Good News For Rare Cancer Treatment, Keytruda Can Help

The immunotherapy Keytruda (pembrolizumab) demonstrated favorable effectiveness and safety in patients with advanced rare cancers, suggesting a much- needed option for this patient population. The findings from an interim analysis in a phase 2 study support further evaluation of the drug for these patients, the researchers concluded.

The ongoing study is testing Keytruda in patients with squamous cell carcinoma of the skin; two types of cancer that arise in the adrenal glands above the kidneys, adrenocortical carcinoma and paraganglioma-pheochro-mocytoma; and carcinoma of unknown primary, which can affect various organs. The interim findings were published in the Journal for ImmunoTherapy of Cancer.

“Studies such as this one are key, since rare cancers collectively accounted for 13% of all new cancer diagnoses and 25% of all cancer-related deaths in adults in 2017,” Dr. Aung Naing, associate professor of investigational cancer therapeutics at The University of Texas MD Anderson Cancer Center in Houston, said in a press release.

“The five-year survival rate is 15% to 20% lower than for more common cancers. The poor outcomes associated with rare cancers have been attributed to difficulty or delay in diagnosis, a dearth of clinical trial data, limited access to centers with expertise such as MD Anderson and limited therapeutic options.”

Between Aug. 15, 2016 and July 27, 2018, the researchers administered IV Keytruda to 127 individuals whose tumors had progressed on standard therapies within the previous six months. The patients, who received 200 mg of IV Keytruda every 21 days, were enrolled in nine tumor- specific groups and a 10th that included those with other rare histologies.

The researchers aimed to measure the non-progression rate at 27 weeks, which was the study’s primary goal. Secondary goals included measuring safety and tolerability; objective response rate, or the percentage of patients whose tumors shrank by a prespecified amount; and clinical benefit rate, or the percentage of patients with an objective response or stable disease.

At 27 weeks, 28% of patients had no disease progression. An objective response was noted in 15 of 110 evaluable patients (14%); one experienced a complete response, with no detectable evidence of remaining cancer, and the other 14 had a partial response. The clinical benefit rate, or the percent of patients who responded or had no disease progression for at least 24 weeks, was 38% (42 people).

Treatment continued for 11 of the 15 responders. Among patients with squamous cell carcinoma, the non-progression rate at 27 weeks was 36%, the objective response rate was 31%, and the clinical benefit rate was 38%. The 27-week non-progression rate, objective response rate and clinical benefit rate were 31%, 15% and 54%, respectively, for those with adrenocortical carcinoma; 33%, 23% and 54% for patients with carcinoma of unknown primary; and 43%, 0% and 75% in the paraganglioma-pheochromo-cytoma group.

Treatment-related side effects occurred in 66 of the 127 patients (52%) and were serious in 12 (9%). The most common side effects were fatigue and rash. Six participants died, five from progressive disease and one due to kidney injury from sepsis. Keytruda’s safety in these patient groups is consistent with that reported for patients with common cancers, such as melanoma and non-small cell lung cancer.

“Findings from our study support further investigation to confirm the clinical activity of pembrolizumab in advanced rare cancers and to identify immune signatures predictive of response to treatment,” Naing said.

The researchers noted some limitations to their findings. Given the small sample size of the tumor-specific groups, the researchers could not apply their findings to all rare cancers.

Additionally, the site in the body from which the tissue was obtained for evaluation, and whether the sample came from a primary or metastatic tumor, could have influenced measurements of response, the researchers reported. Even so, the results shed much-needed light onto potential treatments, they said.