medwireNews: Systemic lupus erythematosus (SLE) is significantly associated with impaired survival among older women with early breast cancer, research findings show.
“These findings suggest that having both [breast cancer] and SLE is detrimental on survival,” say Maria Suarez-Almazor (The University of Texas MD Anderson Cancer Center, Houston, USA) and study co-authors.
They add: “While there were some trends observed for [breast-cancer specific survival], suggesting that having SLE is detrimental for [breast cancer] outcomes, the largest differences were observed for [overall survival], so having [breast cancer] could conceivably also be detrimental for SLE outcomes.”
The team analyzed data for 494 patients with breast cancer and SLE from two databases linked to Medicare claims and a further 9708 patients with breast cancer but no SLE who were matched on age and cancer stage. The mean age of the women was 73.4 years and those with SLE were more likely to be younger, Black, and have more comorbidities than those without SLE.
The overall survival rate at 8 years was significantly worse for the women with breast cancer who had SLE than for those without SLE, at a respective 50% and 67%. This difference was largely driven by women with early breast cancer (stage 0–II), among whom the corresponding rates were 52% and 74%.
For women with stage III to IV breast cancer, survival did not significantly differ among those with and without SLE, the team reports, “suggesting that in women with advanced cancer and shorter survival, these factors are not as impactful on the risk of death.”
Multivariable cox regression analysis identified SLE as a significant and independent risk factor for death among early breast cancer patients, increasing the risk by as much as 98% after adjusting for age, race/ethnicity, hormonal status, sociodemographic factors, and propensity scores. The risk remained similarly high after taking into account cancer treatment but fell to 65% when comorbidities were also accounted for.
The risk for breast cancer-specific death was also numerically increased among women with early breast cancer and SLE, by 62% compared with those who had early breast cancer without SLE; this was not a significant difference.
To further demonstrate that the impaired survival among women with breast cancer and SLE was not attributable to breast cancer alone, the researchers compared survival estimates of women from the two databases who had SLE with or without breast cancer (n=155 in each cohort). The 8-year survival rates were 48% and 65%, respectively, with the risk for death a significant 42% higher with both conditions than with SLE alone.
Patients with breast cancer and SLE had “lower utilization of SLE drug therapies” than those with SLE without cancer, report the researchers, noting that these patients were less likely to receive steroids in the 2 years after breast cancer diagnosis, biologics or immunosuppressants for at least 90 days in the second year, or antimalarials.
“Given our findings, it is conceivable, that the excess mortality observed in women with SLE and [breast cancer] may be multifactorial and attributable to increased SLE-associated comorbidities, but also possibly differences in both SLE and cancer therapy,” say Suarez-Almazor and colleagues.
They conclude in Arthritis Care & Research: “Further research is needed to confirm these findings and develop guidance for the management of women with SLE and cancer.”
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Arthritis Care Res 2021; doi:10.1002/acr.24793