Sirtex

Key takeaways

Sirtex belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Sirtex to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Sirtex from memory before moving on to harder problems.

Reference excerpt

Sirtex Medical Limited is a medical device firm that offers radioactive treatment for inoperable liver cancer called SIR-Spheres microspheres. Sirtex was founded in 1997 in Australia. It has offices and production facilities in the U.S., Australia, Germany, and Singapore. Following its acquisition by China Grand Pharmaceutical and CDH Genetech, Sirtex delisted from the Australian Securities Exchange (ASX:SRX) on Monday, September 24, 2018. The company is currently headed by Kevin R. Smith, who was appointed as CEO on October 16, 2019.

SIR-Spheres & microspheres mechanisms When SIR-Sphere microspheres are used to treat liver cancer, the treatment is called selective internal radiation therapy (called SIRT). This is a relatively new treatment option for people suffering from inoperable liver cancer. SIR-Spheres are very small radioactive beads about one-third the size of a human hair that are injected into tumours within the liver.

Medical uses The radioactive microspheres have a half-life of about 64 hours. They are administered by a trained interventional radiologist who specialises in minimally invasive, targeted treatments. The procedure is usually performed under local sedation. A small incision is made in the patient's groin, and a flexible catheter is guided into the liver through the femoral artery in the leg up to the tumour sites. The catheter is moved through the hepatic artery and positioned by the interventional radiologist to allow for targeted infusion of the SIR-Spheres microspheres to the site of the tumors. The microspheres take approximately 15 minutes to be infused, with the whole procedure taking about an hour. Most patients are discharged within 24 hours.

Cancers treated

Primary liver cancer Primary liver cancer, also known as hepatocellular carcinoma (HCC), is the most frequent type of liver cancer, accounting for approximately 90% of the primary malignant liver tumours in adults. Liver cancer is the sixth most prevalent malignancy and the third greatest cause of cancer-related deaths worldwide. Every year, around 600,000 instances of liver cancer are diagnosed around the world. This includes around 19,000 in the US, 54,000 in Europe, and 390,000 in China, Korea, and Japan. The incidence of HCC is rising in Asia as chronic infection with Hepatitis B and C becomes more common. Additional risk factors include iron overload, alcoholic cirrhosis and some congenital disorders. Patients with liver cancer had a lower fiver-year survival rate than those with other cancer types.

Metastatic colorectal cancer Colorectal cancer (CRC), often known as colon cancer or large bowel cancer, is the third highest cause of cancer-related deaths in the western world. Each year, an estimated 1.6 million people are diagnosed with the condition around the world. An estimated 50% of CRC patients will develop liver metastases. Sirtex targets metastatic colorectal cancer (mCRC) via SIR-Sphere microspheres. It has been thought that in 30-40% of individuals with severe illness, the liver is the only site of dissemination. At presentation, 20-25% of patients will have clinically identifiable liver metastases, and up to 50% of all patients develop liver metastases develop liver metastases within three years of primary tumor removal. On average, 25% of patients with metastatic liver disease are eligible for liver resection surgery, which is the only possible cure available to them. The remaining patients are eligible for alternative treatments such as chemotherapy and SIR-Sphere microspheres.

Research and development Sirtex is currently looking at new ways to treat other forms of cancer using the SIR-Spheres technology. This research is taking place at the Australian National University (ANU) and several institutions in the US and Europe. Sirtex is also working to develop a new technology that will help improve the treatment and survival of cancer patients. At present, this is focused on the three areas listed below.

Targeted Hyperthermia – Preparation for pre-clinical studies started in 2009 with the Australian National University in Canberra, the University of Sydney, and other institutions. The aim is to establish if heating tumours will increase the effectiveness of SIR-Spheres. Hollow Microspheres – Sirtex has exclusive worldwide rights to hollow, biodegradable microsphere technology developed by the University of New South Wales (UNSW). The company is investigating if hollow microspheres can be used to deliver a range of therapeutic agents, including chemotherapy drugs. Radioprotector Technology – Sirtex and the Peter MacCallum Cancer Centre in Melbourne have developed a compound that protects the skin from the effects of exposure to radiation. This has potential benefit for a wide range of cancer patients. It could also expand the number of patients able to be treated with SIR-Sphere microspheres. It may also be used to help protect patients with head, breast, or neck cancer from external beam radiation during treatment. Results from the largest, most comprehensive study to date evaluating SIRT in liver metastases from colorectal cancer were presented at ASCO in 2012, ASCO-GI 2013, and ASCO in 2014. The various subsets of the MORE study, led by Andrew S. Kennedy, M.D., Physician in Chief, Radiation Oncology, Sarah Cannon Research Institute, Nashville, Tenn., have demonstrated safety and efficacy as well as the same in treating the elderly. The most recent set of data presented at ASCO in 2014 documented the ability to predict the success of SIRT using standard laboratory tests prior to treatment. In addition, the global SIRFLOX study, which completed patient recruitment in 2013, will evaluate SIR-Sphere microspheres as a first-line treatment for colorectal liver metastases.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Sirtex

Start with the simplest possible case. Write down what Sirtex claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Sirtex before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Sirtex ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Sirtex

In research: Sirtex appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Sirtex in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Sirtex is common in secondary-school and first-year university syllabi. It links to neighbouring topics Australian companies established in 1997, Companies formerly listed on the Australian Securities Exchange, Medical technology companies of Australia, so understanding it makes those chapters shorter.
In everyday life: Look for Sirtex outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Sirtex in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Sirtex means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Sirtex out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Sirtex in simple terms?

Sirtex Medical Limited is a medical device firm that offers radioactive treatment for inoperable liver cancer called SIR-Spheres microspheres. Sirtex was founded in 1997 in Australia.

Why does Sirtex matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Sirtex?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Sirtex.