B25
Predicting benefit from Fulvestrant in pretreated metastatic breast cancer (MBC) patients
Eitan Amir1, Orit Freedman1, George Dranitsaris1, Julie Napolskikh1, Stephen Chia2, Teresa Petrella3, Susan Dent4, Ritu Kumar1, Michael Fralick1, Mark Clemons1
1Princess Margaret Hospital, Toronto, Canada, 2BC Cancer Agency, Vancouver, Canada, 3Odette Cancer Centre, Toronto, Canada, 4Ottawa General Hospital, Canada
Background
Fulvestrant use in heavily pretreated patients with MBC is associated with highly variable responses. This study aimed to characterise the benefit of fulvestrant therapy and develop a prediction model for clinical benefit in this setting.
Method
A nationwide, retrospective chart review of patients enrolled in a Canadian compassionate use program was performed. This program mandated prior therapy with tamoxifen and both steroidal and non-steroidal aromatase inhibitors. Charts from the seven highest accruing centers were reviewed. Sample size was based on the derivation of a model to predict the probability of a patient remaining on fulvestrant and free from chemotherapy for at least 3 months.
Results
305 women received at least one dose of fulvestrant; 207 went on to receive chemotherapy (68%). Of these, 48 (23%) required chemotherapy at 3 months, 113 (55%) at 6 months, and 170 (82%) by 12 months. Median duration of fulvestrant treatment was 126 days (range 23-1920). Median overall survival from start of fulvestrant was 698 days (25th percentile 316 days-75th percentile 1,359 days). The preliminary prediction model showed that older age (OR 0.96, 95% CI 0.93-0.99) and having received no adjuvant hormonal therapy (OR 0.5, 95% CI 0.2-1.25) predicted a greater chance of remaining chemotherapy-free at 3 months. Presence of lung (OR 2.55, 95% CI 1.1-5.9) or brain metastases (OR12.8, 95% CI 4.1-55.4) predicted a lower chance of remaining chemotherapy-free at 3 months.
Conclusion
Older age and having received no prior adjuvant hormonal therapy predicted a greater chance of remaining chemotherapy free at 3 months, while lung and brain metastases predicted a lower chance. These factors will be validated in an international data set, and may be considered when prescribing fulvestrant. A 6-month prediction model is currently under development.
