When determining treatments for cancer patients, determining standard radiation doses is the product of numerous studies and trials. These standards often evolve with new findings.

Two studies, presented today at the 53rd Annual Meeting of the American Society for Radiation Oncology, further fine-tune accepted radiation dosages in both lung cancer and rectal cancer cases.

When more is less
A study on patients with lung cancer receiving radiation, for example, showed that more isn't always better. An analysis indicates that higher doses of radiation do not improve overall survival in patients with non-small cell lung cancer that has spread to the lymph nodes, according to the randomized phase III study presented by Dr. Jeffrey Bradley, a radiation oncologist at the Washington University School of Medicine.

The study compared a radiation dose of 74 Gy to the standard radiation dose of 60 Gy, Bradley stated. However, consensus has been building about increasing this dosage, which extends radiation treatment by seven extra days.

The phase III trial, which included 423 patients, randomized patients to different treatment arms: standard-dose (60 Gy) versus high-dose (74 Gy) radiation therapy and to chemotherapy with or without cetuximab, according to Bradley.

Based on the study's early findings, patients who received the higher dose of radiation (74 Gy) did not have better survival rates than those receiving the standard dose (60 Gy); therefore, the two arms of the trial which used high-dose radiation therapy were closed to patient accrual.

"The trial provides class I evidence that the standard dose of radiation therapy for stage III lung cancer should remain at its existing level of (60 Gy) and doses as high as 74 Gy are not better in curing Stage III lung cancer," Dr. Bradley said. "We are not sure why this is the case and our data is still being carefully reviewed." The arms of the study testing the standard 60 Gy dose and the cetuximab are ongoing.

When more is more

In the case of patients with rectal cancer, however, research shows that increasing the currently accepted radiation dose from 45 Gy to 50 Gy can increase tumor sterilization, according to a phase III trial presented by Dr. Jean Pierre Gerard, a radiation oncologist at Centre Antoine-Lacassagne in Nice, France.

Rectal cancer patients who use a new combination of the chemotherapy, capecitabine, together with five weeks of radiation (50 Gy) before surgery have an 88 percent chance of surviving the cancer three years after treatment, according to Gerard. The study compared a lower dose of radiation (45 Gy), which is the current accepted standard in France, where preoperative treatment with radiation and chemotherapy is the standard.

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