Cancer: the big questions to address in coming years

Maternal obesity, pregnancy weight gain, and birth weight and risk of colorectal cancer

OBJECTIVE

Colorectal cancer (CRC) is a leading cause of cancer-related death worldwide. Obesity is a well-established risk factor for CRC, and fetal or developmental origins of obesity may underlie its effect on cancer in adulthood. We examined associations of maternal obesity, pregnancy weight gain, and birth weight and CRC in adult offspring.

DESIGN

The Child Health and Development Studies is a prospective cohort of women receiving prenatal care between 1959 and 1966 in Oakland, California (N=18 751 live births among 14 507 mothers). Clinical information was abstracted from mothers' medical records 6 months prior to pregnancy through delivery. Diagnoses of CRC in adult (age ≥18 years) offspring were ascertained through 2019 by linkage with the California Cancer Registry. We used Cox proportional hazards models to estimate adjusted HR (aHR); we examined effect measure modification using single-referent models to estimate the relative excess risk due to interaction (RERI).

RESULTS

68 offspring were diagnosed with CRC over 738 048 person-years of follow-up, and half (48.5%) were diagnosed younger than age 50 years. Maternal obesity (≥30 kg/m²) increased the risk of CRC in offspring (aHR 2.51, 95% CI 1.05 to 6.02). Total weight gain modified the association of rate of early weight gain (RERI -4.37, 95% CI -9.49 to 0.76), suggesting discordant growth from early to late pregnancy increases risk. There was an elevated association with birth weight (≥4000 g: aHR 1.95, 95% CI 0.8 to 4.38).

CONCLUSION

Our results suggest that in utero events are important risk factors for CRC and may contribute to increasing incidence rates in younger adults.

Colorectal Cancer in Younger Adults

Contrary to decreasing incidence rate of colorectal cancer (CRC) in older adults, incidence rates have nearly doubled in younger adults (age <50 years) in the United States since the early 1990s. A similar increase has been observed across the globe. Despite overall population trends in aging, about 15% of CRCs will be diagnosed in younger adults by 2030. The mechanisms and factors contributing to early-onset CRC (EOCRC) remain puzzling, especially because most young adults diagnosed with CRC have no known risk factors or predisposing conditions, such as family history of CRC or polyps or a hereditary syndrome (eg, Lynch syndrome, polyposis). In this up-to-date review, we discuss the current knowledge of EOCRC, including epidemiology, risk factors, clinical and molecular features, treatment and survival, and recognition and screening strategies.

The Chinese Children and Families Cohort Study: The Nutrition, Physical Activity, and Ultraviolet Radiation Data Collection

This article reports the study design, methodological issues and early results of a pilot study testing methods for collecting nutrition, physical activity, and ultraviolet (UV) radiation exposure data in a groundbreaking study in China. Epidemiological studies suggest that exposures across the entire life course, including in utero, early childhood, and adolescence, may be important in the etiology of adult cancers and other chronic diseases. The Chinese Children and Families Cohort Study intends to follow-up subjects from the 1993 to 1995 Community Intervention Program of folic acid supplementation for the prevention of neural tube defects. This cohort is unique in that only folic acid exposure during pregnancy varies between groups as other supplements were not available, and there were nutrient deficiencies in the populations. Prior to launching a large-scale follow-up effort, a pilot study was conducted to assess the feasibility of recontacting original study participants to collect extensive diet, physical activity, and UV radiation exposure data in this population. The pilot study included 92 mothers and 184 adolescent children aged 14 to 17 years from 1 urban and 1 rural Community Intervention Program site. Subjects completed a Food Frequency Questionnaire, a 3-day food record, a physical activity questionnaire, a 3-day sun exposure diary together with 3 days of personal UV dosimetry, and 7 days of pedometry measurements and provided blood, saliva, and toenail samples. Grip strength and body composition measurements were taken, and ambient solar UV radiation was monitored in both study sites. While most of the assessments were successful, future studies would likely require different dietary intake instruments. The purpose of this report is to describe the study design and methodological issues emerging from this pilot work relevant for the follow-up of this large birth cohort.

Reproductive health risks associated with occupational exposures to antineoplastic drugs in health care settings: a review of the evidence

OBJECTIVES

Antineoplastic drugs are known reproductive and developmental toxicants. Our objective was to review the existing literature of reproductive health risks to workers who handle antineoplastic drugs.

METHODS

A structured literature review of 18 peer-reviewed, English language publications of occupational exposure and reproductive outcomes was performed.

RESULTS

Although effect sizes varied with study size and population, occupational exposure to antineoplastic drugs seems to raise the risk of both congenital malformations and miscarriage. Studies of infertility and time to pregnancy also suggested an increased risk for subfertility.

CONCLUSIONS

Antineoplastic drugs are highly toxic in patients receiving treatment, and adverse reproductive effects have been well documented in these patients. Health care workers with long-term, low-level occupational exposure to these drugs also seem to have an increased risk of adverse reproductive outcomes. Additional precautions to prevent exposure should be considered.

Challenges and opportunities in research on early-life events/exposures and cancer development later in life

It is becoming increasingly evident that early-life events and exposures have important consequences for cancer development later in life. However, epidemiological studies of early-life factors and cancer development later in life have had significant methodological challenges such as the long latency period, the distinctiveness of each cancer, and large number of subjects that must be studied, all likely to increase costs. These traditional hurdles might be mitigated by leveraging several existing large-scale prospective studies in the United States (US) and globally, as well as birth databases and birth cohorts, in order to launch both association and mechanistic studies of early-life exposures and cancer development later in life. Dedicated research funding will be needed to advance this paradigm shift in cancer research, and it seems justified by its potential to produce transformative understanding of how cancer develops over the life-course. This in turn has the potential to transform cancer prevention strategies through interventions in early-life rather than later in life, as is the current practice, where it is perhaps less effective.