Grid Treatment of Left Upper Lobe Lung Mass History of Present Illness: Past Medical History:

Transcription

1 1 Ellie Hawk Clinical Practicum I Case Study II April 19, 2015 Grid Treatment of Left Upper Lobe Lung Mass History of Present Illness: The patient is a 79 year-old white gentleman who was diagnosed with sarcoma of the right thigh adductor muscles in the summer of He received preoperative radiation therapy and surgery of the area. This was followed up clinically, as well as with imaging, showing signs of no recurrence at primary site. JA was diagnosed with intermediate risk prostate adenocarcinoma in December He elected to have active surveillance for this disease as he was deemed not an ideal radiation therapy candidate due to possible new fields overlapping his area of prior radiation. During the fall of 2014, the patient experienced progressive discomfort in the left chest and shoulder region for weeks. This was accompanied with occasions of weakness in the left upper extremity and difficulty grasping light items such as cups. His pain radiated through the left shoulder blade with discomfort along the medial aspect of his left arm. Spells of numbness within the left pinky and ring finger were also declared. A chest x-ray in October 2014 showed bilateral pulmonary masses. One of the masses was positioned within the left upper lobe measuring 13 cm in the craniocaudal extension. In October 2014, JA received a CT scan of the chest. The scan identified the large mass in the left upper lung, along with additional bilateral pulmonary masses and bilateral subpleural nodules. Due to his complaints of pain, an MRI was performed in October 2014 of the left shoulder region. The MRI revealed the left apical lung mass came within 1 to 2 mm from the brachial plexus and abutted the posterior, proximal subclavian artery. JA underwent a CT guided biopsy in October 2014 which confirmed metastatic sarcoma in the left upper lobe mass. In regards to his pain, he reported significant discomfort of 10/10 with movement. Lying on his back and wearing a sling helps reduce pain levels. JA requires multiple oxycodone, steroids, gabapentin, and ibuprofen in order to marginally reduce pain. Palliative radiation therapy was suggested for JA. Past Medical History: As stated above, JA has a past medical history of cancer in the right thigh adductor muscles and prostate. He also has medical history of hypothyroidism, hemorrhoids, diverticulitis, hypogonadism, erectile dysfunction, high cholesterol, iron deficiency, neuropathy,

2 2 and GERD. JA has a past surgical history of right groin sarcoma resection surgery in 2011 and back surgeries in 2004, 2012, 2013 and The patient declares he has no known allergies. Social History: JA is retired from the logistics industry and currently resides with his wife. He is the father of 2 daughters and has 3 grandchildren. The patient admitted to being a 0.25 packs per day smoker for 17 years and quit in November of Patient stated no use of chewing tobacco or recreational drugs in the past or present, and does not drink alcohol. Family history displays prior history of high cholesterol and cancer with his paternal father. His father had an abdominal aortic aneurysm along with head and neck cancer. Medications: JA is currently using the following medication doses daily: 100 mg Amitriptyline, 10 mg Atrovastatin, 40 mg Pantoprazole, and 0.4 mg Tamsulosin. The patient also takes 4 mg Dexamethas twice a day, 300 mg Gabapentin four times a day, 600 mg Ibuprofen every 8 hours PRN, 60 mg Oxycodone every 8 hours, an additional 10 mg Oxycodone PRN, 50 mg Tapentadol every 4 hours PRN, 100 mg Topiramate 2 times a day PRN and 15 mg Temazepam PRN. Diagnostic Imaging: In 2014 the patient was experiencing a high level of pain within his left chest and shoulder region for multiple weeks that continued to worsen with time. With this 10/10 pain, he experienced spells of weakness and numbness in the left extremity. Since JA was undergoing surveillance for his prior adductor and prostate cancer he mentioned the pain during an appointment in October He was instructed to have a 2 view chest x-ray done, which he promptly did in October The AP and lateral radiographs revealed bilateral pulmonary masses. A dominate soft tissue mass in the left upper lobe measured 13 cm, while a smaller 4cm mass was found in the right lower lobe. These masses were likely to be of metastatic malignancies. Following the chest x-ray examination JA underwent a CT scan of the chest with contrast. The CT scan confirmed the x-ray s findings of a large mass in the posterior left upper lobe and small mass in the right lower lobe. Additional masses of smaller size were found in the anterior left upper lobe, right middle lobe, right upper lobe, right pleural nodules, bilateral subpleural nodules, lymph nodes, and prevascular nodes all to be suspicious for metastatic disease. Due to pain complaints, the patient underwent an MRI in October An MRI was chosen because it excels in imaging soft tissue and a mass in the brachial plexus can be detected earlier and more consistently with MRI verses CT. 1 The MRI exposed the left upper lung mass to be 1

3 3 to 2 mm from the brachial plexus creating brachial plexopathy. Brachial plexopathy is damage to the nerves in the form of fibrosis whose symptoms include loss of motor function (paresthesia of the arm and hand), weakness, and pain. 2 The mass s proximity to the brachial plexus was abutting the posterior proximal subclavian artery which was to blame for the pain, weakness, and numbness the patient was experiencing. Late October 2014 JA underwent a CT guided biopsy of the left upper lobe lung mass. Five 20- gauge core specimens were obtained which confirmed metastatic sarcoma in the left upper lobe mass. The lungs are a common location for sarcomas and prostate cancers to metastasize to, which JA has prior history of both. 3 The patient was referred to radiation therapy for palliative radiation therapy. Radiation Oncologist Recommendations: Palliative radiation therapy treatment was recommended to JA after evaluation of his past medial history. The radiation oncologist explained that an initial grid radiation therapy treatment would be beneficial, followed by a standard 2 field wedged pair to the left upper lung lobe. The grid treatment is unique within the radiation therapy field. The treatment allows the whole tumor to be treated, with an open field, without major skin breakdown and side effects from the extremely high radiation dose. Typically this treatment is used on very large, bulky tumors. Grid treatments allows for sparing of the skin by using small volumes of high dose radiation, also known as beamlets. The treatment technique is similar to SBRT, considering the high doses of grid treatments are within the Gy range with a single fraction of treatment. 4 Creating these beamlets with a modern linear accelerator allows for deep beam penetration to the area. Combining the high energy, grid device and the Linac s power; deep penetrating beamlets are created for grid therapy that applies skin-sparing theories. In short, grid therapy is a technique used on a large, open treatment field with a single fraction of many small volumes that possess high energy and are deep penetrating. The grid is a made of brass and weighs 34.2 pounds. It is measured to be a 16x16 array of 1 cm diameter holes, creating a shielding ratio of 1:1 (Figure 1). Following the single grid treatment, a 2 field wedged pair was prescribed to the left upper lobe mass. The Plan (prescription): JA had 2 radiation prescriptions for his left upper lung mass. His initial treatment was a single fraction using the grid technique, with a 2 field wedged pair palliative treatment to follow. The single fraction grid treatment had a prescription of 18.0 Gy. In

4 4 order to deliver the fraction the single fraction field was divided into 2 fields with the same angle and dose of 9.0 Gy each. This was due to machine limitations, and not being able to deliver the long, high-energy fraction within a single treatment. The wedged pair treatment followed the grid treatment with a prescription of 30.0 Gy over 10 fractions. An AP and a lateral oblique field were used to deliver the final 10-wedged pair fractions of treatment. Through the course of his grid and wedged pair palliative treatment, JA received a cumulative dose of 48.0 Gy to the upper lobe of his left lung. The single grid treatment fraction contributed 18.0 Gy, while the 10 wedged pair fractions contributed 30.0 Gy to his prescribed cumulative 48.0 Gy dose. Patient Setup/Immobilization: Upon much discussion and consultation, a complex simulation for radiation therapy to the left upper lung lobe was planned. JA arrived and verified himself to staff with name, birthday, and confirmed the treatment site. Upon completing the informed consent documentation, the patient was positioned on the CT/simulator table. He was positioned supine on a Vac-lok bag with arms raised above head holding onto a handle bar and triangle sponge under knees for comfort (Figure 2). The handle bar was a part of the wing board positioned below the Vac-lok; along with a thin table pad and headrest. The air was vacuumed out of the Vac-lok to create a mold around the patient. All of these devices were used to customize patient position and ensure comfort. By ensuring comfort from the beginning patient movement should be prevented and daily treatment position reproducibility should be promoted. After obtaining the ideal patient position for the patient along, with treatment planning and delivery requirements, the CT scan was performed. The patient had disposable CT skin markers placed in a 3-point set up during the scan. These markers were back up positioning aids if treatment marks were to be lost. After the doctor located the mass within the left upper lobe he repositioned the isocenter, causing the lasers to shift within the CT/simulation room. The new laser positions were marked with permanent markers, covered with stickers that help prevent normal wearing away, and recorded into the patient s chart (Figure 2). Upon completion of proper documentation, the CT dataset was transferred to the treatment planning system (TPS). Anatomical Contouring: The CT simulation dataset was sent to the dosimetry department in order to begin the treatment planning process. The dosimetrist imported the dataset into the Varian Eclipse TPS and began contouring structures included within the scan. The radiation

5 5 oncologist then contoured the mass and specified a desired margin. A margin was employed to ensure the contoured mass, or gross tumor volume (GTV), had space to receive satisfactory coverage during treatment. The dosimetrist created the specified margin and finalized contouring. The structures contoured were considered to be organs at risk (OR). This meant that the dose these structures received needed to be monitored to prevent future radiation damage of the area. For a mass with OR within the upper lobe of the left lung include: right and left lung, lungs total, spinal cord, liver, heart, stomach, esophagus, trachea, brachial plexus, thyroid, and bowel which was grouped together as a structure called bowel space. For this case the dosimetrist paid special attention to the brachial plexus due to its proximity of the large mass. The brachial plexus should not receive more than 50.0 to 60.0 Gy in order to prevent, or prevent further progression of, brachial plexopathy. 2 Since the treatment prescription was 48.0 Gy we were below the minimum dose, but it was still a precaution the dosimetrist took for the patient s safety. Once the preliminary work of oncologist target volumes and contouring were complete, the development of a treatment plan could commence. Beam Isocenter/Arrangement: When JA received his complex simulation the radiation oncologist set the isocenter within the upper lobe of the left lung (Figure 4). Changing the isocenter s coordinates caused the simulation room s lasers to shift. After the lasers were settled into their position of the new isocenter s coordinates, marks were made on the patient and documented within the chart. These marks were used for reproducing the position everyday, so permanent marker was used with clear stickers overtop. The stickers were to help prevent wearing away of the marks from everyday activities such as rubbing of clothing or bathing. Following the CT simulation, JA s dataset was imported into the Varian Eclipse TPS that was customized to planning for the cancer center s Varian Clinac ix treatment machine. The grid treatment was planned first in which a single beam arrangement angle was chosen that provided the best coverage to the large upper lobe mass. A left posterior oblique (LPO) beam with 155 gantry rotation was decided upon (Figure 5). This exact LPO beam arrangement was delivered 2 times to achieve the desired 18.0 Gy single fraction prescription. Both beams possessed 18 Megavoltage (MV) energy, while delivering 9.0 Gy each. The subsequent wedged pair treatment of 10 fractions used 2 beams. The beams were an AP beam with 0 rotation, along with an LPO beam of 155 rotation (Figure 6). Each of these beams used 18 MV energy to

6 6 deliver 3.0 Gy per day over 10 fractions, eventually delivering the prescribed 30.0 Gy. The wedged pair treatment utilized wedges on both beams to distribute dose within the treatment field. The AP beam had a wedge from the anterior to posterior orientation, while the LPO beam had a left to right wedge orientation (Figures 7 & 8). In order for the LPO beam s wedge to achieve this orientation a collimator rotation of 90 was used. By rotating the collimator, the wedge situated into a left to right orientation as needed for treatment. The grid and oblique treatments had a margin that was placed around the abnormality, and custom blocks were created. These blocks used multi-leaf collimators (MLC) to block and reduce dose to organs in proximity to the abnormality of interest (Figure 7 & 8). The MLC s had the ability to block out structures, therefore no couch rotations were used during the patient s treatment planning. Treatment Planning: The dosimetrist worked with the Varian Eclipse TPS to develop the ideal treatment plan for the patient. Some goals the dosimetrist worked towards were providing coverage to the radiation oncologist s GTV, while still sparring the surrounding structures like the brachial plexus. This task was more vital during this treatment since such high doses were prescribed. To begin the treatment planning process, the dosimetrist inserted a reference point to the plan in which the beam s doses were normalized, or calculated, to. The initial single fraction grid treatment was delivered through LPO beams weighted 50/50. These beams were separated and delivered through equal weighting to accommodate the Clinac ix monitor unit (MU) limitations. The beams delivered their identical dose of 9.0 Gy to the reference point, totaling the 18.0 Gy. The 10 fraction wedged pair treatment followed, beginning with fraction number 2 to the reference point. Due to the mass s position the beams were unequally weighted. The 0.0 AP beam possessed a weight factor of 57%, while the 155 LPO beam possessed 47% of the weighting to deliver the daily dose of 3.0 Gy. Together, over 10 fractions, these beams delivered 30.0 Gy to the reference point. Wedges were used on the wedged pair treatment in efforts to help distribute dose and minimize hotspots within the plan. The collimator was rotated by 90 on the LPO beam in order to accommodate the need for wedges in the right to left orientation. The AP beam did not need a

7 7 collimator rotation since the wedge was needed in the superior to inferior direction. The AP beam utilized a wedge of 10 positioned out, meaning the heel was superior and toe was inferior on the mass. The LPO had a collimator rotation, therefore positioning the wedges in the right to left orientation. This beam s 15 wedge was positioned with the heel on the masses left lateral side, while the toe was medially positioned. These wedges helped to distribute isodose lines in a more conformal fashion, while reducing the large hotspot that was created by a wedged pair beam arrangement. By utilizing wedges, the GTV received greater coverage with greater dose uniformity. The dose distribution and uniformity was evaluated on all planes of the patient before final plan checks began. Once the isodose lines seemed ideal the dose volume histogram (DVH) was used to evaluate the plan, GTV, and ORs (Figure 9 & 10). Since the DVH confirmed that the ideal coverage by the isodose lines of the GTV and surrounding OR doses were not exceeding dose tolerance levels, the plan was deemed acceptable. The radiation oncologist also determined appropriate coverage was provided, keeping the plan scaled to the 100% isodose line. He then approved the treatment plan allowing it to go to the machine for QA testing and eventually patient treatment delivery. Quality Assurance/Physics Check: After treatment plans are approved, the cancer center runs plans through a MU second check system. RadCalc is used at the clinic to verify treatment plans before patient treatment. The system checks the MU values to ensure the correct doses are delivered in efforts to protect the patient. In order for the treatment plans to pass there cannot be more than a 2% difference for the fields. The grid and wedged pair fields were ran in the RadCalc system. The grid field passed with a 1.1% difference while the wedged pair fields passed with 0.5% and 0.4% difference, respectively. QA was performed following the RadCalc process. The physicists and physicist assistances performed QA to ensure the TPS dose delivery matched what the machine was producing. Due to the high doses being delivered this was another vital step to be performed before patient treatment could commence. The grid was put into the machines accessory slot to measure accurate dose delivery, output factors, depth dose, and valley to peak ratios. Water phantoms, along with Sun Nuclear s Diode Detector, MapCheck, were used for the QA processes. The MapCheck machine possesses 1527 diodes, making it an extremely accurate QA measuring tool.

8 8 After completing QA procedures the entire plan was reviewed again by the physicists then sent to the machine for patient treatment. Conclusion: Grid treatments are an intriguing treatment for patients and staff members within radiation oncology departments. Although this is an older technique, it has been reinvented and improved upon with current technology for patient s needs. Using the grid with modern linacs allows for the beamlets to be high energy and deep penetrating. These penetrating beamlets are then most useful in large, bulky tumors and significantly help to reduce their size, especially when followed with a multi fraction treatment. Grid treatments are fascinating since they are rare within my small clinic therefore when a unique treatment comes along the department gathers in efforts to fully understand the concept. The grid fraction is a high dose that required a long treatment time, enforcing the need for some radiation therapy basics. It refreshed the importance of attention to detail from the beginning of the CT simulation process, to the very last treatment. If attention is not drawn to detail then the patient could be misaligned causing a portion of healthy tissue to receive a large, damaging radiation dose or the mass to not be treated. This could cause serious radiation side effects that could even be life threatening. Also, due to the time needed to deliver the single fraction, attention needs to be drawn to the patient s comfort level during the initial simulation. The patient must be completely immobile, even during the long treatment, otherwise radiation harm could occur. By ensuring comfort from the beginning their treatment molds should be comfortable therefore reducing in treatment movement. Last but not least, the physics behind a treatment of this energy is a vital tool to ensure not only patient but also staff s safety. The patient s safely is ensured before they even undergo treatment through QA procedures, but the staff s safety must be monitored post treatment. The physicist monitors the room post grid treatment delivery using a Geiger Muller. The Geiger Muller is used to identify neutron contamination within the room developed from the high-energy beams. The room is continuously monitored until the levels are low enough for the therapists to safely reenter the room and help the patient off the treatment table. I enjoy grid treatments since they give staff members the ability to gain knowledge while also be creative within their field. All staff members have a vital duty to perform for treatments, but these treatments ensure that all staff members are communicating correctly to deliver the prescribed treatment as precisely as

9 9 possible. I look forward to experiencing more unique treatments, such as grid treatments, within my many years to come as a medical dosimetrist.

10 10 References 1. Cancer Network: Home of the journal oncology. Diagnosis and management of brachial plexus lesions in cancer patients. Accessed April 18, Washington C, Leaver D. Principles and Practice of Radiation Therapy. 3 rd ed. St. Louis, MO: Mosby Elsevier; National Institutes of Health. Lung metastases. Accessed April 18, Reiff J, Huq S, Mohiuddin M, Suntharalingam N. Dosimetric properties of megavoltage grid therapy. Int J Radiat Oncol Biol Phys. 1995;33(4):

11 11 Figures Figure 1. Grid device used for grid treatment.

12 12 Figure 2. Patient position from CT simulation. Figure 3. Patient position from CT simulation, with simulation marks. Figure 4. Isocenter s position for grid and wedged pair treatments.

13 13 Figure 5. Beam position at 155 for grid treatment, in axial plane. Figure 6. Beam positions at 0.0 and 155 for wedged pair treatment, in axial plane.

14 14 Figure 7. AP beam with MLCs and 10 wedge is displayed above. Figure LPO beam with MLC s and 15 wedge is displayed above.

15 15 HEART GTV LEFT LUNG CARINA LUNG TOTAL Figure 9. DVH of grid treatment. ESOPHAGUS, TRACHEA, BRACHIAL PLEXUS SPINAL CORD AND RIGHT LUNG LUNG TOTAL GTV, CTV, PTV ESOPHAGUS LEFT LUNG SPINAL CORD AND TRACHEA HEART RIGHT LUNG Figure 10. DVH of treatment using wedged pair beams, where the GTV, clinical target volume (CTV), and planning target volume (PTV) are all receiving adequate coverage.