Evaluating palbociclib for patients with previously treated breast cancer

This study evaluated how well palbociclib (Ibrance) works in patients with breast cancer who received multiple lines of previous therapy. This study found that palbociclib was effective for these patients.

There are several different treatments for breast cancer depending on the types of receptors found on the cancer cells. If the cancer cells have estrogen receptors (ER+), certain treatments that lower estrogen levels or block the actions of estrogen can be effective. This type of treatment is called endocrine therapy.

Unfortunately, some tumors become resistant or stop responding to endocrine therapy. One new treatment option is adding palbociclib to conventional endocrine therapy. Palbociclib helps block cancer cell growth. How well palbociclib works for patients who had several prior treatments for breast cancer is unclear.

This study had 118 patients with breast cancer. 96.6% of patients had previously received 4 or more lines of prior therapy. All patients received palbociclib. 56 patients also received fulvesterant (Faslodex). 57 patients also received an aromatase inhibitor. 5 patients also received tamoxifen (Nolvadex). Patients received palbociclib for an average of 119 days.

Overall, 15.8% of patients responded to treatment after 12 weeks. 47.5% of patients had some benefit from treatment with palbociclib. 52.5% of patients had tumor growth or spread.

On average, patients remained alive without tumor growth or spread for an average of 4.5 months. The average overall survival (time from treatment until death from any cause) was 15.8 months. At 18 months, 44.5% of patients were still alive.

Patients who had fewer than 3 prior lines of therapy survived for significantly longer compared to patients who had 3 or more prior treatments (not reached vs. 13.4 months).

The most common side effects were low white blood cell count (89.7%), low red blood cell count (66.9%), and tiredness (53.4%). Low platelet count (cells involved in blood clotting; 56.8%) and poorer liver function (32.2%) were also reported.

57.6% of patients had serious side effects. The most common was severely low white blood cell count (56.8%). 48.3% of patients needed a lower dose of palbociclib due to side effects. 3.4% of patients stopped treatment due to side effects.

The study concluded that palbociclib is an effective treatment for patients with breast cancer who received multiple lines of prior therapy. The authors suggest that palbociclib may benefit patients who had endocrine therapy before.

This is a small study. Also, it is difficult to assess how well palbociclib works because many of the patients had different previous treatments.

Lastly, this study was retrospective. This means that it looked back in time to analyze data. More studies are needed to confirm these results.

Talk to your doctor about the potential benefits of palbociclib to see if it may be right for you.