1. MA.17R: Reduced Risk of Recurrence With Extending Adjuvant Letrozole Beyond 5 Yrs in Postmenopausal Women With Early-Stage Breast Cancer
CCO Independent Conference Coverage* of the 2016 ASCO Annual Meeting, June 3-7, 2016
*CCO is an independent medical education company that provides state-of-the-art medical information to healthcare professionals through conference coverage and other educational programs.
This activity is supported by educational grants from Amgen, Ariad, Bayer Healthcare Pharmaceuticals, Celgene Corporation, Genentech, Incyte, Merck, and Taiho Pharmaceuticals.

2. MA.17R Extended Letrozole: Study Background
5 yrs of AI therapy, either initially or after 2-5 yrs of tamoxifen, standard of care for postmenopausal women with HR-positive early breast cancer
Based largely on results of Canadian Cancer Trials Group MA.17 trial, which compared 5 yrs of letrozole vs placebo following 5 yrs of tamoxifen[1,2]
DFS and OS outcomes superior with letrozole
Extending AI treatment with letrozole to 10 yrs may further reduce risk of breast cancer recurrence
Randomized, double-blind, placebo-controlled MA.17R trial designed to test efficacy of extending AI treatment with letrozole out to 10 yrs[3]
AI, aromatase inhibitor; DFS, disease-free survival; HR, hormone receptor.
1. Goss PE, et al. N Engl J Med. 2003;349: Jin H, et al. J Clin Oncol. 2012;30: Goss PE, et al. ASCO Abstract LBA1.
Slide credit: clinicaloptions.com

3. MA.17R: Study Design Primary endpoint: DFS (from randomization)
Secondary endpoints: OS, CBC, safety, QoL
Stratification by lymph node status at diagnosis, prior adjuvant chemotherapy, interval between last AI dose and randomization, duration of prior tamoxifen
Postmenopausal pts with ER+ and/or PgR+ breast cancer who completed yrs of letrozole 2.5 mg PO QD ± prior tamoxifen
(N = 1918)
Letrozole 2.5 mg PO QD
for 5 yrs
(n = 959)
Follow-up
Median follow-up: 6.3 yrs
Placebo
for 5 yrs
(n = 959)
AI, aromatase inhibitor; CBC, contralateral breast cancer; DFS, disease-free survival; ER, estrogen receptor; PgR, progesterone receptor; QoL, quality of life.
Follow-up
Slide credit: clinicaloptions.com
Goss PE, et al. ASCO Abstract LBA1.

4. MA.17R Extended Letrozole: Baseline Characteristics
Letrozole (n = 959)
Placebo (n = 959)
Median age, yrs (range)
65.6 ( )
64.8 ( )
White (non-Hispanic), %
92.2
91.6
ECOG PS 0, %
88.8
89.3
Median time from diagnosis, yrs (range)
10.6 ( )
10.6 ( )
Tumor size T1, %
57.6
55.8
Nodal status N0, %
46.5
46.7
Hormone receptor positive, %
98.5
99.1
> 4.5 yrs on prior tamoxifen, %
70.5
72.2
Adjuvant chemotherapy, %
58.5
58.1
Mastectomy, %
47.9
49.2
ECOG, Eastern Cooperative Oncology Group; PS, performance status
Slide credit: clinicaloptions.com
Goss PE, et al. ASCO Abstract LBA1.

5. MA.17R: DFS and OS After Median Follow-up of 6.3 Yrs
DFS benefit of extended letrozole in all prespecified subgroups
5-yr OS: 93% vs 94% (HR: 0.97; P = NS)
DFS Outcomes
Letrozole
Placebo
HR (95% CI)
P Value
Overall 5-yr DFS, % 95 91
0.66 ( )
.01
Events, n (%)
67 (7.0)
98 (10.2)
New contralateral breast cancers, n (%)
13 (1.4)
31 (3.2)
.007
Locoregional recurrences, n 19 30
Distant recurrences, n 42 53
Bone recurrences, n 28 37
AI, aromatase inhibitor; DFS, disease-free survival; NS, not significant.
Slide credit: clinicaloptions.com
Goss PE, et al. ASCO Abstract LBA1.

6. MA.17R: Safety
Compliance similar between letrozole and placebo arms: 62.5% vs 62.3%
No clinically significant differences in QoL between arms
Adverse Event, %
Letrozole (n = 959)
Placebo (n = 959)
P Value
Hot flashes/flushes 38 37 NS
Arthralgia 53 50
Myalgia 28 25
Bone pain 18 14
.01
Vaginal dryness 11 10
Elevated alkaline phosphatase 12 9
Elevated ALT
.02
Cardiovascular event
ALT, alanine aminotransferase; NS, not significant; QoL, quality of life.
Slide credit: clinicaloptions.com
Goss PE, et al. ASCO Abstract LBA1.

7. MA.17R: Fractures During Treatment
Bone health and bone protection similar between arms at baseline
Bone Events, %
Letrozole (n = 959)
Placebo (n = 959)
P Value
Bone fracture 14 9
.001
Location of bone fracture
Spine
Wrist
Pelvis
Hip
Femur
Tibia
Ankle
Other
1.8
2.8
0.1
0.7
0.9
0.5
2.0
7.1
1.7
0.6
0.4
1.2
5.0
.12
.09
.08
.79
.17
.74
.14
.06
New-onset osteoporosis 11 6
< .0001
Slide credit: clinicaloptions.com
Goss PE, et al. ASCO Abstract LBA1.

8. MA.17R: Conclusions
MA.17R first study to demonstrate benefit of extending AI treatment beyond 5 yrs
Letrozole treatment for 10 yrs decreased risk of disease recurrence by 34%
Majority of benefit in reduction of contralateral breast cancer
No new toxicities observed
Bone health remains important in weighing risks/benefits
Treatment extension did not adversely impact QoL
OS not improved by extending letrozole beyond 5 yrs
Investigators note that AIs readily available worldwide, and introducing 10 yrs of AI therapy as standard of care should improve global burden of breast cancer
AI, aromatase inhibitor; QoL, quality of life
Slide credit: clinicaloptions.com
Goss PE, et al. ASCO Abstract LBA1.

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