Science Spotlight

Diet trajectories: looking at post-diagnosis changes

From the Greenlee Group, Division of Public Health Sciences

Lifestyle factors, including dietary intake patterns, are known to contribute to risk for several types of cancer. Given the adverse health effects associated with some cancer treatments, diet is also an important factor for cancer survivors and medical care teams to consider in the period following a cancer diagnosis. Dietary recommendations from the American Cancer Society and the American Institute of Cancer Research emphasize fruit and vegetable intake, avoidance of high-fat and processed foods, and limited alcohol consumption for cancer survivors. However, current evidence suggests that these recommendations are not met by most cancer survivors. In a recent study from Dr. Heather Greenlee’s group in the Division of Public Health Sciences, researchers investigated how diet changes following a breast cancer diagnosis. The results were published in Breast Cancer Research and Treatment.

Dr. Zaixing Shi, a former postdoctoral fellow in the Greenlee group explained the rationale for the new study, “Population-based surveys in the US show that up to 92% of breast cancer survivors do not adhere to the nutrition recommendations for cancer survivors. However, very few studies examined the longitudinal trajectory of diet after a cancer diagnosis to understand the pattern of dietary change and identify the opportunity of intervention. Previous studies reported inconsistent findings regarding the change in fruit/vegetable intake. The inconsistency may be partly due to their analytical approach, which focused on the mean change and thus ignored the variability of change.” The authors leveraged a more powerful analytical technique to address this limitation, “we used a statistical method called group-based trajectory modeling to identify distinct diet trajectories. Group-based trajectory modeling (GBTM; see Nagin, 1999) is a type of analysis that aims at identifying clusters of participants, also known as trajectory groups, who followed similar developmental trajectories of a single outcome over a period of time,” said Dr. Shi. This was the first study to specifically investigate distinct diet trajectories in the period immediately following breast cancer diagnosis.

Dr. Shi described the study design, “There is a paucity of a large and well-characterized cohort of breast cancer survivors, which have limited analysis of long-term behavior change. This analysis used data from the Pathways Study, a large population-based prospective cohort of 4,505 women with newly diagnosed invasive breast cancer within Kaiser Permanente Northern California (see Kwan et al., 2008). This study enrolled a diverse and representative sample of breast cancer survivors and is enriched by longitudinally collected data on lifestyle behaviors from diagnosis to early survivorship.” Food frequency questionnaires were completed by study participants at baseline, 6 months, and 24 months post-diagnosis to assess dietary intake patterns.    

Graphical representation of diet trajectories for changes in fruit and vegetable, dietary fat, and alcohol in the 24 months following diagnosis of breast cancer.
Diet trajectories for changes in fruit and vegetable (top), dietary fat (middle), and alcohol (bottom) in the 24 months following diagnosis of breast cancer. Image from Dr. Zaixing Shi

The analysis included nearly 2900 women; the mean age was 61 years and the mean time from diagnosis to baseline assessment was two months. Three distinct diet trajectory groups were identified for fruit and vegetable intake, four groups for fat intake, and three groups for alcohol intake (see Figure). “The analyses showed that women may only slightly increase fruit/vegetable intake and temporarily reduce alcohol intake after a cancer diagnosis, while the majority of women consume insufficient fruits/vegetables and excessive dietary fat,” summarized Dr. Shi. The authors also found several factors significantly associated with distinct diet trajectories, including socioeconomic factors, race/ethnicity, and body mass index.

An overall take away from the study is that there is substantial room for dietary counseling of breast cancer survivors to facilitate achieving dietary recommendations. However, more questions have been generated that may be addressed in future studies, “This analysis suggests that breast cancer survivor’s psychosocial and physical health affect their diet trajectories after diagnosis. Notably, low optimism and social support and worsening in physical well-being and neuropathy symptoms were associated with unfavorable diet trajectories. These findings warrant further investigation and may help future dietary interventions identify breast cancer survivors who could be prioritized for dietary interventions,” said Dr. Shi.    

This work was supported by the National Cancer Institute.

Fred Hutch/UW Cancer Consortium member Dr. Heather Greenlee contributed to this research.

Shi Z, Rundle A, Genkinger JM, Cheung YK, Ergas IJ, Roh JM, Kushi LH, Kwan ML, Greenlee H. 2019. Distinct trajectories of fruits and vegetab les, dietary fat, and alcohol intake following a breast cancer diagnosis: the Pathways Study. Breast Cancer Research and Treatment. doi: 10.1007/s10549-019-05457-9.

Additional references:

Kwan ML, Ambrosone CB, Lee MM, Barlow J, Krathwohl SE, Ergas IJ, Ashley CH, Bittner JR, Darbinian J, Stronach K, Caan BJ, Davis W, Kutner SE, Quesenberry CP, Somkin CP, Sternfeld B, Wiencke JK, Zheng S, Kushi LH. 2008. The Pathways Study: a prospective study of breast cancer survivorship within Kaiser Permanente Northern California. Cancer Causes Control. 19(10):1065-1076. doi:10.1007/s10552-008-9170-5.

Nagin DS. 1999. Analyzing developmental trajectories: a semiparametric, group-based approach. Psychological Methods. 4(2):139 – 157.

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