The Multiethnic Cohort (MEC) was designed to study lifestyle and genetic factors in relation to cancer and other chronic diseases among more than 215,000 men and women aged 45 to 75 years living in either Hawaii or California. Patients were followed through linkage with the statewide Surveillance, Epidemiology, and End Results Registry (SEER) registries, the Hawaii Tumor Registry, California Cancer Registry, and Kaiser Permanente Hawaii (HPHI) electronic medical records.
This study evaluated weight changes from the time of BC surgery to 4 years postdiagnosis for MEC female BC patients whose data were linked to HPHI. Of this group, further analysis was performed on 389 women who were diagnosed with invasive BC, were first treated between 2003 and 2017 with BC surgery, and had had weight data available at index and up to 2 months prior to surgery. Information was gathered on the type of treatment, which included surgery alone (S), surgery followed by radiation (SR) with or without additional endocrine therapy, surgery followed by chemotherapy (SC), and surgery followed by endocrine therapy (SE).
Data from seven time points were analyzed for weight changes based on treatment modality. Weight decreases of 5 pounds or more were considered weight loss, weight increases of 5 pounds or greater were deemed weight gain, and a stable weight was defined as a loss or gain of weight within 5 pounds.
The mean age of the study population was 71.1 years (range: 54-94 years). This group was ethnically diverse and consisted of approximately 30% each of the following groups: Native Hawaiians/Pacific Islanders (NH/PI), Asians, and Whites. The BMI at the time of surgery (baseline) was 28.3 kg/m2, which is overweight. BMI varied by ethnicity with the highest being in NHPIs at 31.7 kg/m2, which is obese, and the lowest in Asians at 26.2 kg/m2, which is overweight. NHPIs were more likely to have regional stage disease and be lymph-node positive.
The most common interventions were SR, which occurred in 35% of the population, with the next most common intervention being SE, which was used in 31% of the patients. Few patients received surgery only (18.3%) or surgery followed by chemotherapy (15.2%). There were ethnic differences in treatment patterns, with NHPIs more often receiving SE (35.6%) and with SC occurring more often in Asians (37.9%) and Whites (38.0%).
While weight loss occurred among both those aged <71 years and >71 years at the time of surgery, it was less prominent in the younger group since a higher percentage of these patients gained weight over time. More patients with a BMI >30 kg/m2 at surgery lost weight compared to those with a BMI <30 kg/m2.
Overall, weight changes after surgery were similar between S, SR, and SE groups, with the majority of patients having stable weight (although weight consistently decreased over time). Weight loss was most pronounced in the SC group, especially 3 months postsurgery, while these patients were receiving chemotherapy. Although weight loss plateaued at 3 to 5 months, it continued up to 4 years after surgery. Weight loss occurred two times more often than weight gain.
This article provides valuable insight for pharmacists regarding the weight changes that are associated with treatment options for the management of BC. This information can be utilized to proactively monitor those BC patients at greatest risk for weight loss.
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