Mental Illness May Predispose Women With Breast Cancer to Higher Mortality

Severe mental illnesses that precede a breast cancer diagnosis may increase the risk of both all-cause and cancer-specific mortality among women with Medicaid coverage, according to research findings recently published in Social Science & Medicine.

By linking Medicaid diagnosis claims for preexisting depression or severe mental illness (SMI; schizophrenia, bipolar disorder, other psychotic disorders) with New York State Cancer Registry data on breast cancer diagnoses between 2004 and 2016, the researchers compared survival outcomes with those in patients without a history of mental illness. They noted that Medicaid is the largest payer of mental health–related services in the United States.

“Evidence from epidemiological studies indicates that mental illnesses are associated with elevated cancer risk and poorer cancer outcomes compared with the general population,” the authors stated. “However, differences in survival and cause of death by severity of mental illnesses among women diagnosed with breast cancer remains poorly understood.”

For their retrospective cohort study, included patients (N = 10,444) had to have at least 3 claims for mental illness overall (n = 3203; SMI, n = 1430; depression, n = 1773), with 1 being in the 3 years before their breast cancer diagnosis, as classified by International Classification of Diseases, Ninth Revision, Clinical Modification or Tenth Revision codes for depression or SMI. The women were divided into premenopausal (< 50 years) and postmenopausal (≥ 50 years) age groups.

Of note, according to the findings, all-cause mortality was higher than cancer-specific mortality, despite both being elevated among women with comorbid SMI and breast cancer:

• All-cause mortality had an HR of 1.36 (95% CI, 1.18-1.57).
• Cancer-specific mortality had an HR of 1.27 (95% CI, 1.03-1.44).

The risk for all-cause mortality rose even higher when analyzing outcomes according to race/ethnicity, with non-Hispanic Asians/Pacific Islanders having a 76% higher risk of death compared with non-Hispanic Whites:

• Non-Hispanic Asians/Pacific Islanders had an HR of 2.59 (95% CI, 1.15-5.87).
• Non-Hispanic Whites had an HR of 1.47 (95% CI, 1.19-1.83; P = .13).

In addition, obesity status, postmenopausal age, and documented tobacco use among the women with preexisting SMI and breast cancer increased their risk of death:

• Obesity had an HR of 1.58 (95% CI, 1.26-1.98; P = .13).
• Postmenopausal age had an HR of 1.49 (95% CI, 1.25-1.78; P = .03).
• Documented tobacco use had an HR of 1.42 (95% CI, 1.13-1.78; P = .84).

Adjusted 10-year survival also showed lowered survival rates among the women with comorbid SMI vs depression and no mental illness. Overall survival for women with SMI was the lowest, coming in at approximately 3.8% and 5.2%, respectively, below that for depression and no mental illness. Cancer-specific survival for women who had comorbid SMI was close to 2.1% and 2.8% lower than that for depression and no mental illness, and cardiovascular-specific survival was nearly 0.7% and 0.8% lower.

And when the investigators stratified outcome by breast cancer characteristics, the women with localized disease (HR, 1.53; 95% CI, 1.19-1.96; P < .01) and hormone receptor–negative tumors (HR, 1.56; 95% CI, 1.22-1.99; P = .24) had higher mortality risks.

Not found were associations of increased mortality and preexisting depression for women with diagnosed breast cancer.

Suggested underlying factors contributing to the higher mortality rate in women with comorbid breast cancer and SMI include that schizophrenia tends to worsen and become treatment resistant after menopause; SMI treatment regimens need to change due to interactions with cancer therapies; antipsychotic drugs can have adverse cardiovascular effects for patients considered obese; and smoking cessation rates are lower among persons with SMI. Cancer treatment delays and nonadherence are also more likely among those with mental disorders.

“The present study suggests that Medicaid-insured women with preexisting SMI at breast cancer diagnosis have a greater mortality hazard than women without preexisting mental illnesses,” the authors concluded. “These results highlight the importance of collaboration between oncologists, psychiatrists, and other health care providers to establish a coordinated care plan for breast cancer patients with preexisting SMI.”

How to best integrate breast cancer treatment and SMI care requires further research, they noted.

Reference

Lawrence WR, Kuliszewski MG, Hosler AS, et al. Association between preexisting mental illnesses and mortality among Medicaid-insured women diagnosed with breast cancer. Soc Sci Med. Published online December 23, 2020. doi:10.1016/j.socscimed.2020.113643