCA1 to DNA double-strand breaks (DSBs). However, we and others found that the recruitment of RAP80 and BRCA1 were not absolutely temporally synchronized, indicating that other mechanisms, apart from physical interaction, might be implicated. Recently, liquid-liquid phase separation (LLPS) has been characterized as a novel mechanism for the organization of key signaling molecules to drive their particular cellular functions. Here, we characterized that RAP80 LLPS at DSB was required for RAP80-mediated BRCA1 recruitment. Both cellular and in vitro experiments showed that RAP80 phase separated at DSB, which was ascribed to a highly disordered region (IDR) at its N-terminal. Meanwhile, the Lys63-linked poly-ubiquitin chains that quickly formed after DSBs occur, strongly enhanced RAP80 phase separation and were responsible for the induction of RAP80 condensation at the DSB site. Most importantly, abolishing the condensation of RAP80 significantly suppressed the formation of BRCA1 foci, encovering a pivotal role of RAP80 condensates in BRCA1 recruitment and radiosensitivity. Together, our study disclosed a new mechanism underlying RAP80-mediated BRCA1 recruitment, which provided new insight into the role of phase separation in DSB repair.

Effects of neoadjuvant radiochemotherapy for anorectal function in locally advanced rectal cancer patients: a study protocol for a prospective, observational, controlled, multicentre study.

BACKGROUND: Neoadjuvant chemoradiotherapy (NCRT) and total mesorectal excision are standard treatment regimen for patients with locally advanced rectal cancer (LARC). This sphincter-saving treatment strategy may be accompanied by a series of anorectal functional disorders. Yet, prospective studies that dynamically evaluating the respective roles of radiotherapy, chemotherapy and surgery on anorectal function are lacking. PATIENTS/DESIGN: The study is a prospective, observational, controlled, multicentre study. After screening for eligibility and obtaining informed consent, a total of 402 LARC patients undergoing NCRT followed by surgery, or neoadjuvant chemotherapy followed by surgery, or surgery only would be included in the trial. The primary outcome measure is the average resting pressure of anal sphincter. The secondary outcome measures are maximum anal sphincter contraction pressure, Wexner continence score and low anterior resection syndrome (LARS) score. Evaluations will be carried out at the following stages: baseline (T1), after radiotherapy or chemotherapy (before surgery, T2), after surgery (before closing the temporary stoma, T3), and at follow-up visits (every 3 to 6 months, T4, T5……). Follow-up for each patient will be at least 2 years. DISCUSSION: We expect the program to provide more information of neoadjuvant radiotherapy and/or chemotherapy on anorectal function, and to optimize the treatment strategy to reduce anorectal dysfunction for LARC patients. TRIAL REGISTRATION: ClinicalTrials.gov (NCT05671809). Registered on 26 December 2022.

DNA damage-induced paraspeckle formation enhances DNA repair and tumor radioresistance by recruiting ribosomal protein P0.

Paraspeckles are mammal-specific membraneless nuclear bodies that participate in various biological processes. NONO, a central paraspeckle component, has been shown to play pivotal roles in DNA double-strand breaks (DSB) repair, whereas its underlying mechanism needs to be further disclosed. Here, using co-immunoprecipitation and mass spectrum, we identified ribosomal protein P0 (RPLP0) as a DSB-induced NONO-binding protein; RPLP0 binds to the RRM1 and RRM2 domains of NONO. Similar to NONO, RPLP0 enhances non-homologous end joining-mediated DSB repair, which was ascribed to a ribosome-independent manner. Interestingly, paraspeckles were induced as early as 15 min after irradiation; it further recruited nuclear RPLP0 to enhance its interaction with NONO. Radiation-induced NONO/RPLP0 complex subsequently anchored at the damaged DNA and increased the autophosphorylation of DNA-PK at Thr2609, thereby enhancing DSB repair. Consistently, in vivo and in vitro experiments showed that depletion of NONO sensitizes tumor cells to radiation. For patients with locally advanced rectal cancer, NONO expression was remarkably increased in tumor tissues and correlated with a poor response to radiochemotherapy. Our findings suggest a pivotal role of radiation-induced paraspeckles in DNA repair and tumor radioresistance, and provide a new insight into the ribosome-independent function of ribosomal proteins.

MRNIP condensates promote DNA double-strand break sensing and end resection.

The rapid recognition of DNA double-strand breaks (DSBs) by the MRE11/RAD50/NBS1 (MRN) complex is critical for the initiation of DNA damage response and DSB end resection. Here, we show that MRN complex interacting protein (MRNIP) forms liquid-like condensates to promote homologous recombination-mediated DSB repair. The intrinsically disordered region is essential for MRNIP condensate formation. Mechanically, the MRN complex is compartmentalized and concentrated into MRNIP condensates in the nucleus. After DSB formation, MRNIP condensates move to the damaged DNA rapidly to accelerate the binding of DSB by the concentrated MRN complex, therefore inducing the autophosphorylation of ATM and subsequent activation of DNA damage response signaling. Meanwhile, MRNIP condensates-enhanced MRN complex loading further promotes DSB end resection. In addition, data from xenograft models and clinical samples confirm a correlation between MRNIP and radioresistance. Together, these results reveal an important role of MRNIP phase separation in DSB response and the MRN complex-mediated DSB end resection.

NONO phase separation enhances DNA damage repair by accelerating nuclear EGFR-induced DNA-PK activation.

Radioresistance is one of the main causes of cancer treatment failure, which leads to relapse and inferior survival outcome of cancer patients. Liquid-liquid phase separation (LLPS) of proteins is known to be involved in various biological processes, whereas its role in the regulation of radiosensitivity remains largely unknown. In this study, we characterized NONO, an RNA/DNA binding protein with LLPS capacity, as an essential regulator of tumor radioresistance. In vitro assay showed that NONO involved in DNA repair via non-homologous end joining (NHEJ) manner. NONO knockout significantly reduced DNA damage repair and sensitized tumor cells to irradiation in vitro and in vivo. NONO overexpression was correlated with an inferior survival outcome in cancer patients. Mechanically, NONO was associated with nuclear EGFR (nEGFR). Both irradiation and EGF treatment induced nEGFR accumulation, thereby increased the association between NONO and nEGFR. However, NONO was not a substrate of EGFR kinase. Furthermore, NONO promoted DNA damage-induced DNA-PK phosphorylation at T2609 by enhancing the interaction between EGFR and DNA-PK. Importantly, NONO protein formed high concentration LLPS droplets in vitro, and recruited EGFR and DNA-PK. Disruption of NONO droplets with LLPS inhibitor significantly reduced the interaction between EGFR and DNA-PK, and suppressed DNA damage-induced phosphorylation of T2609-DNA-PK. Taken together, LLPS of NONO recruits nuclear EGFR and DNA-PK and enhances their interaction, further increases DNA damage-activated pT2609-DNA-PK and promotes NHEJ-mediated DNA repair, finally leads to tumor radioresistance. NONO phase separation-mediated radioresistance may serve as a novel molecular target to sensitize tumor cell to radiotherapy.

Glycosylation of Siglec15 promotes immunoescape and tumor growth.

Siglec15 is a recently characterized immunosuppressive transmembrane protein, which expresses in various types of solid tumors and promotes cancer development. Several studies reported that Siglec15 is a prognostic biomarker of cancer patients, and targeting Siglec15 may be a promising strategy for cancer therapy. However, the regulation of Siglec15 function remains unclear. Here we show that the immunosuppression activity of Siglec15 is largely modulated by N-glycosylation. Through mass spectrum and site mutation analysis, we identified that Siglec15 was extensively glycosylated at N172 (N173 for mouse) in cancer cells. Meanwhile, Siglec15 N172Q had a similar molecular weight with PNGase-F-treated Siglec15, suggesting N172 as the only one glycosylation residue. In xenograft model, glycosylation deficiency of Siglec15 reduced tumor growth in C57BL/6 mice, but had no impact in nude mice, indicating the requirement of N-glycosylation for immunosuppressive function of Siglec15. Furthermore, colorectal cancer patients with high Siglec15 expression had a poor response to neoadjuvant chemo-radiotherapy and short survival time. Interestingly, removal of N-glycosylation enhances the detection of Siglec15, which may be employed in the prediction of immunotherapy response. Together, our results disclose a pivotal role of glycosylated Siglec15 in tumor immune escape, which may be a therapeutic target for cancer immunotherapy.

Oncologic and survival outcomes in elderly patients with locally advanced rectal cancer receiving neoadjuvant chemoradiotherapy and total mesorectal excision.

BACKGROUND: The efficacy of the addition of neoadjuvant chemotherapy to neoadjuvant chemoradiotherapy and total mesorectal excision for locally advanced rectal cancer in elderly patients has not been established. METHODS: A total of 3096 locally advanced rectal cancer patients who received neoadjuvant chemotherapy, along with neoadjuvant chemoradiotherapy and total mesorectal excision, with or without adjuvant chemotherapy, between January 2010 and December 2018, were studied retrospectively. Patients were divided into elderly (>75 years) and younger (≤75 years) groups, and propensity score matching was used to balance a potentially confounding clinical bias. Overall survival, cancer-specific survival, disease-free survival, distant metastasis-free survival and local recurrence-free survival rates for the two groups were compared. Hazard ratios (HR) with 95% confidence intervals (CI) for different clinicopathological variables were calculated to determine predictors of 3-year overall survival. RESULTS: Mean follow-up was 39.0 (range, 5-140) months. The overall 3-year overall survival, cancer-specific survival, disease-free survival, distant metastasis-free survival and locoregional relapse-free survival rates were 86.1, 87.6, 80.0, 82.4 and 95.4%, respectively. Only 3-year overall survival rates differed significantly between the elderly (77.2%) and younger (88.9%) groups (P = 0.01). Cancer-specific survival, disease-free survival, distant metastasis-free survival and locoregional relapse-free survival rates did not differ significantly between the two groups. Significant negative independent prognostic factors for 3-year overall survival were age >75 years (HR = 2.016, 95% CI 1.157-23.511, P = 0.01) and high pathologic TNM stage (yp stage III, P < 0.001). CONCLUSION: For elderly locally advanced rectal cancer patients who have good health and performance status, the addition of neoadjuvant chemotherapy to neoadjuvant chemoradiotherapy and total mesorectal excision can result in disease-related survival rates and oncological outcomes similar to those experienced by younger patients. The decision to use this treatment approach in elderly patients should not be based solely on chronological age.

Fibroblast CEBPD/SDF4 axis in response to chemotherapy-induced angiogenesis through CXCR4.

Cancer-associated fibroblasts (CAFs) play an essential role in supporting cancer progression. However, the details and consequent effects in response to the communication between CAFs and angiogenesis remain largely uninvestigated, especially in anticancer drug treatments. We found that cisplatin and 5-fluorouracil could induce fibroblast differentiation toward myofibroblasts via CCAAT/enhancer-binding protein delta (CEBPD) and consequently promote proliferation, migration, and in vitro tube formation of vascular endothelial cells and angiogenesis in vivo. Stromal-cell-derived factor 4 (SDF4) is responsive to anticancer drugs via CEBPD activation in CAFs and contributes to create a permissive environment for tumor cell angiogenesis and promotion of distant metastasis. Importantly, we demonstrated that SDF4 interacts with CXCR4 to trigger VEGFD expression through the activation of the ERK1/2 and p38 pathways in endothelial cells. Taken together, our novel findings support that SDF4 can be a therapeutic target in inhibition of angiogenesis for chemotherapy drug-administrated cancer patients.

Development of a Joint Prediction Model Based on Both the Radiomics and Clinical Factors for Predicting the Tumor Response to Neoadjuvant Chemoradiotherapy in Patients with Locally Advanced Rectal Cancer.

PURPOSE: Neoadjuvant chemoradiotherapy (nCRT) has become the standard treatment for locally advanced rectal cancer (LARC). However, the accuracy of traditional clinical indicators in predicting tumor response is poor. Recently, radiomics based on magnetic resonance imaging (MRI) has been regarded as a promising noninvasive assessment method. The present study was conducted to develop a model to predict the pathological response by analyzing the quantitative features of MRI and clinical risk factors, which might predict the therapeutic effects in patients with LARC as accurately as possible before treatment. PATIENTS AND METHODS: A total of 82 patients with LARC were enrolled as the training cohort and internal validation cohort. The pre-CRT MRI after pretreatment was acquired to extract texture features, which was finally selected through the minimum redundancy maximum relevance (mRMR) algorithm. A support vector machine (SVM) was used as a classifier to classify different tumor responses. A joint radiomics model combined with clinical risk factors was then developed and evaluated by receiver operating characteristic (ROC) curves. External validation was performed with 107 patients from another center to evaluate the applicability of the model. RESULTS: Twenty top image texture features were extracted from 6192 extracted-radiomic features. The radiomics model based on high-spatial-resolution T2-weighted imaging (HR-T2WI) and contrast-enhanced T1-weighted imaging (T1+C) demonstrated an area under the curve (AUC) of 0.8910 (0.8114-0.9706) and 0.8938 (0.8084-0.9792), respectively. The AUC value rose to 0.9371 (0.8751-0.9997) and 0.9113 (0.8449-0.9776), respectively, when the circumferential resection margin (CRM) and carbohydrate antigen 19-9 (CA19-9) levels were incorporated. Clinical usefulness was confirmed in an external validation cohort as well (AUC, 0.6413 and 0.6818). CONCLUSION: Our study indicated that the joint radiomics prediction model combined with clinical risk factors showed good predictive ability regarding the treatment response of tumors as accurately as possible before treatment.

Pathologic-Based Nomograms for Predicting Overall Survival and Disease-Free Survival Among Patients with Locally Advanced Rectal Cancer.

PURPOSE: Preoperative neoadjuvant therapy is standard before surgery for locally advanced rectal cancer in current clinical treatment. However, patients with the same clinical TNM stage before treatment vary in clinical outcomes. More and more studies noted that pathological findings after preoperative neoadjuvant therapy are better prognostic factors to determine prognosis than clinical TNM stage in patients with locally advanced rectal cancer. The purpose of this study is to develop and validate models based on pathological findings to predict overall survival (OS) and disease-free survival (DFS). PATIENTS AND METHODS: A total of 3026 patients from two hospitals were included. The endpoint was OS and DFS. Significant predictors of OS on multivariate analysis were used to establish the nomogram. RESULTS: The Harrell's C index for OS prediction was 0.72 (95% confidence interval [CI], 0.68 to 0.77) in the training cohort, 0.66 (95% CI, 0.60 to 0.72) and 0.68 (95% CI, 0.64 to 0.73) in the internal and external validation cohorts. Using this nomogram, high- and low-risk groups for OS were defined in the training cohort. The 3-year OS was 78.1% (95% CI: 72.4-84.2%) for the high-risk group and 95% (95% CI: 93.6-96.5%) in the low-risk group (HR: 4.42, 95% CI: 3.22-6.05; P<0.001). This finding was also applied in the two external cohorts. Similarly, a nomogram that contained the same indices was developed and validated to predict for DFS. CONCLUSION: Nomograms based on pathological findings are a reliable tool to predict 3-year OS and DFS rate in patients with locally advanced rectal cancer.

College of American Pathologists Tumor Regression Grading System for Long-Term Outcome in Patients with Locally Advanced Rectal Cancer.

BACKGROUND: The National Comprehensive Cancer Network's Rectal Cancer Guideline Panel recommends American Joint Committee of Cancer and College of American Pathologists (AJCC/CAP) tumor regression grading (TRG) system to evaluate pathologic response to neoadjuvant chemoradiotherapy for locally advanced rectal cancer (LARC). Yet, the clinical significance of the AJCC/CAP TRG system has not been fully defined. MATERIALS AND METHODS: This was a multicenter, retrospectively recruited, and prospectively maintained cohort study. Patients with LARC from one institution formed the discovery set, and cases from external independent institutions formed a validation set to verify the findings from discovery set. Overall survival (OS), disease-free survival (DFS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) were assessed by Kaplan-Meier analysis, log-rank test, and Cox regression model. RESULTS: The discovery set (940 cases) found, and the validation set (2,156 cases) further confirmed, that inferior AJCC/CAP TRG categories were closely /ccorrelated with unfavorable survival (OS, DFS, LRFS, and DMFS) and higher risk of disease progression (death, accumulative relapse, local recurrence, and distant metastasis) (all p < .05). Significantly, pairwise comparison revealed that any two of four TRG categories had the distinguished survival and risk of disease progression. After propensity score matching, AJCC/CAP TRG0 category (pathological complete response) patients treated with or without adjuvant chemotherapy displayed similar survival of OS, DFS, LRFS, and DMFS (all p > .05). For AJCC/CAP TRG1-3 cases, adjuvant chemotherapy treatment significantly improved 3-year OS (90.2% vs. 84.6%, p < .001). Multivariate analysis demonstrated the AJCC/CAP TRG system was an independent prognostic surrogate. CONCLUSION: AJCC/CAP TRG system, an accurate prognostic surrogate, appears ideal for further strategizing adjuvant chemotherapy for LARC. IMPLICATIONS FOR PRACTICE: The National Comprehensive Cancer Network recommends the American Joint Committee of Cancer and College of American Pathologists (AJCC/CAP) tumor regression grading (TRG) four-category system to evaluate the pathologic response to neoadjuvant treatment for patients with locally advanced rectal cancer; however, the clinical significance of the AJCC/CAP TRG system has not yet been clearly addressed. This study found, for the first time, that any two of four AJCC/CAP TRG categories had the distinguished long-term survival outcome. Importantly, adjuvant chemotherapy may improve the 3-year overall survival for AJCC/CAP TRG1-3 category patients but not for AJCC/CAP TRG0 category patients. Thus, AJCC/CAP TRG system, an accurate surrogate of long-term survival outcome, is useful in guiding adjuvant chemotherapy management for rectal cancer.

A Genotype Signature for Predicting Pathologic Complete Response in Locally Advanced Rectal Cancer.

PURPOSE: To construct and validate a predicting genotype signature for pathologic complete response (pCR) in locally advanced rectal cancer (PGS-LARC) after neoadjuvant chemoradiation. METHODS AND MATERIALS: Whole exome sequencing was performed in 15 LARC tissues. Mutation sites were selected according to the whole exome sequencing data and literature. Target sequencing was performed in a training cohort (n = 202) to build the PGS-LARC model using regression analysis, and internal (n = 76) and external validation cohorts (n = 69) were used for validating the results. Predictive performance of the PGS-LARC model was compared with clinical factors and between subgroups. The PGS-LARC model comprised 15 genes. RESULTS: The area under the curve (AUC) of the PGS model in the training, internal, and external validation cohorts was 0.776 (0.697-0.849), 0.760 (0.644-0.867), and 0.812 (0.690-0.915), respectively, and demonstrated higher AUC, accuracy, sensitivity, and specificity than cT stage, cN stage, carcinoembryonic antigen level, and CA19-9 level for pCR prediction. The predictive performance of the model was superior to clinical factors in all subgroups. For patients with clinical complete response (cCR), the positive prediction value was 94.7%. CONCLUSIONS: The PGS-LARC is a reliable predictive tool for pCR in patients with LARC and might be helpful to enable nonoperative management strategy in those patients who refuse surgery. It has the potential to guide treatment decisions for patients with different probability of tumor regression after neoadjuvant therapy, especially when combining cCR criteria and PGS-LARC.

PRMT1 enhances oncogenic arginine methylation of NONO in colorectal cancer.

Arginine methylation is an important posttranslational modification catalyzed by protein arginine methyltransferases (PRMTs). However, the role of PRMTs in colorectal cancer (CRC) progression is not well understood. Here we report that non-POU domain-containing octamer-binding protein (NONO) is overexpressed in CRC tissue and is a potential marker for poor prognosis in CRC patients. NONO silencing resulted in decreased proliferation, migration, and invasion of CRC cells, whereas overexpression had the opposite effect. In a xenograft model, tumors derived from NONO-deficient CRC cells were smaller than those derived from wild-type (WT) cells, and PRMT1 inhibition blocked CRC xenograft progression. A mass spectrometry analysis indicated that NONO is a substrate of PRMT1. R251 of NONO was asymmetrically dimethylated by PRMT1 in vitro and in vivo. Compared to NONO WT cells, NONO R251K mutant-expressing CRC cells showed reduced proliferation, migration, and invasion, and PRMT1 knockdown or pharmacological inhibition abrogated the malignant phenotype associated with NONO asymmetric dimethylation in both KRAS WT and mutant CRC cells. Compared to adjacent normal tissue, PRMT1 was highly expressed in the CRC zone in clinical specimens, which was correlated with poor overall survival in patients with locally advanced CRC. These results demonstrate that PRMT1-mediated methylation of NONO at R251 promotes CRC growth and metastasis, and suggest that PRMT1 inhibition may be an effective therapeutic strategy for CRC treatment regardless of KRAS mutation status.

The watch-and-wait strategy versus surgical resection for rectal cancer patients with a clinical complete response after neoadjuvant chemoradiotherapy.

BACKGROUND: The watch-and-wait strategy offers a non-invasive therapeutic alternative for rectal cancer patients who have achieved a clinical complete response (cCR) after chemoradiotherapy. This study aimed to investigate the long-term clinical outcomes of this strategy in comparation to surgical resection. METHODS: Stage II/III rectal adenocarcinoma patients who received neoadjuvant chemoradiotherapy and achieved a cCR were selected from the databases of three centers. cCR was evaluated by findings from digital rectal examination, colonoscopy, and radiographic images. Patients in whom the watch-and-wait strategy was adopted were matched with patients who underwent radical resection through 1:1 propensity score matching analyses. Survival was calculated and compared in the two groups using the Kaplan-Meier method with the log rank test. RESULTS: A total of 117 patients in whom the watch-and-wait strategy was adopted were matched with 354 patients who underwent radical resection. After matching, there were 94 patients in each group, and no significant differences in term of age, sex, T stage, N stage or tumor location were observed between the two groups. The median follow-up time was 38.2 months. Patients in whom the watch-and-wait strategy was adopted exhibited a higher rate of local recurrences (14.9% vs. 1.1%), but most (85.7%) were salvageable. Three-year non-regrowth local recurrence-free survival was comparable between the two groups (98% vs. 98%, P = 0.506), but the watch-and-wait group presented an obvious advantage in terms of sphincter preservation, especially in patients with a tumor located within 3 cm of the anal verge (89.7% vs. 41.2%, P < 0.001). Three-year distant metastasis-free survival (88% in the watch-and-wait group vs. 89% in the surgical group, P = 0.874), 3-year disease-specific survival (99% vs. 96%, P = 0.643) and overall survival (99% vs. 96%, P = 0.905) were also comparable between the two groups, although a higher rate (35.7%) of distant metastases was observed in patients who exhibited local regrowth in the watch-and-wait group. CONCLUSION: The watch-and-wait strategy was safe, with similar survival outcomes but a superior sphincter preservation rate as compared to surgery in rectal cancer patients achieving a cCR after neoadjuvant chemoradiotherapy, and could be offered as a promising conservative alternative to invasive radical surgery.

Prognostic Value of Interval Between the Initiation of Neoadjuvant Treatment to Surgery for Patients With Locally Advanced Rectal Cancer Following Neoadjuvant Chemotherapy, Radiotherapy and Definitive Surgery.

Background: The addition of intensive preoperative chemotherapy and using of a longer waiting period between neoadjuvant radiotherapy and total mesorectal excision (TME) surgery lengthen the time interval from the initiation of neoadjuvant treatment to definitive surgery in patients with locally advanced rectal cancer (LARC). Here, we evaluated the prognostic value of different time intervals between the initiation of neoadjuvant treatment to TME surgery for LARC. Methods: A total of 2,267 patients with LARC, who received neoadjuvant radiochemotherapy and TME surgery, between January 2010 through December 2018 were recruited. The entire cohort was divided into 4 subgroups based on total-time-to surgery, defined as the time interval between initiation of neoadjuvant treatment and TME surgery (TTS): <13 weeks (TTS-1), 13 to <15 weeks (TTS-2), 15 to <17 weeks (TTS-3), ≥17 weeks (TTS-4). Overall survival (OS), disease-free survival (DFS), distant metastasis-free survival (DMFS), and local recurrence-free survival (LRFS) rates in different TTS subgroup patients were compared, and hazard ratios (HR) for different demographic and clinicopathological variables, including TTS, were calculated to determine their prognostic significance. Results: The median follow-up time was 42.0 (range, 5-162) months. The 3-year OS, DFS, DMFS, and LRFS rates were 87.0, 79.4, 80.9, and 93.8%, respectively. The varied OS, DFS, and DFMS rates were detected among these different TTS subgroups (P = 0.010, P < 0.001, and P < 0.001, respectively). Particularly, the lower survival outcome was mainly observed at patients in the shortest TTS group (TTS-1). Cox regression analysis confirmed that the only significant positive independent prognostic factor for 3-year DFS was a longer TTS (TTS 2-4 vs. TTS-1; HR 0.884, 95% CI 0.778-0.921, P < 0.001), while the significant negative independent prognosticfactors were moderate to poor tumor differentiation (vs. well-differentiated; HR 1.191, 95% CI 1.004-1.414, P = 0.045) and clinical N1-2 stage (vs. N0 stage; HR 1.190, 95% CI 1.052-1.347, P = 0.006). Conclusion: For patients with LARC, an interval between the initiation of neoadjuvant treatment and TME surgery of longer than 13 weeks is associated with favorable disease-free survival.

Effects of neoadjuvant chemotherapy with or without intensity-modulated radiotherapy for patients with rectal cancer.

Neoadjuvant chemoradiotherapy (nCRT) followed by total mesorectal excision and adjuvant chemotherapy is the standard regimen for patients with locally advanced rectal cancer (LARC). However, whether and to which extent neoadjuvant radiotherapy could be removed from nCRT for patients with LARC is still unclear. This was a multicenter, retrospectively recruited, prospectively maintained cohort study. A propensity score matching model was employed to minimize potential confounding factors between subgroup patients treated with neoadjuvant chemotherapy (nCT) or nCRT. Overall survival (OS), disease-free survival (DFS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) were assessed between subgroup patients by Kaplan-Meier analysis, log-rank test, and Cox regression model. In total, 3233 consecutive patients, consist of 571 nCT and 2662 nCRT-treated cases, were included. After propensity score matching (1:4), 565 nCT-treated patients were matched to 1852 nCRT-treated patients. Compared with nCT, nCRT treatment indeed decreased 3-y local recurrence (10.0% vs 6.6%, P = .026), but had no impact on OS, DFS and DMFS (all P > .05) for LARC. Stratified analysis further confirmed that nCRT treatment was associated with higher 3-y LRFS and 3-y DFS than nCT treatment for baseline high-risk subgroup (cT4, cN+, and cIII stage) patients (all P < .05). Conversely, for the baseline low-risk subgroup patients (cT3, cN0, and cII stage), nCRT and nCT treatment had similar 3-y OS, LRFS, DFS, and DMFS (all P > .05). The administration of neoadjuvant radiotherapy for LARC patients might be determined by baseline risk classification, the high-risk individuals could be delivered while low-risk patients might be omitted.

Association between adjuvant chemotherapy and survival in patients with rectal cancer and pathological complete response after neoadjuvant chemoradiotherapy and resection.

BACKGROUND: For patients with locally advanced rectal cancer (LARC), it is unclear whether neoadjuvant chemoradiotherapy-induced pathologic complete response (pCR) individuals would further benefit from adjuvant chemotherapy (ACT). METHODS: The pCR individuals who received different ACT cycles were paired by propensity score matching. Overall survival (OS), disease-free survival (DFS), local recurrence-free survival (LRFS), and distant metastasis-free survival (DMFS) were calculated by Kaplan-Meier and log-rank test. RESULTS: In total, 1041 pCR individuals were identified from 5567 LARC cases. Specifically, 303 pCR cases had no ACT treatment, and 738 pCR patients received fluoropyrimidine-based ACT (median, 4 cycles) treatment. After 1:3 propensity score matching, 297 cases without ACT treatment were matched to 712 cases who received ACT treatment. Kaplan-Meier analysis showed that pCR individuals treated with or without ACT had the similar 3-year outcome (OS, DFS, LRFS and DMFS) (all P > 0.05). Moreover, the pCR patients received different ACT cycle(s) (0 vs. 1-4 cycles, 0 vs. ≥5 cycles) had comparable 3-year OS, DFS, LRFS and DMFS (all P > 0.05). In stratified analysis, ACT treatment did not improve 3-year survival (OS, DFS, LRFS and DMFS) for the baseline high-risk (cT3-4/cN1-2) subgroup patients (all P > 0.05). CONCLUSION: ACT, which did not improve survival, is unnecessary to neoadjuvant treatment-induced pCR LARC patients. TRIAL REGISTRATION: 2019ZSLYEC-136 (24-6-2019).