Volumetric Modulated Arc Therapy (VMAT)

Volumetric modulated arc therapy (VMAT) is a form of radiation therapy used to treat cancer. During treatment, a machine rotates around your body, sending multiple energy beams of varying strengths to kill cancer cells and destroy tumors. It treats various cancers, including prostate cancer, lung cancer and head and neck cancers, among others.

What is volumetric modulated arc therapy (VMAT)?

Volumetric modulated arc therapy, or VMAT, is a type of external beam radiation therapy (EBRT)  healthcare providers use to treat cancer. With EBRT, a machine that never touches your body sends radiation to destroy tumors. VMAT is a newer form of EBRT that was introduced in 2007. With VMAT, the machine rotates around your body while you’re lying down, delivering continuous doses of radiation toward a tumor. No radiation source is placed inside your body, so there’s no concern of being radioactive during or after the radiation treatments.

VMAT is also a form of intensity-modulated radiation therapy(IMRT). IMRT sends various doses of radiation toward a tumor across multiple smaller beams instead of using a single radiation beam. This technique allows healthcare providers to direct high doses of radiation toward tumors without exposing the surrounding healthy tissue to harmful amounts of radiation.

During VMAT, you receive customized doses of radiation as a machine encircles your body in one or more rotations, or arcs.

What is VMAT used for?

The precise dosage and delivery volumetric modulated arc therapy provides makes it a good option for treating oddly shaped tumors or tumors close to vital organs. For example, your cancer provider, or oncologist, may recommend VMAT if you have a tumor wrapped around an organ.

VMAT is a common form of radiation therapy used for prostate cancer, head and neck cancers, and lung cancers, among many others, including:

• Anal cancer
• Brain cancer
• Breast cancer
• Cervical cancer
• Colorectal cancer
• Esophageal cancer
• Lung cancer
• Nasopharyngeal cancer
• Oropharyngeal cancer
• Many others.

What type of radiation does VMAT use?

Volumetric modulated arc therapy uses photons (X-rays) generated by a medical linear accelerator. This machine is called a LINAC. The machine aims small beams of varying intensities at a tumor as it rotates around you.

Procedure Details

How does VMAT work?

Volumetric modulated arc therapy (VMAT) delivers the maximum radiation dose to the cancerous tumor without exposing healthy tissue to harmful radiation levels. As the machine rotates around you, it continually adjusts the shape and strength of the radiation beams directed toward the tumor. High doses of radiation reach the tumor and destroy cancer cell DNA, causing these cells to die.

What happens before VMAT?

Treatment planning is an essential part of VMAT. As part of your diagnosis, your cancer care team generates 3D images (usually using CT scans or MRI and/or PET scans) of your body. They use these images to identify the tumor and nearby organs that need to be protected from the radiation. They determine the radiation dose required to destroy the tumor.

During a planning or mapping session called simulation, or “sim,” your care team will position you on a treatment couch. They’ll line you up in relation to the LINAC machine so that the radiation will strike your tumor at the precise location once it’s time for your treatment session. You may receive:

• Temporary or permanent markings (like a small tattoo) on your body that show the tumor’s location.
• Special accessories like a mold or mask that hold your body in place during treatment sessions.

Sim may take place during a single session. Or it may take a few visits for your care team to design radiation beams that conform to your tumor’s shape and location exactly. VMAT radiation beams can be as small as 2.5 x 5 millimeters, roughly the size of a pencil tip.

What happens during VMAT?

A healthcare provider called a radiation therapist will position you as you were during the mapping session (or simulation). They’ll operate the LINAC machine from a separate room. You’ll be able to communicate via a two-way microphone.

During the treatment session, the machine will rotate slowly around you. As it moves, radiation beams of varying shapes and dose intensities target your tumor. You won’t feel the beams. The radiation therapist will monitor your treatment in real-time to ensure you’re receiving the right amount of radiation in the right spots.

This precise delivery method usually only requires a rotation or two per treatment session for you to receive a full radiation dose.

How long does VMAT treatment take?

Treatment sessions take about 20 minutes. Most of that time will involve the radiation therapist positioning you for treatment. It takes approximately two minutes for the LINAC machine to deliver the radiation.

Depending on your diagnosis, you may need daily VMAT treatment sessions for several weeks. Ask your oncologist about your treatment schedule.

What happens after VMAT?

You’ll be able to leave the treatment facility that same day and resume your regular schedule.

Risks / Benefits

What are the advantages of VMAT?

The main advantages of volumetric modulated arc therapy (VMAT) are precision and speed.

• Precision: VMAT focuses the radiation on the tumor while sparing healthy tissue.
• Speed: Each VMAT treatment takes around two minutes — often less. Faster treatments improve the accuracy of radiation delivery. They also reduce the time you have to lie still for treatment and take less time out of your day.

What are the side effects of VMAT radiation?

Because VMAT spares healthy tissue from harmful radiation, you’re less likely to experience cell damage. This leads to reduced side effects. Still, some cell damage is unavoidable. Most side effects following VMAT affect the part of your body that received direct radiation.

Side effects depend on the area that’s getting treated and may include:

• Fatigue (most common).
• Nausea and vomiting
• Diarrhea
• Headaches
• Hair loss
• Skin irritation (itching, dryness, redness, swelling or peeling skin).

Recovery and Outlook

What is the recovery time?

Everyone’s experience is different. You may experience side effects and feel better shortly after treatment ends or you may need a few months to recover completely.

Ask your oncologist what to expect based on your health and treatment plan.

When should I see my healthcare provider?

You’ll need follow-up appointments to check on your progress after VMAT. Keep all scheduled appointments. Come prepared to ask questions about your treatment response and report any symptoms or side effects you’re experiencing.

Additional Common Questions

What is the difference between VMAT and IMRT?

Volumetric modulated arc therapy (VMAT) is a type of IMRT (intensity-modulated radiation therapy). Both treatments destroy tumors by sending customized doses of radiation that kill cancer cells without exposing healthy tissue to harmful radiation levels. The biggest difference is that while VMAT uses a machine that rotates continuously around you to send the beams, IMRT doesn’t.

A note from Cleveland Clinic

Volumetric modulated arc therapy (VMAT) is a newer form of radiation therapy that customizes radiation treatment to target tumors without exposing healthy tissue to harmful radiation. Members of your cancer care team work hard behind the scenes to design multiple energy beams that target your tumor precisely. Although you’ll likely need multiple treatment sessions, the actual treatment time is quick. It only takes a few rotations of the machine (a few minutes) to deliver the optimal radiation dose to kill cancer cells.

 

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Blood test accurately detects over 50 types of cancer, often before symptoms show

Researchers have developed the first blood test that can accurately detect more than 50 types of cancer and identify in which tissue the cancer originated, often before there are any clinical signs or symptoms of the disease.

In a paper published in the leading cancer journal Annals of Oncology [1] today (Tuesday) the researchers show that the test, which could eventually be used in national cancer screening programmes, has a 0.7% false positive rate for cancer detection, meaning that less than 1% of people would be wrongly identified as having cancer. As a comparison, about 10% of women are wrongly identified as having cancer in national breast cancer screening programmes, although this rate can be higher or lower depending on the number and frequency of screenings and the type of mammogram performed.

The test was able to predict the tissue in which the cancer originated in 96% of samples, and it was accurate in 93%.

Tumours shed DNA into the blood, and this contributes to what is known as cell-free DNA (cfDNA). However, as the cfDNA can come from other types of cells as well, it can be difficult to pinpoint cfDNA that comes from tumours. The blood test reported in this study analyses chemical changes to the DNA called "methylation" that usually control gene expression. Abnormal methylation patterns and the resulting changes in gene expression can contribute to tumour growth, so these signals in cfDNA have the potential to detect and localise cancer.

The blood test targets approximately one million of the 30 million methylation sites in the human genome. A machine learning classifier (an algorithm) was used to predict the presence of cancer and the type of cancer based on the patterns of methylation in the cfDNA shed by tumours. The classifier was trained using a methylation database of cancer and non-cancer signals in cfDNA. The database is believed to be the largest in the world and is owned by the company involved in this research, GRAIL, Inc. (California, USA).

Senior author of the paper, Dr Michael Seiden (MD, PhD), President of US Oncology (Texas, USA), said: "Our earlier research showed that the methylation approach outperformed both whole genome and targeted sequencing in the detection of multiple deadly cancer types across all clinical stages, and in identifying the tissue of origin. It also allowed us to identify the most informative regions of the genome, which are now targeted by the refined methylation test that is reported in this paper."

In the part of the Circulating Cell-free Genome Atlas (CCGA) study reported today, blood samples from 6,689 participants with previously untreated cancer (2482 patients) and without cancer (4207 patients) from North America were divided into a training set and a validation set. Of these, results from 4316 participants were available for analysis: 3052 in the training set (1531 with cancer, 1521 without cancer) and 1264 in the validation set (654 with cancer and 610 without cancer). Over 50 types of cancer were included.

The machine learning classifier analysed blood samples from the participants to identify methylation changes and to classify the samples as cancer or non-cancer, and to identify the tissue of origin.

The researchers found that the classifier's performance was consistent in both the training and validation sets, with a false positive rate of 0.7% in the validation set.

The classifier's ability to correctly identify when cancer was present (the true positive rate) was also consistent between the two sets. In 12 types of cancer that are often the most deadly (anal, bladder, bowel, esophageal, stomach, head and neck, liver and bile duct, lung, ovarian and pancreatic cancers, lymphoma, and cancers of white blood cells such as multiple myeloma), the true positive rate was 67.3% across clinical stages I, II and III. These 12 cancers account for about 63% of cancer deaths each year in the USA and, at present, there is no way of screening for the majority of them before symptoms show. The true positive rate was 43.9% for all cancer types in the study across the three clinical stages.

Detection improved with each cancer stage. In the 12 pre-specified cancers, the true positive rate was 39% in stage I, 69% in stage II, 83% in stage III and 92% in stage IV. In all of more than 50 cancer types, the corresponding rates were 18%, 43%, 81% and 93%, respectively.

The test was also consistent between the training and validation sets in its ability to identify the tissue where cancer had originated, with an accuracy of 93% in the validation set.

Dr Seiden said: "These data support the ability of this targeted methylation test to meet what we believe are the fundamental requirements for a multi-cancer early detection blood test that could be used for population-level screening: the ability to detect multiple deadly cancer types with a single test that has a very low false positive rate, and the ability to identify where in the body the cancer is located with high accuracy to help healthcare providers to direct next steps for diagnosis and care.

"Considering the burden of cancer in our society, it is important that we continue to explore the possibility that this test might intercept cancers at an earlier stage and, by extension, potentially reduce deaths from cancers for which screening is either not available or has poor adherence. To our knowledge, this is the largest clinical genomics study, in participants with and without cancer, to develop and validate a blood test for early detection of multiple cancers."

The study is funded by GRAIL, the maker of the blood test. Researchers are continuing to validate the test in large, prospective studies in the USA (STRIVE and PATHFINDER studies) and the UK (SUMMIT study), and to examine its feasibility for screening populations [2].

A strength of the CCGA study is that it includes more than 15,000 participants from 142 clinics in North America, ensuring results are generalisable to a diverse population. The ongoing studies are assessing the test's performance in even broader populations. Limitations include: all the participants with cancer had already been diagnosed with cancer (e.g. via screening or patients presenting with symptoms); the study was not designed to establish the test's impact on death from cancer or other causes; at the time of this analysis, not all patients had been followed for a year, which is needed to ensure their non-cancer status was accurate; and some inaccuracy occurred in the detection of the tissue of origin for cancers that are driven by the human papilloma virus (HPV), such as cancers of the cervix, anus, and head and neck - this information is being used to improve the test's performance.

Editor-in-chief of Annals of Oncology, Professor Fabrice André, Director of Research at the Institute Gustave Roussy, Villejuif, France, said: "This is a landmark study and a first step toward the development of easy-to-perform screening tools. Earlier detection of more than 50% of cancers could save millions of lives every year worldwide and could dramatically reduce morbidity induced by aggressive treatments.

"While numbers are still small, the performance of this new technology is particularly intriguing in pancreatic cancer, for which mortality rates are very high because it is usually diagnosed when it's at an advanced stage."

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Every 25th person in the world has a sexually transmitted infection

More than one million new cases of curable sexually transmitted infections are diagnosed everyday in the age group of 15-59. The World Health Organization (WHO) came out with this finding in a new report on four sexually transmitted infections’ (STIs) burden in 2016. The total estimated burden in the year was 376.4 million.

There were 127 million new cases of chlamydia, 87 million cases of gonorrhoea, 6.3 million of syphilis and 156 million of trichomoniasis.

Approximately 13.5 per cent (50.8 million) of these infections occurred in low-income countries, 31.4 per cent (118.1 million) in lower middle-income countries, 47.1 per cent (177.3million) in upper middle-income countries and 8 per cent (30.1 million) in high-income nations, according to the report.

The research also showed that the prevalence of chlamydia, gonorrhoea and trichomoniasis increased more in women than men.

Chlamydia, syphilis and gonorrhoeaare bacterial infections spread through vaginal, anal or oral sex. And trichomoniasis is caused by a parasite called Trichomonasvaginalis.

Like Chlamydia, syphilis and gonorrhoea, trichomoniasis also spreads through sexual contacts. Both males and females are susceptible to all these four infections.

On an average, one in every 25 people in the world has at least one of these infections and some have more than one. And there is no subsequent decline in the condition since the last research in 2012.

“We’re seeing a concerning lack of progress in stopping the spread of sexually transmitted infections worldwide,” said a WHO executive. “This is a wake-up call for a concerted effort to ensure everyone, everywhere can access the services they need to prevent and treat these debilitating diseases.”

STIs spread through unprotected sexual contact and can also be transmitted during pregnancy and or in case of syphilis, through contact with infected blood.

If untreated, STIs can lead to many health problems including infertility, problems in pregnancy, and increased risk of HIV. According to an estimation mentioned in the WHO report, syphilis caused two lakh stillbirth and newborn deaths in 2016.

All bacterial STIs can be treated and cured with widely available medications. However, an article published by WHO stated that recent shortages in the global supply of benzathine penicillin, which is an antibiotic useful for the treatment of a number of bacterial infections, have made it more difficult to treat syphilis.

Rapidly increasing resistance to gonorrhoea treatments is also a growing health threat. The World Health Assembly in 2016 aims to take necessary steps to end STIs as public health concern by 2030.

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