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Cone beam CT offers detailed imaging for precise RS delivery

A novel technique called radiation segmentectomy (RS), that delivers high doses of radiation to tumours while sparing the surrounding healthy tissue, shows promise as a curative treatment option for patients with early-stage liver cancer, according to a recent study.

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Curative treatment options for early-stage hepatocellular carcinoma (HCC) – the most common type of liver cancer – include surgery, liver transplantation and radiofrequency ablation. However, many patients are not candidates for these therapies due to the presence of other conditions. In addition, these treatments carry significant costs and potential complications. Another newly investigated option, however, is Radiation segmentectomy (RS). 

RS, conversely, is a minimally invasive option that uses the radioisotope yttrium-90 (Y90) to destroy tumours. The isotope is embedded into tiny beads that are delivered through a catheter into a blood vessel in the liver. They then travel to the site of the tumour, where they come to rest and deliver their radioactive effect while sparing much of the surrounding healthy tissue.

The procedure’s name derives from the fact that surgeons divide the liver into several segments. Using an imaging approach called cone beam CT, interventional radiologists gain a detailed view of the complex liver vasculature and can focus delivery of the Y90 to the relevant segment.

Commenting on the benefits of this imaging approach, senior study author Riad Salem, MD, chief of vascular interventional radiology in the Department of Radiology at the Northwestern University Feinberg School of Medicine in Chicago, said: “Cone beam CT has revolutionised our ability to perform segmental injections isolated to very small tumours, sparing the majority of normal tissue.”  

“Before cone beam CT, we had the ability to focus radiation, but not with this level of accuracy.”

Dr Salem and colleagues studied long-term outcomes in 70 early-stage HCC patients who had undergone RS between 2003 and 2016. They analysed the patients’ responses to treatment based on two commonly employed sets of criteria.

Based on one criteria, 90% of patients showed positive response to the therapy, of which 59% showed complete response (ie, the disappearance of all signs of cancer). Based on the second criteria, 71% achieved positive response, of which 16% achieved complete response.

RS demonstrates high degree of efficacy

RS controlled the target tumour, slowed the time to disease progression and improved survival outcomes at rates comparable to radiofrequency ablation, surgery and transplantation for early-stage HCC patients.

Almost three-quarters of patients had no progression of cancer in the target tumour five years after treatment. Median overall survival was 6.7 years, and one-, three-, and five-year survival probabilities were 98%, 66% and 57%, respectively. One-, three-, and five-year overall survival probability was 100%, 82% and 75% in patients with a baseline tumour size of 3cm or less.

“The results show that we are able to impart curative outcomes to these patients,” Dr Salem said. “Our numbers with radiation segmentectomy match or outperform those of other curative treatments in terms of tumour control, survival rate and recurrence.”

Key benefits over transarterial chemoembolisation

RS is performed on an outpatient basis, is minimally invasive and has a low toxicity profile, Dr Salem said. Given the potency of the radiation, RS outperforms transarterial chemoembolisation, another minimally invasive procedure in which cancer-killing drugs are injected into the liver’s main artery under imaging guidance and travels to the tumour microvasculature. Transarterial chemoembolisation has the additional disadvantage of requiring hospitalisation.

The researchers are continuing to follow the patients from the study group as they work on means to optimise the treatment.

“We want to see these outcomes validated in patients over the longer term,” said Dr Salem. “We also want to minimise the time from clinic visit to treatment, and fine-tune dosimetry so that we can find the optimal dose that will kill the tumour. In the right patient setting, RS can be considered curative.”

These study results were published in the journal Radiology.

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