Activating mutations in the epidermal growth factor receptor gene occur as early cancer-driving clonal events in a subset of patients with non-small cell lung cancer (NSCLC) and result in increased sensitivity to EGFR-tyrosine-kinase-inhibitors (EGFR-TKIs). Despite very frequent and often prolonged clinical response to EGFR-TKIs, virtually all advanced EGFR-mutated (EGFRM+) NSCLCs inevitably acquire resistance mechanisms and progress at some point during treatment. Additionally, 20–30% of patients do not respond or respond for a very short time (<3 months) because of intrinsic resistance. While several mechanisms of acquired EGFR-TKI-resistance have been determined by analyzing tumor specimens obtained at disease progression, the factors causing intrinsic TKI-resistance are less understood. However, recent comprehensive molecular-pathological profiling of advanced EGFRM+ NSCLC at baseline has illustrated the co-existence of multiple genetic, phenotypic, and functional mechanisms that may contribute to tumor progression and cause intrinsic TKI-resistance. Several of these mechanisms have been further corroborated by preclinical experiments. Intrinsic resistance can be caused by mechanisms inherent in EGFR or by EGFR-independent processes, including genetic, phenotypic or functional tumor changes. This comprehensive review describes the identified mechanisms connected with intrinsic EGFR-TKI-resistance and differences and similarities with acquired resistance and among clinically implemented EGFR-TKIs of different generations. Additionally, the review highlights the need for extensive pre-treatment molecular profiling of advanced NSCLC for identifying inherently TKI-resistant cases and designing potential combinatorial targeted strategies to treat them.

Determining the presence of MYC gene rearrangements is becoming an increasingly important part of the diagnostic workup in aggressive lymphoma. Cytogenetic MYC alterations aid in differentiating diffuse large B-cell lymphoma (DLBCL) from Burkitt lymphoma. In addition, MYC aberrations are associated with poor prognosis in DLBCL. Fluorescence in situ hybridization and karyotyping are standard tests for detecting MYC aberrations, but these techniques are laborious and expensive. Here, we studied MYC status of 219 DLBCLs and Burkitt lymphomas using fluorescence in situ hybridization, immunohistochemistry, and quantitative real-time polymerase chain reaction (QRT-PCR). Overall, 15% of the cases had an MYC break. QRT-PCR analysis of MYC expression showed that 72% of DLBCLs with an MYC break had aberrantly high or low levels of MYC transcript. Excluding the cases with aberrantly low MYC expression, we found a significant positive correlation between levels of MYC transcripts and MYC tumor cells; however, QRT-PCR is not readily applicable as a screening tool. Immunohistochemically, all tumors showed a nuclear staining pattern that was simple to evaluate. The percentage of MYC lymphoma cells correlated closely with MYC rearrangement status. In all, 93% of cases with an MYC break had ≥80% MYC cells, in contrast to 3% of nonrearranged cases (P<0.0001). Receiver operating characteristic curve analysis showed ≥70% MYC tumor cells to be the optimal cutoff (sensitivity=100%, specificity=93%). Area under the receiver operating characteristic curve was 0.992, indicating that immunostaining for Myc protein is an excellent screening test to predict whether an MYC rearrangement is present.

Polycythemia vera (PV) is characterized by the presence of the JAK2V617F mutation in virtually all patients. Several studies have shown that the JAK2V617F mutational load decreases during treatment with alpha-interferon 2. We report on molecular and histomorphological bone marrow responses in seven PV patients with profound molecular responses during and after long-term treatment with alpha-interferon 2b. All patients obtained a major molecular response (MMR). Subsequently all patients discontinued alpha-interferon and sustained complete hematological remission with a follow-up period of median 10 months (range 4-30 months). Complete normalization of the bone marrow was seen in three of five patients. Long term treatment with IFN2b is able to induce 'minimal residual disease' with very low JAK2 V617F allele burden and may induce profound, and in some patients total, regression of histomorphological bone marrow features of PV. Finally, hematological remissions and major molecular responses can be sustained after discontinuation of long-term treatment with IFN2b.

Learning Objectives After completing this course, the reader will be able to: Identify the most frequent errors made in KRAS testing in this study and the possible consequences for a patient. Describe factors that could increase the chance of an error during KRAS testing. This article is available for continuing medical education credit at http://CME.TheOncologist.com The use of epidermal growth factor receptor–targeting antibodies in metastatic colorectal cancer has been restricted to patients with wild‐type KRAS tumors by the European Medicines Agency since 2008, based on data showing a lack of efficacy and potential harm in patients with mutant KRAS tumors. In an effort to ensure optimal, uniform, and reliable community‐based KRAS testing throughout Europe, a KRAS external quality assessment (EQA) scheme was set up. The first large assessment round included 59 laboratories from eight different European countries. For each country, one regional scheme organizer prepared and distributed the samples for the participants of their own country. The samples included unstained sections of 10 invasive colorectal carcinomas with known KRAS mutation status. The samples were centrally validated by one of two reference laboratories. The laboratories were allowed to use their own preferred method for histological evaluation, DNA isolation, and mutation analysis. In this study, we analyze the setup of the KRAS scheme. We analyzed the advantages and disadvantages of the regional scheme organization by analyzing the outcome of genotyping results, analysis of tumor percentage, and written reports. We conclude that only 70% of laboratories correctly identified the KRAS mutational status in all samples. Both the false‐positive and false‐negative results observed negatively affect patient care. Reports of the KRAS test results often lacked essential information. We aim to further expand this program to more laboratories to provide a robust estimate of the quality of KRAS testing in Europe, and provide the basis for remedial measures and harmonization.