|Year : 2012 | Volume
| Issue : 3 | Page : 361-366
Impact of adjuvant radiation therapy photon energy on quality of life after breast conservation therapy: Linear accelerator versus the cobalt machine
Anusheel Munshi1, Debnarayan Dutta1, Ashwini Budrukkar1, Rakesh Jalali1, Rajiv Sarin1, Sudeep Gupta2, Jaya Ghosh2, Jyoti Bajpai2, Vani Parmar3, Nita Nair3, Rajendra Badwe3
1 Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India
2 Department of Medical Oncology, Tata Memorial Hospital, Mumbai, India
3 Department of Surgical Oncology, Tata Memorial Hospital, Mumbai, India
|Date of Web Publication||17-Nov-2012|
Radiation Oncology, 120, Tata Memorial Hospital, Parel, Mumbai - 400012
Source of Support: None, Conflict of Interest: None
Background: Breast conservative therapy (BCT) is a standard treatment option in early operable breast cancers (OBC) and a select group of large or locally advanced tumors. The present study deals with prospective evaluation of quality of life (QOL) score in consecutive patients treated with BCT employing adjuvant RT treated with either a cobalt machine or a linear accelerator (LA).
Material and Methods: Patients of carcinoma breast who underwent BCT were taken into the study. Patients with larger breasts (inter-field separation >18-20 cm) were treated on LA and those with smaller breasts were treated on cobalt machine. All patients received a uniform RT dose (45-50 Gy/25#/5 weeks) to whole breast followed by tumor bed boost with suitable energy electrons. Prospective evaluation of QOL was done using EORTC QLQ C30 and breast cancer-specific EORTC QLQ BR23. QOL evaluation was done at pre-RT, at half completion of RT treatment (at 20-23 fractions) and at completion of RT.
Results: Pre-RT evaluation GQOL scores in patients treated with cobalt and LA were 71.6 and 71.7, respectively (P = 0.8). QLQ C30 functional and symptom domain scores were also similar in the groups. At RT completion, Global quality of life (GQOL) scores were 67.7 in patients treated with cobalt as compared to 77.7 in patients treated with LA (P = 0.75). Physical function domain scores in cobalt and LA patients were 70.8 and 80.3, respectively (P = 0.26). Fatigue score was higher in patients treated with cobalt (39.1 versus 29.7; P = 0.9). However, there was no difference in other functional and symptom domains. There was no significant change in any of the EORTC QLQ C30 domains at RT completion as compared to the pre-RT scores.
Conclusion: There is no significant difference in QOL domains between appropriately selected patients treated with cobalt and LA. There are no significant changes in QOL domain scores at RT conclusion as compared to pre-RT baseline in patients treated with cobalt or LA source. A cobalt machine may be effectively used to deliver adjuvant RT in appropriately selected BCT patients especially in developing countries with limited resources.
Keywords: Cobalt, linear accelerator, radiation therapy, quality of life
|How to cite this article:|
Munshi A, Dutta D, Budrukkar A, Jalali R, Sarin R, Gupta S, Ghosh J, Bajpai J, Parmar V, Nair N, Badwe R. Impact of adjuvant radiation therapy photon energy on quality of life after breast conservation therapy: Linear accelerator versus the cobalt machine. J Can Res Ther 2012;8:361-6
|How to cite this URL:|
Munshi A, Dutta D, Budrukkar A, Jalali R, Sarin R, Gupta S, Ghosh J, Bajpai J, Parmar V, Nair N, Badwe R. Impact of adjuvant radiation therapy photon energy on quality of life after breast conservation therapy: Linear accelerator versus the cobalt machine. J Can Res Ther [serial online] 2012 [cited 2021 Sep 24];8:361-6. Available from: https://www.cancerjournal.net/text.asp?2012/8/3/361/103513
| > Introduction|| |
Breast conservation is the standard treatment options in early operable breast cancers (OBC). Also a select group of patients who have large or locally advanced tumors can safely undergo breast conservation. , Radiotherapy (RT) to whole breast followed by tumor bed boost is the standard adjuvant treatment option after breast conserving surgery (BCS).  RT after breast conservation in developed countries is usually done by linear accelerators (LA).  It is a well-known fact of physics that patients treated with cobalt have higher skin and subcutaneous dose. This is especially of concern while treating patients with BCS as more skin and breast tissue is irradiated. It follows that that larger breast size treated with high-energy photon with LAs has dosimetric advantages.  Cobalt machines are cheaper but this treatment suffers from a poorer depth dose characteristics as compared to a LA. Our previous study had demonstrated that large size breast needs higher energy and more sophisticated techniques.  Developing countries have limited resources and thus have less LA machines than required. ,,
Breast conservation therapy rates are low in the developing world. The reasons for this are varied and include lack of awareness among patients and lack of appropriate infrastructure especially appropriate RT facilities. These countries have a low machine:population ratio and most of the machines are simple cobalt units. , As per NCCP task force report XI plan, present tele-density in India is 0.33 per million populations, whereas WHO recommendation is 2 per million populations. Generally, because of superior energy, sharp penumbra and better percentage depth dose patterns, LA have replaced cobalt units in most of the developed world.
Patients from developing countries have smaller body structure compared with western counterparts.  Thus, a selected proportion of patients from developing countries with small body structure may be appropriately treated with adjuvant RT using cobalt sources after BCS.
In the present era, a randomized study to assess the disease control or quality of life (QOL) in breast cancer patients treated with LA versus Cobalt machine would be nearly impossible to conduct. The reasons would be ethical issues and a likely possibility of poor accrual. The present study deals with prospective evaluation of QOL scores or cosmetic outcome data in consecutive patients treated with BCS followed by adjuvant RT treated with either a cobalt machine or a LA.
| > Materials and Methods|| |
Our previous study analyzed all consecutive patients registered at our Hospital in 6 months and treated with RT.  In that study, we compared QOL scores in patients treated with mastectomy and BCS in updated data. In the present analysis, subgroup of patients treated with BCS was selected to assess the impact of photon energy in this subgroup of patients. In the present analysis (with some updated data), patients who were treated with Cobalt beams were compared with those treated with a LA. Patients with larger breasts (inter field separation >18-20 cm) were treated on LA and those with smaller breasts were treated on cobalt. An inclined breast board was used to make the chest wall parallel to the couch. All patients irrespective of their treatment machine received equivalent RT dose (45-50 Gy/25#/5 weeks) to whole breast and tumor bed boost with suitable energy electrons. The boost schedule was 15 Gy in 6 fractions (2.5 Gray per fraction for a total of 6 fractions, 1 fraction per day) for 6MV LA treatments and 12.5 Gy in 5 fractions (2.5 Gy per fraction for a total of 5 fractions, 1 fraction every week on Saturday, concomitant with whole breast RT) for Cobalt treatment. A tangential beam pair was planned and wedges were appropriately placed as seen by the dose distribution on the planning system. Prospective evaluation of QOL was done using EORTC QLQ C30 and breast cancer-specific EORTC QLQ BR23. EORTC QLQ-30 version-3 is a core measure and BR23 domain scores were measured as per EORTC guidelines.  In EORTC QLQ-30 and BR23, higher score in functional domains suggests higher level of functioning and higher scores in symptom domains suggest more symptoms. QOL evaluation was done at pre-RT, at half completion of RT treatment (at 20-23 fractions) and at completion of RT.
Patient-related characteristics of both groups have been described in [Table 1]. Among the 188 patients of breast conservation accrued in the study, 53 were treated with cobalt and 135 with LA. Proportion of menopausal status, positive family history, chemotherapy, and hormonal therapy schedules were comparable between patients treated with cobalt or LA [Table 1].
Items on both questionnaires were scaled and scored with recommended EORTC scoring procedures.  Mean and standard deviation of different QOL domains at baseline and subsequent follow ups were documented. Changes in QOL scores at RT completion from pre-RT scores in different domains were recorded. A comparison of QOL scores at each follow up between patients treated with cobalt and LA was done using the non-parametic unpaired t-test.
| > Results|| |
Pre-RT QOL Scores
EORTC QLQ C30 and BR23 domain scores at pre-RT, mid-RT, and at RT completion have been documented in [Table 2]. Pre-RT evaluation GQOL score in patients treated with cobalt and LA were 71.6 and 71.7, respectively [Figure 1]. QLQ C30 functional and symptom domain scores were also similar in the groups [Table 2]. In BR23 functional domains such as body image, sexual functioning, sexual enjoyment, future perspective scores in patients treated with cobalt and LA were 76.5, 79.9, 50, 33.3 and 78.4, 76.8, 43.8, 37.6, respectively. In symptom scales, scores were 84.8, 86.4, 69.4, and 48.1 in patients treated with cobalt compared to 86.1, 88.2, 73.6, and 49.4 in patients treated with LA.
|Figure 1: Comparison of global quality of life (GQOL) at pre, mid, and at completion of radiation therapy in patients treated with either telecobalt (Co60) or linear accelerator (LA)|
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|Table 2: EORTC QOL C30 and BR23 domain mean scores at pre-RT evaluation in patients underwent breast conservation followed by adjuvant radiation therapy with either tele-cobalt (Co60) or linear accelerator machine|
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QOL Scores at Subsequent Evaluations
GQOL scores at mid-RT evaluation were 71.6 and 71.7, respectively. QLQ C30 functional and symptom domain scores were maintained at mid-RT evaluation [Figure 1]. BR23 domain scores were also maintained at mid-RT evaluation [Figure 2].
|Figure 2: Comparison of EORTC QLQ C30 and BR 23 quality of life parameters at pre, mid and at completion of radiation therapy in patients treated with either tele-cobalt (Co60) or linear accelerator (LA)|
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At RT completion, GQOL scores were 67.7 in patients treated with cobalt as compared to 77.7 in patients treated with LA (10 point difference; P = 0.75). Physical function domain scores in cobalt and LA patients were 70.8 and 80.3, respectively (10-point difference; P = 0.26). Fatigue score was higher in patients treated with cobalt (39.1 versus 29.7; P = 0.9). However, there was no difference in other functional and symptom domains. In BR23 domains, at RT completion sexual enjoyment (7.1 versus 38.3; P = 0.34) scores were poorer in patients treated with cobalt source, whereas future perspective was better (43.8 versus 13.2; P = 0.32). There was no difference in breast symptom and arm symptom domain scores between these two groups.
Change in QOL Scores at RT Completion from Pre-RT Scores
Change in QOL domain scores at RT completion from pre-RT scores are tabulated in [Table 3]. There was no significant change in any of the EORTC QLQ C30 domains at RT completion as compared to the pre-RT scores. Change in the QOL score at RT completion from pre-RT scores in physical function, role function, emotional function, and social function in patients treated with the cobalt source were 2.8, 1.4, 1.6, 9.3, and 3.8, whereas in the LA source it was 1.7, 1.4, 2, 0.3, and 0.9, respectively. In BR23 domain, change in scores at RT completion from pre-RT scores in body image, sexual function, future prospective, systemic therapy side effect, breast symptom, and arm symptom domains in the cobalt source was 5.1, 14.1, 2.8, 1.4, 1.6, and 9.3, whereas in patients treated with the LA source it was 5.4, 4.8, 1.7, 1.4, 2, and 0.3, respectively. Hence, post-RT change in the sexual function domain score was higher with cobalt treatment, however not significant (14.1 versus 4.8; P-value = 0.704).
|Table 3: Difference in EORTC QOL C30 and BR23 domains scores at RT completion from pre-RT scores|
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| > Discussion|| |
Conventionally adjuvant RT after BCS is delivered with bilateral tangential portals using 6 MV (occasionally 10 MV) photons followed by electron boost to the tumor bed. Treatment with a Cobalt source, having inherent poorer beam penetration characteristics, has been considered not suitable for adjuvant RT treatment after BCS.  However, dosimetric studies have shown that cobalt may be used for tangential portals even after BCS if inter-field separation is less than 19.5 cm.  Compared to a 6 MV LA, a cobalt source has certain clear dosimetric differences. The build-up of maximum dose is deeper in a 6 MV LA (1.5 cm) as compared to a cobalt source (0.5 cm).  This can potentially result in lesser penetration and a higher breast skin dose in a patient treated with a cobalt machine. The present study was aimed to assess the difference in QOL in patients who receive post BCS adjuvant RT with cobalt as compared to those who receive the same with LA. We wish to re-emphasize that the breast sizes in the two groups were different with patients having smaller breast sizes being allocated to the cobalt therapy arm and relatively larger breast ones to LA. This is in fact based on our institutional treatment policy where a proportion of patients after BCS are treated with the cobalt source by tangential portals if the inter-field separation is less than 18 cm. It is allocation based on this criterion that has led to a difference in the total patient number in the two groups.
Our previous dosimetric study had evaluated that in lesser inter-field separation target coverage is comparable with plans generated using 6- or 10-MV photon beams.  We have also shown that variation in breast dose is higher with large breasts compared to medium and small breasts.  However, breast boost with electron may be an issue if LA is not available. There is minimal published literature dealing with the impact of cobalt or LA on toxicities and QOL. Further, as per institutional protocol, in our center all suitable patients who underwent BCS and treated with cobalt source were treated with weekly electron boost to tumor bed.  This has been employed as an effective resource sparing strategy in suitable patients at our institution.  Literatures regarding the impact of cobalt source external beam RT on the QOL domain scores are limited. The use of cobalt machines in suitable patients, as employed in our study to treat intact breasts after conservation would be a viable option in developing countries where cobalt forms the major bulk of radiation therapy machines.  Therefore, the results of our study have special relevance for developing countries.
In the present study, at pre-RT evaluation mean EORTC QLQ C30 symptom and functional domain scores as well as BR23 domain scores were similar between patients treated with cobalt and LA sources. This suggests that there was no difference in the QOL domain scores between the cobalt and LA before starting RT. At pre-RT QOL evaluation GQOL score in patients treated with cobalt and LA were very similar at 71.6 and 71.7, respectively. At RT completion, GQOL score was comparable between patients treated with cobalt and LA. There was no further significant deterioration of either functional or symptom domain scores at mid-RT and also at RT completion. Thus, it may be assumed that in appropriately selected patients there no significant difference in QOL scores at RT completion between patients treated with cobalt or LA.
There is a general intuition that BCS patients treated with cobalt may have higher arm and breast symptoms mainly due to higher skin dose compared with LA.  However, in our study with appropriately selected patient population, breast and arm symptoms at RT completion were comparable between the two study arms. There was no significant difference in sexual functioning and sexual enjoyment domain scores as well between these two arms. Thus, it is assumed that in appropriately selected patients there is no difference in at least early QOL scores between patients treated with cobalt or LA. In recent years, preserving sexual activity-related domain has become useful and important end point after breast conservation. Apart from cosmesis and other functional domains, QOL is also used to evaluate the sexual function-related domains after treatment. In our study, there was no significant difference in sexual function-related domains after treatment with cobalt or LA.
Our study while providing important QOL information regarding breast cancer patients treated with cobalt and LA but has its limitations. It is not a randomized study but a randomized study for addressing this question is unlikely to be designed. There is considerable heterogeneity of patient number in the two groups. However, besides the intergroup comparison, an intragroup comparison has been done as well (pre and post RT scores). While we have reported baseline scores and scores at RT conclusion, we have not provided long-term assessment of QOL in our patient subgroup. However, we believe that the present analysis has addressed an appropriate clinical question which is unlikely to be dealt by any prospective randomized study in future. 
In summary, there is no significant difference in QOL domains after RT between appropriately selected patients treated with cobalt and LA. No significant changes in QOL domain scores at RT conclusion from pre-RT in patients treated with cobalt or LA source at least in early follow up evaluation. Hence, a cobalt machine may be used to deliver adjuvant RT in appropriately selected patients after BCS especially in developing countries with limited resources.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]