medwireNews: A database analysis has revealed poor adherence to adjuvant tamoxifen in older men with early-stage breast cancer.
Nearly half of the patients had discontinued tamoxifen before the end of year 5, and “even among those patients continuing tamoxifen, a substantial number of patients [were] nonadherent,” report Sharon Giordano and colleagues from The University of Texas MD Anderson Cancer Center in Houston, USA.
They write in Cancer: “It is important that oncologists are aware of these rates of discontinuation to be mindful to encourage [male breast cancer] patients to adhere to their tamoxifen.”
The team drew on the 2007–2013 records of the SEER–Medicare database to identify 451 men aged 65 years or older who received a tamoxifen prescription within a year of being diagnosed with hormone receptor-positive, stage I–III breast cancer.
Giordano et al found that 15.8% of patients had discontinued adjuvant tamoxifen 1 year after being prescribed the drug, with a respective 24.3%, 31.3%, 36.9%, and 48.3% following suit at 2, 3, 4, and 5 years.
Among those who continued to fill tamoxifen prescriptions, adherence rates fell from 76.9% at year 1 to 73.6% at year 2, 68.7% at year 3, 64.8% at year 4, and 60.2% at year 5, where adherence was defined as a medication possession ratio of at least 80%.
Multivariable analysis identified several significant predictors of adherence, including age of 76–80 years (hazard ratio [HR]=2.75 vs 65–70 years) and residence in a metro or less urban area (HRs=2.40 and 8.54, respectively, vs big metro).
By contrast, men with a Charlson comorbidity score of 2 or more were significantly less likely to adhere to tamoxifen treatment relative to those with a score of 0 (HR=0.46), and an age greater than 80 years was significantly associated with discontinuation (HR=1.73 vs 65–70 years).
“Further studies looking at the root causes for discontinuation and the patient population at risk for nonadherence are essential,” conclude the researchers.
Writing in an accompanying editorial, Carla Falkson (University of Rochester Medical Center, New York, USA) notes that the analysis “is the largest of its kind reported to date” but highlights several limitations that the authors also acknowledge, such as the focus on older patients, reliance on prescriptions filled to extrapolate adherence, and lack of data on reasons for discontinuation, including whether patients discontinued due to toxicities or disease progression.
She continues: “Because discontinuing or irregularly taking adjuvant tamoxifen is a multifactorial problem and may be more frequent than previously perceived, there is a critical need to reliably estimate both its incidence and causes so that corrective measures can be implemented.”
The editorialist believes that “[o]nly when the multitude of reasons for discontinuing adjuvant tamoxifen are clearly delineated will the next step be meaningful, namely devising strategies to encourage and support male patients with breast cancer to successfully complete their adjuvant tamoxifen therapy.”
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Cancer 2021; doi:10.1002/cncr.33899
Cancer 2021; doi:10.1002/cncr.33898