Challenges to the effectiveness of next-generation sequencing in formalin-fixed paraffin-embedded tumor samples for non-small cell lung cancer.

INTRODUCTION: Next-generation sequencing (NGS) of Formalin-Fixed and Paraffin-Embedded (FFPE) specimens is routine in precision oncology practice. However, results are not always conclusive, and it is important to identify which factors may influence FFPE tumor sequencing success. MATERIALS AND METHODS: Here, we evaluated the influence of pre-analytical factors on 705 samples of non-small cell lung cancer specimens that underwent NGS testing. Factors such as tumor site, tumor cell percentage, fragment size, primary tumor or metastasis, presence of necrosis, DNA purity, DNA concentration, sample origin and year of testing. RESULTS: The overall NGS success rate was 84.9 % (n = 599). Bone site specimens had a very low success rate (42.1 %), differing from lung samples (79.8 %) (P < 0.05). Samples with tumor percentages <5 % (success rate of 44.4 %) represented 14.1 % of failed sequencings. Moreover, samples with tumor percentages >10 %-20 % (82 %) did not differ from those with >30 % (88.9 %) on sequencing outcomes (P = 0.086). Specimens that provided DNA concentrations >2.0 ng/uL, 1.0-2.0 ng/uL, 0.5-1.0 ng/uL and <0.5 ng/uL had success rates of 92 %, 77.1 %, 61.3 % and 20.4 %, respectively. Small fragments (≤0.2 cm2) had a success rate of 74.7 % and were more prevalent in the unsuccessful group (P < 0.05). CONCLUSIONS: Our results suggest that tumor percentage, fragment size, decalcified bone specimens, and DNA concentration are potential modifiers of NGS success rates. Interestingly, specimens with tumor percentages between 10 % and 20 % have the same sequencing outcome than specimens with >30 %. These results can strengthen the understanding of factors that lead to NGS success variability.

TP53 p.R337H is a conditional cancer-predisposing mutation: further evidence from a homozygous patient.

BACKGROUND: Adrenocortical carcinomas (ACCs) are among the most common childhood cancers occurring in infants affected with the Li-Fraumeni and Li- Fraumeni-like (LFS/LFL) syndromes, which are caused by dominant germline mutations in the TP53 gene. In Brazil, a particular mutation, occurring in the tetramerisation domain of the gene, p.R337H, is exceedingly common due to a founder effect and is strongly associated with ACC. In this report, we describe the phenotype and long-term clinical follow-up of a female child diagnosed with ACC and homozygous for the TP53 p.R337H founder mutation. CASE PRESENTATION: At age 11 months, the patient was diagnosed with a virilising anaplastic adrenal cortical tumour, which was completely excised without disturbing the adrenal capsule. Family history was consistent with an LFL tumour pattern, and genotyping identified the TP53 p.R337H mutation in both alleles in genomic DNA from lymphocytes and fibroblasts. Haplotype analysis confirmed the occurrence of the mutation in the same founder haplotype previously described in other Brazilian patients. No other germline or somatic TP53 mutations or rearrangements were identified. At age 9 years, the child was asymptomatic and had no evidence of endocrine derangements. Full body and brain magnetic resonance imaging (MRI) failed to detect any suspicious proliferative lesions, and cardiopulmonary exercise testing results were within the normal reference for the child's age, ruling out a major exercise capacity deficiency. CONCLUSION: This is the first clinical and aerobic functional capacity documentation of a patient who carries two mutant TP53 alleles and no wild-type allele. Our results support the hypothesis that TP53 p.R337H, the most common TP53 mutation ever described in any population, is a conditional mutant. Furthermore, our observations over a long period of clinical follow-up suggest that TP53 p.R337H homozygotes do not have a more severe disease phenotype than do heterozygote carriers of the same mutation. Patients with the homozygous TP53 p.R337H genotype will require careful surveillance for lifetime cancer risk and for effects on metabolic capacity later in life.