Discoveries in radiation oncology and cancer treatment presented at annual ASTRO meeting

November 08, 2001

SAN FRANCISCO, November 6-7, 2001 - Following are highlights from research presented by researchers at Memorial Sloan-Kettering Cancer Center (MSKCC) during this week's annual meeting of the American Society for Therapeutic Radiation and Oncology (ASTRO).

Embargoed for Release on November 7, 2001, 5:30 pm ET: Certain Risk Factors Help Predict Outcome of Radiation Therapy after Prostate Surgery Fails

MSKCC researchers have developed an effective prognostic model based on a number of risk factors for patients whose prostate cancer has returned after surgery and are considering radiation therapy as a next step.

At least 20-25 percent of patients develop a rising prostate specific antigen (PSA) level within 10 years after surgery. For some that means that the prostate cancer is present in the prostate bed or in the circulating blood stream. MSKCC researchers retrospectively analyzed 115 patients whose lymph nodes were cancer-free at the time of surgery, had a rising PSA, and then received three-dimensional conformal radiation therapy. At four years, 45 percent of patients had a negligible PSA level of less than 0.2 ng/ml. Those who had a higher PSA level were considered to have failed treatment.

"Because the definition of PSA failure is controversial and many doctors do not agree on the ideal cutoff after surgery or postoperative radiation therapy, this study used a very conservative measure of PSA to determine how these patients responded to radiation," said Matthew Katz, MD, radiation oncologist at MSKCC and lead author of the study.

The authors found that the patients most likely to fail radiation treatment fit into four groups: patients whose pathology showed involvement of the seminal vesicles (which make fluid essential for ejaculation); patients who had a high Gleason score; patients whose margins were clean after surgery (the rising PSA indicated tumor cells were circulating in the blood rather than present in the tumor bed); and patients who had a higher PSA (more than 0.6 ng/ml) at the time radiation therapy was delivered.

The data indicate that 94 percent of patients without any of these risk factors responded well to treatment and had stable PSA levels four years later. If they had one of these risk factors, they had a 73 percent chance of success with radiation therapy. If they had two risk factors, they had a 22 percent chance of success.

Patients who had three or four risk factors did not respond well to treatment.

"This information will help urologists and radiation oncologists decide which patients with a rising PSA after prostatectomy are most likely to be successfully treated with radiation therapy," said Dr. Katz.

Embargoed for Release on November 6, 2001, 3:00 pm ET: PET Scans Useful in Assessing Lung Cancer Patients' Response to Radiation Therapy

A new study finds that Positron Emission Tomography (PET) scanning can be used to determine the effectiveness of high-dose radiation therapy for non-small cell lung cancer (NSCLC).

While PET scans have been shown in previous studies to be useful in the pre-treatment evaluation of patients with NSCLC, its role after radiation therapy had remained unclear up until now because the radiation itself could be misinterpreted as tumor on the scan. "This study has given us a measure of how much abnormality is acceptable on a PET scan so we can be more confident about what is tumor and what is a change due to radiation," said Kenneth Rosenzweig, MD, radiation oncologist at MSKCC and lead author of the study.

PET is a non-invasive diagnostic imaging procedure that measures the level of metabolic activity in various organs.

The number used to measure this metabolic activity is called the standard uptake value (SUV).

The study evaluated 45 patients with NSCLC, the most common type of lung cancer. It is usually associated with a history of smoking and affects about 150,000 people in the US each year. The research shows that patients whose PET scan showed a post-treatment SUV of less than or equal to 3.5 had a 17 percent chance of local failure whereas 77 percent of those whose scan showed an SUV greater than 3.5 were likely to have their cancer return.

The patients in the study were treated with three-dimensional conformal radiation therapy between 1998 and 2000 at MSKCC. The median time from the end of treatment to the first post-treatment PET scan was four months. Doctors used clinical assessment, pathology, and computed tomography (CT) to determine whether a patient's cancer returned to the site after treatment and compared those results with a PET scan.

"A PET scan reassures the patient early on that cancer is not present without having to go through invasive procedures and biopsies, which carry greater discomfort and expense," said Dr. Rosenzweig. "If cancer is present, early detection of recurrence with PET allows doctors to initiate appropriate treatment - or palliation - sooner in the course of the disease."

Embargoed for Release on Tuesday, November 7, 2001, 3:00 pm ET: High Dose Radiation Therapy Improves Survival in Patients with Mesothelioma

Mesothelioma, a rare but extremely lethal type of lung cancer affecting the lining of the lung, has always been a challenge to treat. A new study finds that extensive surgery (removal of the lung and the lining of the lung) followed by high dose radiation therapy is well tolerated, and may improve local disease control and survival rates.

About 2,200 cases of mesothelioma are diagnosed per year, the majority of which are caused by environmental exposure to asbestos.

"For many years we were unable to give too much radiation to the chest because of extreme toxicity, but new technologies and treatment techniques have helped us get around that," said Santosh Yajnik, MD, radiation oncologist at MSKCC and lead author of the study. One of the reasons doctors were able to give higher doses of radiation therapy to patients in this study was because the affected lung had been completely removed.

In the last four years, MSKCC has seen about 365 patients with mesothelioma, and approximately 63 patients were treated with this type of extensive surgery. This experience makes the Center one of only a handful of hospitals in the country with expertise in this area.

In this study, 32 patients with various stages of mesothelioma who had surgery at MSKCC between 1990 and 2000 were treated with high dose radiation therapy. The median overall survival was 17 months compared to median survival rates of about 12 months historically seen in patients who have surgery alone. Researchers noted that patients with earlier stage disease experienced better survival rates than those with late stage cancer. They also observed that patients tolerated the treatment well without suffering high levels of toxicity.

Four patients had local tumor recurrence, seven had local and distant recurrence, and nine patients had distant disease recurrence. "Now that we know radiation helps with local control, the next step is to study whether chemotherapy can further reduce mortality rates and improve distant control of the tumor," concluded Dr. Yajnik.

Memorial Sloan Kettering Cancer Center

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