Patients with breast cancer can be trained to hold their breath for more than 5 minutes while undergoing radiotherapy treatment, according to results of a study led by researchers in the United Kingdom.
This could allow radiation to be administered in one dose, minimizing the risk for damage to healthy surrounding tissue.
Michael J. Parkes
Most radiotherapy treatments result in damage to healthy tissue when the body moves as the patient breathes.
Michael J. Parkes, MA, DPhil, FHEA, of the School of Sport and Exercise Sciences at University of Birmingham, and colleagues evaluated whether patients could be trained to achieve a single breath hold to reduce damage to healthy tissue, thereby increasing long-term OS and improving quality of life.
The study included 15 women undergoing radiation treatment for breast cancer. All women were nonsmokers. None had respiratory, cardiovascular or neurological diseases, diabetes or obesity.
Results showed women were able to hold their breath for an average of 5.3 minutes, with the longest breath hold of 6.6 minutes.
Parkes spoke with HemOnc Today about the potential for the breath-holding technique to improve outcomes among patients undergoing targeted radiotherapy.
Question: Can you explain this technique?
Answer: When breath-holding, breathing stops. However, the body continues to consume oxygen from air in the lungs and oxygen stored in blood to produce carbon dioxide. Eventually, a person will pass out. We give patients a head start by putting more oxygen into their lungs than normal and by approximately halving the carbon dioxide levels in blood. Putting more oxygen into the blood is impossible — it is already approximately 97% saturated with oxygen — but breathing 60% oxygen instead of room air, which is approximately 21% oxygen, is easy. This means more oxygen is stored in the lungs. There are only two ways of lowering blood carbon dioxide levels: voluntary hyperventilation, which is difficult and unpleasant, or mechanical ventilation by facemask. We train patients to let a mechanical ventilator breathe for them. They lie there listening to music and sometimes even fall into a light sleep. We increase the ventilation above their normal levels and, therefore, can reduce their blood carbon dioxide levels. We then tell them to inhale maximally and breath-hold.
Q: How are patients
A: We allow about 2 hours on the first training session and demonstrate to patients that, even on day 1, they can breath-hold safely for far longer than they think. We get patients to demonstrate how long they think they can breath-hold, and this typically is around 40 seconds. We then start training them to use breathing techniques singers use to inhale better and to relax. They breath-hold for about 1 minute, then breathe 60% oxygen, after which they can breath-hold for about 1.6 minutes. We train them to let a mechanical ventilator take over their breathing. Next, we use preoxygenation and hypocapnia, and they can hold for about 3 minutes on day 1. Once they master this technique, believe they can do it and realize they are safe, they relax and start breath-holding longer in each subsequent session. They tend to stabilize at just over 5 minutes and can deliver these breath-holds on repeated sessions.
Q: Is this something that other physicians can easily train their patients to do?
A: Yes, very much so. The training can also be done outside a busy radiotherapy department, so patients can learn in their own time and build their confidence. Once ready, they can go to the radiotherapy department. We have published the safety limits for such breath-holds and what equipment is required to monitor safety. We tell patients to stop breath-holding once they reach our safety limit. Most patients break their breath-hold above 5 minutes but have not yet reached our safety limits.
Q: What are the potential implications for radiotherapy?
: All tumors in the chest and abdomen move with breathing, sometimes by several centimeters per breath. The simplest and long-established way to manage this is to treat a margin of healthy tissue around the tumor to guarantee to hit this moving tumor. The irradiation process also takes a finite time, perhaps 2 minutes for breast radiotherapy but much longer for some other tumors. The approach that is becoming widespread for patients with breast cancer is treatment during a series of repeated short breath-holds of around 20 seconds. Although this is likely to be a big improvement on treatment during free breathing, the amount of movement during the first 20 seconds of any breath-hold is still significant.
The goal for radiotherapy is to know exactly where the tumor is and to ‘freeze’ its position during treatment. The longer the patient can breath-hold in a single session, the less the tumor will move. Breath-holding should offer a large improvement for radiotherapy by reducing the volume of healthy tissue that is irradiated.
By expanding the chest, the lungs are less dense and, therefore, less sensitive to radiation damage. Also, the left breast is moved away from the heart, thereby reducing the long-term risk for heart disease from radiotherapy. There is much work to be done to further improve the accuracy with which radiotherapy can be delivered, and our approach is an important strand of this work. We happen to have done our experiments on patients with breast cancer, but it is applicable to all other chest and abdominal tumors.
Q: How does
movement during breath-holding compare with that of
A: Tumors do not stay still even during breath-holding. The chest has some initial settlement during the first 20 seconds of breath-holding, then gradually deflates throughout the breathing. This happens because oxygen gas extracted from the lungs cannot be replaced by an equal volume of carbon dioxide gas, which stays in blood because the air in the lungs is no longer refreshed. The chest surface deflates by about 2 mm per minute, which is about 10 times less movement than with breathing.
Q: Were you surprised by any of your findings?
A: We know from previous work that healthy volunteers could breath-hold for about 7 minutes with this technique. The longest we have seen is 12 minutes, and we would love to do more research to find out why some can hold safely for so much longer than others. We had no idea how long patients with cancer would be able to hold, but we guessed because of illness, age, fitness, etc, that they would hold for much less. As long as they could hold for 2 to 3 minutes, we would have something useful. We were astonished that our first patient on her first day held for more than 3 minutes. We were even more astonished when all could hold for longer and longer on subsequent days.
Q: What is the take-away message from your study?
A: Clinicians should be aware that patients can breath-hold, with the help of preoxygenation and hypocapnia, for far longer than the 20 seconds that patients are currently expected to hold. We are keen to work with clinicians to make this simple, cheap and noninvasive technique something that could be offered in every radiotherapy department.
Q: What should future research entail?
A: The physiology of breath-holding is not taught in medical schools because, until now, it had no obvious medical application. Now, we need to raise the awareness of clinicians about the breath-holding capability of patients and how this might improve both radiotherapy and diagnostic imaging. We need to raise more funding to sort out the equipment and logistical issues to make this a routine technique that any radiotherapy department can use. We also need to fund clinical studies to provide the evidence for a cost–benefit analysis that will justify its adoption.
Q: Is there anything else you would like to mention
A: For patients, the whole cancer treatment process often seems ‘passive.’ For the first time, we are training them to do something where they can contribute, and they can see themselves getting better. It gave them a great feeling of satisfaction to go home and tell their partners that they could breath-hold for far longer than their partners have ever done. It is incredibly satisfying for us to work with each patient and to share their pleasure when they hold for longer. It is often thought that the older you are, the less well you can breath-hold, but this is not the case. We were delighted when our oldest patient, at age 74 years, held for 5.3 minutes. During the experiments, we deliberately did not tell patients how others were doing, because we did not want them to feel pressure to perform. However, we did not realize how competitive patients were and they would talk to each other in the waiting room and compare times anyway. – by Jennifer Southall
For more information:
Michael J. Parkes, MA, DPhil, FHEA, can be reached at School of Sport Exercise and Rehabilitation Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom; email: firstname.lastname@example.org.
Parkes MJ, et al. Br J Radiol. 2016;Published online ahead of print May 11.
Disclosure: Parkes reports no relevant financial disclosures.