SAN FRANCISCO – A new chemotherapy regimen of capecitabine and temozolomide was highly active against advanced treatment-resistant neuroendocrine tumors, based on the interim results of a phase II trial.
Tumors shrank in 43% of the 28 patients with various types of differentiated metastatic neuroendocrine tumors given the regimen, which is abbreviated CAPTEM. Disease stabilized in 54%.
Responses were durable, with a median progression-free survival approaching 2 years, reported lead investigator Dr. Robert Fine of the department of medicine at New York Presbyterian Hospital–Columbia University Medical Center.
"In this study, we’re seeing patients who had been given 6 months to live and are still alive 8 years after starting CAPTEM," he said in a prepared statement. "The regimen was effective even in patients with tumors that hadn’t responded to any other standard treatment, including chemotherapy, high-dose octreotide, small molecule inhibitors, radiation, or surgery."
For example, 42% of the patients with carcinoid tumors had a complete or partial response, and the others had stabilization of their disease. Median progression-free survival in this subset exceeded 31 months.
"Pituitary tumors were extraordinarily sensitive – end-stage people on respirators who were intubated with pituitary masses [compressing the spinal cord] were 100% responsive to the regimen, he said. Two of three patients had a complete response and were able to come off the ventilator and remain disease free with ongoing treatment at nearly 4 years out. The other patient had a partial response.
Toxicities were mild, and none of the patients had to be hospitalized or died as a result of the treatment, Dr. Fine commented in a press briefing before the results were presented at the annual Gastrointestinal Cancers Symposium sponsored by the American Society of Clinical Oncology.
Dr. Smitha S. Krishnamurthi of Case Western Reserve University, Cleveland, who was the press briefing moderator, concurred that the regimen offers a new treatment option to patients who have exhausted the standard options.
"This regimen of CAPTEM vs. TEM (temozolomide) is under study now in a cooperative group trial for patients with pancreatic neuroendocrine cancer," she noted.
Dr. Fine and his team enrolled patients in the trial who had well- or moderately differentiated neuroendocrine tumors and either experienced progression despite standard therapy with high-dose octreotide (Sandostatin) or were ineligible for this treatment because of a negative octreotide scan. Other prior treatments, with the exception of the two drugs being studied, were allowed.
CAPTEM contains capecitabine (Xeloda), currently approved by the Food and Drug Administration for the treatment of breast and colorectal cancers, and temozolomide (Temodar), currently approved for the treatment of anaplastic astrocytoma and glioblastoma multiforme.
The drugs are given in sequence to maximize efficacy, according to Dr. Fine, as the capecitabine depletes tumor thymidine stores, which dramatically potentiates the antitumor effect of the temozolomide.
Of the 28 patients, 12 had carcinoid tumors, 11 had pancreatic tumors, 3 had pituitary tumors, and 2 had medullary thyroid tumors.
The patients were treated with CAPTEM on 28-day cycles, with capecitabine alone for 9 days, both capecitabine and temozolomide for 5 days, and the next 14 days off.
Overall, 11% of patients had a complete response, 32% had a partial response, 54% had stable disease, and 3% had progressive disease. These values translated to a response rate of 43% and a clinical benefit rate of 97%.
Median progression-free survival exceeded 22 months, and median overall survival, although still maturing, exceeded 29 months.
"The toxicities were extraordinarily light," commented Dr. Fine, who disclosed that he receives research funding from Merck.
The most common grade 3 or 4 toxicities were lymphopenia (seen in 35% of patients), hyperglycemia (6%), thrombocytopenia (3%), and diarrhea (3%).
None of the patients were hospitalized, developed opportunistic infections, or died as a result of CAPTEM treatment.