Suspected Germline TP53 Variants and Clonal Hematopoiesis of Indeterminate Potential: Lessons Learned From a Molecular Tumor Board.

OBJECTIVE: Li-Fraumeni syndrome (LFS) is a pan-cancer predisposition syndrome caused by germline pathogenic variants in the gene TP53. The interpretation of TP53 variants in clinical scenarios outside the classic LFS criteria may be challenging. Here, we report a patient affected by 2 primary cancers at later ages, who harbored a likely pathogenic TP53 at low allele frequency detected in a blood sample. METHODS: The Molecular Tumor Board committee at our institution revisited the case of a patient who was enrolled in a research protocol for the investigation of genetic conditions associated with neuroendocrine tumors. Clinical, familial, and molecular data were reviewed. The patient received germline testing using a next generation sequencing multi-gene panel and was incidentally found to harbor a TP53 likely pathogenic variant, with 22% of variant allele fraction. Additional samples, including a second blood sample, oral swab, and saliva, were collected for DNA analysis. A new TP53 sequencing round was performed with the attempt to distinguish between a true constitutional germline variant and a somatically acquired variant due to aberrant clonal expansion of bone marrow precursors. RESULTS: Patient's personal and familial history of cancer did not meet classic nor Chompret LFS criteria. Environmental risk factors for cancer were identified, such as alcohol abuse and tobacco exposure. The TP53 variant initially found in the next-generation sequencing was confirmed by Sanger sequencing in the previous DNA sample extracted from blood for the first analysis and in a second blood sample collected 6 years later. The TP53 variant was not detected in the DNA extracted from the oral swab and saliva samples. CONCLUSION: Considering the low TP53 variant allele fraction in blood, absence of variant detection in oral swab and saliva samples, the lack of LFS clinical criteria, and history of exposure to environmental risk factors for cancer, the main hypothesis for this case was aberrant clonal expansion due to clonal hematopoiesis. Oncologists should interpret TP53 findings during germline testing with caution.

A multi-centre randomized controlled trial investigating Consolidation Chemotherapy with and without oxaliplatin in distal rectal cancer and Watch & Wait.

BACKGROUND: Neoadjuvant chemoradiation(nCRT) has been considered the preferred initial treatment strategy for distal rectal cancer. Advantages of this approach include improved local control after radical surgery but also the opportunity for organ preserving strategies (Watch and Wait-WW). Consolidation chemotherapy(cCT) regimens using fluoropyrimidine-based with or without oxalipatin following nCRT have demonstrated to increase complete response and organ preservation rates among these patients. However, the benefit of adding oxaliplatin to cCT compared to fluoropirimidine alone regimens in terms of primary tumor response remains unclear. Since oxalipatin-treatment may be associated with considerable toxicity, it becomes imperative to understand the benefit of its incorporation into standard cCT regimens in terms of primary tumor response. The aim of the present trial is to compare the outcomes of 2 different cCT regimens following nCRT (fluoropyrimidine-alone versus fluoropyrimidine + oxaliplatin) for patients with distal rectal cancer. METHODS: In this multi-centre study, patients with magnetic resonance-defined distal rectal tumors will be randomized on a 1:1 ratio to receive long-course chemoradiation (54 Gy) followed by cCT with fluoropyrimidine alone versus fluoropyrimidine + oxaliplatin. Magnetic resonance(MR) will be analyzed centrally prior to patient inclusion and randomization. mrT2-3N0-1 tumor located no more than 1 cm above the anorectal ring determined by sagittal views on MR will be eligible for the study. Tumor response will be assessed after 12 weeks from radiotherapy(RT) completion. Patients with clinical complete response (clinical, endoscopic and radiological) may be enrolled in an organ-preservation program(WW). The primary endpoint of this trial is decision to organ-preservation surveillance (WW) at 18 weeks from RT completion. Secondary endpoints are 3-year surgery-free survival, TME-free survival, distant metastases-free survival, local regrowth-free survival and colostomy-free survival. DISCUSSION: Long-course nCRT with cCT is associated with improved complete response rates and may be a very attractive alternative to increase the chances for organ-preservation strategies. Fluoropyrimidine-based cCT with or without oxaliplatin has never been investigated in the setting of a randomized trial to compare clinical response rates and the possibility of organ-preservation. The outcomes of this study may significantly impact clinical practice of patients with distal rectal cancer interested in organ-preservation. TRIAL REGISTRATION: www. CLINICALTRIALS: gov NCT05000697; registered on August 11th, 2021.

Monoallelic deleterious MUTYH germline variants as a driver for tumorigenesis.

MUTYH encodes a glycosylase involved in the base excision repair of DNA. Biallelic pathogenic germline variants in MUTYH cause an autosomal recessive condition known as MUTYH-associated adenomatous polyposis and consequently increase the risk of colorectal cancer. However, reports of increased cancer risk in individuals carrying only one defective MUTYH allele are controversial and based on studies involving few individuals. Here, we describe a comprehensive investigation of monoallelic pathogenic MUTYH germline variants in 10,389 cancer patients across 33 different tumour types and 117,000 healthy individuals. Our results indicate that monoallelic pathogenic MUTYH germline variants can lead to tumorigenesis through a mechanism of somatic loss of heterozygosity of the functional MUTYH allele in the tumour. We confirmed that the frequency of monoallelic pathogenic MUTYH germline variants is higher in individuals with cancer than in the general population, although this frequency is not homogeneous among tumour types. We also demonstrated that the MUTYH mutational signature is present only in tumours with loss of the functional allele and found that the characteristic MUTYH base substitution (C>A) increases stop-codon generation. We identified key genes that are affected during tumorigenesis. In conclusion, we propose that carriers of the monoallelic pathogenic MUTYH germline variant are at a higher risk of developing tumours, especially those with frequent loss of heterozygosity events, such as adrenal adenocarcinoma, although the overall risk is still low. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Organ Preservation in cT2N0 Rectal Cancer After Neoadjuvant Chemoradiation Therapy: The Impact of Radiation Therapy Dose-escalation and Consolidation Chemotherapy.

OBJECTIVE: To demonstrate the difference in organ-preservation rates and avoidance of definitive surgery among cT2N0 rectal cancer patients undergoing 2 different chemoradiation (CRT) regimens. BACKGROUND: Patients with cT2N0 rectal cancer are more likely to develop complete response to neoadjuvant CRT. Organ preservation has been considered an alternative treatment strategy for selected patients. Radiation dose-escalation and consolidation chemotherapy have been associated with increased rates of response and may improve chances of organ preservation among these patients. METHODS: Patients with distal and nonmetastatic cT2N0 rectal cancer managed by neoadjuvant CRT were retrospectively reviewed. Patients undergoing standard CRT (50.4 Gy and 2 cycles of 5-FU-based chemotherapy) were compared with those undergoing extended CRT (54 Gy and 6 cycles of 5-FU-based chemotherapy). Patients were assessed for tumor response at 8 to 10 weeks. Patients with complete clinical response (cCR) underwent organ-preservation strategy ("Watch and Wait"). Patients were referred to salvage surgery in the event of local recurrence during follow-up. RESULTS: Thirty-five patients underwent standard and 46 patients extended CRT. Patients undergoing extended CRT were more likely to undergo organ preservation and avoid definitive surgical resection at 5years (67% vs 30%; P = 0.001). After development of a cCR, surgery-free survival is similar between extended and standard CRT groups at 5 years (78% vs 56%; P = 0.12). CONCLUSIONS: Dose-escalation and consolidation chemotherapy leads to increased long-term organ-preservation rates among cT2N0 rectal cancer. After achievement of a cCR, the risk for local recurrence and need for salvage surgery is similar, irrespective of the CRT regimen.

Safety and efficacy of cytotoxic chemotherapy in hepatocellular carcinoma after first-line treatment with sorafenib.

BACKGROUND: Before the targeted therapies era, cytotoxic chemotherapy (CCT) was an option for advanced hepatocellular carcinoma (HCC), even with the lack of supporting evidence. Since the last decade, sorafenib has been established as the first-line therapy. Although new agents are being incorporated, CCT is still considered in regions where new drugs are not available or for patients who progressed through the approved therapies and remain in good clinical condition. We aimed to describe our experience regarding the use of CCT as second-line treatment after sorafenib. METHODS: A database of 273 patients was evaluated. Patients that received CCT after sorafenib progression were selected for the analysis. Descriptive statistics was used for categorical and continue variables. Median survival was estimated with Kaplan-Meier curves. Variables were found to be significant if the two-sided p value was ≤ 0.05 on multivariate testing using the Cox regression model. RESULTS: Forty-five patients received CCT; 33 (73.3%) had Child-Pugh classification A, and 34 (75.6%) had stage C according to the Barcelona Clinic Liver Cancer (BCLC) staging system. The most used regimen was doxorubicin in 25 patients (55.6%). Median overall survival (OS) was 8.05 months (95% confidence interval [CI] 2.73 - 9.88 months). The 6-month and 1-year survival probability was 52.4% and 27.36%, respectively. Eastern Cooperative Oncology Group performance status (ECOG PS) 0-1 and disease control with sorafenib was independently associated with better OS in patients treated with CCT. Any-grade toxicities were observed in 82.2% and grade 3-4 in 44.4% of the patients. CONCLUSION: In accordance with previous studies, CCT had a notable rate of adverse events. The poor prognosis of this cohort suggests that CCT may not alter the natural history of HCC after sorafenib progression.

Chemoradiotherapy versus chemotherapy as adjuvant treatment for localized gastric cancer: a propensity score-matched analysis.

BACKGROUND: Treatment of localized gastric cancer (LGC) consists of surgical resection followed by adjuvant treatment. Both chemoradiation (CRT) and chemotherapy (CT) regimens have shown benefit in survival outcomes versus observation. However, there are few data comparing these approaches. METHODS: This study included consecutive patients with LGC treated at Instituto do Cancer do Estado de Sao Paulo (ICESP) from 2012 to 2015. CRT was based on the INT-0116 regimen and CT consisted of a platinum and fluoropyrimidine doublet. Treatment choice was based on physician preference. Toxicity was evaluated for every cycle. Overall survival (OS) analysis was performed by Kaplan-Meier. A propensity score-matched analysis was performed to minimize selection bias. RESULTS: A total of 309 patients were evaluated, 227 in CRT group and 82 in CT group. The most prevalent grade 3/4 toxicities in CRT and CT groups were: nausea/vomiting (9.25 vs 4.9%), fatigue (9.3% vs 2.4%), mucositis (4.4% vs 1.2%), neutropenia (37.8% vs 20.9%), febrile neutropenia (3.9% vs 0%), anemia (4.3% vs 6.1%), thrombocytopenia (2.6% vs 4.9%), neuropathy (0 vs 2.4%) and hand-foot syndrome (0.4% vs 2.4%). Two grade 5 toxicities (febrile neutropenia and anemia) occurred in CRT group. There was no difference in the pattern of recurrence. After a median follow-up of 23.5 months (CRT) and 20.6 months (CT), there was no difference in OS between groups. CONCLUSIONS: CT and CRT present similar efficacy and tolerability as adjuvant treatment for LGC.

A phase II trial with anti-Lewis-Y monoclonal antibody (hu3S193) for the treatment of platinum resistant/refractory ovarian, fallopian tube and primary peritoneal carcinoma.

OBJECTIVES: The primary objective was to evaluate the clinical efficacy of hu3S193, a humanized monoclonal antibody against the Lewis-Y antigen, in patients with platinum resistant/refractory ovarian, fallopian tube and primary peritoneal carcinoma. Secondary objectives were safety and pharmacokinetics. In addition, we sought to determine the potential interaction of clinical benefit and patient characteristics. METHODS: This two-stage, multicenter, single arm, phase II trial enrolled eligible patients to receive hu3S193 weekly at a dose of 20mg/m(2) intravenously for 8 weeks (1 cycle) to a maximum of 3 cycles. Efficacy was measured as clinical benefit rate (objective response or stable disease for at least 24 weeks). RESULTS: 26 of 31 patients were eligible for efficacy analysis. No complete/partial responses were observed. Six patients had stable disease for 24+weeks [clinical benefit rate 23% (95% CI=9.77%-46.71%)]. Median PFS was 8.4 weeks (95% CI=6.0 to 16.1). Median PFS differed between patients with no ascites and no visceral disease and patients with ascites and/or visceral disease [16.1 vs. 8.1 weeks (p=0.0058)]. The most commonly reported treatment-related adverse events were fatigue (19.3%) and nausea (16.2%). Allergic reactions occurred in 6 patients (5 with Grade 1/2; 1 with Grade 3). CONCLUSIONS: Hu3S193 lacked sufficient activity in the first stage of the study to open enrollment to the second stage. However, based on the longer PFS in patients with no ascites and no visceral disease, consolidation strategies in platinum sensitive disease are currently being tested.

Is surgery always necessary in rectal cancer?

Rectal cancer is a major health problem around the world, representing about one-third of the total colorectal cancer cases. Because of its anatomical location, there is a higher risk of local recurrence, and treatment often requires a complex multidisciplinary approach which includes neoadjuvant radiotherapy, chemotherapy, and a radical surgical procedure that commonly leads to a permanent colostomy. The cure rate with this strategy is good, with some patients having no residual disease in the surgical specimen. While the prognosis for those patients is excellent, their quality of life is permanently compromised. In this article, we review risks and benefits of the standard treatment approach and compare standard treatment with alternative methods aimed at rectal preservation.

Prognostic Impact of Primary Tumor Sidedness in Stage III Colorectal Cancer: Real-World Evidence from a Brazilian Cohort.

BACKGROUND: Primary tumor sidedness (PTS) is an independent prognostic factor in patients with metastatic colorectal cancer (CRC), with a worse prognosis for right-sided tumors. There are limited data on the prognostic impact of PTS in stage III CRC. The main objective of this study was to analyze the prognostic impact of PTS in stage III CRC. PATIENTS AND METHODS: A retrospective and uni-institutional cohort study was performed in an oncology reference center. Patients with stage III CRC treated with a 5-fluorouracil and oxaliplatin-based chemotherapy regimen (mFLOX regimen) from October 2007 to February 2013 were included. The primary outcome was the probability of overall survival (OS) at 5 years stratified by PTS. Secondary outcomes were the probability of disease-free survival (DFS) at 5 years and an analysis of the prognostic impact of clinical and molecular biomarkers. Kaplan‒Meier curves were used, and Cox models were used to evaluate prognostic factors associated with OS and DFS. RESULTS: Overall, 265 patients were evaluated. Transverse colon tumors, multicentric tumors, and undetermined primary subsites were excluded, resulting in 234 patients classified according to PTS: 95 with right sidedness (40.6%) and 139 with left sidedness (59.4%). The median follow-up time was 66 months [interquartile range (IQR): 39-81]. The 5-year OS probabilities for right-sided and left-sided tumors were 67% (95% CI: 58%-77%) and 82% (75%-89%), respectively [hazard ratio (HR): 2.02, 95% CI: 1.18-3.46; P = .010]. The 5-year probabilities of DFS for right-sided and left-sided tumors were 58% (49%-69%) and 65% (58%-74%), respectively (HR: 1.29, 0.84-1.97; P = 0.248). CONCLUSION: These data suggest that there may be a worse prognosis (inferior OS at 5 years) for resected right-sided stage III CRC patients treated in the real world. However, these data need to be confirmed by prospective studies with a larger number of participants.

Watch and wait approach following extended neoadjuvant chemoradiation for distal rectal cancer: are we getting closer to anal cancer management?

BACKGROUND: No immediate surgery (Watch and Wait) has been considered in select patients with complete clinical response after neoadjuvant chemoradiation to avoid postoperative morbidity and functional disorders after radical surgery. OBJECTIVE: The purpose of this study was to demonstrate the long-term results of patients who had a complete clinical response following an alternative chemoradiation regimen and were managed nonoperatively. DESIGN: This is a prospective study. SETTINGS: This study was conducted at a single center. PATIENTS: Seventy consecutive patients with T2-4N0-2M0 distal rectal cancer were studied. Neoadjuvant chemoradiotherapy included 54 Gy and 5-fluorouracil/leucovorin delivered in 6 cycles every 21 days. Patients were assessed for tumor response at 10 weeks from radiation completion. Patients with incomplete clinical response were referred to immediate surgery. Patients with complete clinical response were not immediately operated on and were monitored. MAIN OUTCOME MEASURES: The primary outcomes measured were the initial complete clinical response rates after 10 weeks and the sustained complete clinical response rates after 12 months from chemoradiotherapy. RESULTS: One patient died during chemoradiotherapy because of cardiac complications. Forty-seven (68%) patients had initial complete clinical response. Of these, 8 developed local regrowth within the first 12 months of follow-up (17%). Thirty-nine sustained complete clinical response at a median follow-up of 56 months (57%). An additional 4 patients (10%) developed late local recurrences (>12 months of follow-up). Overall, 35 patients never underwent surgery (50%). LIMITATIONS: This study is limited by the short follow-up and small sample size. CONCLUSION: Extended chemoradiation therapy with additional chemotherapy cycles and 54 Gy of radiation may result in over 50% of sustained (>12 months) complete clinical response rates that may ultimately avoid radical rectal resection. Local failures occur more frequently during the initial 12 months of follow-up in up to 17% of cases, whereas late recurrences are less common but still possible, leading to 50% of patients who never required surgery. Strict follow-up may allow salvage therapy in the majority of these patients (see Video, Supplemental Digital Content 1, http://links.lww.com/DCR/A113.).

Low-energy amplitude-modulated electromagnetic field exposure: Feasibility study in patients with hepatocellular carcinoma.

BACKGROUND: Patients with advanced hepatocellular carcinoma (HCC) and poor liver function lack effective systemic therapies. Low-energy electromagnetic fields (EMFs) can influence cell biological processes via non-thermal effects and may represent a new treatment option. METHODS: This single-site feasibility trial enrolled patients with advanced HCC, Child-Pugh A and B, Eastern Cooperative Oncology Group 0-2. Patients underwent 90-min amplitude-modulated EMF exposure procedures every 2-4 weeks, using the AutEMdev (Autem Therapeutics). Patients could also receive standard care. The primary endpoints were safety and the identification of hemodynamic variability patterns. Exploratory endpoints included health-related quality of life (HRQoL), overall survival (OS). and objective response rate (ORR) using RECIST v1.1. RESULTS: Sixty-six patients with advanced HCC received 539 AutEMdev procedures (median follow-up, 30 months). No serious adverse events occurred during procedures. Self-limiting grade 1 somnolence occurred in 78.7% of patients. Hemodynamic variability during EMF exposure was associated with specific amplitude-modulation frequencies. HRQoL was maintained or improved among patients remaining on treatment. Median OS was 11.3 months (95% confidence interval [CI]: 6.0, 16.6) overall (16.0 months [95% CI: 4.4, 27.6] and 12.0 months [6.4, 17.6] for combination therapy and monotherapy, respectively). ORR was 24.3% (32% and 17% for combination therapy and monotherapy, respectively). CONCLUSION: AutEMdev EMF exposure has an excellent safety profile in patients with advanced HCC. Hemodynamic alterations at personalized frequencies may represent a surrogate of anti-tumor efficacy. NCT01686412.

Efficacy and safety of sorafenib in elderly patients with advanced hepatocellular carcinoma.

OBJECTIVES: To evaluate the efficacy and safety of sorafenib in elderly patients with advanced hepatocellular carcinoma (HCC). METHODS: We analyzed data from a cohort of patients with advanced HCC treated using systemic treatment according to the local institutional protocol. Patients were divided into two groups, Group A, individuals <70 years of age, and Group B, individuals 70 years of age or older at the time of treatment initiation. Efficacy, measured based on overall survival (OS) and time to treatment failure (TTF), and toxicity were compared between groups. RESULTS: A total of 238 patients with advanced HCC who received sorafenib between 2007 and 2018 were evaluated. The median age for Group A was 59.1 years and that for Group B 73.6 years. The major prognostic characteristics were balanced between the groups. There were no significant differences in OS between Group A (8.0 months, 95%CI 6.34-9.3) and Group B (9.0 months, 95%CI 5.38-12.62), p=0.433, or in TTF between Group A (3.0 months, 95%CI 2.39-3.60) and Group B (3.0 months, 95%CI 1.68-4.32), p=0.936. There were no significant differences between Groups A and B with respect to the incidence of adverse events or treatment discontinuation because of toxicity. CONCLUSION: Efficacy and safety of sorafenib did not differ significantly between younger and older patients with HCC. Our data suggest that age alone should not restrict clinical decision-making for patients with advanced HCC.

Epidemiology and Outcomes of Patients With Brain Metastases From Colorectal Cancer-Who Are These Patients?

BACKGROUND: Brain metastases (BMs) from colorectal cancer (CRC) are unusual; however, an increase in incidence has been reported. The evidence available on the subject is scarce, and a better understanding is warranted. We aimed to characterize the epidemiology and the outcomes of patients with BMs from CRC. PATIENTS AND METHODS: A cohort of patients with BMs from CRC was retrospectively evaluated. Patients were treated in a single center between May 2008 and April 2019. BMs were confirmed by brain computed tomography or magnetic resonance imaging. RESULTS: A total of 247 consecutive patients were evaluated. Most patients had a left-sided primary tumor (193, 78%) and at least two extra-cranial metastatic sites (194, 78%). Ninety-six patients (39%) were RAS wild-type; 68 patients (27%) were RAS mutated; and 83 patients (34%) were not characterized. Median time from the initial diagnosis to BMs was 27.6 months (interquartile range, 13.1-46.9). Regarding local therapy, 43 patients (17.4%) were treated with BM surgery alone, 76 patients (30.8%) with radiotherapy (RT) alone, and 58 patients (23.5%) with both surgery and RT. Median overall survival (OS) was 2.9 months (95% confidence interval [CI], 2.2-3.5). Six-month and 1-year OS rates were 29% (95% CI, 23-25) and 13.5% (95% CI, 9.2-18.6), respectively. In a multivariable analysis, BM surgery alone (hazard ratio [HR], 0.56; P = .018), RT alone (HR, 0.51; P = .001), and surgery plus RT (HR, 0.27; P < .001) were associated with superior OS, whereas Eastern Cooperative Oncology Group Performance Status 3 or 4 (HR, 2.01; P = .009) and male gender (HR, 1.46; P = .012) were negative prognostic factors. RAS status was not associated with OS. CONCLUSION: BMs occur late during the course of colorectal cancer and are more common in patients with a left-sided primary tumor and a high volume of metastatic disease. BMs from colorectal cancer are still associated with an extremely poor prognosis; however, selected patients may benefit from treatment with surgical resection and radiotherapy.

Real-world Data for High-risk Stage II Colorectal Cancer - The Role of Tumor Side in the Adjuvant Setting.

BACKGROUND: The impact of sidedness in the high-risk stage II colorectal cancer (CRC) setting is uncertain. Although controversial, available data suggest a possible modest benefit of adjuvant chemotherapy (CT) in the adjuvant scenario. The aim of this study is to analyze the overall survival (OS) and recurrence-free survival (RFS) according to the tumor side. PATIENTS AND METHODS: In this single-center retrospective cohort, we analyzed patients treated between January 2011 and December 2018. We evaluated OS and RFS of high-risk patients according to the tumor side and considering adjuvant CT exposure and clinical and molecular features. RESULTS: A total of 1047 patients with stage II CRC were evaluated. Of these, 540 had high-risk criteria and microsatellite stability (MSS) or unknown status. One hundred fifty-seven (29%) patients had right-sided tumors, and 352 (65.2%) had left-sided tumors. Most patients received adjuvant CT, and the majority of them had T3 stage tumors, ≥ 12 lymph node resection, left tumor, MSS, and moderate differentiation. OS did not differ according to tumor side (5-year OS rates: 81.9% for right-sided tumors vs. 83% for left-sided tumors; hazard ratio, 0.91; 95% confidence interval, 0.55-1.53; P = .744). Adjuvant CT was associated with a superior RFS and OS, with 5-year OS rates of 87.7% versus 76.1% in the no-adjuvant group (hazard ratio, 0.46; 95% CI, 0.28-0.73; P = .001). CONCLUSION: The tumor side did not influence the outcomes in this study. Adjuvant CT was associated with improved RFS and OS in patients with high-risk stage II CRC, with a total gain of 11.6% in 5-year OS.

A Prospective Cohort Study of Biomarkers in Squamous Cell Carcinoma of the Anal Canal (SCCAC) and their Influence on Treatment Outcomes.

Background: Although Chemoradiation (CRT) is the curative treatment for SCCAC, many patients present primary resistance. Since it is a rare tumor, response predictors remain unknown. Methods: We performed a prospective cohort study to evaluate biomarkers associated with CRT response, progression-free survival (PFS), and overall survival (OS). The primary endpoint was response at 6 months (m). Tumor DNA and HPV were analyzed by next-generation sequencing, while KI-67 and PD-L1 by immunohistochemistry in tumor tissue. Results: Seventy-eight patients were recruited between October/2011 and December/2015, and 75 were response evaluable. The median age was 57 years, 65% (n=49) were stage III and 12% (n=9) were HIV positive (HIV+). At 6m, 62.7% (n=47) presented CR. On multivariate analyses, stage II patients were 4.7 more likely to achieve response than stage III (OR, 4.70; 95%CI, 1.36-16.30; p=0.015). HIV+ was associated with a worse response (OR, 5.72; 95%CI, 2.5-13.0; p<0.001). 5-year PFS and OS rates were 63.3% and 76.4%, respectively, with a median follow up of 66m. On multivariate analyses, older age (HR 1.06, p=0.022, 95%IC 1.01-1.11) and absence of CR at 6m (HR 3.36, p=0.007, 95%IC 1.39-8.09) were associated with inferior OS. The 5-year OS rate was 62.5% in HIV+ group compared to 78% among HIV- pts, although this difference was not statistically significant (p=0.4). PIK3CA, MET and TP53 mutations, HPV, Ki-67 expression, and PD-L1 expression, were not associated with PFS and OS. Conclusions: Clinical stage III and HIV+ were associated with worse response to CRT at 6m. The absence of CR was the main factor associated with poor 5-year OS.

Malignant bowel obstruction: effectiveness and safety of systemic chemotherapy.

OBJECTIVES: Although systemic chemotherapy is often administered to patients with malignant bowel obstruction (MBO), its benefit remains unknown. This study assessed the outcomes of patients who received systemic chemotherapy as part of MBO treatment. METHODS: For this retrospective cohort study, data were extracted from records of patients hospitalised due to MBO in a tertiary cancer centre from 2008 to 2020. Eligible patients were not candidates for surgery and received systemic chemotherapy targeting the underlying malignancy causing MBO. Primary objective was to assess patient outcomes after chemotherapy; secondary objectives were rates of intestinal function recovery, hospital discharge and grade ≥3 toxicities. The primary endpoint was overall survival (OS). RESULTS: A total of 167 patients were included: median age was 55 (18-81) years, 91% had an Eastern Cooperative Oncology Group (ECOG) performance status ≥2, 75.5% had gastrointestinal tumours and 70% were treatment-naive. The median OS after chemotherapy was 4.4 weeks (95% CI 3.4 to 5.5) in the overall population. No OS difference was observed according to treatment line (p=0.24) or primary tumour (p=0.13). Intestinal function recovery occurred in 87 patients (52%), out of whom 21 (24.1%) had a reobstruction. Hospital discharge was possible in 74 patients (44.3%). Grade≥3 adverse events occurred in 26.9% of the patients, and a total of 12 deaths (7%) attributed to toxicities were observed after chemotherapy. CONCLUSIONS: MBO was associated with a dismal prognosis in this mostly treatment-naive population. The administration of chemotherapy yielded a significant risk of toxicities, whereas it did not appear to provide any relevant survival benefit in this scenario.

Circulating Tumour DNA Sequencing Identifies a Genetic Resistance-Gap in Colorectal Cancers with Acquired Resistance to EGFR-Antibodies and Chemotherapy.

Epidermal growth factor receptor antibodies (EGFR-Abs) confer a survival benefit in patients with RAS wild-type metastatic colorectal cancer (mCRC), but resistance invariably occurs. Previous data showed that only a minority of cancer cells harboured known genetic resistance drivers when clinical resistance to single-agent EGFR-Abs had evolved, supporting the activity of non-genetic resistance mechanisms. Here, we used error-corrected ctDNA-sequencing (ctDNA-Seq) of 40 cancer genes to identify drivers of resistance and whether a genetic resistance-gap (a lack of detectable genetic resistance mechanisms in a large fraction of the cancer cell population) also occurs in RAS wild-type mCRCs treated with a combination of EGFR-Abs and chemotherapy. We detected one MAP2K1/MEK1 mutation and one ERBB2 amplification in 2/3 patients with primary resistance and KRAS, NRAS, MAP2K1/MEK1 mutations and ERBB2 aberrations in 6/7 patients with acquired resistance. In vitro testing identified MAP2K1/MEK1 P124S as a novel driver of EGFR-Ab resistance. Mutation subclonality analyses confirmed a genetic resistance-gap in mCRCs treated with EGFR-Abs and chemotherapy, with only 13.42% of cancer cells harboring identifiable resistance drivers. Our results support the utility of ctDNA-Seq to guide treatment allocation for patients with resistance and the importance of investigating further non-canonical EGFR-Ab resistance mechanisms, such as microenvironmentally-mediated resistance. The detection of MAP2K1 mutations could inform trials of MEK-inhibitors in these tumours.

Increasing the rates of complete response to neoadjuvant chemoradiotherapy for distal rectal cancer: results of a prospective study using additional chemotherapy during the resting period.

OBJECTIVES: Addition of chemotherapy in the resting period between radiotherapy completion and response assessment during neoadjuvant treatment for distal rectal cancer could potentially increase rates of complete tumor regression. The purpose of this study was to evaluate toxicity rates and the impact of an extended neoadjuvant chemoradiation regimen on complete response rates. METHODS: Thirty-four consecutive patients with nonmetastatic distal rectal cancer were prospectively included. Patients were managed by 5,400 Gy of radiation and 5-fluorouracil/leucovorin-based chemotherapy given for three consecutive days every 21 days for six cycles (three cycles concomitant with radiotherapy). Tumor response assessment was performed at ten weeks from radiation completion. Patients with complete clinical response were strictly monitored and were not immediately operated on. Patients with incomplete clinical response were referred to surgery. RESULTS: Twenty-nine patients had completed 12 months of follow-up and were included in this preliminary analysis. Twenty-eight (97%) successfully completed treatment. Fifteen of 16 patients had Grade III toxicities that were skin-related (93%). Median follow-up was 23 months. Fourteen patients (48%) were considered as complete clinical responders sustained for at least 12 months (median, 24 months) after chemoradiation completion by clinical assessment alone. An additional five patients (17%) were considered as complete responders with ypT0 results after full-thickness local excision. Overall, the complete response rate was 65%. CONCLUSIONS: The addition of chemotherapy during the resting period after neoadjuvant chemoradiation is associated with acceptable toxicity and high tolerability rates. The considerably high rates of complete response in this preliminary series requires further follow-up, but they may provide valuable information for future prospective, randomized trials.

Circulating Tumor DNA Detection in the Management of Anti-EGFR Therapy for Advanced Colorectal Cancer.

Background: Anti-EGFR antibodies are a standard care for advanced KRAS-wild type colorectal cancers. Circulating tumor DNA (ctDNA) monitoring during therapy can detect emergence of KRAS mutant clones and early resistance to therapy. Case Presentation: We describe a 61-years-old man presenting a metastatic and recurrent rectal cancer treated with different chemotherapy regimens. His tumor was KRAS wild-type based on tissue analysis and he was treated sequentially with cetuximab-based chemotherapy, chemotherapy alone and panitumumab-based chemotherapy. We performed sequential analysis of ctDNA using droplet digital PCR (ddPCR) and a commercial assay designed for the detection of frequent KRAS mutations during his clinical follow-up. Prior to the first cetuximab-based chemotherapy ctDNA analysis demonstrated an absence of KRAS mutations. Emergence of KRAS mutations in ctDNA occurred ~3 months after treatment initiation and preceded clinical and imaging progression in about 2 months. Fractional abundance of KRAS mutation rapidly increased to 70.7% immediately before a chemotherapy alone regimen was initiated. Interestingly, KRAS mutation abundance decreased significantly during the first two months of chemotherapy, reaching a fractional abundance of 3.0%, despite minimal clinical benefit with this therapy. Re-challenge with a different anti-EGFR antibody was attempted as later line, but high levels of KRAS mutations in ctDNA before therapy correlated with an absence of clinical benefit. Conclusions: The monitoring of resistance mutations in KRAS using ctDNA during the treatment of KRAS wild-type advanced colorectal cancers can detect the emergence of resistant clones prior to clinical progression. Dynamics of resistant clones may alter during periods on and off anti-EGFR antibodies, detecting window of opportunities for a re-challenge with these therapies.