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Patients with Carcinoma of Unknown Primary Site Respond to Gemcitabine/Carboplatin

Susman, Ed

doi: 10.1097/01.COT.0000291627.12626.6d
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CHICAGO—A combination of gemcitabine and carboplatin appears to effectively control disease in patients with carcinoma of unknown primary site, a condition for which prognosis is unfortunately poor, since, by definition, the disease is metastatic at presentation.

In a poster study here at the ASCO Annual Meeting reported by physicians in Australia, more than half of patients treated with a combination of gemcitabine and carboplatin achieved clinical benefit from the regimen.

“In the 32 currently evaluable patients with carcinoma of unknown primary site, the regimen achieved a response rate of 25%,” said Kenneth Pittman, MD, Head of Cancer Services at Queen Elizabeth Hospital in Adelaide, South Australia, “with 62.5% achieving overall disease stabilization.”

Most Adenocarcinomas

Between 5% and 10% of all cancer diagnoses are listed as carcinoma of unknown primary site, with most being adenocarcinomas, he noted.

Of the 37 people treated in the ongoing Phase II trial, 58% had liver metastases, 28% had lung metastases, 17% had metastases in the pleura, 17% had metastases in the peritoneum, 17% had metastases in the abdomen or pelvic nodes, and 11% had metastases in the bone.

Eight patients achieved documented partial responses, including one 75-year-old man with liver metastases whose disease has not progressed for 85 weeks, Dr Pittman said.

More than half of patients treated with a combination of gemcitabine and carboplatin achieved clinical benefit.

While some adenocarcinomas have fairly distinctive and histological patterns that occasionally help specialists with diagnosis, such patterns are usually not specific enough to result in a definite diagnosis.

Doctors have speculated that metastatic cancer found in the upper part of the body is likely to have evolved from an original site above the diaphragm and that metastatic cancer found in the lower part of the body is likely to have evolved from an original site below the diaphragm, Dr. Pittman said.

“Regardless of such clues, the prognosis for patients with cancer of unknown primary site has been poor,” he said.

The combination of gemcitabine and carboplatin was selected for these patients because the therapy is known to be effective against several tumor types and the regimen is generally well tolerated.

35 Cycles Delayed

Of the 138 cycles analyzed for toxicity by the research team—the Adelaide Cancer Trials and Education Collaborative—35 cycles required some delay, primarily due to development of cytopenias.

Seven of the 32 evaluable patients experienced a Grade 3 or 4 toxicity, Dr. Pittman reported.

Sepsis may have contributed to the death of one patient, he said. The main adverse, high-grade toxicities were thrombocytopenia, anemia, and nausea/vomiting.

The researchers did not report any incidents of significant alopecia.

Of the 37 patients enrolled, 18 were men and 19 were women; their average age was 69, with a range of 43 years to 83 years. All the patients had formal tumor evaluations after every third cycle of chemotherapy.

The patients were administered an intravenous infusion of 1,000 mg/m2of gemcitabine on the first day of the treatment cycle, and a similar infusion on Day 8. Carboplatin was given intravenously on Day 8.

The cycles were repeated every three weeks, until patients had received a maximum of nine cycles. Four patients have completed eight or nine cycles.

“The median overall survival of approximately six months compares favorably with other studies of chemotherapy in carcinoma of unknown primary site, most of which have studied cohorts with a median age 10 years younger than in this study,” he said.

“Our early follow-up suggests that this gemcitabine and carboplatin regimen is well tolerated with an encouraging level of activity in poor-prognosis elderly patients with carcinoma of unknown primary site.”

The combination of gemcitabine and carboplatin was selected because the regimen is known to be effective against several tumor types and is generally well tolerated.

A 1986 retrospective study from Yale-New Haven Hospital that covered more than 1,500 cases of carcinoma of unknown primary site over nearly 60 years reported a median survival of about five months.

A quality-of-life analysis is being performed, Dr. Pittman added.

Barbara McAneny, MD, a medical oncologist with New Mexico Oncology/Hematology Consultants, Ltd., in Albuquerque, said she has been using the combination in her patients with carcinoma of unknown primary site.

Dr. McAneny, who represents ASCO in the House of Delegates of the American Medical Association, said in an interview after the ASCO meeting that she and her colleagues have seen “a nice response” with the combination—“The 25% objective response rate reported in this study is significant for patients with this disease,” she said

The study received funding support from Eli Lilly Australia.

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