Download Breast Cancer Treatment: Aromatase Inhibitors vs. Tamoxifen

Breast Cancer Treatment :
Aromatase Inhibitors
vs. Tamoxifen
Elizabeth Geddes
March 9, 2006
Advisor - Dr. Hadley
Breast Cancer Brief
• Breast cancer is the MOST common
cancer in women
• 2nd leading cause of cancer deaths in
women
• Over 212,000 women will be
diagnosed with breast cancer and
over 40,000 will die in 2006
Types of Cancer
• Ductal vs. Lobular
• Lobular – can be in lobes or lobules
• In Situ vs. Invasive
• Ductal Invasive is most common
• Hormone receptor positive or negative
• Estrogen receptor / Progesterone receptor
• Hormone receptor positive cancers are
dependent on estrogen/progesterone for
growth
Treatment Options
• Chemotherapy
• Radiation
• Mastectomy
• Lumpectomy
• Alternative Medicine
• HORMONE THERAPY
Hormone Therapy
• Hormone therapy is effective in
hormone receptor positive tumors
• 75% of all breast cancers are receptor
positive
• Treatment is non-invasive, fairly nontoxic
• Used to inhibit progression or
recurrence of disease
Tamoxifen
• Selective estrogen receptor modulator
• Estrogen agonist and antagonist
• Reversibly blocks estrogen binding to
receptor in tumor cells
• Agonist effects include decreased blood
lipid changes, and increased bone
density
Adverse Effects
• Thromboembolic events
• Endometrial cancer
• Hepatic carcinomas
• Menstrual dysregularities
• Vaginal dryness and bleeding
• Hot flushes
Tamoxifen Resistance
• Tamoxifen has only been proven
effective for a maximum of 5 years
• The risks are greater than the benefits
past this time frame
• Resistance of the tumors is attributed to
this decrease in efficacy
• Resistance is thought to be due to the
tumor becoming estrogen independent
Aromatase Inhibitors
• Block aromatase,
inhibiting estrogen
synthesis
• Steroidal
• Exemestane
• Irreversibly inhibit
• Non-Steroidal
• Anastrozole and
Letrozole
• Reversibly inhibit
Aromatase Inhibitors
• Only useful in postmenopausal women
• Production of estrogen in
premenopausal women overrides
aromatase inhibitors
Adverse Effects
• Osteoporosis
• Thromboembolic Events
• Cardiac Events
• Vaginal dryness
Clinical Trials
Aromatase Inhibitors vs. Tamoxifen
• ATAC trial
• 68 months follow-up there was improved
disease free survival with Anastrozole over
Tamoxifen
• Big 1-98
• 25.8 months follow-up there was improved
disease free survival with Letrozole over
Tamoxifen
Sequential Treatments
• It has been proven that there is an
increased disease free survival after 5
years of therapy in patients who
switched to aromatase inhibitors after
2-3 years of Tamoxifen compared to
those who remained on Tamoxifen
•ABSCG/ARNO - Anastrozole
•ITA - Anastrozole
•IES – Exemestane
Long term treatments
• Early results of the MA.17 clinical trial
show promise for aromatase inhibitor
effectiveness after 5 years of treatment
• Increased disease free survival in
patients continuing treatments
compared to those on no treatment
• Letrozole has shown positive effect in
overall survival
Current Debates
• Aromatase inhibitors as initial treatment
versus post-Tamoxifen treatment
• How many years of Tamoxifen before
beginning aromatase inhibitors?
• Effective length of treatment with
aromatase inhibitors
• Efficacy between different aromatase
inhibitors
Tolerability
• In ATAC trial fewer patients
withdrew and there were less
reported side effects in the aromatase
inhibitor population
Why should a primary care PA care?
• Some of our patients will be diagnosed
with breast cancer
• Patients will follow-up with PCP after
seeing oncologist
• We need to be aware of these drugs
• When to use them
• Which is the best option for our patient
• Adverse Effects
• Be knowledgeable for patient education
Conclusion
• Tamoxifen was gold standard
• Aromatase inhibitors are proving to be
more effective
• Increased disease free survival
• Longer treatment options
• Better tolerability
• Several questions remain unanswered
• Hormonal therapies are effective in
halting the progression and recurrence
of breast cancer
References
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