Mismatch repair-deficient (MMRd) colorectal cancers (CRCs) have high mutation burdens, which make these tumours immunogenic and many respond to immune checkpoint inhibitors. The MMRd hypermutator phenotype may also promote intratumour heterogeneity (ITH) and cancer evolution. We applied multiregion sequencing and CD8 and programmed death ligand 1 (PD-L1) immunostaining to systematically investigate ITH and how genetic and immune landscapes coevolve. All cases had high truncal mutation burdens. Despite pervasive ITH, driver aberrations showed a clear hierarchy. Those in WNT/β-catenin, mitogen-activated protein kinase, and TGF-β receptor family genes were almost always truncal. Immune evasion (IE) drivers, such as inactivation of genes involved in antigen presentation or IFN-γ signalling, were predominantly subclonal and showed parallel evolution. These IE drivers have been implicated in immune checkpoint inhibitor resistance or sensitivity. Clonality assessments are therefore important for the development of predictive immunotherapy biomarkers in MMRd CRCs. Phylogenetic analysis identified three distinct patterns of IE driver evolution: pan-tumour evolution, subclonal evolution, and evolutionary stasis. These, but neither mutation burdens nor heterogeneity metrics, significantly correlated with T-cell densities, which were used as a surrogate marker of tumour immunogenicity. Furthermore, this revealed that genetic and T-cell infiltrates coevolve in MMRd CRCs. Low T-cell densities in the subgroup without any known IE drivers may indicate an, as yet unknown, IE mechanism. PD-L1 was expressed in the tumour microenvironment in most samples and correlated with T-cell densities. However, PD-L1 expression in cancer cells was independent of T-cell densities but strongly associated with loss of the intestinal homeobox transcription factor CDX2. This explains infrequent PD-L1 expression by cancer cells and may contribute to a higher recurrence risk of MMRd CRCs with impaired CDX2 expression. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

BACKGROUND:BRAF+MEK inhibitors extend life expectancy of patients with BRAFV600 mutant advanced melanoma. Acquired resistance limits duration of benefit, but preclinical and case studies suggest intermittent dosing could overcome this limitation. INTERIM was a phase 2 trial evaluating an intermittent dosing regimen. METHODS:Patients with BRAFV600 mutant advanced melanoma due to start dabrafenib+trametinib were randomised to receive either continuous (CONT), or intermittent (INT; dabrafenib d1-21, trametinib d1-14 every 28 days) dosing. A composite primary endpoint included progression-free survival (PFS) and quality of life (QoL). Secondary endpoints included response rate (ORR), overall survival (OS) and adverse events (AEs). Mutant BRAFV600E ctDNA was measured by droplet digital PCR (ddPCR), using mutant allele frequency of > 1 % as the detection threshold. RESULTS:79 patients (39 INT, 40 CONT) were recruited; median age 67 years, 65 % AJCC (7th ed) stage IV M1c, 29 % had brain metastases. With 19 months median follow-up, INT was inferior in all efficacy measures: median PFS 8.5 vs 10.7mo (HR 1.39, 95 %CI 0.79-2.45, p = 0.255); median OS 18.1mo vs not reached (HR 1.69, 95 %CI 0.87-3.28, p = 0.121), ORR 57 % vs 77 %. INT patients experienced fewer treatment-related AEs (76 % vs 88 %), but more grade > 3 AEs (53 % vs 42 %). QoL favoured CONT. Detection of BRAFV600E ctDNA prior to treatment correlated with worse OS (HR 2.55, 95 %CI 1.25-5.21, p = 0.01) in both arms. A change to undetected during treatment did not significantly predict better OS. CONCLUSION:INTERIM findings are consistent with other recent clinical trials reporting that intermittent dosing does not improve efficacy of BRAF+MEK inhibitors.

Decades of research into the management of cutaneous malignant melanoma have proven it to be a 'tough nut to crack', and its incidence has continued to increase over the last 30 years. Surgery remains a gold standard for early-stage melanoma with five-year survival of 98% for stage I disease, and 90% for stage II. Nonetheless, patients with stage III disease are at a higher risk, resulting in local recurrence as well as distant metastasis. Research regarding the control of metastatic malignant melanoma of the head and neck has evolved. Currently the search is on to understand metastatic malignant melanoma as a heterogeneous disease both at the molecular and clinical level. This paper focuses on the latest systemic therapy for metastatic disease of the head and neck, including cytotoxic chemotherapy, immunotherapy, and target therapy. The new eighth edition of tumour staging, and the sequelae for malignant melanoma, sentinel lymph node biopsy (SLNB), surgical intervention, and its benefits and shortfalls, are discussed. Also, the outcome of our cohort series of patients with metastatic cutaneous malignant melanoma who were treated with systemic combination therapy in Dorset is presented.

BACKGROUND:The orally administered combination trifluridine/tipiracil has been approved as third line treatment in mCRC, demonstrating survival benefit and acceptable toxicity profile in the phase III RECOURSE study.PATIENT AND METHODS:We performed a multicenter retrospective real-world analysis of patients with mCRC receiving trifluridine/tipiracil between 2016 and 2019 in eight cancer centers across the United Kingdom.RESULTS:A total of 236 patients were included with median age of 69 years. All patients had received at least 2 lines of fluoropyrimidine-based chemotherapy doublet with oxaliplatin or irinotecan. About 10% of patients had ECOG ≥ 2. Median duration of trifluridine/tipiracil treatment was 3 months with an ORR of 2.1% and disease control rate of 21.6%. Median OS was 7.6 and median PFS 3.3 months. A dose reduction was required in 27% of patients, while 7.6% discontinued treatment due to toxicity. The most common grade 3 toxicities were neutropenia (34%), fatigue (10%), anemia (9%) and febrile neutropenia (5%). Baseline NLR <5 and CEA <200 had favorable prognostic (HR: 0.52 and 0.39, P≤ .001) and predictive value (OR: 4.1 and 6.7, P< .05). Development of grade 3 neutropenia predicted treatment response (OR: 0.32, P< .001). Following treatment with trifluridine/tipiracil 41% were referred for phase I trial or rechallenged with chemotherapy.CONCLUSION:Trifluridine/tipiracil is well tolerated in refractory mCRC patients with comparable efficacy and toxicity profile to that of the phase III RECOURSE. Pretreatment NLR and CEA could serve as potential markers for patient selection, while treatment-induced grade 3 neutropenia predicted response. Prospective validation is needed.