Implanted materials and radiotherapy – what is safe?

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René Botha explains the impact that implanted materials have on radiotherapy treatment.

Radiotherapy is a treatment modality used to treat various malignancies throughout the body. Treatment courses generally range from one to 10 days for palliative treatments to five to seven weeks for cases treated with curative intent. 

Delivery of contemporary radiotherapy involves personalised planning using sophisticated computer software that takes into account the various densities of different tissues. Implanted materials, like dental restorations, orthopaedic implants, breast expanders and medical devices, all need to be carefully considered in the radiotherapy planning process. Not only do we consider their impact on the radiotherapy treatment delivery, we also consider their functionality after the treatment is given. 

Unlike systemic therapies, which circulate through the entire body, radiotherapy mainly effects the local area where the treatment is applied. The impact is greatest if the implanted material is in or close to the treated area. For example, if a patient’s breast is treated, the oral cavity with dental restorations shouldn’t be affected, however, a patient receiving head and neck radiotherapy would definitely need dose compensation. 

The next important consideration is the dose given to the patient. Patients who are receiving lower doses of radiotherapy may not have the same recommendations as those who require higher doses of radiotherapy. Your oncologist will guide you as to which recommendations are applicable to your specific case based on the treated area and the dose prescribed. 

Different implanted materials and their special considerations

Dental restorations 

Dental restorations, such as fillings, crowns or implants, are only relevant for patients who are receiving treatment of the oral cavity, however, they usually don’t need removal prior to treatment. Patients with dental restorations may still receive radiotherapy. When the radiotherapy planning is done, these materials are considered so that the patient still receives the optimal dose to the area that requires treatment. A personalised bite block or mouthpiece may be made to optimise the position of the jaw for the radiotherapy treatment. 

The side effects of radiotherapy in the head and neck area may affect future dental health. For this reason, your oncologist may recommend that you consult a dentist prior to radiotherapy for a dental assessment and professional cleaning. The dentist will evaluate the teeth and may recommend that compromised teeth be extracted prior to the start of the radiotherapy course. The gums will need to heal adequately before the course may commence. It’s not necessary to remove any good quality fillings, crowns or implants if the dentist is confident that these are unlikely to give problems in the future.

It’s imperative that patients who have received radiotherapy to the head and neck area continue to maintain good oral hygiene during and following the treatment to reduce the risk of serious long-term complications.

Breast expanders and implants

Following mastectomy surgery for breast cancer, breast expanders or silicone implants may be used for breast reconstruction. If the patient undergoes a skin-sparing mastectomy, a silicone implant may be implanted immediately, however, sometimes there may not be enough skin to cover an implant. In such cases, an expander may be placed under the skin. Once the skin has healed after the surgery, the surgeon then fills the expander with fluid over a few weeks and the skin stretches. The aim of this is to stretch the skin enough to allow for a permanent implant to be placed at a later stage. Neither of these exclude a patient from receiving radiotherapy.

If a patient with an expander in place requires radiotherapy, the expander should be filled to the desired size prior to the start of the radiotherapy planning. The expander contains a high-density port which is taken into account during the radiotherapy planning process, and the dose is adjusted around the port to ensure that the optimal dose is delivered. The radiotherapy shouldn’t damage the expander, however, there is a risk of extrusion (moving out of a normal position), in which case it will need to be removed.

In the case of silicone implants, the implant is similar in density to the normal tissue. As a late effect of radiotherapy in the months to years following the treatment, there is a risk of capsular contracture. This is due to formation of a scar tissue ‘capsule’ around the implant. It may cause a change in size and shape of the reconstructed breast. In these cases, the plastic surgeon would advise on surgical options to correct this. 

Orthopaedic devices 

Orthopaedic devices used to repair or replace broken or worn bones or joints include pins, plates or complete joint replacements. Like dental restorations, these are usually only of concern if they are near the treated area. 

When planning the radiotherapy, the planning radiotherapist will adjust the beam entry points so that the radiation beam doesn’t enter through the orthopaedic device. This helps compensate for the dose that would be absorbed by the joint replacement, ensuring that the target area receives the optimal dose. The radiation shouldn’t damage the orthopaedic device or its functioning. 

Medical devices

Modern medicine allows for medical devices, such as pacemakers or nerve stimulators, to be implanted for medical conditions as required. These devices are more complex than non-electronic devices as they transmit signals to improve or regulate specific organ function. These are generally more sensitive to radiation. 

If the device is in the area that requires treatment, there is a risk the device might be damaged. In certain instances, the patient may require surgery to move the device prior to treatment. If the device is an adequate distance from the treatment area and the dose to the device can be kept below its specific threshold, the patient may be treated with the device in place. 

When a patient with a medical device is planned for radiotherapy, special care is always taken to ensure that the device will not be damaged. In some cases, the supplier of the device may be contacted to attend the radiotherapy sessions to monitor the functioning of the device. In some cases, the device may also be switched off during the radiotherapy session to ensure there are no disruptions to the transmitted signals.

Should you have an implanted medical device ensure that your oncologist is informed about it and has all the details of the device so that the correct safety measures can be taken. 

Final thought

Radiotherapy techniques have improved significantly over time. We are able to deliver more conformal treatment plans than ever before which has in turn allowed for reduced side effects. In most cases, we are able to compensate for implanted materials and safely treat patients with implanted materials. It’s important to remember that radiotherapy is not a one-size-fits-all treatment. The recommendations for one patient may significantly differ from another. Always discuss your concerns with your treating oncologist. They will be able to give the best advice about your specific implanted material with regards to your treatment.

References

1. Devi S, Singh N. Dental care during and after radiotherapy in head and neck cancer. Natl J Maxillofac Surg. 2014 Jul-Dec;5(2):117-25. doi: 10.4103/0975-5950.154812. PMID: 25937720; PMCID: PMC4405951.
2. Hoffman R, Kelly J et al. Dental oncology in patients treated with radiation for head and neck cancer. CSO 2016; 14(9):374-379. Frontline medical communications. Doi: 10.12788/jsco.0294
3. https://www.plasticsurgery.org/news/blog/what-is-capsular-contracture-and-how-can-it-be-treated.
4. Zaremba T, Jakobsen AR, Søgaard M, Thøgersen AM, Riahi S. Radiotherapy in patients with pacemakers and implantable cardioverter defibrillators: a literature review. Europace. 2016 Apr;18(4):479-91. doi: 10.1093/europace/euv135. Epub 2015 Jun 3. PMID: 26041870.

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