Total calcium, dairy foods and risk of colorectal cancer: a prospective cohort study of younger US women

BACKGROUND

Although colorectal cancer (CRC) incidence is declining among adults aged ≥65 years, CRC incidence in younger adults has been rising. The protective role of calcium in colorectal carcinogenesis has been well established, but evidence is lacking on whether the association varies by age at diagnosis. We investigated the association between total calcium intake and risk of overall CRC and CRC before age 55 years.

METHODS

In the Nurses' Health Study II (1991-2015), 94 205 women aged 25-42 years at baseline were included in the analysis. Diet was assessed every 4 years through validated food frequency questionnaires. Multivariable-adjusted hazard ratios (HRs) and 95% CIs for CRC were estimated using the Cox proportional hazards model.

RESULTS

We documented 349 incident CRC cases during 2 202 604 person-years of follow-up. Higher total calcium intake was associated with a reduced risk of CRC. Compared with those with <750 mg/day of total calcium intake, the HR of CRC was 0.61 (95% CI, 0.38-0.97) for those who consumed ≥1500 mg/day (P for trend = 0.01). The HR per 300 mg/day increase was 0.85 (95% CI, 0.76-0.95). There was a suggestive inverse association between total calcium intake and CRC before age 55 years (HR per 300 mg/day increase, 0.87; 95% CI, 0.75-1.00), suggesting the importance of calcium intake in the younger population.

CONCLUSIONS

In a cohort of younger women, which reflects the birth cohorts, time periods and age ranges paralleling the recent rise in CRC, higher calcium intake was associated with a decreased risk of CRC.

Haplotype-resolved germline and somatic alterations in renal medullary carcinomas

BACKGROUND

Renal medullary carcinomas (RMCs) are rare kidney cancers that occur in adolescents and young adults of African ancestry. Although RMC is associated with the sickle cell trait and somatic loss of the tumor suppressor, SMARCB1, the ancestral origins of RMC remain unknown. Further, characterization of structural variants (SVs) involving SMARCB1 in RMC remains limited.

METHODS

We used linked-read genome sequencing to reconstruct germline and somatic haplotypes in 15 unrelated patients with RMC registered on the Children's Oncology Group (COG) AREN03B2 study between 2006 and 2017 or from our prior study. We performed fine-mapping of the HBB locus and assessed the germline for cancer predisposition genes. Subsequently, we assessed the tumor samples for mutations outside of SMARCB1 and integrated RNA sequencing to interrogate the structural variants at the SMARCB1 locus.

RESULTS

We find that the haplotype of the sickle cell mutation in patients with RMC originated from three geographical regions in Africa. In addition, fine-mapping of the HBB locus identified the sickle cell mutation as the sole candidate variant. We further identify that the SMARCB1 structural variants are characterized by blunt or 1-bp homology events.

CONCLUSIONS

Our findings suggest that RMC does not arise from a single founder population and that the HbS allele is a strong candidate germline allele which confers risk for RMC. Furthermore, we find that the SVs that disrupt SMARCB1 function are likely repaired by non-homologous end-joining. These findings highlight how haplotype-based analyses using linked-read genome sequencing can be applied to identify potential risk variants in small and rare disease cohorts and provide nucleotide resolution to structural variants.

Plasma sex hormones and risk of conventional and serrated precursors of colorectal cancer in postmenopausal women

BACKGROUND

Sex hormones have been suggested to play a role in colorectal cancer (CRC), but their influence on early initiation of CRC remains unknown.

METHODS

We retrospectively examined the associations with risk of CRC precursors, including conventional adenomas and serrated polyps, for plasma estrone, estradiol, free estradiol, testosterone, free testosterone, sex hormone-binding globulin (SHBG), and the ratio of estradiol to testosterone among 5404 postmenopausal women from the Nurses' Health Study I and II. Multivariable logistic regression was used to calculate the odds ratio (OR) and 95% confidence intervals (CI). Given multiple testing, P < 0.005 was considered statistically significant.

RESULTS

During 20 years of follow-up, we documented 535 conventional adenoma cases and 402 serrated polyp cases. Higher concentrations of SHBG were associated with lower risk of conventional adenomas, particularly advanced adenomas (multivariable OR comparing the highest to the lowest quartile, 0.40, 95% CI 0.24-0.67, P for trend < 0.0001). A nominally significant association was found for SHBG with lower risk of large serrated polyps (≥ 10 mm) (OR, 0.47, 95% CI 0.17-1.35, P for trend = 0.02) as well as free estradiol and free testosterone with higher risk of conventional adenomas (OR, 1.54, 95% CI 1.02-2.31, P for trend = 0.03 and OR, 1.33, 95% CI 0.99-1.78, P for trend = 0.03, respectively).

CONCLUSIONS

The findings suggest a potential role of sex hormones, particularly SHBG, in early colorectal carcinogenesis.