NICE approval for life-extending therapy

Colorectal cancer kills around 16,000 people every year, making it the UK’s second biggest cancer killer, after lung cancer. Around 40,000 people are diagnosed with colorectal cancer every year. Generally, it occurs in people older than 50 years of age, although figures for diagnosis in younger people is increasing rapidly, particularly in the under 30s, which has seen increases of 120% in the past decade. The liver is often the dominant site of metastatic disease in colorectal cancer, with around 50% of colorectal cancer patients presenting with hepatic metastates at some point during the course of their illness. Treatment of hepatic metastases depends on the extent and location of the tumour, with options including surgical resection, thermal ablation, chemotherapy, different types of arterial embolisation therapy and external beam radiotherapy.

Treating non-selectable metastases

Radioembolisation, or selective internal radiation therapy (SIRT) is a therapy developed for the treatment of nonresectable colorectal metastases in the liver. It involves the injection of around 30 million radioactive microspheres into the liver, via the hepatic artery. Each microsphere is coated with a radioactive isotope which emits beta radiation, delivering localised treatment to tumour cells, while conserving normal liver cells. The SIRT procedure enables radiation to be targeted directly into the liver tumours by using the tumour’s own blood supply. Healthy liver tissue derives up to 90% of its blood supply from the portal vein, which delivers nutrients to the liver from the gut, with only a small amount of the blood supply being derived from the hepatic artery. Liver tumours, however, derive up to 90% of their blood supply from the hepatic artery, because they need a profuse supply of highly oxygenated blood. This, therefore, provides an ideal channel to deliver targeted treatment directly into the tumour. One brand of microspheres used in the SIRT procedure are SIR Spheres, which are approximately 32 microns in diameter. This means that, following infusion, they are small enough to become lodged in the arterioles within the growing rim of the tumour. Here, they emit a high dose of radiation, while being too large to pass through the capillaries and into the venous system. SIR-Spheres contain the radioactive element Yttrium-90, which delivers beta radiation over a relatively short distance: an average of 2.4 mm in human tissue and a maximum of 11 mm. Yttrium-90 has a half-life of approximately two-and-a-half days, so most of the radiation is delivered to the tumour within two weeks of treatment. Unlike conventional external beam radiation, the microspheres selectively irradiate liver tumours, giving the ability to deliver a potent dose of radiation directly to the cancer cells over a longer period of time. The therapeutic ratio with SIRT, compared to external beam radiotherapy, is significantly improved and the tumour-absorbed doses from SIRT are typically between four and six times higher than those to the healthy liver tissue. SIRT was originally assessed by the National Institute for Health and Clinical Excellence (NICE) in 2004 and, during the course of a more recent reassessment, which has taken two years to complete, there has been confusion among Primary Care Trusts (PCTs) as to whether they should fund the treatment for eligible patients on the NHS. The recent publication of new NICE guidance,1 to replace previous guidance, supports the routine use of SIRT across the NHS, meaning that there could be greater uptake of the treatment for NHS patients, which will hopefully also increase the evidence base on the efficacy of this treatment. Commenting on the introduction of the new NICE guidance, Dr Harpreet Wasan, consultant oncologist at Hammersmith Hospital, Imperial College said: “SIRT is a pioneering treatment, which provides an innovative therapy for patients with inoperable liver tumours that complements chemotherapy. It is excellent news that NICE has now clarified its guidance with the latest evidence and this should ensure appropriately eligible patients can access SIRT on the NHS. I hope that, as a result, postcode prescribing and lengthy delays in approving eligible patients for the treatment will be eradicated.”