A unique case of sustained OS on CDK 4/6 inhibitor (palbociclib) in a case of de novo metastatic breast intraductal carcinoma to liver and bone. Over the coarse of 6 years of hormonal therapy in addition to a CDK 4/6 inhibitor, the patient achieved a full metabolic response, with no evidence of disease locally or distally. One major aspect of the remarkable response is the consistency by which the patient received her regimen in a low-to-middle income country in which providing the medication in a regular manner constitutes a major challenge in the treatment or cancer patients.

1. Sustained Overall Survival on Palbociclib in
Metastatic Breast Cancer
f
CDK 4/6 Inhibitors in the Palestinian Setting
Presented by: Hasan Arafat, Medical House Officer
Augusta Victoria Hospital

2. • A 58-year-old female patient, with an unremarkable past medical
history, presented to an orthopedic clinic in late 2016 complaining of
right lower limb pain.
• MRI showed a femoral mass, suspicious in nature.
• Whole-body CT: huge right breast mass with suspicious liver lesions
• Histopathology of breast biopsy: IDC grade III.
• Diagnosed as having metastatic breast cancer to bone, liver, ER +, PR
+, Her2 -, Ki67: 30%
• Baseline tumor markers: CEA: 26, CA 15.3: 48

3. • Plan by medical oncology:
• For palliative breast radiation, in addition to femoral fixation
• To start goserelin, tamoxifen
• Request a CDK 4/6 inhibitor (palbociclib)
• Add denosumab

4. • On the 17th of November 2016, the patient started on the following
regimen:
• Tamoxifen, 20 mg PO OD
• Goserelin, 10.8 mg SQ q3 months
• On the 28th of November, the referral request for a CDK 4/6 inhibitor
was accepted, so the patient was started on palbociclib, 125 mg PO
OD

5. • Her first assessment took place in February 2017, CT was suggestive
of response, manifesting as a decrease in the size of the breast mass
and the bony lytic lesions becoming sclerosed, with no definitive new
lesions
• CA 15.3: 11.39, CEA: 7.65
• Continued on the same regimen

6. • The second assessment was in June 2017, showed stable disease.
• CA 15.3: 11.61, CEA: 6.18
• The patient received a total of 8 months of tamoxifen, then switched
to letrazole, 2.5 mg PO OD, starting July 2017
• Otherwise continued on the same regimen

7. • Palbociclib was held for 1 month (September 2017) due to
neutropenia, 700
• Resumed in October
• The third assessment, in November 2017, showed response, negative
tumor markers (CA 15.3: 12, CEA: 5)
• Clinically, the patient was completely asymptomatic
• The fourth assessment took place January 2018, CT showed a great
response, while tumor markers were negative (CA 15.3: 17, CEA: 3.8)

8. • The fifth assessment took place in June 2018, showing a stable
metastatic disease, tumor markers were negative.
• Sixth assessment, in November 2018, showed a stable disease, with
negative markers (CEA: 3.4, CA 15.3: 14.92).
• Seventh assessment, April 2019, stable disease with negative tumor
markers
• Eighth assessment, July 2019, stable CT scan, CA 15.3: 14, CEA: 3.4
• Ninth assessment, December 2019, stable scan, negative tumor
markers

9. • The tenth assessment was made relatively late in August 2020 due to
COVID-19 closure, the scan showed a stable metastatic disease with
negative tumor markers.
• Continued on the same regimen
• Eleventh assessment, March 2021, stable scan
• Goserelin was stopped as the patient reached menopause
• Assessment twelfth, August 2021, stable scan
• Assessment thirteenth, January 2022, stable scan
• Assessment fourteenth, July 2022, stable scan

10. • Last assessment in October 2022, fifteenth in total, via PET scan:
• Inactive sclerotic lesion on D9
• Severe degenerative changes in the lumbar region with disc sequestration in
L2-L3
• No evidence of active disease

18. Conclusion
• In total, our patient has received 73 cycles of Palbociclib over 6 years
• This constitutes an exceptionally long progression-free survival for a
patient with metastatic breast cancer
• The unusual consistency by which the patient received her regimen is
one major factor behind her remarkable response.
• Now, what is the next step?