Athena
06-01-2008, 06:28 AM
Carbon ions tackle radioresistant tumours
Renal-cell carcinoma (RCC) is a particularly radioresistant tumour and there have been few reports of curative radiotherapy for primary RCC. Now a pilot study led by researchers at the National Institute of Radiological Sciences in Japan has shown that carbon-ion radiotherapy may provide a better option for patients with RCC (Int. J. Radiat. Oncol. Biol. Phys. doi:10.1016/j.ijrobp.2008.01.043).
The researchers examined data from 10 patients treated at the Heavy Ion Medical Accelerator in Chiba (HIMAC) between January 1997 and June 2007.
"We chose carbon-ion therapy because the relative biological effectiveness [the cell-killing effect] of a carbon beam is two to three times that of a proton or photon beam," explained lead author Takuma Nomiya. "Furthermore, the margin of the irradiation field is sharper for a carbon-ion than a proton beam. Thus, the spec of a carbon beam is definitely superior."
The patients in the study received a median total dose of 72 GyE (gray equivalents), administered in 16 fractions over four weeks. Seven patients had stage I carcinoma and three had stage IV disease.
Tumour sizes ranged from 24 to 120 mm in diameter. Six of the patients received carbon-ion treatment as they were considered inoperable. The other four, however, were deemed operable but preferred to receive the particle therapy.
After the treatment, the team performed follow-up imaging with CT and/or MRI at least twice per year. The median follow-up for surviving patients was 57.5 months (nine to 111 months). Despite the inclusion of advanced-stage and massive tumours, the carbon ions induced tumour shrinkage in all cases.
The researchers noted that this shrinkage was very slow, but in one particular case, continued for more than nine years.
The five-year local control rate, progression-free survival rate and cause-specific survival rate were all 100%, making this study one of the few reports on curative radiotherapy for primary RCC. The overall survival rate was 74%, with the two patient deaths unrelated to the cancer.
One patient developed Grade 4 skin toxicity from the treatment, which was attributed to the tumour being located closer to the skin than the other cases. Another possible cause, say the authors, could be insufficient experience with skin sparing in carbon-ion therapy. They added:
"We believe that toxicity would not occur if the same patient were treated at the present time with sufficient experience and knowledge."
The authors concluded that "although this study was conducted in only a few patients, carbon-ion radiotherapy for RCC showed very high local controllability, similar to that associated with radical surgery but with less invasiveness and greater preservation of renal function."
"Next, we want to carry out a clinical phase I/II trial of carbon-ion radiotherapy for RCC," Nomiya told medicalphysicsweb. "But that is not specifically scheduled, because the number of patients treated with the HIMAC keeps increasing and the number has exceeded the capacity of the institution."
The National Institute of Radiological Sciences is currently performing definitive carbon therapy for skull-base, head-and-neck, lung, liver, prostate, bone and soft-tissue, and pelvic cancers (recurrent rectal cancer and uterine adenocarcinoma). It is also running several phase I/II clinical trials using the HIMAC, which include studies of brain, cervical, pancreatic and oesophageal cancers.
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Renal-cell carcinoma (RCC) is a particularly radioresistant tumour and there have been few reports of curative radiotherapy for primary RCC. Now a pilot study led by researchers at the National Institute of Radiological Sciences in Japan has shown that carbon-ion radiotherapy may provide a better option for patients with RCC (Int. J. Radiat. Oncol. Biol. Phys. doi:10.1016/j.ijrobp.2008.01.043).
The researchers examined data from 10 patients treated at the Heavy Ion Medical Accelerator in Chiba (HIMAC) between January 1997 and June 2007.
"We chose carbon-ion therapy because the relative biological effectiveness [the cell-killing effect] of a carbon beam is two to three times that of a proton or photon beam," explained lead author Takuma Nomiya. "Furthermore, the margin of the irradiation field is sharper for a carbon-ion than a proton beam. Thus, the spec of a carbon beam is definitely superior."
The patients in the study received a median total dose of 72 GyE (gray equivalents), administered in 16 fractions over four weeks. Seven patients had stage I carcinoma and three had stage IV disease.
Tumour sizes ranged from 24 to 120 mm in diameter. Six of the patients received carbon-ion treatment as they were considered inoperable. The other four, however, were deemed operable but preferred to receive the particle therapy.
After the treatment, the team performed follow-up imaging with CT and/or MRI at least twice per year. The median follow-up for surviving patients was 57.5 months (nine to 111 months). Despite the inclusion of advanced-stage and massive tumours, the carbon ions induced tumour shrinkage in all cases.
The researchers noted that this shrinkage was very slow, but in one particular case, continued for more than nine years.
The five-year local control rate, progression-free survival rate and cause-specific survival rate were all 100%, making this study one of the few reports on curative radiotherapy for primary RCC. The overall survival rate was 74%, with the two patient deaths unrelated to the cancer.
One patient developed Grade 4 skin toxicity from the treatment, which was attributed to the tumour being located closer to the skin than the other cases. Another possible cause, say the authors, could be insufficient experience with skin sparing in carbon-ion therapy. They added:
"We believe that toxicity would not occur if the same patient were treated at the present time with sufficient experience and knowledge."
The authors concluded that "although this study was conducted in only a few patients, carbon-ion radiotherapy for RCC showed very high local controllability, similar to that associated with radical surgery but with less invasiveness and greater preservation of renal function."
"Next, we want to carry out a clinical phase I/II trial of carbon-ion radiotherapy for RCC," Nomiya told medicalphysicsweb. "But that is not specifically scheduled, because the number of patients treated with the HIMAC keeps increasing and the number has exceeded the capacity of the institution."
The National Institute of Radiological Sciences is currently performing definitive carbon therapy for skull-base, head-and-neck, lung, liver, prostate, bone and soft-tissue, and pelvic cancers (recurrent rectal cancer and uterine adenocarcinoma). It is also running several phase I/II clinical trials using the HIMAC, which include studies of brain, cervical, pancreatic and oesophageal cancers.
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