SUPR-3D: Simple Unplanned Palliative Radiotherapy Versus 3D Conformal Radiotherapy for Patients With Bone Metastases

For this study, SUPR (simple unplanned palliative radiotherapy) refers to the delivery of radiation to the treatment area with a simple technique, either two opposed fields (parallel opposed pair), or a single direct field. The entire portal is exposed to the specified dose and therefore does not spare normal tissue. This technique requires minimal calculation, and typically the dose distribution is not reviewed by the radiation oncologist or medical physics.

In general, the adverse event profile of RT is associated with irradiation of normal tissue within the treatment field. With the dose prescribed in this study, the probability of serious adverse effects is exceedingly low. However, fatigue, soreness, pain flare, and skin-redness in the irradiated area are relatively common adverse events. In addition, site-specific toxicity could occur, including esophagitis, nausea, or diarrhea when there is dose delivered to the GI tract. Avoiding this toxicity is a motivating factor for the study.

In order to deliver 3D Conformal Radiotherapy, a computerized tomography (CT) simulation is used to develop the treatment plan. The goal is to deliver a conformal radiation dose to the target volume with maximal sparing of the normal tissue. VMAT (Volumetric Modulated Arc Therapy) is a type of 3D conformal RT, and delivers the radiation dose more conformally than SUPR, possibly reducing acute and late toxicity. The disadvantages of VMAT include more complex planning and quality assurance processes compared with SUPR. The complex planning required can be time-consuming, which can have a significant impact on departmental resources, and the wait time for the patient.

Bone metastases are the most common site of distant metastases and can cause severe and disabling effects, including pain, spinal cord compression and pathologic fracture. These complications can greatly affect a patient's quality of life and cause immense suffering.

Radiotherapy (RT) is an effective treatment for palliative patients with painful bone metastases. It is also efficacious in preserving function and maintaining skeletal integrity, while minimizing the occurrence of adverse skeletal related events. There is a significant amount of evidence showing that a single fraction (SF) of RT provides equivalent pain relief as multiple fractions (MF), which are associated with more acute toxicity, are less convenient for patients and costlier for the health care system. Therefore, single fraction radiation therapy (SFRT) is encouraged, but 20 Gy in 5 fractions is also allowed in this study, though should be chosen only in patients with a complicated bone metastases by fracture, neurological deficit (e.g. spinal cord compression), or a large soft tissue component. In patients with advanced disease, management strategies focus on improving quality of life (QOL), rather than conventional endpoints such as survival.

Currently, the standard of care in British Columbia for palliative patients with bone metastases is SUPR. In other jurisdictions, however, factors such as physician remuneration make other complex planning techniques more popular.

BC Cancer is publicly funded with no direct costs to patients. All RT in the province is provided by 6 centres where radiation oncologists receive an annual salary, which are independent of RT treatment technique and duration. Due to the lack of financial incentive associated with a more complex RT plan, BC Cancer is a unique clinical setting to assess the use of VMAT versus SUPR.

As facilities providing RT have gained more experience with VMAT and improvements to VMAT planning software have been made, the planning time required has been reduced. Previously, approximately 2 weeks was required for a team at the BC Cancer to create a VMAT plan for a palliative patient with bone metastases; however, we hypothesize this can now be reduced to three days in settings with low dose prescription.

This study will allow the investigators to determine if there is reduced toxicity associated with VMAT compared to SUPR with only a modest impact on resources. The investigators hypothesis is that VMAT will have reduced toxicity compared with SUPR for palliative patients with bone metastases. The investigators also hypothesize that there will be no difference between the two arms in terms of pain response, due to the fact that the doses are equal. This hypothesis is driven by the radiobiologic rationale, which defines effective RT as the ability of radiation to induce tumour cell death while sparing normal cells.

The importance in determining if there is any benefit in terms of toxicity with VMAT compared with SUPR for palliative patients with bone metastases is obvious when consequences related to its adoption are considered. As previously discussed, although the planning time has been drastically reduced, there is still an expected modest increase in resources required to carry out a VMAT plan. For patients, the pre-treatment process of VMAT is more burdensome, i.e. patients have to wait longer before receiving VMAT as compared to SUPR, due to the increased plan complexity. Therefore, it is important to consider the patient experience in relation to the RT administration.

In summary, evidence that either supports or refutes the hypothesis that VMAT will have reduced toxicity compared with SUPR for patients with bone metastases will be helpful in guiding future practices. We are not aware of any other randomized control trials (completed or ongoing) that have addressed this issue, though a London Ontario study is randomizing patients receiving palliative lung RT to SUPR vs VMAT. Due to the implications of VMAT on departmental resources and patient experience, better evidence from a randomized control trial is required before the widespread use of this technique can be justified.