Background: Extended endocrine therapy (> 5 years; EET) is recommended for many ESBC patients following the results of the MA.17, ATLAS, and aTTom clinical trials. Clinical practice guidelines recommend consideration of 10 years of endocrine therapy; however, they note the challenging risk vs benefit profile given the modest benefit of EET in terms of preventing disease recurrence (∼3-5%) and the potential for adverse effects and tolerability challenges. Studies examining the long-term impact of EET are lacking. The objective of this study was to assess the impact of EET in ESBC patients on symptom burden and health-related quality of life (HRQoL).

Methods: Retrospective review of existing medical records for patients (N=308) with ER+ ESBC. Eligible patients had completed 5 years of adjuvant endocrine therapy without disease progression, minimum of 1 year additional follow-up, and at least one Patient Care Monitor (PCM) survey, a validated 86-item, patient reported outcomes measure that assesses symptoms common in patients undergoing cancer treatment, during the 1 to 3 year follow-up period. Primary analysis included 6 PCM index scores and 12 PCM items representing symptoms of particular interest. Patients were classified as having received EET (minimum 8 months) vs. Control (no extended therapy). Linear mixed models were employed to examine differences in symptom burden between EET and Control groups during the 3-year follow-up period, including differences in change over time across groups, and whether patterns of symptoms lead to discontinuation of EET.

Results: This analysis included 156 EET and 152 Control patients [75.0% Caucasian, 22.7% African American, with mean age of 61 (±11) years, and predominantly from the Southern US (93.8%)]. The sample was 40.9% Stage I at diagnosis, 48.4% stage II, and 10.1% stage III. EET patients were younger (59 vs. 63 years, p = .0008), and more likely to have stage III disease (p =<.0001). Results from preliminary interim analyses indicate that EET vs no EET was associated with statistically significant differences in symptom burden in certain PCM items (eg, increased vaginal dryness, reduced sexual enjoyment). Final analyses will be available on Sept 1st and the abstract will be updated at that time.

Conclusions: Based on interim analyses from this study, EET may be associated with continued symptom burden and impact on HRQoL. These results suggest that the decision whether to extend endocrine therapy in patients with ESBC should be multi-faceted, including discussion of the potential benefit of extended therapy, risk of ongoing/worse symptomatology, and long-term impact on patients QoL.

Citation Format: Fisher MD, Schroeder BE, Miller PJ, Schnabel CA, Schwartzberg L, Walker MS. The impact of extended endocrine therapy on symptom burden and health-related quality of life in patients with early-stage breast cancer. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P4-11-03.