Evaluation of NTRK expression and fusions in a large cohort of early-stage lung cancer

Tropomyosin receptor kinases (TRK) are attractive targets for cancer therapy. As TRK-inhibitors are approved for all solid cancers with detectable fusions involving the Neurotrophic tyrosine receptor kinase (NTRK)-genes, there has been an increased interest in optimizing testing regimes. In this project, we wanted to find the prevalence of NTRK fusions in a cohort of various histopathological types of early-stage lung cancer in Norway and to investigate the association between TRK protein expression and specific histopathological types, including their molecular and epidemiological characteristics. We used immunohistochemistry (IHC) as a screening tool for TRK expression, and next-generation sequencing (NGS) and fluorescence in situ hybridization (FISH) as confirmatory tests for underlying NTRK-fusion. Among 940 cases, 43 (4.6%) had positive TRK IHC, but in none of these could a NTRK fusion be confirmed by NGS or FISH. IHC-positive cases showed various staining intensities and patterns including cytoplasmatic or nuclear staining. IHC-positivity was more common in squamous cell carcinoma (LUSC) (10.3%) and adenoid cystic carcinoma (40.0%), where the majority showed heterogeneous staining intensity. In comparison, only 1.1% of the adenocarcinomas were positive. IHC-positivity was also more common in men, but this association could be explained by the dominance of LUSC in TRK IHC-positive cases. Protein expression was not associated with differences in time to relapse or overall survival. Our study indicates that NTRK fusion is rare in early-stage lung cancer. Due to the high level of false positive cases with IHC, Pan-TRK IHC is less suited as a screening tool for NTRK-fusions in LUSC and adenoid cystic carcinoma.

"Evaluation of ROS1 expression and rearrangements in a large cohort of early-stage lung cancer"

BACKGROUND

ROS1 fusion is an infrequent, but attractive target for therapy in patients with metastatic non- small-cell lung cancer. In studies on mainly late-stage disease, the prevalence of ROS1 fusions is about 1-3%. In early-stage lung cancer ROS1 might also provide a fruitful target for neoadjuvant or adjuvant therapy. In the present study, we investigated the prevalence of ROS1 fusion in a Norwegian cohort of early-stage lung cancer. We also explored whether positive ROS1 immunohistochemical (IHC) stain was associated with certain mutations, clinical characteristics and outcomes.

METHODS

The study was performed using biobank material from 921 lung cancer patients including 542 patients with adenocarcinoma surgically resected during 2006-2018. Initially, we screened the samples with two different IHC clones (D4D6 and SP384) targeting ROS1. All samples that showed more than weak or focal staining, as well as a subgroup of negative samples, were analyzed with ROS1 fluorescence in situ hybridization (FISH) and next-generation sequencing (NGS) with a comprehensive NGS DNA and RNA panel. Positive ROS1-fusion was defined as those samples positive in at least two of the three methods (IHC, FISH, NGS).

RESULTS

Fifty cases were IHC positive. Of these, three samples were both NGS and FISH-positive and considered positive for ROS1 fusion. Two more samples were FISH positive only, and whilst IHC and NGS were negative. These were also negative with Reverse Transcription quantitative real time Polymerase Chain Reaction (RT-qPCR). The prevalence of ROS1 fusion in adenocarcinomas was 0.6%. All cases with ROS1 fusion had TP53 mutations. IHC-positivity was associated with adenocarcinoma. Among SP384-IHC positive cases we also found an association with never smoking status. There was no association between positive IHC and overall survival, time to relapse, age, stage, sex or pack-year of smoking.

CONCLUSIONS

ROS1 seems to be less frequent in early-stage disease than in advanced stages. IHC is a sensitive, but less specific method and the results need to be confirmed with another method like FISH or NGS.

Educational differences in life expectancy over five decades among the oldest old in Norway

BACKGROUND

Socioeconomic inequalities in life expectancy have been shown among the middle aged and the youngest of the old individuals, but the situation in the oldest old is less clear. The aim of this study was to investigate trends in life expectancy at ages 85, 90 and 95 years by education in Norway in the period 1961-2009.

METHODS

This was a register-based population study including all residents in Norway aged 85 and over. Individual-level data were provided by the Central Population Register and the National Education Database. For each decade during 1961-2009, death rates by 1-year age groups were calculated separately for each sex and three educational categories. Annual life tables were used to calculate life expectancy at ages 85 (e85), 90 (e90) and 95 (e95).

RESULTS

Educational differentials in life expectancy at each age were non-significant in the early decades, but became significant over time. For example, for the decade 2000-9, a man aged 90 years with primary education had a life expectancy of 3.4 years, while a man with tertiary education could expect to live for 3.8 years. Similar numbers in women were 4.1 and 4.5 years, respectively. Even among 95-year-old men, statistically significant differences in life expectancy were found by education in the two last decades.

CONCLUSION

Education matters regarding remaining life expectancy also for the oldest old in Norway. Life expectancy at these ages is low, so a growth of 0.5 years in the life expectancy differential is sizeable.

Trends in remaining life expectancy at retirement age (65 years) by educational level in Norway 1961-2009

<p><em><strong>Background</strong></em>: Over the last half a century education based inequalities in life expectancy have increased in younger populations, but our knowledge of long-term trends in old-age life expectancy differentials is sparse. We investigated the trends in remaining life expectancy at age 65 (e65) according to education in Norway for the period 1961-2009.</p><p><em><strong>Methods</strong></em>: This was a register-based population study including all Norwegian residents aged 65 years and older. Individual-level data were provided by the Central Population Registry and the National Educational Database. We classified education into higher and lower education and constructed one life table for each calendar year, sex, and educational group. We tested for trends using weighted least square regression models.</p><p><em><strong>Results</strong></em>: e65 increased over the observation period for all educational groups, but the difference in e65 increased by 0.060 life years per calendar year in men and 0.025 life years per calendar year in women (P &lt; 0.001). The increase in e65 in less-educated men slowed in the 1980s and 1990s, whereas e65 in less-educated women decelerated from the 1980s, and significantly so from 2001 (P = 0.029).</p><p><em><strong>Conclusions</strong></em>: Educational-based inequalities in e65 increased over the last half century. The increase seems to be temporal in men and might be ongoing in women. Increasing inequalities in e65 challenge public health policy and will become increasingly important in the ageing societies of the future. In addition, they imply increasing deviation from the overall life expectancy of the population, which forms the basis of the recently implemented adjustment of pension levels according to life expectancy. Divergent trends in e65 according to educational level may also have implications for future demographic projections.</p>

Trends in educational inequalities in old age mortality in Norway 1961-2009: a prospective register based population study

BACKGROUND

The vast majority of deaths occur in older adults. Paradoxically, knowledge on long-term trends in mortality inequalities among the aged, and particularly for those aged 80 years and over, is sparse. The historical trends in size and impact of socioeconomic inequalities on old age mortality are important to monitor because they may give an indication on future burden of inequalities. We investigated trends in absolute and relative educational inequalities in old age mortality in Norway between 1961 and 2009.

METHODS

We did a register-based population study covering the entire Norwegian population aged 65-94 in the years 1961-2009 (1,534,513 deaths and 29,312,351 person years at risk). By examining 1-year mortality rates by gender, age and educational level we estimated trends in mortality rate ratios and rate differences.

RESULTS

On average, age-standardised absolute inequalities increased by 0.17 deaths per 1000 person-years per year in men (P<0.001), and declined by 0.07 deaths per 1000 person-years per year in women (P<0.001). Trends in rate differences were largest in men aged 75-84 years, but differed in direction by age group in women. The corresponding mean increase in age-standardised relative inequalities was 0.4% and 0.1% per year in men and women, respectively (P<0.001). Trends in rate ratios were largest in the youngest age groups for both genders and negligible among women aged 85-94 years.

CONCLUSIONS

While relative educational inequalities in old age mortality increased for both genders, absolute educational inequalities increased only temporarily in men and changed little among women. Our study show the importance of including absolute measures in inequality research in order to present a more complete picture of the burden of inequalities to policy makers. As even in older ages, inequalities represent an unexploited potential to public health, old age inequalities will become increasingly important as many countries are facing aging populations.

Trends in life expectancy by education in Norway 1961-2009

Educational attainment and longevity are strongly related. Large population studies covering long periods to provide evidence of trends in educational inequalities regarding life expectancy are scarce though, especially prior to the 1980s. Our objective was to document changes in life expectancy by education in Norway in the period 1961-2009, and to determine whether the patterns differ between sexes. This is a register-based population study of all Norwegian residents over 34 years, with data from the National Central Population Registry and the National Education Database. For each calendar year during 1961-2009, death rates by 1 year age groups were calculated separately for each sex and three educational categories (primary, secondary and tertiary). Annual life tables were used to calculate life expectancy at age 35 (e ( 35 )) and survival probability for the three age-intervals 35-44, 45-64, and 65-90. All education groups increased their e ( 35 ) over time, but inequalities in e ( 35 ) between tertiary and primary educational categories widened 5.3 years for men and 3.2 years for women during the study period. The probability for women with primary education to survive to age 64 did not improve from 1961 to 2009. The gain in life expectancy lagged about 10 years in lower compared to higher education groups which might suggest that improvements in life sustaining factors reach different segments of the population at different times. The widening of the gap seems to have partly tapered off over the last two decades, and the changes in life expectancy should be followed carefully in the future to document the development.