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25th May 2021
Cancer of the breast is the most common form of cancer in women although with an early diagnosis, the 5-year survival prognosis ranges from 86 to 99%. Nevertheless, women who survive breast cancer have a 17% increased risk for a second cancer compared to the general population. One factor known to be associated with cancer is obesity with one US study estimating that 40% of all cancer diagnoses occurred in people who were either overweight or obese. However, while much attention has been paid to the effect of obesity on the development of an initial cancer, far less is known about how obesity impacts on the development of a second cancer. As a result, a team from Kaiser Permanente, Denver, US, sought to examine the association between body mass index (BMI) and a second cancer among women who survived invasive breast cancer. Data were extracted from an electronic database and a surveillance tumour registry which provided information on the incidence and type of secondary cancers that occurred. Height and weight measurements within two years prior through one year after the date of the initial breast cancer diagnosis were used to calculate the BMI. All women included had surgery as part of their initial breast cancer and had no evidence of a second cancer one year later. The study outcomes included all second cancers, cancers for which there was a known association with obesity (e.g., oesophageal adenocarcinoma), and ER-positive second breast cancers.
A total of 6481 women were included in the analysis with a mean age of 60.2 years, of whom 33.4% were classed as overweight or obese (33.8%) at the time of their initial breast cancer diagnosis. During a median follow-up of 88 months, 822 (12.7%) women developed a second cancer, of which 508 (61.8%) were obesity-related and 333 (40.5%) were breast cancer, the majority of which (69.4%) were ER-positive. The authors calculated that every 5 unit increase in BMI was associated with a 7% increased risk of developing any second cancer (relative risk, RR = 1.07, 95% CL 1.01–1.14), a 13% increased for an obesity-related cancer and by 15% for a second ER-positive breast cancer.
The authors calculated that the risk of a second cancer was increased by 5% for every 5 unit increase in BMI. They concluded that these data had important public health implications given the prevalence of obesity and underscored the need for effective preventative strategies.
Feigelson HS et al. Body Mass Index and Risk of Second Cancer Among Women with Breast Cancer. J Natl Cancer Inst 2021
2nd December 2020
Preliminary data has suggested that being overweight can contribute towards poorer health outcomes for those with COVID-19 and such patients are more likely to require mechanical ventilation. In contrast, far less attention has been paid to the possible relationship between low body mass index (BMI) and clinical outcomes. As a result, a team from the Department of Medicine, Donald and Barbara Zucker School of Medicine, New York, USA, set out to retrospectively analyse the overall association between different levels of BMI and outcomes for patients with COVID-19. The team included 10,861 patients admitted with COVID-19 into their hospital during March to the end of April 2020. The BMI was documented on admission to hospital as either self-reported or obtained from nursing staff. It was classified as follows with the BMI range in brackets: underweight (under 18.5kg/m2), normal (18.5 to 24.9), overweight (25 to 29.9) and obese class I (30 – 34), II (35 – 39) and III (40 or more). Data on patient outcomes were collected from electronic health records and the primary outcome used was the need for mechanical ventilation and death. All patients were followed until discharge, death or until early May 2020.
For the 10,861 patients with a median age of 65 years (59.6% male), 2.2% were classed as underweight, 23.1% normal, 37% overweight and 37.7% obese. In total, 2,220 (20.4%) patients required mechanical ventilation and 2,596 (23.9%) died. There were significant differences in both the need for mechanical ventilation and death among the different BMI categories. For instance, 12.4% of those classed as underweight and 73.8% of those classed as obese (all classes) required mechanical ventilation. In addition, 39.2% of those who were underweight died as did 62.9% of those in the obese category. Regression analysis revealed that patients who were underweight an increased risk of death (hazard ratio, HR = 1.46, 95% CI 1.17 – 1.81) which was actually higher than the risk for those with class III obesity (HR – 1.23, 95% CI 1.03 – 1.48). The reason for the increased risk of death among underweight patients was unclear but the authors speculated that this may have been related to increased frailty.
They concluded that the findings suggest that worse outcomes after COVID-19 are not restricted to obese patients and those who are underweight are also at a higher risk.
Kim T et al. Body Mass Index as a Risk Factor for Clinical Outcomes in Patients Hospitalised with COVID- 19 in New York. Obesity 2020 doi.org/10.1002/oby.23076