ESMO expert consensus statements on the management of EGFR mutant non-small-cell lung cancer.

The European Society for Medical Oncology (ESMO) held a virtual consensus-building process on epidermal growth factor receptor (EGFR)-mutant non-small-cell lung cancer in 2021. The consensus included a multidisciplinary panel of 34 leading experts in the management of lung cancer. The aim of the consensus was to develop recommendations on topics that are not covered in detail in the current ESMO Clinical Practice Guideline and where the available evidence is either limited or conflicting. The main topics identified for discussion were: (i) tissue and biomarkers analyses; (ii) early and locally advanced disease; (iii) metastatic disease and (iv) clinical trial design, patient's perspective and miscellaneous. The expert panel was divided into four working groups to address questions relating to one of the four topics outlined above. Relevant scientific literature was reviewed in advance. Recommendations were developed by the working groups and then presented to the entire panel for further discussion and amendment before voting. This manuscript presents the recommendations developed, including findings from the expert panel discussions, consensus recommendations and a summary of evidence supporting each recommendation.

Final overall survival results of WJTOG3405, a randomized phase III trial comparing gefitinib versus cisplatin with docetaxel as the first-line treatment for patients with stage IIIB/IV or postoperative recurrent EGFR mutation-positive non-small-cell lung cancer.

BACKGROUND: Primary analysis of the phase III study WJTOG 3405 demonstrated superiority of progression-free survival (PFS) for gefitinib (G) in patients treated with the epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) gefitinib compared with cisplatin plus docetaxel (CD) as the first-line treatment of stage IIIB/IV or postoperative recurrent EGFR mutation-positive non-small-cell lung cancer. This report presents final overall survival (OS) data. PATIENTS AND METHODS: Patients were randomized between G (250 mg/day orally) and cisplatin (80 mg/m2 intravenously) plus docetaxel (60 mg/m2 i.v.), administered every 21 days for three to six cycles. After the exclusion of 5 patients, 172 patients (86 in each group, modified intention-to-treat population) were included in the survival analysis. OS was re-evaluated using updated data (data cutoff, 30 September 2013; median follow-up time 59.1 months). The Kaplan-Meier method and the log-rank test were used for analysis, and hazard ratios (HRs) for death were calculated using the Cox proportional hazards model. RESULTS: OS events in the G group and CD group were 68 (79.1%) out of 86 and 59 (68.6%) out of 86, respectively. Median survival time for G and CD were 34.9 and 37.3 months, respectively, with an HR of 1.252 [95% confidence interval (CI): 0.883-1.775, P = 0.2070]. Multivariate analysis identified postoperative recurrence and stage IIIB/IV disease as independent prognostic factors, with an HR of 0.459 (95% CI: 0.312-0.673, P < 0.001). Median survival time (postoperative recurrence versus stage IIIB/IV disease) were 44.5 and 27.5 months in the G group and 45.5 and 32.8 months in the CD group, respectively. CONCLUSION: G did not show OS benefits over CD as the first-line treatment. OS of patients with postoperative recurrence was better than that of stage IIIB/IV disease, even though both groups had metastatic disease.This study was registered with UMIN (University Hospital Medical Information Network in Japan), number 000000539.

Pan-Asian adapted Clinical Practice Guidelines for the management of patients with metastatic non-small-cell lung cancer: a CSCO-ESMO initiative endorsed by JSMO, KSMO, MOS, SSO and TOS.

The most recent version of the European Society for Medical Oncology (ESMO) Clinical Practice Guidelines for the diagnosis, treatment and follow-up of metastatic non-small-cell lung cancer (NSCLC) was published in 2016. At the ESMO Asia Meeting in November 2017 it was decided by both ESMO and the Chinese Society of Clinical Oncology (CSCO) to convene a special guidelines meeting immediately after the Chinese Thoracic Oncology Group Annual Meeting 2018, in Guangzhou, China. The aim was to adapt the ESMO 2016 guidelines to take into account the ethnic differences associated with the treatment of metastatic NSCLC cancer in Asian patients. These guidelines represent the consensus opinions reached by experts in the treatment of patients with metastatic NSCLC representing the oncological societies of China (CSCO), Japan (JSMO), Korea (KSMO), Malaysia (MOS), Singapore (SSO) and Taiwan (TOS). The voting was based on scientific evidence, and was independent of both the current treatment practices and the drug availability and reimbursement situations in the six participating Asian countries. During the review process, the updated ESMO 2018 Clinical Practice Guidelines for metastatic NSCLC were released and were also considered, during the final stages of the development of the Pan-Asian adapted Clinical Practice Guidelines.

CNS response to osimertinib in patients with T790M-positive advanced NSCLC: pooled data from two phase II trials.

Background: Central nervous system (CNS) metastases are common in patients with non-small-cell lung cancer (NSCLC). Osimertinib has shown systemic efficacy in patients with CNS metastases, and early clinical evidence shows efficacy in the CNS. To evaluate osimertinib activity further, we present a pre-specified subgroup analysis of CNS response using pooled data from two phase II studies: AURA extension (NCT01802632) and AURA2 (NCT02094261). Patients and methods: Patients with T790M-positive advanced NSCLC, who had progressed following prior epidermal growth factor receptor-tyrosine kinase inhibitor treatment, received osimertinib 80 mg od (n = 411). Patients with stable, asymptomatic CNS metastases were eligible for enrolment; prior CNS treatment was allowed. Patients with ≥1 measurable CNS lesion (per RECIST 1.1) on baseline brain scan by blinded independent central neuroradiology review (BICR) were included in the evaluable for CNS response set (cEFR). The primary outcome for this CNS analysis was CNS objective response rate (ORR) by BICR; secondary outcomes included CNS duration of response, disease control rate (DCR) and progression-free survival (PFS). Results: Of 128 patients with CNS metastases on baseline brain scans, 50 were included in the cEFR. Confirmed CNS ORR and DCR were 54% [27/50; 95% confidence interval (CI) 39-68] and 92% (46/50; 95% CI 81-98), respectively. CNS response was observed regardless of prior radiotherapy to the brain. Median CNS duration of response (22% maturity) was not reached (range, 1-15 months); at 9 months, 75% (95% CI 53-88) of patients were estimated to remain in response. Median follow-up for CNS PFS was 11 months; median CNS PFS was not reached (95% CI, 7, not calculable). The safety profile observed in the cEFR was consistent with the overall patient population. Conclusions: Osimertinib demonstrated clinically meaningful efficacy against CNS metastases, with a high DCR, encouraging ORR, and safety profile consistent with that reported previously. ClinicalTrials.gov number: NCT01802632; NCT02094261.

Tumor immune microenvironment and nivolumab efficacy in EGFR mutation-positive non-small-cell lung cancer based on T790M status after disease progression during EGFR-TKI treatment.

BACKGROUND: The efficacy of programmed death-1 blockade in epidermal growth factor receptor gene (EGFR) mutation-positive non-small-cell lung cancer (NSCLC) patients with different mechanisms of acquired resistance to EGFR tyrosine kinase inhibitors (TKIs) is unknown. We retrospectively evaluated nivolumab efficacy and immune-related factors in such patients according to their status for the T790M resistance mutation of EGFR. PATIENTS AND METHODS: We identified 25 patients with EGFR mutation-positive NSCLC who were treated with nivolumab after disease progression during EGFR-TKI treatment (cohort A). Programmed death-ligand 1 (PD-L1) expression and tumor-infiltrating lymphocyte (TIL) density in tumor specimens obtained after acquisition of EGFR-TKI resistance were determined by immunohistochemistry. Whole-exome sequencing of tumor DNA was carried out to identify gene alterations. The relation of T790M status to PD-L1 expression or TIL density was also examined in an independent cohort of 60 patients (cohort B). RESULTS: In cohort A, median progression-free survival (PFS) was 2.1 and 1.3 months for T790M-negative and T790M-positive patients, respectively (P = 0.099; hazard ratio of 0.48 with a 95% confidence interval of 0.20-1.24). Median PFS was 2.1 and 1.3 months for patients with a PD-L1 expression level of ≥1% or <1%, respectively (P = 0.084; hazard ratio of 0.37, 95% confidence interval of 0.10-1.21). PFS tended to increase as the PD-L1 expression level increased with cutoff values of ≥10% and ≥50%. The proportion of tumors with a PD-L1 level of ≥10% or ≥50% was higher among T790M-negative patients than among T790M-positive patients of both cohorts A and B. Nivolumab responders had a significantly higher CD8+ TIL density and nonsynonymous mutation burden. CONCLUSION: T790M-negative patients with EGFR mutation-positive NSCLC are more likely to benefit from nivolumab after EGFR-TKI treatment, possibly as a result of a higher PD-L1 expression level, than are T790M-positive patients.

Genetic features of pulmonary adenocarcinoma presenting with ground-glass nodules: the differences between nodules with and without growth.

BACKGROUND: Pulmonary ground-glass nodules (GGNs) include both malignant and benign lesions. Some GGNs become larger, whereas others remain unchanged for years. We have previously reported that smoking history and large diameters are predictors for growth. However, the genetic differences among GGNs remain unclear. PATIENTS AND METHODS: GGNs with ground-glass component of ≥50% on a thin-section computed tomography scan that were resected between 2012 and 2014 were evaluated for clinicopathological features and the presence of EGFR/KRAS/ALK/HER2 mutations. 'Incidence of 2-mm growth' and 'Time to 2-mm growth' were analyzed according to the mutational status. RESULTS: Among 104 GGNs in 96 patients, this study included 3 atypical adenomatous hyperplasia (AAH), 19 adenocarcinoma in situ (AIS), 27 minimally invasive adenocarcinoma (MIA), and 55 invasive adenocarcinoma (IA). Among the 71 lesions evaluable for growth, 30 GGNs exhibited growth and 5 lesions remained unchanged for ≥2 years before surgery was carried out. We identified mutations or rearrangements in 75% of GGNs (78/104). EGFR mutations were noted in 64% of samples, KRAS in 4%, ALK in 3%, and HER2 in 4%. The remaining 26 quadruple-negative tumors were significantly associated with AAH/AIS (P < 0.01) and no-growth (P < 0.01) compared with driver mutation-positive tumors, whereas EGFR mutation-positive tumors were correlated with MIA/IA (P < 0.01) and growth (P < 0.01) compared with EGFR-negative tumors. CONCLUSIONS: Three fourths of resected GGNs were positive for EGFR, KRAS, ALK, or HER2 mutations. Quadruple-negative tumors were associated with a lack of GGN growth, whereas EGFR mutation-positive tumors displayed a correlation with growth.

Clinical application of amplicon-based next-generation sequencing to therapeutic decision making in lung cancer.

BACKGROUND: The clinical implementation of genomic profiling for lung cancer with high-throughput, multiplex tests is warranted to allow prioritization of appropriate therapies for individual patients. We have now applied such testing to detect actionable mutations that may inform treatment recommendations in lung cancer. PATIENTS AND METHODS: We prospectively applied amplicon sequencing panels that cover both mutational hotspots in 22 genes related to lung and colon tumorigenesis as well as 72 major variants of ALK, RET, ROS1, and NTRK1 fusion transcripts. We then determined the proportion of patients who received genotype-directed therapy and their overall survival (OS). RESULTS: Tumor specimens from 110 patients with lung cancer recruited between July 2013 and March 2015 were analyzed. The most common genetic alterations were TP53 mutations in 42 patients, followed by EGFR mutations in 25, STK11 mutations in 12, and KRAS mutations in 10. Potentially actionable mutations were identified in 44 patients including 50% of those with adenocarcinoma and 14% of those with squamous cell carcinoma. The OS of patients with advanced or recurrent cancer who had an actionable mutation and received targeted therapy (median OS not achieved) was significantly longer than that of those with no mutation (18.1 months, P = 0.041) or of those with a mutation not so treated (6.1 months, P = 0.0027). CONCLUSIONS: Multiplex genomic testing was performed on formalin-fixed, paraffin-embedded tumor specimens with a success rate of ≥95%. Such testing can assist physicians in matching patients with approved or experimental targeted treatments. CLINICAL TRIAL REGISTRATION: The University Medical Hospital Information Network (UMIN) Clinical Trials Registry under the identifier UMIN000014782.

A randomized, double-blind, placebo-controlled, phase III trial of erlotinib with or without a c-Met inhibitor tivantinib (ARQ 197) in Asian patients with previously treated stage IIIB/IV nonsquamous nonsmall-cell lung cancer harboring wild-type epidermal growth factor receptor (ATTENTION study).

BACKGROUND: A previous randomized phase II study demonstrated that the addition of a c-Met inhibitor tivantinib to an epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib might prolong progression-free survival (PFS) in patients with previously treated, nonsquamous nonsmall-cell lung cancer (NSCLC). On a subset analysis, the survival benefit was greater in patients with wild-type EGFR (WT-EGFR) than in those with activating EGFR mutations. Herein, this phase III study compared overall survival (OS) between Asian nonsquamous NSCLC patients with WT-EGFR who received erlotinib plus tivantinib (tivantinib group) or erlotinib plus placebo (placebo group). METHODS: A total of 460 NSCLC patients were planned to be randomized to the tivantinib or placebo group. Primary end point was OS. Secondary end points were PFS, tumor response, and safety. Tissue was collected for biomarker analysis, including c-Met and HGF expression. RESULTS: Enrollment was stopped when 307 patients were randomized, following the Safety Review Committee's recommendation based on an imbalance in the interstitial lung disease (ILD) incidence between the groups. ILD developed in 14 patients (3 deaths) and 6 patients (0 deaths) in the tivantinib and the placebo groups, respectively. In the enrolled patients, median OS was 12.7 and 11.1 months in the tivantinib and the placebo groups, respectively [hazard ratio (HR) = 0.891, P = 0.427]. Median PFS was 2.9 and 2.0 months in the tivantinib and the placebo groups, respectively (HR = 0.719, P = 0.019). The commonly observed grade ≥ 3 adverse events in the tivantinib group were neutropenia (24.3%), leukopenia (18.4%), febrile neutropenia (13.8%), and anemia (13.2%). CONCLUSIONS: This study was prematurely terminated due to the increased ILD incidence in the tivantinib group. Although this study lacked statistical power because of the premature termination and did not demonstrate an improvement in OS, our results suggest that tivantinib plus erlotinib might improve PFS than erlotinib alone in nonsquamous NSCLC patients with WT-EGFR. TRIAL REGISTRATION NUMBER: NCT01377376.

Time to first cigarette and lung cancer risk in Japan.

BACKGROUND: Cigarette smoking is the major cause of lung cancer (LC). Although the time to first cigarette (TTFC) of the day is a distinct indicator of nicotine dependence, little information is available on its possible relation to LC. PATIENTS AND METHODS: This case-control study includes a total of 1572 incident LC cases and 1572 non-cancer controls visiting for the first time the Aichi Cancer Center Hospital between 2001 and 2005. We estimated the odds ratio (OR) and 95% confidence interval (CI) for TTFC using a logistic regression model after adjustment for several potential confounders. RESULTS: TTFC was inversely associated with the risk of LC. This association was consistent across histological subtypes of LC. For all LCs considered among ever smokers and after accurate allowance for smoking quantity and duration, besides other relevant covariates, compared with TTFC >60 min, the adjusted ORs were 1.08 (95% CI, 0.73-1.61) for TTFC of 31-60 min, 1.40 (0.98-2.01) for 6-30 min and 1.86 (1.28-2.71) for within 5 min (Ptrend, < 0.001). Statistically marginally significant heterogeneity by histological subtype was observed (Pheterogeneity, 0.002). CONCLUSIONS: Nicotine dependence, as indicated by the TTFC, is associated with increased risk of LC and is therefore an independent marker of exposure to tobacco smoking.

An evaluation study of EGFR mutation tests utilized for non-small-cell lung cancer in the diagnostic setting.

BACKGROUND: Epidermal growth factor receptor (EGFR) mutation is predictive for the efficacy of EGFR tyrosine kinase inhibitors in advanced non-small-cell lung cancer (NSCLC) treatment. We evaluated the performance, sensitivity, and concordance between five EGFR tests. MATERIALS AND METHODS: DNA admixtures (n = 34; 1%-50% mutant plasmid DNA) and samples from NSCLC patients [116 formalin-fixed paraffin-embedded (FFPE) tissue, 29 matched bronchofiberscopic brushing (BB) cytology, and 20 additional pleural effusion (PE) cytology samples] were analyzed. EGFR mutation tests were PCR-Invader, peptide nucleic acid-locked nucleic acid PCR clamp, direct sequencing, Cycleave, and Scorpion Amplification Refractory Mutation System (ARMS). Analysis success, mutation status, and concordance rates were assessed. RESULTS: All tests except direct sequencing detected four mutation types at ≥1% mutant DNA. Analysis success rates were 91.4%-100% (FFPE) and 100% (BB and PE cytology), respectively. Inter-assay concordance rates of successfully analyzed samples were 94.3%-100% (FFPE; kappa coefficients: 0.88-1.00), 93.1%-100% (BB cytology; 0.86-1.00), and 85.0%-100% (PE cytology; 0.70-1.00), and 93.1%-96.6% (0.86-0.93) between BB cytology and matched FFPE. CONCLUSIONS: All EGFR assays carried out comparably in the analysis of FFPE and cytology samples. Cytology-derived DNA is a viable alternative to FFPE samples for analyzing EGFR mutations.

Surgical implications of the new IASLC/ATS/ERS adenocarcinoma classification.

A new adenocarcinoma classification was recently introduced by a joint working group of the International Association for the Study of Lung Cancer (IASLC), American Thoracic Society (ATS) and European Respiratory Society (ERS). A distinction is made between pre-invasive lesions, and minimally invasive and invasive adenocarcinoma. The confusing term "bronchioloalveolar carcinoma" is not used any more and new subcategories include adenocarcinoma in situ and minimally invasive adenocarcinoma. Due to a renewed interest in screen-detected nodules and early-stage lung cancers of <2 cm, this classification also has profound implications for thoracic surgeons. In this article, surgical topics are discussed: the role of a minimally invasive approach, especially video-assisted thoracic surgery, limited resection for early-stage lung cancer, the extent of lymph node dissection, the accuracy of intraoperative frozen section analysis, management of multiple lung nodules and prognostic factors in operated patients. Specific key issues are presented based on the current evidence and areas of surgical uncertainty are defined providing a basis for further studies. Thoracic surgeons will play a major role in the application and global introduction of this new adenocarcinoma classification. The remaining controversies regarding the precise diagnosis and management of early-stage lesions will have to be resolved by multidisciplinary and international collaboration.

Final overall survival analysis from the phase III J-ALEX study of alectinib versus crizotinib in ALK inhibitor-naïve Japanese patients with ALK-positive non-small-cell lung cancer.

BACKGROUND: Mature progression-free survival (PFS) data from the phase III J-ALEX study showed superiority for alectinib versus crizotinib [hazard ratio (HR) 0.37, 95% confidence interval (CI) 0.26-0.52; median PFS 34.1 versus 10.2 months, respectively] in advanced ALK (anaplastic lymphoma kinase)-positive non-small-cell lung cancer (NSCLC). Overall survival (OS) data were immature (HR 0.80, 99.8799% CI 0.35-1.82) at the time of data cut-off (30 June 2018). We report final OS data after ≥5 years of follow-up. PATIENTS AND METHODS: ALK inhibitor naive Japanese patients who were chemotherapy naive or had received one prior chemotherapy regimen were enrolled. Patients were randomized to receive alectinib 300 mg (n = 103) or crizotinib 250 mg (n = 104) twice daily until progressive disease, unacceptable toxicity, death, or withdrawal. The primary endpoint was independent review facility-assessed PFS, with OS (not fully powered) as a secondary endpoint. RESULTS: Median duration of OS follow-up was 68.6 months with alectinib and 68.0 months with crizotinib. Treatment with alectinib did not prolong OS relative to crizotinib (HR 1.03, 95.0405% CI 0.67-1.58; P = 0.9105). Five-year OS rates were 60.9% (95% CI 51.4-70.3) with alectinib and 64.1% (95% CI 54.9-73.4) with crizotinib. In total, 91.3% (n = 95/104) of crizotinib-treated patients and 46.6% (n = 48/103) of alectinib-treated patients received at least one subsequent anticancer therapy. After study drug discontinuation, 78.8% of patients in the crizotinib arm switched to alectinib, while 10.7% of patients in the alectinib arm switched to crizotinib as a first subsequent anticancer therapy. Patients randomized to crizotinib tended to switch treatment earlier than those randomized to alectinib. CONCLUSION: Final OS analysis from J-ALEX did not show superiority of alectinib to crizotinib; this result was most likely confounded by treatment crossover. Alectinib remains a standard of care for the treatment of patients with advanced ALK-positive NSCLC.

Consensus for HER2 alterations testing in non-small-cell lung cancer.

Human epidermal growth factor receptor 2 (HER2) is a transmembrane glycoprotein receptor with intracellular tyrosine kinase activity. Its alterations, including mutation, amplification and overexpression, could result in oncogenic potential and have been detected in many cancers such as non-small-cell lung cancer (NSCLC). Such alterations are, in general, considered markers of poor prognosis. Anti-HER2 antibody-drug conjugates, e.g. trastuzumab deruxtecan (T-DXd, DS-8201) and disitamab vedotin (RC48), were recently approved for HER2-positive breast and gastric cancers. Meanwhile, several HER2-targeted drugs, such as T-DXd, neratinib, afatinib, poziotinib and pyrotinib, have been evaluated in patients with advanced NSCLC, with several of them demonstrating clinical benefit. Therefore, identifying HER2 alterations is pivotal for NSCLC patients to benefit from these targeted therapies. Recent guidelines on HER2 testing were developed for breast and gastric cancer, however, and have not been fully established for NSCLC. The expert group here reached a consensus on HER2 alteration testing in NSCLC with the focus on clinicopathologic characteristics, therapies, detection methods and diagnostic criteria for HER2-altered NSCLC patients. We hope this consensus could improve the clinical management of NSCLC patients with HER2 alterations.

Identification of a metastasis signature and the DLX4 homeobox protein as a regulator of metastasis by combined transcriptome approach.

Although widespread metastasis is the major cause of human lung cancer-related deaths, its underlying mechanism remains largely unclear. Our genome-wide comparison of the expression profiles of a highly metastatic lung cancer cell line, NCI-H460-LNM35 (LNM35), and its parental clone, NCI-H460-N15 (N15), resulted in the identification of a cancer metastasis signature composed of 45 genes. Through gene ontology analysis, our study also provided insights into how this 45-gene metastasis signature may contribute to the acquisition of metastatic potential. By applying the signature to datasets of human cancer cases, we could demonstrate significant associations with a subset of cases with poor prognosis not only for the two datasets of cancers of the lung but also for cancers of the breast. Furthermore, we were able to show that enforced expression of the DLX4 homeobox gene, which was identified as a gene with significant downregulation in LNM35 as well as with significant association with favorable prognosis for lung cancer patients, markedly inhibited in vitro motility and invasion as well as in vivo metastasis via both hematogenous and lymphogenous routes. Taken together, these findings indicate that our combined transcriptome analysis is an efficient approach in the search for genes possessing both clinical usefulness in terms of prognostic prediction in human cancer cases and clear functional relevance for studying cancer biology in relation to metastasis.

Absence of hereditary p53 mutations in 10 familial leukemia pedigrees.

Germline p53 mutations have been identified in the Li-Fraumeni syndrome but the role of such mutations in familial leukemia is not established. The p53 gene was examined by single-strand conformation polymorphism analysis of exons 4-8 in 10 families with multiple members affected with leukemia. The diagnoses included acute and chronic leukemias and Hodgkin's disease. Identified in two families were p53 mutations that were nonhereditary. These included a 2-bp deletion in exon 6 found in the lymphoblast DNA of one child whose sibling, cousin, and several adult relatives had acute leukemia. The other nonhereditary p53 mutation was a transition at codon 248 (CGG to CAG, arginine to glutamine) found in the lymphoblasts of a patient with a preleukemic syndrome and acute lymphoblastic leukemia (ALL) whose brother is a long-term survivor of ALL. Thus, p53 mutations were found to occur in two families but both were nonhereditary. Moreover, in the remaining eight families no p53 mutation was identified in the regions of p53 where most mutations have been found in other cancers. Although p53 mutations sometimes may be present, they do not appear to be a primary event responsible for hereditary susceptibility to familial leukemia. This study suggests involvement of other genes or mechanisms.

Hereditary and acquired p53 gene mutations in childhood acute lymphoblastic leukemia.

The p53 gene was examined in primary lymphoblasts of 25 pediatric patients with acute lymphoblastic leukemia by the RNase protection assay and by single strand conformation polymorphism analysis in 23 of 25 cases. p53 mutations were found to occur, but at a low frequency (4 of 25). While all four mutations were identified by single strand conformation polymorphism, the comparative sensitivity of RNase protection was 50% (2 of 4). Heterozygosity was retained at mutated codons in 3 of 4 cases. One pedigree was consistent with the Li-Fraumeni syndrome, and bone marrow from both diagnosis and remission indicated a germline G to T transversion at codon 272 (valine to leucine). Although members of another family were affected with leukemia, a 2-bp deletion in exon 6 was nonhereditary. The other two nonhereditary p53 mutations included a T to G transversion at codon 270 (phenylalanine to cysteine) and a G to C transversion at codon 248 (arginine to proline). These data support the role of both hereditary and acquired p53 mutations in the pathogenesis and/or progression of some cases of childhood acute lymphoblastic leukemia.