US researchers suggest palbociclib may be effective in treating appendiceal cancer.
A small prospective cohort study suggests palbociclib could be beneficial for patients with a particular kind of appendiceal cancer.
Appendiceal cancer is rare and is most frequently diagnosed after it metastasises to other parts of the abdomen, leading to mucinous carcinomatosis peritonei (PMC) or a mucinous adenocarcinoma. This type of cancer is primarily treated with surgery, although chemotherapy is used in patients with advanced or inoperable tumours. The chemotherapy – which usually follows a colorectal cancer treatment approach – does not appear to be particularly effective.
Now, a small US study suggests that palbociclib, a cyclin-dependent kinase 4/6 inhibitor used to treat breast cancer, stabilises tumour growth and lowers tumour marker levels in blood in patients with PMC.
“Finding that a breast cancer drug is successful in treating a subset of appendix cancer – where treatment options are currently limited – marks a significant advancement in our fight against this disease,” said Professor Andrew Lowy, chief of surgical oncology at UC San Diego’s School of Medicine and joint senior author of the new paper.
“This breakthrough introduces the first targeted therapy for this rare cancer.”
Researchers recruited 16 patients with PMC as part of the single-centre prospective cohort study. Each patient received 125mg of palbociclib a day for three weeks, followed by a week of no treatment. Three patients were placed on a lower dose and changed to a two-weeks on, one-week off regimen due to fatigue.
Eleven of the 16 patients were female, and the primary tumours were located in the appendix for 13 patients. The median age of recruited patients was 61 years, with patients followed up for a median of 17 months.
Palbociclib treatment reduced carcinoembryonic antigen (CEA) in 13 of the 16 patients. Twelve patients displayed stable tumour growth six months after finishing the treatment, with eight of the 10 eligible patients also displaying stable growth after a further six months. There were three deaths within the first 12 months after stopping palbociclib.
The beneficial effects of palbociclib were particularly prominent in patients whose tumours carried a GNAS mutation, leading the researchers to hypothesise that these particular cancers were more sensitive to palbociclib.
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The researchers felt the discovery represented a new dawn for the treatment of appendix cancer and other rare types of cancer carrying the GNAS mutation.
“This medication can be implemented immediately without the need to wait for a new drug to be developed or for FDA approval,” said Associate Professor Shumei Kato, medical oncologist and joint senior author.
The Cancer Council considers appendix cancer to be a rare cancer, with the organisation estimating 874 people will be diagnosed with appendiceal cancer in 2024. The cancer may be asymptomatic in its early stages, but is associated with appendicitis, waist/abdominal bloating and changes in bowel movements.
The TGA first approved palbociclib as a breast cancer treatment in 2018 and it is listed on the PBS for certain patients.
