Palbociclib is well-tolerated in HER2-negative MBC patients
Consistent with literature findings, palbociclib is generally well-tolerated and effective in controlling the disease of Asian patients with human epidermal growth factor receptor 2 (HER2)-negative metastatic breast cancer (MBC), reports a new study from Hong Kong presented at the recently concluded European Society for Medical Oncology (ESMO) Asia 2017 Congress.
The research team assessed the treatment response and toxicity profiles of 61 MBC patients (median age 52 years [34 to 81 years]) who were recruited from both public and private hospitals. All patients received pablociclib and response was evaluated according to tumour marker response and imaging.
While all recruited patients had oestrogen receptor-positive tumours, only 82 percent (n=50) tested positive for progesterone receptor while the remaining 18 percent (n=11) tested negative. Majority of the study sample (67 percent) had recurrent metastatic disease. [ESMO Asia 2017, abstract 116P]
In terms of menopause status, 97 percent (n=59) of the participants were postmenopausal at the time of the study, of whom 70 percent (n=43) were naturally menopaused and 21 percent (n=13) had medically-induced menopause. Oophorectomy (11 percent; n=7) and growth hormone–releasing hormone agonists (10 percent; n=6) were common agents used to induce menopause.
The most common adverse event observed was grade 3 or 4 neutropoenia. In patients who were given 125 mg of palbociclib on the first cycle, 37 percent (n=20) and 6 percent (n=3) were reported to have the respective neutropoenia grades.
Notably, none of the patients had symptomatic neutropoenia and no cases of neutropoenic fever were reported.
Other adverse events reported included anaemia (3 percent; n=2), stomatitis (8 percent; n=5), hand-foot syndrome (3 percent; n=2), fatigue (3 percent; n=2) and loss of appetite (3 percent; n=2), none of which reached grade 3 or 4.
Out of 53 patients who were eligible for treatment response evaluation, 75 percent (n=40) were identified as responders while 25 percent (n=13) were nonresponders. A greater percentage of responders had visceral (55 vs 54 percent) and bone (68 vs 62 percent) disease than nonresponders.
Additionally, prior treatments in the metastatic setting were also common in responders, with 22 percent (n=9) having received 1 line of previous chemotherapy and 30 percent (n=12) having received ≥2 lines of chemotherapy. By comparison, 54 percent (n=7) of the nonresponders also received ≥2 lines of chemotherapy.
These findings show that despite an apparent efficacy in controlling the disease, palbociclib remains a choice for second or later lines of treatment. Concern over the drug’s effect on neutrophils may contribute to this, as researchers said that “[s]ome doctors opted for a lower starting dose of 100 mg,” while others even lowered the dose in subsequent cycles.
“Longer follow-up is needed to explore the progression-free survival for patients who received palbociclib beyond second line setting,” they added.