|Year : 2019 | Volume
| Issue : 2 | Page : 128-130
Three-Dimensional Conformal focal radiotherapy (30 Gy in 5 fractions) – An useful substitute for Stereotactic radiosurgery In Brain oligometastases: A Single-institutional Case Series
Jyotirup Goswami, Suman Mallik, Kazi Sazzad Manir, Sayan Das, Arijit Sen, Monidipa Mondal, Bipasha Pal, Suresh Das, Soura Palit, Papai Sarkar
Department of Radiation Oncology, Narayana Super-Specialty Hospital, Howrah, West Bengal, India
|Date of Submission||19-Sep-2019|
|Date of Acceptance||03-Nov-2019|
|Date of Web Publication||10-Jan-2020|
Dr. Kazi Sazzad Manir
Department of Radiation Oncology, Narayana Super.Specialty Hospital, 120/1, Andul Road, Howrah - 711 103, West Bengal
Source of Support: None, Conflict of Interest: None
Stereotactic Radiosurgery/Radiotherapy (SRS/SRT) or neurosurgery is the standard of care for brain oligometastases (≤4 in number). SRS/SRT is only applicable for highly selected patients due to stringent size criteria (≤4 cm) and unavailability of this advanced technology in majority radiation centers in India. Hypofractionated focal 3-dimensional conformal radiotherapy (30 Gy in 5 fractions in 5 consecutive days) represents an attractive clinical alternative to SRS/SRT. In our series, we report dosimetric and clinical outcomes of nine patients (single brain metastatic foci, median size 3.4 cm). Radiotherapy was planned using coplanar and noncoplanar beams, conventional 1 cm multileaf collimators, and 3-mm planning target volume margins on a 6 MV linear accelerator. We were able to achieve sharp-dose falloff and excellent clinical outcome in our short follow-up. This protocol seems to be a feasible and well-tolerated alternative to SRS/SRT. We have designed a long-term Phase III prospective study to validate this regimen in larger population (ineligible for SRS/SRT).
Keywords: Focal three-dimensional radiotherapy, oligometastases, stereotactic radiosurgery
|How to cite this article:|
Goswami J, Mallik S, Manir KS, Das S, Sen A, Mondal M, Pal B, Das S, Palit S, Sarkar P. Three-Dimensional Conformal focal radiotherapy (30 Gy in 5 fractions) – An useful substitute for Stereotactic radiosurgery In Brain oligometastases: A Single-institutional Case Series. Int J Neurooncol 2019;2:128-30
|How to cite this URL:|
Goswami J, Mallik S, Manir KS, Das S, Sen A, Mondal M, Pal B, Das S, Palit S, Sarkar P. Three-Dimensional Conformal focal radiotherapy (30 Gy in 5 fractions) – An useful substitute for Stereotactic radiosurgery In Brain oligometastases: A Single-institutional Case Series. Int J Neurooncol [serial online] 2019 [cited 2022 Jun 25];2:128-30. Available from: https://www.Internationaljneurooncology.com/text.asp?2019/2/2/128/275532
| Introduction|| |
Metastatic cancer to the brain is particularly common for lung and breast cancers. For brain oligometastases (≤4 in number), particularly with systemically controlled primary, options were surgical resection followed by whole-brain radiotherapy (WBRT), WBRT with stereotactic boost, or stereotactic radiotherapy (SRT) alone. Recent studies have confirmed that SRT alone achieves equivalent local control (LC) to WBRT, which improves distant brain control (DBC) but does not improve the overall survival. Nowadays, standard treatment of solitary or oligometastases,,, of brain is either neurosurgery with or without postoperative radiation therapy or stereotactic radiation surgery (SRS)/stereotactic radiation therapy., However, a limited number of patients are eligible for SRS/SRT (size <4 cm, fewer than four metastases, good general health status, and well-controlled systemic disease).
While SRS/SRT represents a technically advanced and clinically attractive paradigm, it is impossible to deliver routinely in resource-constrained settings. In this background, we planned to analyze focal conformal radiotherapy and evaluate whether it can achieve comparable outcomes at much lower expenses and using less work hours.
| Case Report|| |
Our study comprises 9 patients of oligometastasis to the brain treated between 2015 and 2016. All selected patients had an expected survival of >6 months, though some had uncontrolled primary disease. All patients selected were either unsuitable for or had rejected surgery. SRS/SRT was not considered for them due to the technology being unavailable at our center at that time. All patients were included for focal 3-dimensional conformal radiotherapy (3DCRT). Immobilization was done with conventional 3-clamp thermoplastic mold in neutral neck position on air-equivalent base plate. They underwent simulation contrast-enhanced computed tomography (CT) scan with 3 mm slices, on 16-slice CT scanner. Images were fused with planning magnetic resonance images (MRI) (T1-weighted gadolinium contrast images). The gross tumor volume (GTV) was contoured as the contrast-enhancing lesion as seen on T1-weighted MRI. Perilesional edema was excluded from the GTV; as per convention, no separate clinical target volume was generated. An isotropic margin of 3 mm was applied for the planning target volume (PTV). Treatment was delivered on a 6 MV linear accelerator equipped with 1 cm multileaf collimators (MLCs) and camera-based electron portal imaging device (EPID). Treatment planning was done using both coplanar and noncoplanar 6 MV photons. Dose prescribed to the isocenter was 30 Gy/5# while the dose to the periphery of the PTV was set at 80% of the same. Standard dose–volume parameters were used to optimally spare the surrounding normal brain and important organs at risk (OAR), such as brainstem, optic structures, and temporal lobes. Treatments were delivered on 5 consecutive days, using pretreatment EPID image verification. All patients received corticosteroids in tapering doses during this period. Posttreatment, all patients proceeded for appropriate systemic therapy. They underwent clinical evaluation (along with Neurocognitive evaluation by Mini-Mental State Examinations [MMSE]) at 6 weeks and 3 months (additionally, a MRI scan at 3 months).
| Results|| |
Of 9 patients, 4 were male and were female. Median age was 51 years (38–67 years). The most common primary site was lung (6 patients), followed by breast (2 patients) and head–neck (1 patient). Performance status was 0–2 for all patients. Seven patients had controlled primary while two had disseminated disease.
All patients successfully completed their course of radiotherapy. No patient had treatment-induced worsening of headache. No patient had worse than grade 0–1 nausea–vomiting.
Dosimetric results are provided in [Table 1].
All patients had at least partial response as per Response Evaluation Criteria in Solid Tumors (RECIST version 1.0) on posttreatment MRI (one could not be assessed as she had passed away prior). At a median follow-up of 13 months (7–19 months), the LC rate was 100%. DBC was 90% (one patient had distant brain relapse). There was no MMSE score deterioration at 6 weeks and 3 months.
| Discussion|| |
Standard treatment of brain oligometastases is either neurosurgery of SRS/SRT. Due to the unavailability of SRS/SRT in majority of centers and rigid size and number criteria, management of limited brain metastases remained challenging. In a survey published by our group in 2018, among the Indian radiation oncologists, only 25.8% have SRS/SRT facility, and among them, only 26.1% use SRS/SRT in suitable patients. The reasons are mostly due to the procedure being highly expensive, labor intensive, and technically challenging. Although debatable, hypofractionated focal 3DCRT may be a suitable (radiobiological and technical) alternative solution in this setting. Levy et al., in their study, reported 30 Gy/6 fractions focal RT schedule in single cerebellar metastasis. Aoki et al. reported actuarial tumor control rate of 78.4% and 71.9% in 6 months and 1 year, respectively, using 24 Gy/3–5 fractions focal 3DCRT.
In our series of 9 patients (median size 3.4 cm), treated using conventional MLCs with a dose of 30 Gy/5 fractions, we were able to achieve a sharp dose falloff (median distance between 50% isodose line and GTV was 2.7 cm). OAR doses were within acceptable limits. Outcome (LC and DBC) of the present study corroborates published literatures. There was no significant MMSE score decrease.
This reported case series was a pilot study to evaluate the safety and tolerability of 30 Gy/5 fractions regimen in the Indian context. In our institute where we now have SRS facility, we have already initiated a prospective study to evaluate this regimen in brain oligometastases patients who are not suitable for SRS/SRT, using either focal 3DCRT or volume-modulated arc therapy. Long-term outcome will be assessed along with neurocognitive evaluation (with specific and robust tools).
| Conclusion|| |
Our study suggests that for resource-constrained settings, using focal 3DCRT can serve as an effective and well-tolerated alternative to the standard of care, SRS/SRT. We envisage that this should become the norm for this setting in the short and medium term.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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