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Orthovoltage energies for palliative care in the 21st century: Is there a need?
Radiography 17 (2011) 84e87
Contents lists available at ScienceDirect
Radiography journal homepage: www.elsevier.com/locate/radi
Technical Note
Orthovoltage energies for palliative care in the 21st century: Is there a need? Laura D’Alimonte a, *, Emily Sinclair a, b, Sharon Seed c a
Radiation Therapy, Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, Canada M4N 3M5 University of Toronto, Department of Radiation Oncology, Toronto, Ontario, Canada c Radiation Therapy, Department of Radiation Oncology, The Ottawa Hospital Cancer Centre, Ottawa, Ontario, Canada b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 May 2010 Received in revised form 4 August 2010 Accepted 19 September 2010 Available online 13 October 2010
Objective: The primary objective was to describe the patterns of practice for patients with rib metastases who were treated with radiation therapy for pain relief. The secondary objective was to determine if wait times and better access to radiation treatment for this patient population could be improved with the utilization of an orthovoltage treatment machine. Methods and Materials: Cancer registry data for patients with rib disease and radiation therapy technique were collected from January 2007 to December 2008. The data was examined to establish the utilization rate of orthovoltage treatment. Results: The data demonstrated that orthovoltage treatment was an underutilized technique for the palliative treatment of rib disease. More than half of the patients were treated with high energy (6 MV) photon beam with either a single direct photon field (16.2%) or a two field photon technique (47.4%). Electron beam technique represented 35.1% of treatments while orthovoltage constituted only 1.2% of rib treatments. Conclusion: The use of orthovoltage X-ray beams has been demonstrated to be an underutilized radiotherapy treatment technique at this institution. Orthovoltage treatment is a simple radiotherapy technique with a short setup time that may be a solution for minimizing treatment burden for an already overburdened patient population. Ó 2010 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.
Keywords: Orthovoltage Rib metastasis Palliation Radiotherapy
Introduction According to the World Health Organization (WHO) the number of new cancer cases is estimated to jump from 11.3 million in 2007e15.5 million in 2030.1 An aging population and a greater awareness of the effectiveness of radiation therapy have led to a higher demand for radiotherapy services.2 Radiation therapy can effectively be used for cure, as adjuvant treatment, or palliation of symptoms of advanced disease.2 Local radiation therapy is usually the treatment of choice for localized bone pain caused by cancer, with a large body of published data confirming the efficacy of this treatment.2,8,9,13,16 Response rates of local radiotherapy are high with over 70%e80% of patients having some response and up to one third achieving a complete response.13 However, the delivery of timely palliative radiotherapy to patients remains a critical problem due to limitations in resources, including personnel and radiation therapy equipment.14 Palliation implies that the person is suffering from some illness or process in their body that cannot be cured and will eventually lead to * Corresponding author. Tel.: þ1 416 480 5000x89638; fax: þ1 416 480 4672. E-mail address: [email protected] (L. D’Alimonte).
the patients decline and eventual death. When a tumor spreads from its primary location to a distant site it is called metastatic disease. “Metastases” as they are known can arise in many types of tissue and will cause a variety of symptoms that negatively impact the patient’s life (i.e. pain, haemoptysis, dysphasia etc). The radiation treatment technique to be utilized depends upon available equipment resources including megavoltage photons, kilovoltage photons, and electrons. The advantages of higher energy photon beams for radical intent are numerous and include better skin sparing, better penetration characteristics, sharper field edges, less perturbation at different tissue interfaces and improvement in dose distributions which has led to improved cure rates with lower complication rates.5 However, for palliative intent, lower energy photon beams can be as beneficial as using higher energy photon beams for some disease sites.3 Orthovoltage photon beams may be used for the palliative treatment of superficial lesions including skin lesions, neck nodes, fungating breast, superficial bone metastases and lymphomas.3 Pain relief can be obtained by the use of orthovoltage treatment with little acute or late toxicity.3 With the increasing awareness of the effectiveness of radiation therapy for palliative care, an increase in the demand for treatment has ensued.12 This has led to palliative care accounting for approximately half of a radiotherapy
1078-8174/$ e see front matter Ó 2010 The College of Radiographers. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.radi.2010.09.005
L. D’Alimonte et al. / Radiography 17 (2011) 84e87
department’s workload.2,12 Radiation therapy plays a critical role in the symptomatic management of bone pain with pain relief and functional improvement occurring for up to one year in approximately 80% of patients.9 Unlike most patients receiving a radical course of treatment, patients receiving palliative radiation therapy often present at their planning appointment with existing pain. One must consider that a patient may not be experiencing pain under normal circumstances but may develop it when lying on a hard treatment bed or in a sustained position. This type of pain is known as “incidental pain”. Although temporary and short lived incidental pain is significant to the patient and must be considered when planning their treatment. On the orthovoltage unit (Fig. 1) the patient’s set up position can be varied depending on their comfort level unlike the higher energy machines where the patient must lie flat on a firm bed with little to aid in their comfort. Background Orthovoltage treatment refers to X-rays produced at energy potentials ranging from 150 to 500 kV.6 At these energy potentials, the photoelectric effect plays a role in the interaction of photons with matter. In brief, photons interact with an atom and eject one of the orbital electrons from the atom.6 Photoelectric effect depends strongly on the atomic number (Z value) of the absorbing material which is important to remember when using low energy therapeutic energies such as superficial or orthovoltage treatment machines.6 Since the advent of modern day linear accelerators, equipped with electron beams, the use of orthovoltage treatment units has declined with the primary use being for the treatment of skin cancers3,4 (Fig. 2). There are several significant limitations for the utilization of orthovoltage X-ray beams in clinical practice. A high entrance dose and a high bone dose are noted when orthovoltage X-ray beams are used.4 Bone, which has a high Z value, could unnecessarily receive a high, X-ray absorption with the use of orthovoltage energies. In fact, high dose to bone is a severe problem at low kilovoltage energies (<100 keV), but decreases with increasing energies and nearly disappears at 180 keV.6 However, if bone is the target volume to receive high dose then orthovoltage energies could be useful. Another limitation in the reluctance of centers to use orthovoltage units is the limited capability of dosimetric analysis available with these units.10 There are few published studies available that deal with the use of orthovoltage photon beams for the treatment of cancers other
85
Fig. 2. A comparison of depth dose fall-off for orthovoltage, electron and 6 MV X-ray energies.
than skin however, the value of orthovoltage photon beams should still be considered. One of the earliest reported studies by Gao and Raeside4 studied the efficacy of using orthovoltage photon beams to treat the anterior boost field for neuroendocrine carcinoma of the maxillary sinus. Conventionally, the anterior field is treated with electrons. The rationale for orthovoltage photon beams is that dose to critical structures such as lens, and posterior brain is much less than with electron beams. Another advantage to using orthovoltage energies over electrons to treat cancers near the eye is the target volume can be covered by a smaller field size therefore resulting in lower dose to the eyes.15 One patient diagnosed with stage IV undifferentiated neuroendocrine carcinoma of the maxillary sinus was planned and treated with two lateral 6 MV photon beams and an anterior 6 MeV electron beam. In addition, an orthovoltage anterior field dose distribution was modeled using the Monte Carlo method to compare and determine the efficacy of using an anterior orthovoltage X-ray field. Gao and Raeside4 determined that an anterior orthovoltage photon beam can effectively deliver a reasonable dose distribution to the entire target volume while minimizing dose to critical structures.4 They concluded that orthovoltage energy fields can be advantageous when treating cancers near the eye compared to electron beams. In a subsequent study by Keall et al.,7 they determined the efficacy and accuracy of treating cancers involving the sternum with kilovoltage X-rays compared with electron beams. They acknowledged that if dosimetric considerations predominate and dose to bone needs no significant increase, electron beams are the better energy choice for treating the sternum with radical intent.7 However, if the intent is for palliation, or for high dose within the bone is needed, they concluded that low energy photons are the more suitable choice.7 At our institution, the Gulmay orthovoltage unit (Gulmay Medical, Buford, GA) has been clinically operational since the late fall of 2007. Since the introduction of this unit, the majority of cases treated are lesions involving the skin. The clinical workload usage of the orthovoltage unit is significantly less than a high energy linear accelerator at our centre. Orthovoltage energies may be an optional treatment energy in the palliative setting particularly bone metastases that are close to skin surface and are referred for radiation treatment. Therefore, the aim of this study was to examine the patterns of practice for patients with rib metastases who were treated with radiation therapy for pain relief at a large academic cancer centre in Toronto, Ontario, Canada. Also, to determine if the utilization of an orthovoltage treatment machine could improve wait times and increases access to treatment for this patient population. Methods and materials
Fig. 1. Image of the adjustable treatment bed and an orthovoltage unit.
We began with an examination of the practice of orthovoltage usage at our institution to gain an understanding of the throughput
86
L. D’Alimonte et al. / Radiography 17 (2011) 84e87
on this machine. In addition, communications with the Palliative Care Radiation Therapist at The Ottawa Hospital Cancer Centre began to learn their treatment care plan model for palliative patients who present with rib disease. Data from patients with definitive rib disease treated with radiation therapy at our institution from January 2007 to December 2008 was pulled from the Outpatient Information System (OPIS). Techniques adopted included high energy photons (6 MV), electrons, and low energy photons (orthovoltage). The information collected was descriptively analyzed using percentages to describe the utilization rate of each treatment energy. In addition, informal interviews with several Medical Physicists and Radiation Oncologists were conducted to gain insight on the feasibility of utilizing orthovoltage X-ray energies to treat superficial metastatic rib disease. Finally, all of the collected data was collated and presented to the members of the Rapid Response Radiation Therapy Program (RRRP) at their Palliative Research Rounds at the Odette Cancer Centre, to begin the discussion and gain insight on possible hurdles to implementing the use of orthovoltage energies for the treatment of rib metastases. Results Examining of the practice of orthovoltage usage revealed that on an average day, the machine sat idle 9 h out of a 10 h operating day, treating mainly skin. At The Ottawa Hospital Cancer Centre (with 2 clinical operating sites, one of which has a fully operational orthovoltage unit), orthovoltage X-rays are often used as a treatment for rib metastases provided that depth and site of the lesion is suitable for orthovoltage energy range. Rib metastases are an ideal site for treatment by orthovoltage X-ray beams due to the fact that ribs are anatomically very close to skin surface and field sizes are generally not large. Patients arrive at the palliative clinic (by community referral) and undergo a consultation with a Radiation Oncologist. Once radiation treatment is decided upon, the Radiation Oncologist maps out the area of pain and chooses a cone size that best fits the problem area. This clinical markup (CMU) is completed on the orthovoltage unit with the patient lying in the treatment position. The Radiation Oncologist prescribes to Dmax (surface) with a dose (Gy)/fractionation scheme of 700/1# or 800/1#. Depth dose data is readily available to the Radiation Oncologist to verify dose at rib depth. Treatment calculations are completed by the treating Radiation Therapists while the patient remains on the treatment bed. This patient population is typically treated with 200 kV or 300 kV X-rays. At these higher energies, the z-dependence of photon interaction is minimal, and the dose to bone is not much different from the dose to tissue. An evaluation of utilization rate of the different radiation therapy energy options, for the treatment of rib disease at our institution revealed that more than half (63.6%) of patients who presented with rib disease were treated with high energy (6 MV) photon beams. Treatment with electron energies represented 35.1% of treatment choice while orthovoltage X-ray treatment constituted only 1.2% of total rib treatments. From the informal discussions with Radiation Oncologists to gain insight into the reasons for the low utilization rate of lower photon energies, several reasons were acknowledged. Oversight of orthovoltage being an option was felt to be a major contributor to the low utilization of these energies as a treatment option for superficial rib disease. For some patients, more than one disease site was to be planned and treated. This was cited as another reason for the overlooking of orthovoltage. It was felt that it would be more convenient and less of a disturbance to the patient to be treated on one treatment bed. Finally, some patients required a CT scan to be done prior to their treatment to help determine extent of disease
and to aid in choosing the most appropriate energy for treatment. Based on these acquired images, orthovoltage energies were deemed to be suboptimal for treatment. Discussion Since the advent of modern high energy linear accelerators and their more common use in palliative care, it is easy to overlook the simple and straightforward orthovoltage machine. However, we suggest some patients could benefit from having their superficial bone lesions treated with orthovoltage energies. The Ottawa Hospital Cancer Centre utilizes a streamlined and efficient treatment care plan for patients who present with rib metastases (Figs. 3 and 4). By utilizing this strategy, the use of orthovoltage X-ray beams is a simple and feasible radiotherapy technique with a short setup time that may be a solution for minimizing treatment burden for an already overburdened patient population. However, depth of the rib lesion and involvement of disease to surrounding tissue need to be considered when choosing orthovoltage energies for treatment. In any radiation therapy department, a balance needs to be struck between the quantity of services provided and the quality of services provided.17 Assessment of efficiency and throughput of high energy linear accelerators has been published in literature17,18 however, to date only one study has considered workload usage of the orthovoltage unit alone.19 Donaghey conducted a pilot study to evaluate the impact of factors (patient related factors, treatment factors, and equipment factors) on the workload and treatment times of two orthovoltage units in the UK.19 She found that pain and skin viability symptoms (patient related factors) and number of fields treated and first fraction (treatment related factors) had the greatest impact on treatment times.19 This study suggests that there would be a cost benefit in using orthovoltage in that the number of fields and fractions prescribed with orthovoltage treatments is less than with high energy linear accelerators. However, further investigation would be required to determine the cost benefit of using orthovoltage energies over higher energies. The general principle of palliative radiation therapy is to minimize treatment burden to the patient who is suffering from pain and other disease associated symptoms, and as a result, unable to tolerate lengthy planning and treatment sessions.10,11 When utilizing orthovoltage energies for radiation treatments, the patient can lie or sit in a position that is most comfortable to them. The
Fig. 3. Photo of a CMU of a rib metastasis to be treated with orthovoltage energies.
L. D’Alimonte et al. / Radiography 17 (2011) 84e87
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treatment is still a suitable palliative treatment option and should be considered for the needs of multi-symptomatic palliative patients.
References
Fig. 4. Planning image of a rib fracture for treatment using high energy photons.
technology conforms and accommodates the patient rather than the patient conforming to the technology. Increasing the use of orthovoltage X-ray treatment may be one solution to improving quality of life for these patients, by decreasing planning and treatment time while still maintaining a dosimetrically relevant plan. Further investigation and discussions are required to determine whether validity and efficacy exists for the use of orthovoltage X-ray beams for palliative rib metastases. Future directions include a pilot study comparing the relief of pain and patient satisfaction with orthovoltage compared to higher energy machines. Conclusion Orthovoltage treatment offers a suitable and uncomplicated treatment option for a number of palliative scenarios including superficial rib metastases. However, its use is limited by the depth of lesion to be treated and the surrounding tissues involvement. Orthovoltage has several advantages including; simplicity in operation and technique, it is associated with a limited number of fractionated treatments and causes minimal stress to patients in terms of equipment and immobilization.19 Therefore, orthovoltage
1. World Cancer Report. Retrieved July 26, 2010 from the WHO website, http:// who.int/features/qa/15/en/index.html. 2. Hoegler D. Radiotherapy for palliation of symptoms in incurable cancer (review). Current Problems in Cancer 1997;21(3):129e83. 3. Grant M, Kron T, Back M. High dose behind inhomogeneities during mediumenergy X-ray irradiation. Physics in Medicine and Biology 1998;43(5):1343e50. 4. Gao W, Raeside DE. Orthovoltage radiation therapy treatment planning using Monte Carlo simulation: treatment of neuroendocrine carcinoma of the maxillary sinus. Physics in Medicine and Biology 1997;42:2421e33. 5. Das IJ, Kase KR. Higher energy: is it necessary, is it worth the cost for radiation oncology? Medical Physics 1992;19(4):917e25. 6. Khan FM. The physics of radiation therapy. 2nd ed. Baltimore: Lippincott Williams & Wilkins; 1994. pp. 79e81. 7. Keall P, Monti di Sopra F, Beckham W, Delaney G. Comparison of kilovoltage X-ray and electron beam dose distributions for radiotherapy of the sternum. Medical Dosimetry 1999;24(2):141e4. 8. Lin A, Ray ME. Targeted and systemic radiotherapy in the treatment of bone metastasis. Cancer and Metastasis Review 2006;25:669e75. 9. Frassica DA, Gunderson LL. Principles of radiation therapy in the treatment of bone metastases. Orthopedics 1992;15:579e81. 10. Haddad P, Cheung F, Pond G, et al. Computerized tomographic simulation compared with clinical mark-up in palliative radiotherapy: a prospective study. International Journal of Radiation Oncology Biology Physics 2006;65 (3):824e9. 11. Mackillop WJ. The principles of palliative radiotherapy: a radiation oncologist’s perspective. Canadian Journal of Oncology 1996;6:S5e11. 12. Danjoux C, Chow E, Drossos A, et al. An innovative rapid response radiotherapy program to reduce waiting time for palliative radiotherapy. Supportive Care Cancer 2006;14:38e43. 13. Agarawal JP, Swangsilpa T, van der Linden Y, Rades D, Jeremic B, Hoskin PJ. The role of external beam radiotherapy in the management of bone metastases. Clinical Oncology 2006;18:747e60. 14. Chow E, Wong R, Connolly R, et al. Prospective assessment of symptom palliation for patients attending a rapid response radiotherapy program: feasibility of telephone follow-up. Journal of Pain Symptom Management 2001;22(2): 649e56. 15. Amdur RJ, Kalbaugh KJ, Ewald LM, et al. Radiation therapy for skin cancer near the eye: kilovoltage X rays vs. electrons. International Journal of Radiation Oncology Biology Physics 1992;23:769e79. 16. Li KK, Sinclair E, Pope J, Farhadian M, Harris K, Napolskikh J, et al. A multidisciplinary bone metastases clinic at Toronto Sunnybrook regional cancer centre-a review of the experience from 1999 to 2005. 17. Barbera L, Jackson LD, Schulze K, Groome PA, Foroudi F, Delaney GP, et al. Performance of different radiotherapy workload models. International Journal of Radiation Oncology Biology Physics 2003;55(4):1143e9. 18. Delaney GP, Shafiq RJ, Jalaludin BB, Barton MB. The development of a new basic treatment equivalent model to assess linear accelerator throughput. Clinical Oncology 2005;17:311e8. 19. Donaghey SL. Palliative radiotherapy: modeling and evaluating the impact of factors in the treatment times and workload of orthovoltage units e a pilot study. Journal of Radiotherapy in Practice 2009;8(3):119e29.
Contents lists available at ScienceDirect
Radiography journal homepage: www.elsevier.com/locate/radi
Technical Note
Orthovoltage energies for palliative care in the 21st century: Is there a need? Laura D’Alimonte a, *, Emily Sinclair a, b, Sharon Seed c a
Radiation Therapy, Department of Radiation Oncology, Odette Cancer Centre, Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Toronto, Ontario, Canada M4N 3M5 University of Toronto, Department of Radiation Oncology, Toronto, Ontario, Canada c Radiation Therapy, Department of Radiation Oncology, The Ottawa Hospital Cancer Centre, Ottawa, Ontario, Canada b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 31 May 2010 Received in revised form 4 August 2010 Accepted 19 September 2010 Available online 13 October 2010
Objective: The primary objective was to describe the patterns of practice for patients with rib metastases who were treated with radiation therapy for pain relief. The secondary objective was to determine if wait times and better access to radiation treatment for this patient population could be improved with the utilization of an orthovoltage treatment machine. Methods and Materials: Cancer registry data for patients with rib disease and radiation therapy technique were collected from January 2007 to December 2008. The data was examined to establish the utilization rate of orthovoltage treatment. Results: The data demonstrated that orthovoltage treatment was an underutilized technique for the palliative treatment of rib disease. More than half of the patients were treated with high energy (6 MV) photon beam with either a single direct photon field (16.2%) or a two field photon technique (47.4%). Electron beam technique represented 35.1% of treatments while orthovoltage constituted only 1.2% of rib treatments. Conclusion: The use of orthovoltage X-ray beams has been demonstrated to be an underutilized radiotherapy treatment technique at this institution. Orthovoltage treatment is a simple radiotherapy technique with a short setup time that may be a solution for minimizing treatment burden for an already overburdened patient population. Ó 2010 The College of Radiographers. Published by Elsevier Ltd. All rights reserved.
Keywords: Orthovoltage Rib metastasis Palliation Radiotherapy
Introduction According to the World Health Organization (WHO) the number of new cancer cases is estimated to jump from 11.3 million in 2007e15.5 million in 2030.1 An aging population and a greater awareness of the effectiveness of radiation therapy have led to a higher demand for radiotherapy services.2 Radiation therapy can effectively be used for cure, as adjuvant treatment, or palliation of symptoms of advanced disease.2 Local radiation therapy is usually the treatment of choice for localized bone pain caused by cancer, with a large body of published data confirming the efficacy of this treatment.2,8,9,13,16 Response rates of local radiotherapy are high with over 70%e80% of patients having some response and up to one third achieving a complete response.13 However, the delivery of timely palliative radiotherapy to patients remains a critical problem due to limitations in resources, including personnel and radiation therapy equipment.14 Palliation implies that the person is suffering from some illness or process in their body that cannot be cured and will eventually lead to * Corresponding author. Tel.: þ1 416 480 5000x89638; fax: þ1 416 480 4672. E-mail address: [email protected] (L. D’Alimonte).
the patients decline and eventual death. When a tumor spreads from its primary location to a distant site it is called metastatic disease. “Metastases” as they are known can arise in many types of tissue and will cause a variety of symptoms that negatively impact the patient’s life (i.e. pain, haemoptysis, dysphasia etc). The radiation treatment technique to be utilized depends upon available equipment resources including megavoltage photons, kilovoltage photons, and electrons. The advantages of higher energy photon beams for radical intent are numerous and include better skin sparing, better penetration characteristics, sharper field edges, less perturbation at different tissue interfaces and improvement in dose distributions which has led to improved cure rates with lower complication rates.5 However, for palliative intent, lower energy photon beams can be as beneficial as using higher energy photon beams for some disease sites.3 Orthovoltage photon beams may be used for the palliative treatment of superficial lesions including skin lesions, neck nodes, fungating breast, superficial bone metastases and lymphomas.3 Pain relief can be obtained by the use of orthovoltage treatment with little acute or late toxicity.3 With the increasing awareness of the effectiveness of radiation therapy for palliative care, an increase in the demand for treatment has ensued.12 This has led to palliative care accounting for approximately half of a radiotherapy
1078-8174/$ e see front matter Ó 2010 The College of Radiographers. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.radi.2010.09.005
L. D’Alimonte et al. / Radiography 17 (2011) 84e87
department’s workload.2,12 Radiation therapy plays a critical role in the symptomatic management of bone pain with pain relief and functional improvement occurring for up to one year in approximately 80% of patients.9 Unlike most patients receiving a radical course of treatment, patients receiving palliative radiation therapy often present at their planning appointment with existing pain. One must consider that a patient may not be experiencing pain under normal circumstances but may develop it when lying on a hard treatment bed or in a sustained position. This type of pain is known as “incidental pain”. Although temporary and short lived incidental pain is significant to the patient and must be considered when planning their treatment. On the orthovoltage unit (Fig. 1) the patient’s set up position can be varied depending on their comfort level unlike the higher energy machines where the patient must lie flat on a firm bed with little to aid in their comfort. Background Orthovoltage treatment refers to X-rays produced at energy potentials ranging from 150 to 500 kV.6 At these energy potentials, the photoelectric effect plays a role in the interaction of photons with matter. In brief, photons interact with an atom and eject one of the orbital electrons from the atom.6 Photoelectric effect depends strongly on the atomic number (Z value) of the absorbing material which is important to remember when using low energy therapeutic energies such as superficial or orthovoltage treatment machines.6 Since the advent of modern day linear accelerators, equipped with electron beams, the use of orthovoltage treatment units has declined with the primary use being for the treatment of skin cancers3,4 (Fig. 2). There are several significant limitations for the utilization of orthovoltage X-ray beams in clinical practice. A high entrance dose and a high bone dose are noted when orthovoltage X-ray beams are used.4 Bone, which has a high Z value, could unnecessarily receive a high, X-ray absorption with the use of orthovoltage energies. In fact, high dose to bone is a severe problem at low kilovoltage energies (<100 keV), but decreases with increasing energies and nearly disappears at 180 keV.6 However, if bone is the target volume to receive high dose then orthovoltage energies could be useful. Another limitation in the reluctance of centers to use orthovoltage units is the limited capability of dosimetric analysis available with these units.10 There are few published studies available that deal with the use of orthovoltage photon beams for the treatment of cancers other
85
Fig. 2. A comparison of depth dose fall-off for orthovoltage, electron and 6 MV X-ray energies.
than skin however, the value of orthovoltage photon beams should still be considered. One of the earliest reported studies by Gao and Raeside4 studied the efficacy of using orthovoltage photon beams to treat the anterior boost field for neuroendocrine carcinoma of the maxillary sinus. Conventionally, the anterior field is treated with electrons. The rationale for orthovoltage photon beams is that dose to critical structures such as lens, and posterior brain is much less than with electron beams. Another advantage to using orthovoltage energies over electrons to treat cancers near the eye is the target volume can be covered by a smaller field size therefore resulting in lower dose to the eyes.15 One patient diagnosed with stage IV undifferentiated neuroendocrine carcinoma of the maxillary sinus was planned and treated with two lateral 6 MV photon beams and an anterior 6 MeV electron beam. In addition, an orthovoltage anterior field dose distribution was modeled using the Monte Carlo method to compare and determine the efficacy of using an anterior orthovoltage X-ray field. Gao and Raeside4 determined that an anterior orthovoltage photon beam can effectively deliver a reasonable dose distribution to the entire target volume while minimizing dose to critical structures.4 They concluded that orthovoltage energy fields can be advantageous when treating cancers near the eye compared to electron beams. In a subsequent study by Keall et al.,7 they determined the efficacy and accuracy of treating cancers involving the sternum with kilovoltage X-rays compared with electron beams. They acknowledged that if dosimetric considerations predominate and dose to bone needs no significant increase, electron beams are the better energy choice for treating the sternum with radical intent.7 However, if the intent is for palliation, or for high dose within the bone is needed, they concluded that low energy photons are the more suitable choice.7 At our institution, the Gulmay orthovoltage unit (Gulmay Medical, Buford, GA) has been clinically operational since the late fall of 2007. Since the introduction of this unit, the majority of cases treated are lesions involving the skin. The clinical workload usage of the orthovoltage unit is significantly less than a high energy linear accelerator at our centre. Orthovoltage energies may be an optional treatment energy in the palliative setting particularly bone metastases that are close to skin surface and are referred for radiation treatment. Therefore, the aim of this study was to examine the patterns of practice for patients with rib metastases who were treated with radiation therapy for pain relief at a large academic cancer centre in Toronto, Ontario, Canada. Also, to determine if the utilization of an orthovoltage treatment machine could improve wait times and increases access to treatment for this patient population. Methods and materials
Fig. 1. Image of the adjustable treatment bed and an orthovoltage unit.
We began with an examination of the practice of orthovoltage usage at our institution to gain an understanding of the throughput
86
L. D’Alimonte et al. / Radiography 17 (2011) 84e87
on this machine. In addition, communications with the Palliative Care Radiation Therapist at The Ottawa Hospital Cancer Centre began to learn their treatment care plan model for palliative patients who present with rib disease. Data from patients with definitive rib disease treated with radiation therapy at our institution from January 2007 to December 2008 was pulled from the Outpatient Information System (OPIS). Techniques adopted included high energy photons (6 MV), electrons, and low energy photons (orthovoltage). The information collected was descriptively analyzed using percentages to describe the utilization rate of each treatment energy. In addition, informal interviews with several Medical Physicists and Radiation Oncologists were conducted to gain insight on the feasibility of utilizing orthovoltage X-ray energies to treat superficial metastatic rib disease. Finally, all of the collected data was collated and presented to the members of the Rapid Response Radiation Therapy Program (RRRP) at their Palliative Research Rounds at the Odette Cancer Centre, to begin the discussion and gain insight on possible hurdles to implementing the use of orthovoltage energies for the treatment of rib metastases. Results Examining of the practice of orthovoltage usage revealed that on an average day, the machine sat idle 9 h out of a 10 h operating day, treating mainly skin. At The Ottawa Hospital Cancer Centre (with 2 clinical operating sites, one of which has a fully operational orthovoltage unit), orthovoltage X-rays are often used as a treatment for rib metastases provided that depth and site of the lesion is suitable for orthovoltage energy range. Rib metastases are an ideal site for treatment by orthovoltage X-ray beams due to the fact that ribs are anatomically very close to skin surface and field sizes are generally not large. Patients arrive at the palliative clinic (by community referral) and undergo a consultation with a Radiation Oncologist. Once radiation treatment is decided upon, the Radiation Oncologist maps out the area of pain and chooses a cone size that best fits the problem area. This clinical markup (CMU) is completed on the orthovoltage unit with the patient lying in the treatment position. The Radiation Oncologist prescribes to Dmax (surface) with a dose (Gy)/fractionation scheme of 700/1# or 800/1#. Depth dose data is readily available to the Radiation Oncologist to verify dose at rib depth. Treatment calculations are completed by the treating Radiation Therapists while the patient remains on the treatment bed. This patient population is typically treated with 200 kV or 300 kV X-rays. At these higher energies, the z-dependence of photon interaction is minimal, and the dose to bone is not much different from the dose to tissue. An evaluation of utilization rate of the different radiation therapy energy options, for the treatment of rib disease at our institution revealed that more than half (63.6%) of patients who presented with rib disease were treated with high energy (6 MV) photon beams. Treatment with electron energies represented 35.1% of treatment choice while orthovoltage X-ray treatment constituted only 1.2% of total rib treatments. From the informal discussions with Radiation Oncologists to gain insight into the reasons for the low utilization rate of lower photon energies, several reasons were acknowledged. Oversight of orthovoltage being an option was felt to be a major contributor to the low utilization of these energies as a treatment option for superficial rib disease. For some patients, more than one disease site was to be planned and treated. This was cited as another reason for the overlooking of orthovoltage. It was felt that it would be more convenient and less of a disturbance to the patient to be treated on one treatment bed. Finally, some patients required a CT scan to be done prior to their treatment to help determine extent of disease
and to aid in choosing the most appropriate energy for treatment. Based on these acquired images, orthovoltage energies were deemed to be suboptimal for treatment. Discussion Since the advent of modern high energy linear accelerators and their more common use in palliative care, it is easy to overlook the simple and straightforward orthovoltage machine. However, we suggest some patients could benefit from having their superficial bone lesions treated with orthovoltage energies. The Ottawa Hospital Cancer Centre utilizes a streamlined and efficient treatment care plan for patients who present with rib metastases (Figs. 3 and 4). By utilizing this strategy, the use of orthovoltage X-ray beams is a simple and feasible radiotherapy technique with a short setup time that may be a solution for minimizing treatment burden for an already overburdened patient population. However, depth of the rib lesion and involvement of disease to surrounding tissue need to be considered when choosing orthovoltage energies for treatment. In any radiation therapy department, a balance needs to be struck between the quantity of services provided and the quality of services provided.17 Assessment of efficiency and throughput of high energy linear accelerators has been published in literature17,18 however, to date only one study has considered workload usage of the orthovoltage unit alone.19 Donaghey conducted a pilot study to evaluate the impact of factors (patient related factors, treatment factors, and equipment factors) on the workload and treatment times of two orthovoltage units in the UK.19 She found that pain and skin viability symptoms (patient related factors) and number of fields treated and first fraction (treatment related factors) had the greatest impact on treatment times.19 This study suggests that there would be a cost benefit in using orthovoltage in that the number of fields and fractions prescribed with orthovoltage treatments is less than with high energy linear accelerators. However, further investigation would be required to determine the cost benefit of using orthovoltage energies over higher energies. The general principle of palliative radiation therapy is to minimize treatment burden to the patient who is suffering from pain and other disease associated symptoms, and as a result, unable to tolerate lengthy planning and treatment sessions.10,11 When utilizing orthovoltage energies for radiation treatments, the patient can lie or sit in a position that is most comfortable to them. The
Fig. 3. Photo of a CMU of a rib metastasis to be treated with orthovoltage energies.
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treatment is still a suitable palliative treatment option and should be considered for the needs of multi-symptomatic palliative patients.
References
Fig. 4. Planning image of a rib fracture for treatment using high energy photons.
technology conforms and accommodates the patient rather than the patient conforming to the technology. Increasing the use of orthovoltage X-ray treatment may be one solution to improving quality of life for these patients, by decreasing planning and treatment time while still maintaining a dosimetrically relevant plan. Further investigation and discussions are required to determine whether validity and efficacy exists for the use of orthovoltage X-ray beams for palliative rib metastases. Future directions include a pilot study comparing the relief of pain and patient satisfaction with orthovoltage compared to higher energy machines. Conclusion Orthovoltage treatment offers a suitable and uncomplicated treatment option for a number of palliative scenarios including superficial rib metastases. However, its use is limited by the depth of lesion to be treated and the surrounding tissues involvement. Orthovoltage has several advantages including; simplicity in operation and technique, it is associated with a limited number of fractionated treatments and causes minimal stress to patients in terms of equipment and immobilization.19 Therefore, orthovoltage
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