Atypical pattern of response in rectal cancer after neoadjuvant pembrolizumab treatment: a case report, literature review, and proposed management model

Background

Immunotherapy is the first-line treatment in patients with advanced microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) colorectal cancer (CRC). Although immune checkpoint inhibitors (ICIs) for locally advanced rectal cancer (LARC) are not yet a standard, the results are very encouraging and raise the question of whether patients with clinical complete response (cCR) could receive nonoperative management (NOM). However, different patterns of response have challenged management strategies.

Case Description

A 34-year-old woman diagnosed with dMMR LARC started treatment with capecitabine 2,000 mg/m² on day 1 to 14 and oxaliplatin 130 mg/m² on day 1 and every 21 days. Magnetic resonance imaging (MRI), performed three cycles later, showed local progression of the primary rectal lesion, which at that time had new peritoneal reflex involvement. A new hepatic lesion in segment V was observed. Due to disease progression, she was administered pembrolizumab 200 mg every 21 days. After three cycles, a discordant radiological response was observed on a new MRI scan that showed a complete response of the liver lesion and magnetic resonance tumor regression grade (mrTRG) 1 in the rectum. However, new involvement of the mesentery and enlargement of the regional lymph nodes (LNs) were also evident. A new colonoscopic biopsy was performed, showing no cancerous cells. She underwent surgery on the rectum and liver lesion. Pathology showed a complete response of the rectal wall and liver lesion, but 1 of 22 LNs was positive for adenocarcinoma (ypT0 N1 M0). The patient continued on pembrolizumab, and 14 months after surgery, she had not relapsed.

Conclusions

Neoadjuvant immunotherapy for rectal cancer requires new recommendations for the assessment of clinical response. Pseudoprogression should be ruled out as an atypical response before deciding on surgical treatment. We propose an algorithm to address pseudoprogression in this setting.

Short-course radiotherapy for rectal cancer: real-world evidence in Argentina

Background

Short-course radiotherapy (SCRT) of 25 Gy in five daily fractions is a recommended strategy in the neoadjuvant setting for resectable locally advanced rectal cancer (LARC), as well as in cases of metastatic disease for local control. There is scarce information regarding the use of SCRT for patients who have received nonoperative management.

Objectives

To describe the characteristics of patients who received treatment with SCRT for LARC and metastatic rectal cancer, toxicity, and the approach after radiation treatment.

Methods

This is a retrospective analysis of all patients who underwent SCRT for rectal cancer at the Alexander Fleming Institute from March 2014 to June 2022.

Results

In total, 44 patients were treated with SCRT. The majority were male (29, 66%), with a median age of 59 years (interquartile range 46-73). Most patients had stage IV disease (26, 59.1%), followed by LARC (18, 40.9%). Most lesions were located in the middle rectum (30, 68%). The majority of LARC patients underwent SCRT followed by consolidation chemotherapy (ChT) (16/18, 89%), while most patients with metastatic disease underwent SCRT followed by consolidation ChT (14/26, 53.8%). A clinical complete response (cCR) was documented in 8/44, 18.2% of patients. Most patients with LARC and cCR were managed by a watch and wait approach (5/18, 27.7%). Local recurrence was observed in LARC cases (2/18, 11.1%). Patients who underwent SCRT following consolidation ChT were more likely to have adverse events (AEs) than those undergoing induction ChT following SCRT (11/30, 36.7% versus 3/12, 25%, p = 0.02).

Conclusion

In a subgroup of patients diagnosed with LARC and treated with SCRT followed by ChT, surgical treatment could be omitted after they achieved a cCR. Local recurrence was similar to that reported in a previous study. SCRT is a reasonable option for local disease control in stage IV disease, yielding low toxicity rates. Therefore, decisions must be made by a multidisciplinary team. Prospective studies are necessary to reach further conclusions.

Short-course radiotherapy in rectal cancer: A single-center experience in Argentina

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Background: Short-course radiotherapy (SCRT) is an option in the neoadjuvant setting of resectable stage II-III rectal cancer, as well as in stage IV disease for local control without delay to initiate systemic treatment. Short-course radiotherapy is reported to be a comparable strategy for locally advanced rectal cancer. Limited data exist regarding the use of short-course radiation therapy when used as part of a non-surgical watch and wait approach. Methods: This is a retrospective analysis of all patients that underwent SCRT for rectal cancer at the Alexander Fleming Institute from 3/2014 to 6/2022. Results: 44 patients were treated with SCRT, 29 (66%) were male, with a median age of 59 years (46-73). Most of the patients had stage IV disease (26, 59,1%) followed by clinical stage II-III (18, 40,9%). 30 (68%) were localized in the middle with 14 (32%) in the lower rectum, by MRI imaging. In locally advanced disease 5/18 had T4 disease and 7/18 had N≥2. 14/18 patients (89%) underwent SCRT followed by consolidation chemotherapy (ChT) and 4 (11%) had induction ChT followed by SCRT. In metastatic disease 14/26 patients (53.84%) underwent SCRT followed by consolidation ChT, 10 (38.46%) had induction ChT followed by SCRT, and 2 (7.7%) received only SCRT. 29 (65.9%) of patients underwent surgery. 17/29(58.6%) had metastatic disease and 12/29 (41.4%) had locally advanced disease. Pathological response rates in operated patients were 2 (6.9%). 8 (18.2%) cases had a clinical complete response (cCR) (n=6 stage II-III and n=2 stage IV). Five (27.7% of the locally advanced group) patients with cCR underwent watch and wait with 1 local recurrence after 14 months. The remainder is disease free with a median follow-up time of 20 months (IC 95%: 15.14-24.85). Those that underwent SCRT following chemotherapy were more likely to have AEs compared to those that had chemotherapy following SCRT (11/30, 36.7% vs 25%, p=0.02). Conclusions: Our work shows that in a subgroup of patients diagnosed with LARC treated with SCRT followed by Chemotherapy, surgical treatment could be deferred after achieving a complete clinical response. The shorter time involved by SCRT allowed for less treatments with similar toxicity to long-course treatment regimens. SCRT is a reasonable option for local disease control in stage IV disease.

Liquid biopsy for KRAS, NRAS and BRAF mutation testing in advanced colorectal cancer patients: the Argentinean experience

Objective: To analyze the frequency of KRAS, NRAS and BRAF hotspot mutations in circulating tumor DNA (ctDNA) from patients with metastatic colorectal cancer (mCRC). Methods: Observational, descriptive and retrospective study in mCRC patients with available ctDNA-based genotype of KRAS, NRAS and BRAF. Results: The frequencies of plasma mutations for KRAS, NRAS and BRAF were 34% (± 7), 4% (± 3) and 4% (± 3), respectively. Median overall survival of plasma-tested RAS/BRAF-mutated patients was 26.6 months (95% CI: 14.4-not estimable [NE]), while RAS/BRAF wild-type patients did not reach the median survival during follow-up. Median progression-free survival for RAS/BRAF wild-type and RAS/BRAF-mutated patients was 12 (95% CI: 7-NE) and 4 months (95% CI: 4-NE), respectively. Conclusion: Our work supports the utility of KRAS, NRAS and BRAF analysis in liquid biopsy from mCRC patients.

Implementation of a virtual multicenter gastrointestinal tumor board to reduce cancer disparities in Argentina

Given the increasing complexity of cancer care, multidisciplinary tumor boards have become essential in daily clinical oncology practice. The Project Extension for Community Healthcare Outcomes (ECHO) initiative developed an innovative telementoring model using a "hub and spoke" design consisting of a team of experts (hub) that offers a full service to multiple participants (the spokes) during regularly scheduled sessions discussing patients' clinical cases. The Alexander Fleming Cancer Institute in Buenos Aires was the first hub in Latin America to implement Project ECHO for gastrointestinal tumors. In our 3-year experience, 80 patients from 37 centers were evaluated within Project ECHO and a range of three to five cases were discussed in each meeting. From our perspective, the impact of this novel approach was a remarkable strategy to reduce care disparities by equalizing access to high-quality medical knowledge in a multidisciplinary environment for medical discussions. Additionally, it was shown to have a cost-effective impact directly on the patients and the local health system, since relevant costs were saved after unnecessary treatments, studies and travel expenses were avoided.

The LEGACy study: a European and Latin American consortium to identify risk factors and molecular phenotypes in gastric cancer to improve prevention strategies and personalized clinical decision making globally

BACKGROUND

Gastric Cancer (GC) is the fourth most deadly cancer worldwide. Enhanced understanding of its key epidemiological and molecular drivers is urgently needed to lower the incidence and improve outcomes. Furthermore, tumor biology in European (EU) and Latin American (LATAM) countries is understudied. The LEGACy study is a Horizon 2020 funded multi-institutional research approach to 1) detail the epidemiological features including risk factors of GC in current time and 2) develop cost-effective methods to identify and integrate biological biomarkers needed to guide diagnostic and therapeutic approaches with the aim of filling the knowledge gap on GC in these areas.

METHODS

This observational study has three parts that are conducted in parallel during 2019-2023 across recruiting centers from four EU and four LATAM countries: Part 1) A case-control study (800 cases and 800 controls) using questionnaires on candidate risk factors for GC, which will be correlated with clinical, demographic and epidemiological parameters. Part 2) A case-control tissue sampling study (400 cases and 400 controls) using proteome, genome, microbiome and immune analyses to characterize advanced (stage III and IV) GC. Patients in this part of the study will be followed over time to observe clinical outcomes. The first half of samples will be used as training cohort to identify the most relevant risk factors and biomarkers, which will be selected to propose cost-effective diagnostic and predictive methods that will be validated with the second half of samples. Part 3) An educational study, as part of our prevention strategy (subjects recruited from the general public) to test and disseminate knowledge on GC risk factors and symptoms by a questionnaire and informative video. Patients could be recruited for more than one of the three LEGACy studies.

DISCUSSION

The LEGACy study aims to generate novel, in-depth knowledge on the tumor biological characteristics through integrating epidemiological, multi-omics and clinical data from GC patients at an EU-LATAM partnership. During the study, cost-effective panels with potential use in clinical decision making will be developed and validated.

TRIAL REGISTRATION

ClinicalTrials.gov Identifiers: Part 1: NCT03957031 . Part 2: NCT04015466 . Part 3: NCT04019808 .

Adverse event management costs for first-line treatment with cetuximab or panitumumab of RAS wild-type metastatic colorectal cancer patients in Latin America

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Background: Anti-EGFR treatment of RAS wild-type metastatic colorectal cancer (mCRC) in Latin America includes cetuximab or panitumumab, added to chemotherapy (cet+CT and pan+CT, respectively). Adverse event (AE) profiles for each regimen may influence the treatment decision. This study aimed to estimate the associated financial impact of AE management in three countries: Argentina (AR), Brazil (BR) and Panama (PA) from a healthcare payer perspective. Methods: We revised a published Microsoft Excel-based economic model to calculate average patient- and population-level costs from a payer perspective of mCRC AE management for first-line cet+CT and pan+CT treatment, using AE frequency and severity data derived from the authorization relevant FDA prescribing information (PI), multiplied by the country-specific unit costs of managing AEs. Costs of AE management were obtained from publicly available sources in each country and converted to US dollars (USD). Country-specific market research data were applied to calculate costs at the eligible mCRC population level. The model structure and input parameters were endorsed by local practising oncologists. Results: A 17.5% (all-grade) and 31.6% (grade 3-4) lower average per patient AE frequency were estimated from the PI, for cet+CT vs pan+CT. Cost results are presented in the table. Projected AE management costs of cet+CT for the eligible mCRC population are $297,643 (AR), $124,981 (BR) and $65,895 (PA), annually, reducing current annual estimated AE costs by $42,181 (AR), $8,548 (BR) and $4,691 (PA). Conclusions: According to the average estimated AE frequencies, patients treated with cet+CT are expected to experience fewer AEs than with pan+CT. According to our analyses, the lower frequency rates could result in lower overall and severe AEs’ management costs, resulting in 12.4% (AR), 6.4% (BR) and 6.6% (PA) lower costs of AE management for cet+CT versus pan+CT.[Table: see text]

Implementation of a molecular tumour board in LATAM: the impact on treatment decisions for patients evaluated at Instituto Alexander Fleming, Argentina

BACKGROUND

The role of the molecular tumour board (MTB) is to recommend personalised therapy for patients with cancer beyond standard-of-care treatment. A comprehensive molecular analysis of the tumour in a molecular pathology laboratory is important for all targeted therapies approaches. Here we report the 1-year experience of the Instituto Alexander Fleming Molecular Tumour Board.

PATIENTS AND METHODS

The MTB of the Instituto Alexander Fleming was launched in December 2019 in a monthly meeting. In each interactive monthly session, five cases were presented and discussed by the members. These cases were referred by the treating oncologists. The MTB recommendations were sent to each physician individually, and to the rest of the meeting participants. This was discussed with the patients/families by the treating oncologist. The final decision to choose therapy was left to the treating physicians. Of the 32 patients presented at MTB, 28 (87.5%) had potentially actionable alterations and only 4 (12.5%) had no actionable mutation. Six (19%) patients received a local regulatory agency approved drug recommendation, nine (28%) patients received an off-label approval treatment recommendation and three (9%) patients did not receive the treatment due to access and reimbursement of the drug.

CONCLUSION

In most of the cases evaluated, the MTB was able to provide treatment recommendations based on targetable genetic alterations. Molecular-guided extended personalised patient care is effective for a small but clinically significant proportion of patients in challenging clinical situations. We believe that the implementation of a MTB is feasible in the Latin America (LATAM) region.