Carbon Ion Radiotherapy Promising for Inoperable Spinal Tumors

Megan Brooks

August 12, 2013

Carbon ion radiotherapy (CIRT) is a promising option for patients with spinal tumors that cannot be surgically removed, say researchers from Japan. This form of radiation is not currently available in the United States but is being tested in Germany.

CIRT can control cancer growth and prolong life in this "challenging" patient population, they report online today in the journal Cancer.

"In Japan, there are 3 working facilities providing [CIRT]," Reiko Imai, MD, PhD, from the Research Center Hospital for Charged Particle Therapy, National Institute of Radiological Sciences in Chiba, told Medscape Medical News. "The access is open for patients with unresectable sarcomas considered to be radioresistant tumors."

Safe and Effective, Preserves QoL

Dr. Imai and colleagues carried out a retrospective review on data on 47 patients (24 men and 23 women) with 48 medically unresectable spinal sarcomas, excluding sacral tumors, who received CIRT between 1996 and 2011. Most of the patients (88%) had tumors located less than 5 mm from the spinal cord.

The median age of the patients was 54 years; they were enrolled in phase 1/2 and phase 2 clinical trials of CIRT for bone and soft tissue sarcoma. The applied dose ranged from 52.8 gray equivalents (GyE) to 70.4 GyE (median, 64.0 GyE) in 16 fixed fractions during a 4-week period.

The median follow-up was 25 months, and the median survival was 44 months (range, 5.2 to 148 months).

The researchers say CIRT yielded a 5-year local tumor control rate of 79% and overall and progression-free survival rates of 52% and 48%, respectively. None of the 15 patients with tumors measuring less than 100 cm3 had a local recurrence.

No fatal toxicities occurred from treatment. One patient had a grade 3 late skin reaction, and 1 had a grade 4 late skin reaction. Seven patients suffered vertebral body compression, which was salvaged by surgical intervention. One patient had a grade 3 late spinal cord reaction.

Twenty-two of the 28 patients who were alive at last follow-up could walk without supportive devices.

Overall, these findings indicate that CIRT is "both safe and feasible," the investigators say.

"In this analysis, we would like to emphasize that [CIRT] has the potential to overcome sarcomas and to preserve patients' quality of life, even if the patients are not candidates for surgery," Dr. Imai told Medscape Medical News.

"A String of Impressive Papers"

In a telephone interview with Medscape Medical News, David Kirsch, MD, PhD, who specializes in treating sarcoma but who was not involved in the study, noted that this group from Chiba, Japan, has been conducting CIRT trials since 1996 for medically inoperable bone and soft tissue sarcomas and has published "a string of impressive papers." This includes a study reported by Medscape Medical News in 2002.

Dr. Kirsch is an associate professor of radiation oncology at Duke University School of Medicine in Durham, North Carolina. He thinks CIRT is "an important type of radiation; it has high linear energy transfer [LET] and the potential to kill cells by different mechanisms. These [new] results are good, and I think it's an important modality to test head to head with standard radiation therapy or proton radiation therapy."

CIRT is not currently available in the United States. "It would be really nice to have a carbon ion facility in the US and to do a randomized study to figure out if high LET radiation is really killing tumor cells that low LET radiation can't; that's kind of the theory," Dr. Kirsch said.

The problem is cost. "To put up a carbon ion facility is about double the cost of proton therapy, which is also really expensive, although there are certain academic centers [in the United States] that are talking about building a carbon ion center," Dr. Kirsch said.

He noted that a group in Germany is also testing CIRT against proton therapy in a randomized study.

The study was supported by the Heavy Ions Research Project at the National Institute of Radiological Sciences–Heavy Ion Medical Accelerator in Chiba (NIRS-HIMAC). The authors and Dr. Hirsch have disclosed no relevant financial relationships.

Cancer. Published online August 12, 2013. Abstract

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