TP53 mutational pattern in Spanish and Polish non-small cell lung cancer patients: null mutations are associated with poor prognosis.

Inactivation of TP53 tumor suppressor gene is the most frequent molecular alteration in NSCLC, involving up to 60% of cases. Furthermore, TP53 mutational spectrum is related to the type of mutagen exposure, as well as racial and/or diet differences. Nearly 95% of TP53 perturbations affect codons included within exons 5-8 which encode for almost the entire DNA-binding domain. In this study we addressed the possible prognostic value of the molecular alterations identified in exons 5-8 of the TP53 gene in DNAs from 151 paraffin-embedded NSCLC sections corresponding to 59 Spanish and 92 Polish stage I-IIIA resected patients. PCR/single-strand conformation polymorphism (SSCP) analysis revealed that the occurrence of TP53 exon 5-8 mutations was 17/59 (29%) in the Spanish cohort and 17/92 (18%) in the Polish group. However, when DNA sequencing analysis was performed, these frequencies were reduced because of the presence of SSCP-false positive, intronic and silent mutations and polymorphisms. Fifteen of the 59 Spanish NSCLC tumors (25%) harbored TP53 mutations affecting exons 5-8 coding sequences, whereas only 12 of 92 Polish neoplasms (13%) contained alterations in the central hydrophobic region of p53. Our results indicate that the occurrence of TP53 mutations affecting exon 5-8 coding sequences in some European NSCLC populations may be lower than previously reported, and that the TP53 mutational patterns of these cohorts differ somewhat. The Spanish NSCLC patients contained missense mutations (9/59, 15%) and a relatively high percentage of null mutations (5/59, 8%) while the Polish patients mostly harbored missense mutations (9/92, 10%) and only one tumor contained a null type (1/92, 1%). Moreover, most TP53 missense mutations in the Spanish group were located outside the conserved regions, whereas the same mutations in the Polish group affected conserved amino acids. Furthermore, the Polish patients harbored a high percentage of G-->A transitions (most of them at non-CpG sites), while G-->T transversions were predominant in the Spanish group. Our findings suggest that there may be different racial or exogenous factors in these two populations which may help to explain both the distinct TP53 mutational pattern and the lower frequency obtained in the Polish group. The presence of missense mutations did not confer a worse clinical outcome in these subsets of NSCLC patients. However, patients whose tumors contained null TP53 gene mutations had a 5 month median disease-free survival time in contrast with 42 months in those patients without mutations (P=0.008). These findings suggest that loss of p53 function may enhance tumor progression in NSCLC patients independently of whether dominant negative TP53 missense mutations are present.

[Positron emission tomography detection of residual disease in a case of lung cancer]. / Detección por tomografía de emisiíon de positrones de enfermedad residual en un case do cáncer de pulmón.

To date, computed tomography is considered the best procedure to detect either relapse or residual disease in non-small cell lung cancer. However, in recent years several studies have stressed the value of F-18 fluorodeoxyglucose positron emission tomography (FDG PET) which takes advantage of the enhanced glucose uptake observed in neoplastic cells. We present the case of a patient with a locally advanced non-small cell lung cancer who received trimodal treatment with induction chemotherapy followed by surgical resection and postoperative irradiation and lately developed brain metastases which were treated with chemoradiotherapy plus radiosurgery. However a small residual lesion remained in the brain magnetic resonance. Such abnormality was evaluated by means of FDG PET which did not show any increase on FDG uptake. The present case prompt us to review the role of FDG PET as a procedure that enable to detect subclinical disease and its potential usefulness taking into account the improvement in management strategies that has been attained in non-small cell lung cancer.