Adapting to Patient’s Limitations

Ella Horgan (00:04):

Hi everyone. My name is Ella. I’m a radiation therapist working in the Prince of Wales Hospital in Sydney. Today, I’ll discuss with you a case study titled Adapting to Patients’ Limitations. This case study discusses a head and neck cancer patient with multiple limitations, making his treatment a little bit challenging. However, with the use of SGRT along with daily Cone Beam CTs, we were able to treat this man completely massless, all while making very minimal moves with our imaging scans.

Ella Horgan (00:33):

This patient is a 91-year-old man diagnosed with a preauricular metastatic squamous cell carcinoma on the left side. After careful consideration, the radiation oncologist determined the most appropriate treatment approach would be radiation therapy targeting the left parotid bed and upper neck. However, this case presented significant challenges due to the patient’s numerous comorbidities including chronic obstructive pulmonary disease, a high body mass index, and increased risk of falls due to instability and vertigo. These factors made the treatment plan more complex and required careful management. As you know, the standard immobilization for a head and neck cancer patient would be a five point serum plastic mask, a comfortable headrest elevating the chin and a knee block supporting the knees.

Ella Horgan (01:22):

Some departments even use an open face, head and neck mask. However, due to the patient’s comorbidities, a modified immobilization approach was necessary. Given the severe vertigo he experienced, he was unable to lie flat. As a result, the patient was positioned on an elevated breast board with a 20-degree tilt. A VAC bag was utilized to provide head support and a knee rest was placed under the patient’s knees for comfort. Micro port tape was applied as an optional aid in the setup, which the patient agreed to as it had provided additional stability and reassurance, ensuring that he remains still. An IMRT plan was developed for this patient with the Isocenter strategically positioned 10 centimeter inferior to the planning target volume to avoid the risk of collision. The dose constraints for the organs at risk were all within the specified tolerances outlined by the EVQ guidelines. A 0.5 CENTIMES meter, CTV-PTV margin was decided by the radiation oncologist. This margin size is in line with the recommended guidelines for standard head and neck treatments using a mask. A study by Eser Al looked at the setup and fractional motion of using SGRT for head and neck cancer patients. The results of this study found the massless setup with SGRT and Cone BEAM CT were just as accurate as treatment with a mask. SGRT showed that inaction motion was gradual during the treatment and the CTV-PTV margin correcting for the inaction motion was 1.7 millimeters per OSUs treatment. This study agrees with our 0.5 centimeter margin being sufficient for accurate PTV coverage.

Ella Horgan (03:09):

After the plan was exported to SGRT, a region of interest was created. This region of interest included the nose, cheeks, chin and neck. After the plan was exported to SGRT, a tolerance of 0.2 centimeters was set across the translations and two degrees per rotations. The setting for beam control was turned on for the treatment to ensure any movement greater than 0.2 would pause the treatment. The patient was prescribed 48 gram and 20 fractions at 2.4 gram per fraction. SGRT was used for the patient set up and during treatment, a Cone Beam CT was created and used daily to ensure accurate patient positioning. A dummy run was performed on the Linac prior to day one to assess if collisions would occur. The result of this determined that HEXA pod could not be utilized, therefore, only translational shifts could be applied during treatment for a patient set up. Translations and rotations on SGRT were corrected for. The video function was also used daily to ensure the patient’s head and shoulders were in the correct position. After the patient was positioned on day one, the gantry was rotated around the treatment couch with imaging panels extended to assess whether the gantry blocked the cameras potentially causing the SGRT to flicker. This dummy run showed us that the cameras were not obstructed.

Ella Horgan (04:48):

Once this was complete, a Cone Beam CT was required. Due to the Isocenter positioning. The superior part of the PTV was caught from our imaging scans. This is another challenge experienced during treatment. However, as you can see from the Cone Beam CT above, there were enough slices to make a good clinical judgment on the patient’s positioning. All translations were then applied. The imaging panels were put away to ensure the SGRT cameras were not blocked during treatment. A new reference capture was taken to monitor the new acquired position and the SGRT response button was turned on. The results from the 20 fractions are shown here on fraction one, three and four. The largest translational ships were 0.6, 0.8 and 0.6, respectively. As you can see from the line graphs, the shift was decreasing. The shifts are decreasing from fraction four onwards. These shifts are 0.5 centimeters and reasons for this could be consistent staff treating him daily, understanding his setup, and altering the region of interest as necessary after the first few fractions. However, with the help of SGRT for set up, these post-imaging shifts were minimal. While the patient’s treatment was ultimately successful, several challenges were encountered throughout the process. As discussed previously, the Isocenter positioning presented some difficulties in reviewing the Cone Beam CT as certain slices of the PTV were missing from the image. Furthermore, due to the inability to use the HEXA pod, rotational shifts could not be made, which added complexity to the treatment setup. Additionally, the patient faces challenges in getting on and off the treatment couch. This issue was overcome by the presence of additional staff members during treatment, ensuring the patient’s safety and comfort.

Ella Horgan (06:44):

After completing the patient’s treatment, it was interesting to evaluate the result of the Cone Beam CT scans and reflect on the advantages and drawbacks of massless treatment. The benefits of massless treatment include enhanced patient comfort, cost savings for the department, reduced time spent on mass creation, alleviated patient anxiety and greater flexibility and positioning. However, the drawbacks include the need for monitor closer monitoring of the patient, specific patient criteria for eligibility such as pediatric cases, and the potential for longer setup times. In conclusion, by using SGRT, we successfully provided effective treatment to a patient with numerous limitations, all while eliminating the need for thermoplastic mass for immobilization. Importantly, the CTV-PTV margin remained consistent between the massless approach and the traditional mass-based method, ensuring the treatment precision was maintained. This approach highlights the potential of SCRT and Cone Beam CTs as a reliable and effective alternative to conventional immobilization techniques, especially with patients with treatment limitations. Thank you.