Impact of volume of irradiation on survival and quality of life in glioblastoma: a prospective, phase 2, randomized comparison of RTOG and MDACC protocols

Magnetic resonance imaging in glioblastoma radiotherapy - beyond treatment adaptation

Background and Purpose

The treatment of glioblastoma remains a challenging task for modern radiation oncology. Adaptive radiotherapy potentially improves local control and reduces toxicity to healthy brain tissue. The purpose of the study was to examine the safety of adaptive radiotherapy in glioblastoma, using a margin-reduction approach based on an interim magnetic resonance image (MRI). Furthermore, it aimed to identify radiomorphological features that may correlate with disease outcome.

Materials and Methods

108 glioblastoma patients receiving standard chemoradiotherapy underwent repeated MRI after 40 Gy. The images were compared to the pre-radiotherapy MRI, based on the following criteria: midline shift, perifocal edema, contrast enhancement, ventricular compression, new lesion outside the radiation field, gross tumor volume (GTV) and planning target volume (PTV) size. Target volumes were adjusted by taking into consideration the new intracranial conditions and the remaining 20 Gy was delivered. Statistical analysis consisted of the comparison of the radiomorphological features to overall and progression free survival.

Results

Increased or unchanged contrast enhancement (HR: 2.11 and 1.18 consecutively) and ventricular compression (HR: 13.58 and 2.53) on the interim MRI resulted in significantly poorer survival. GTV size (initial: 61.4 [3.8-170.9], adapted: 45.3 [0-206.8] cm3) reduction (absolute: -16.2 [-115.3-115.5] cm3, relative: -24.5 [-100-258.9] %) also had demonstrable impact on survival. Changes in PTV, however, did not significantly correlate with survival.

Conclusions

By reducing PTV based on an interim MRI, we achieved substantial sparing of critical normal tissues, without compromising survival. The established evaluation categories can facilitate the systematic review of interim MRI findings.

Reduced Treatment Volumes for Glioblastoma Associated With Lower Rates of Radionecrosis and Lymphopenia: A Pooled Analysis

Purpose

There is marked variability in treatment fields for glioblastoma. We performed a retrospective study comparing outcomes of patients treated according to MD Anderson Cancer Center (MDACC) or Radiation Therapy Oncology Group (RTOG) guidelines and identified differences in treatment-related toxicity.

Methods and Materials

Adult patients with glioblastoma treated with surgery and adjuvant radiation treatment were included in this study. Primary outcomes were local control, progression-free survival (PFS), overall survival (OS), and radiation-related toxicity. PFS and OS were estimated using the Kaplan-Meier estimator. Univariate and multivariate analyses were conducted using Cox regression models.

Results

In total, 257 patients met the inclusion criteria with a median age of 60.1 years at diagnosis. There were 162 and 95 patients treated according to the MDACC or RTOG guidelines, respectively. Despite having similar gross tumor volumes, the RTOG cohort had a larger median planning target volume (303.2 cm³ vs 430.7 cm³, P < .001) and worse PFS (6 months vs 9 months, P = .031). There was no difference in OS between treatment techniques. Patients treated according to RTOG guidelines experienced higher rates of radionecrosis (34% vs 21%, P = .024) and severe lymphopenia (15% vs 7%, P = .044).

Conclusions

Patients treated according to MDACC guidelines had smaller treatment volumes, improved PFS, and lower rates of radionecrosis and severe lymphopenia. However, when adjusting for prognostic factors, treatment type was not associated with PFS in multivariate analysis. Prospective investigation is warranted to confirm these differences in outcomes.

Radiotherapeutic advances in the management of glioblastoma

Glioblastoma remains a fatal diagnosis despite continuous efforts to improve upon the current standard backbone management paradigm of surgery, radiation therapy, systemic therapy and Tumor Treating Fields. Radiation therapy (RT) plays a pivotal role, with progress recently achieved in multiple key areas of research. The evolving landscape of dose and fractionation schedules and dose escalation options for different patient populations is explored, offering opportunities to better tailor treatment to a patient's overall status and preferences; novel efforts to modify treatment volumes are presented, such as utilizing state-of-the-art MRI-based linear accelerators to deliver adaptive therapy, hoping to reduce normal tissue exposure and treatment-related toxicity; specialized MR techniques and functional imaging using novel PET agents are described, providing improved treatment accuracy and the opportunity to target areas at risk of disease relapse; finally, the role of particle therapy and new altered dose-rate photon and proton therapy techniques in the treatment paradigm of glioblastoma is detailed, aiming to improve tumor control and patient outcome by exploiting novel radiobiological pathways. Improvements in each of these aforementioned areas are needed to make the critical necessary progress and allow for new approaches combining different advanced treatment modalities. This plethora of multiple new treatment options currently under investigation provides hope for a new outlook for patients with glioblastoma in the near future.

Amide proton transfer-weighted CEST MRI for radiotherapy target delineation of glioblastoma: a prospective pilot study

BACKGROUND

Extensive glioblastoma infiltration justifies a 15-mm margin around the gross tumor volume (GTV) to define the radiotherapy clinical target volume (CTV). Amide proton transfer (APT)-weighted imaging could enable visualization of tumor infiltration, allowing more accurate GTV delineation. We quantified the impact of integrating APT-weighted imaging into GTV delineation of glioblastoma and compared two APT-weighted quantification methods-magnetization transfer ratio asymmetry (MTRasym) and Lorentzian difference (LD) analysis-for target delineation.

METHODS

Nine glioblastoma patients underwent an extended imaging protocol prior to radiotherapy, yielding APT-weighted MTRasym and LD maps. From both maps, biological tumor volumes were generated (BTVMTRasym and BTVLD) and added to the conventional GTV to generate biological GTVs (GTVbio,MTRasym and GTVbio,LD). Wilcoxon signed-rank tests were performed for comparisons.

RESULTS

The GTVbio,MTRasym and GTVbio,LD were significantly larger than the conventional GTV (p ≤ 0.022), with a median volume increase of 9.3% and 2.1%, respectively. The GTVbio,MTRasym and GTVbio,LD were significantly smaller than the CTV (p = 0.004), with a median volume reduction of 72.1% and 70.9%, respectively. There was no significant volume difference between the BTVMTRasym and BTVLD (p = 0.074). In three patients, BTVMTRasym delineation was affected by elevated signals at the brain periphery due to residual motion artifacts; this elevation was absent on the APT-weighted LD maps.

CONCLUSION

Larger biological GTVs compared to the conventional GTV highlight the potential of APT-weighted imaging for radiotherapy target delineation of glioblastoma. APT-weighted LD mapping may be advantageous for target delineation as it may be more robust against motion artifacts.

RELEVANCE STATEMENT

The introduction of APT-weighted imaging may, ultimately, enhance visualization of tumor infiltration and eliminate the need for the substantial 15-mm safety margin for target delineation of glioblastoma. This could reduce the risk of radiation toxicity while still effectively irradiating the tumor.

TRIAL REGISTRATION

NCT05970757 (ClinicalTrials.gov).

KEY POINTS

Integration of APT-weighted imaging into target delineation for radiotherapy is feasible. The integration of APT-weighted imaging yields larger GTVs in glioblastoma. APT-weighted LD mapping may be more robust against motion artifacts than APT-weighted MTRasym.

Evolving concepts in margin strategies and adaptive radiotherapy for glioblastoma: A new future is on the horizon

Chemoradiotherapy is the standard treatment after maximal safe resection for glioblastoma (GBM). Despite advances in molecular profiling, surgical techniques, and neuro-imaging, there have been no major breakthroughs in radiotherapy (RT) volumes in decades. Although the majority of recurrences occur within the original gross tumor volume (GTV), treatment of a clinical target volume (CTV) ranging from 1.5 to 3.0 cm beyond the GTV remains the standard of care. Over the past 15 years, the incorporation of standard and functional MRI sequences into the treatment workflow has become a routine practice with increasing adoption of MR simulators, and new integrated MR-Linac technologies allowing for daily pre-, intra- and post-treatment MR imaging. There is now unprecedented ability to understand the tumor dynamics and biology of GBM during RT, and safe CTV margin reduction is being investigated with the goal of improving the therapeutic ratio. The purpose of this review is to discuss margin strategies and the potential for adaptive RT for GBM, with a focus on the challenges and opportunities associated with both online and offline adaptive workflows. Lastly, opportunities to biologically guide adaptive RT using non-invasive imaging biomarkers and the potential to define appropriate volumes for dose modification will be discussed.

The need for paradigm shift: prognostic significance and implications of standard therapy-related systemic immunosuppression in glioblastoma for immunotherapy and oncolytic virotherapy

Despite significant advances in our knowledge regarding the genetics and molecular biology of gliomas over the past two decades and hundreds of clinical trials, no effective therapeutic approach has been identified for adult patients with newly diagnosed glioblastoma, and overall survival remains dismal. Great hopes are now placed on combination immunotherapy. In clinical trials, immunotherapeutics are generally tested after standard therapy (radiation, temozolomide, and steroid dexamethasone) or concurrently with temozolomide and/or steroids. Only a minor subset of patients with progressive/recurrent glioblastoma have benefited from immunotherapies. In this review, we comprehensively discuss standard therapy-related systemic immunosuppression and lymphopenia, their prognostic significance, and the implications for immunotherapy/oncolytic virotherapy. The effectiveness of immunotherapy and oncolytic virotherapy (viro-immunotherapy) critically depends on the activity of the host immune cells. The absolute counts, ratios, and functional states of different circulating and tumor-infiltrating immune cell subsets determine the net immune fitness of patients with cancer and may have various effects on tumor progression, therapeutic response, and survival outcomes. Although different immunosuppressive mechanisms operate in patients with glioblastoma/gliomas at presentation, the immunological competence of patients may be significantly compromised by standard therapy, exacerbating tumor-related systemic immunosuppression. Standard therapy affects diverse immune cell subsets, including dendritic, CD4+, CD8+, natural killer (NK), NKT, macrophage, neutrophil, and myeloid-derived suppressor cell (MDSC). Systemic immunosuppression and lymphopenia limit the immune system's ability to target glioblastoma. Changes in the standard therapy are required to increase the success of immunotherapies. Steroid use, high neutrophil-to-lymphocyte ratio (NLR), and low post-treatment total lymphocyte count (TLC) are significant prognostic factors for shorter survival in patients with glioblastoma in retrospective studies; however, these clinically relevant variables are rarely reported and correlated with response and survival in immunotherapy studies (e.g., immune checkpoint inhibitors, vaccines, and oncolytic viruses). Our analysis should help in the development of a more rational clinical trial design and decision-making regarding the treatment to potentially improve the efficacy of immunotherapy or oncolytic virotherapy.

The need of radiotherapy optimization for glioblastomas considering immune responses

Glioblastoma is the most common of malignant primary brain tumors and one of the tumors with the poorest prognosis for which the overall survival rate has not significantly improved despite recent advances in treatment techniques and therapeutic drugs. Since the emergence of immune checkpoint inhibitors, the immune response to tumors has attracted increasing attention. Treatments affecting the immune system have been attempted for various tumors, including glioblastomas, but little has been shown to be effective. It has been found that the reason for this is that glioblastomas have a high ability to evade attacks from the immune system, and that the lymphocyte depletion associated with treatment can reduce its immune function. Currently, research to elucidate the resistance of glioblastomas to the immune system and development of new immunotherapies are being vigorously carried out. Targeting of radiation therapy for glioblastomas varies among guidelines and clinical trials. Based on early reports, target definitions with wide margins are common, but there are also reports that narrowing the margins does not make a significant difference in treatment outcome. It has also been suggested that a large number of lymphocytes in the blood are irradiated by the irradiation treatment to a wide area in a large number of fractionations, which may reduce the immune function, and the blood is being recognized as an organ at risk. Recently, a randomized phase II trial comparing two types of target definition in radiotherapy for glioblastomas was conducted, and it was reported that the overall survival and progression-free survival were significantly better in a small irradiation field group. We review recent findings on the immune response and the immunotherapy to glioblastomas and the novel role of radiotherapy and propose the need to develop an optimal radiotherapy that takes radiation effects on the immune function into account.

Prognostic factors for pediatric, adolescent, and young adult patients with non-DIPG grade 4 gliomas: a contemporary pooled institutional experience

PURPOSE

WHO grade 4 gliomas are rare in the pediatric and adolescent and young adult (AYA) population. We evaluated prognostic factors and outcomes in the pediatric versus AYA population.

METHODS

This retrospective pooled study included patients less than 30 years old (yo) with grade 4 gliomas treated with modern surgery and radiotherapy. Overall survival (OS) and progression-free survival (PFS) were characterized using Kaplan-Meier and Cox regression analysis.

RESULTS

Ninety-seven patients met criteria with median age 23.9 yo at diagnosis. Seventy-seven patients were ≥ 15 yo (79%) and 20 patients were < 15 yo (21%). Most had biopsy-proven glioblastoma (91%); the remainder had H3 K27M-altered diffuse midline glioma (DMG; 9%). All patients received surgery and radiotherapy. Median PFS and OS were 20.9 months and 79.4 months, respectively. Gross total resection (GTR) was associated with better PFS in multivariate analysis [HR 2.00 (1.01-3.62), p = 0.023]. Age ≥ 15 yo was associated with improved OS [HR 0.36 (0.16-0.81), p = 0.014] while female gender [HR 2.12 (1.08-4.16), p = 0.03] and DMG histology [HR 2.79 (1.11-7.02), p = 0.029] were associated with worse OS. Only 7% of patients experienced grade 2 toxicity. 62% of patients experienced tumor progression (28% local, 34% distant). Analysis of salvage treatment found that second surgery and systemic therapy significantly improved survival.

CONCLUSION

Age is a significant prognostic factor in WHO grade 4 glioma, which may reflect age-related molecular alterations in the tumor. DMG was associated with worse OS than glioblastoma. Reoperation and systemic therapy significantly increased survival after disease progression. Prospective studies in this population are warranted.

ESTRO-EANO guideline on target delineation and radiotherapy details for glioblastoma

BACKGROUND AND PURPOSE

Target delineation in glioblastoma is still a matter of extensive research and debate. This guideline aims to update the existing joint European consensus on delineation of the clinical target volume (CTV) in adult glioblastoma patients.

MATERIAL AND METHODS

The ESTRO Guidelines Committee identified 14 European experts in close interaction with the ESTRO clinical committee and EANO who discussed and analysed the body of evidence concerning contemporary glioblastoma target delineation, then took part in a two-step modified Delphi process to address open questions.

RESULTS

Several key issues were identified and are discussed including i) pre-treatment steps and immobilisation, ii) target delineation and the use of standard and novel imaging techniques, and iii) technical aspects of treatment including planning techniques and fractionation. Based on the EORTC recommendation focusing on the resection cavity and residual enhancing regions on T1-sequences with the addition of a reduced 15 mm margin, special situations are presented with corresponding potential adaptations depending on the specific clinical situation.

CONCLUSIONS

The EORTC consensus recommends a single clinical target volume definition based on postoperative contrast-enhanced T1 abnormalities, using isotropic margins without the need to cone down. A PTV margin based on the individual mask system and IGRT procedures available is advised; this should usually be no greater than 3 mm when using IGRT.

Location of Recurrences after Trimodality Treatment for Glioblastoma with Respect to the Delivered Radiation Dose Distribution and Its Influence on Prognosis

BACKGROUND

While prognosis of glioblastoma after trimodality treatment is well examined, recurrence pattern with respect to the delivered dose distribution is less well described. Therefore, here we examine the gain of additional margins around the resection cavity and gross-residual-tumor.

METHODS

All recurrent glioblastomas initially treated with radiochemotherapy after neurosurgery were included. The percentage overlap of the recurrence with the gross tumor volume (GTV) expanded by varying margins (10 mm to 20 mm) and with the 95% and 90% isodose was measured. Competing-risks analysis was performed in dependence on recurrence pattern.

RESULTS

Expanding the margins from 10 mm to 15 mm, to 20 mm, to the 95%- and 90% isodose of the delivered dose distribution with a median margin of 27 mm did moderately increase the proportion of relative in-field recurrence volume from 64% to 68%, 70%, 88% and 88% (p < 0.0001). Overall survival of patients with in-and out-field recurrence was similar (p = 0.7053). The only prognostic factor significantly associated with out-field recurrence was multifocality of recurrence (p = 0.0037). Cumulative incidences of in-field recurrences at 24 months were 60%, 22% and 11% for recurrences located within a 10 mm margin, outside a 10 mm margin but within the 95% isodose, or outside the 95% isodose (p < 0.0001). Survival from recurrence was improved after complete resection (p = 0.0069). Integrating these data into a concurrent-risk model shows that extending margins beyond 10 mm has only small effects on survival hardly detectable by clinical trials.

CONCLUSIONS

Two-thirds of recurrences were observed within a 10 mm margin around the GTV. Smaller margins reduce normal brain radiation exposure allowing for more extensive salvage radiation therapy options in case of recurrence. Prospective trials using margins smaller than 20 mm around the GTV are warranted.

Pattern of Recurrence of Glioblastoma Versus Grade 4 IDH-Mutant Astrocytoma Following Chemoradiation: A Retrospective Matched-Cohort Analysis

Background and Purpose: To quantitatively compare the recurrence patterns of glioblastoma (isocitrate dehydrogenase-wild type) versus grade 4 isocitrate dehydrogenase-mutant astrocytoma (wild type isocitrate dehydrogenase and mutant isocitrate dehydrogenase, respectively) following primary chemoradiation. Materials and Methods: A retrospective matched cohort of 22 wild type isocitrate dehydrogenase and 22 mutant isocitrate dehydrogenase patients were matched by sex, extent of resection, and corpus callosum involvement. The recurrent gross tumor volume was compared to the original gross tumor volume and clinical target volume contours from radiotherapy planning. Failure patterns were quantified by the incidence and volume of the recurrent gross tumor volume outside the gross tumor volume and clinical target volume, and positional differences of the recurrent gross tumor volume centroid from the gross tumor volume and clinical target volume. Results: The gross tumor volume was smaller for wild type isocitrate dehydrogenase patients compared to the mutant isocitrate dehydrogenase cohort (mean ± SD: 46.5 ± 26.0 cm³ vs 72.2 ± 45.4 cm³, P = .026). The recurrent gross tumor volume was 10.7 ± 26.9 cm³ and 46.9 ± 55.0 cm³ smaller than the gross tumor volume for the same groups (P = .018). The recurrent gross tumor volume extended outside the gross tumor volume in 22 (100%) and 15 (68%) (P= .009) of wild type isocitrate dehydrogenase and mutant isocitrate dehydrogenase patients, respectively; however, the volume of recurrent gross tumor volume outside the gross tumor volume was not significantly different (12.4 ± 16.1 cm³ vs 8.4 ± 14.2 cm³, P = .443). The recurrent gross tumor volume centroid was within 5.7 mm of the closest gross tumor volume edge for 21 (95%) and 22 (100%) of wild type isocitrate dehydrogenase and mutant isocitrate dehydrogenase patients, respectively. Conclusion: The recurrent gross tumor volume extended beyond the gross tumor volume less often in mutant isocitrate dehydrogenase patients possibly implying a differential response to chemoradiotherapy and suggesting isocitrate dehydrogenase status might be used to personalize radiotherapy. The results require validation in prospective randomized trials.

Impact of Immunohistochemical profiling of Glioblastoma multiforme on clinical outcomes: Real-world scenario in resource limited setting

OBJECTIVE

Intuition into the molecular pathways of glioblastoma multiforme (GBM) has changed the diagnostic, prognostic, and therapeutic approaches. We investigated the influence of various clinical and molecular prognostic factors on survival outcomes in radically treated GBM patients.

METHODS

Medical records of 160 GBM patients treated between January-2012 and December-2018 with surgery followed by post-operative external beam radiotherapy (EBRT) with/without temozolomide (TMZ) were reviewed. Immunohistochemical (IHC) assays were performed for IDH1mutation, ATRX loss, TP53 overexpression and Ki-67% index. Apart from disease and treatment-related factors' influence on clinical outcomes, the impact of IHC markers in prognostication was analyzed using appropriate statistical tests.

RESULTS

The median overall survival (OS) was 14 months. EBRT with concurrent TMZ was given to 60% of patients and 42.5% completed the standard Stupp-protocol. Significant improvements in OS was observed in patients aged ≤ 50years (2-year OS: 22.1% vs. 12.5%, p = 0.001), those who underwent gross total resection (2-year OS: 21.8% vs. 12.8%, p = 0.002), received concurrent TMZ (21.9% vs. 12.5%, p = 0.005), completed the entire Stupp-protocol (2-year OS: 23.4% vs. 6.5%, p = 0.000), and with Ki-67 index <20% (2-year OS: 23.3% vs. 11.6%, p = 0.015). On multivariate analysis, IDH1 mutation, ATRX loss, TP53 expression, and Ki-67 ≤ 20% were significant prognosticators of outcomes.

CONCLUSION

GBM patients treated with concurrent chemoradiation and those who completed the full Stupp-protocol experienced better survival outcomes. Molecular biology significantly impacts clinical outcomes and plays a key deterministic role in newer management strategies.

Quantitative mapping of individual voxels in the peritumoral region of IDH-wildtype glioblastoma to distinguish between tumor infiltration and edema

PURPOSE

The peritumoral region (PTR) in glioblastoma (GBM) represents a combination of infiltrative tumor and vasogenic edema, which are indistinguishable on magnetic resonance imaging (MRI). We developed a radiomic signature by using imaging data from low grade glioma (LGG) (marker of tumor) and PTR of brain metastasis (BM) (marker of edema) and applied it on the GBM PTR to generate probabilistic maps.

METHODS

270 features were extracted from T1-weighted, T2-weighted, and apparent diffusion coefficient maps in over 3.5 million voxels of LGG (36 segments) and BM (45 segments) scanned in a 1.5T MRI. A support vector machine classifier was used to develop the radiomics model from approximately 50% voxels (downsampled to 10%) and validated with the remaining. The model was applied to over 575,000 voxels of the PTR of 10 patients with GBM to generate a quantitative map using Platt scaling (infiltrative tumor vs. edema).

RESULTS

The radiomics model had an accuracy of 0.92 and 0.79 in the training and test set, respectively (LGG vs. BM). When extrapolated on the GBM PTR, 9 of 10 patients had a higher percentage of voxels with a tumor-like signature over radiological recurrence areas. In 7 of 10 patients, the areas under curves (AUC) were > 0.50 confirming a positive correlation. Including all the voxels from the GBM patients, the infiltration signature had an AUC of 0.61 to predict recurrence.

CONCLUSION

A radiomic signature can demarcate areas of microscopic tumors from edema in the PTR of GBM, which correlates with areas of future recurrence.

Evaluation of interim MRI changes during limited-field radiation therapy for glioblastoma and implications for treatment planning

BACKGROUND AND PURPOSE

Consensus for defining gross tumor volume (GTV) and clinical target volume (CTV) for limited-field radiation therapy (LFRT) of GBM are not well established. We leveraged a department MRI simulator to image patients before and during LFRT to address these questions.

MATERIALS AND METHODS

Supratentorial GBM patients receiving LFRT (46 Gy + boost to 60 Gy) underwent baseline MRI (MRI1) and interim MRI during RT (MRI2). GTV1 was defined as T1 enhancement + surgical cavity on MRI1 without routine inclusion of T2 abnormality (unless tumor did not enhance). The initial CTV margin was 15 mm from GTV1, and the boost CTV margin was 5-7 mm. The GTV1 characteristics were categorized into three groups: identical T1 and T2 abnormality (Group A), T1 only with larger T2 abnormality not included (Group B), and T2 abnormality when tumor lacked enhancement (Group C). GTV2 was contoured on MRI2 and compared with GTV1 plus 5-15 mm expansions.

RESULTS

Among 120 patients treated from 2014-2019, 29 patients (24%) underwent replanning based on MRI2. On MRI2, 84% of GTV2 were covered by GTV1 + 5 mm, 93% by GTV1 + 7 mm, and 98% by GTV1 + 15 mm. On MRI1, 43% of GTV1 could be categorized into Group A, 39% Group B, and 18% Group C. Group B's patterns of failure, local control, or progression-free survival were similar to Group A/C.

CONCLUSIONS

Initial CTV margin of 15 mm followed by a boost CTV margin of 7 mm is a reasonable approach for LFRT of GBM. Omitting routine inclusion of T2 abnormality from GTV delineation may not jeopardize disease control.

Return to work in survivors of Primary Brain Tumours treated with Intensity Modulated Radiotherapy

MINI: Primary Brain Tumour survivors usually have significant morbidity, especially cognitive and neurological dysfunction. Return to pre-diagnosis work can be an important QoL indicator and outcomes measure in these patients. We did a retrospective study to assess return to work amongst the patients who underwent radiotherapy at our centre.

BACKGROUND

Primary brain tumour (PBT) survivors have a high burden of morbidity. Return to work (RTW) is an important survivorship parameter and outcomes measure in these patients, especially in developing countries. This study was done to assess RTW after radiotherapy, reasons for no RTW, and relationship of RTW with treatment and patient factors.

PATIENTS AND METHODS

A single centre study was done amongst PBT patients. Baseline and treatment details, education, employment was assessed. RTW assessed as: time to RTW, full/ part-time, reasons for no RTW and RTW at 6 months post-therapy, and last follow up.

RESULTS

67 PBT patients with a median age of 42 years were assessed. Most common diagnosis was low grade glioma. Over 66% patients were illiterate, and 62% had semi-skilled and unskilled jobs, mostly agriculture. About 64.4% patients returned to employment in a median time of 3 months. At 6 months post-treatment 58.2% had a job, with only 42% working full-time. 'Limb weakness' (21.4%), followed by 'loss of job/ no job' (16.7%), 'fatigue'/ 'tiredness' (14.3%), 'poor vision/ diminished vision' (11.9%) were the common reasons for no RTW. The factors found to be significantly associated with return to work were younger age (p = 0.042), male sex (0.013), the absence of complications during radiotherapy (p = 0.049), part time job prior to diagnosis (p = 0.047), and early return to work after RT (p < 0.001).

CONCLUSION

Studies are needed to identify the barriers in re- employment and steps to overcome them in cancer patients.

Can 3D-CRT meet the desired dose distribution to target and OARs in glioblastoma? A tertiary cancer center experience

Aim: The purpose of the study is to perform a dosimetric analysis of the doses received by planning target volume and organ at risks in the postoperative glioblastoma by using 3D-conformal radiotherapy to a total dose of 60 Gy in 30 fractions. Materials & Methods: All patients received concurrent temozolomide every day, and this was followed by adjuvant temozolomide of 5 days of treatment per month. Results: More than 98% of patients were treated with a dose of 60 Gy. Doses were analyzed for the normal whole brain, tumor volume, as well as all the organs at risk. Conclusion: Given the grave prognosis and the limited survival of glioblastoma despite the best treatment available, makes 3D-conformal radiotherapy an equally acceptable treatment option.