Efficacy of the collapsed cone algorithm calculated radiotherapy plans in intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT): A comparative dosimetric study in tumors of thorax.

AIM: In this study, efficacy of collapsed cone algorithm-generated intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) were evaluated for treatment of thoracic esophageal cancer. MATERIALS AND METHODS: Ten previously treated patients with VMAT were considered for evaluation. The planning parameters were evaluated in terms of max dose, mean dose, Homogeneity Index, Conformity Index for planning target volume, and organ at risk doses. Total monitor unit, treatment time, and gamma passing index were also reported. RESULTS: The target dose coverage of the VMAT and IMRT plans achieved the clinical dosimetric criteria for all ten patients in the evaluation. Under the condition of equivalent target dose distribution, the VMAT plan's Conformity Index, monitor unit, treatment time, and gamma passing index rate were superior than in the IMRT plan, and the result was statistically significant. CONCLUSION: Collapsed cone algorithm-based VMAT can have a more effective and better approach for esophageal cancer than IMRT.

Dosimetric Comparision of Coplanar versus Noncoplanar Volumetric Modulated Arc Therapy for Treatment of Bilateral Breast Cancers.

Introduction: The purpose of this study was to compare the dosimetric parameters of volumetric modulated arc therapy (VMAT) treatment plans using coplanar and noncoplanar beams in patients with bilateral breast cancer/s (BBCs) in terms of organ at risk sparing and target volume coverage. The hypothesis was to test whether VMAT with noncoplanar beams can result in lesser dose delivery to critical organs such as heart and lung, which will result in lesser overall toxicity. Materials and Methods: Data of nine BBC cases treated at our hospital were retrieved. Computed tomography simulation data of these cases was used to generate noncoplanar VMAT plans and the parameters were compared with standard VMAT coplanar plans. Contouring was done using radiation therapy oncology group guidelines. Forty-five Gray in 25 fractions was planned followed by 10 Gy in five fractions boost in breast conservation cases. Results: No significant difference in planning target volume (PTV) coverage was found for the right breast/chestwall (P = 0.940), left breast/chestwall (P = 0.872), and in the total PTV (P = 0.929). Noncoplanar beams resulted in better cardiac sparing in terms of Dmean heart. The difference in mean dose was >1 Gy (8.80 ± 0.28 - 7.28 ± 0.33, P < 0.001). The Dmean, V20 and V30 values for total lung slightly favor noncoplanar beams, although there was no statistically significant difference. The average monitor units (MUs) were similar for coplanar plans (1515 MU) and noncoplanar plans (1455 MU), but the overall treatment time was higher in noncoplanar plans due to more complex setup and beam arrangement. For noncoplanar VMAT plans, the mean conformity index was slightly better although the homogeneity indices were similar. Conclusion: VMAT plans with noncoplanar beam arrangements had significant dosimetric advantages in terms of sparing of critical organs, that is Dmean of heart doses with almost equivalent lung doses and equally good target coverage. Larger studies with clinical implications need to be considered to validate this data.

Combination of image-guided IMRT and IGBT in locally advanced carcinoma cervix: Prospective evaluation of toxicities and clinical outcomes from a tertiary cancer center in India.

Purpose: We aimed to assess the toxicity profile and clinical outcome in patients with locally advanced cervical cancer (LACC) treated with a combination of image-guided intensity-modulated radiation therapy (IG-IMRT) and image-guided brachytherapy (IGBT). Material and methods: 25 LACC patients were recruited in this single-arm prospective study. Whole pelvis IG-IMRT was delivered (45 Gy with simultaneously integrated nodal boost of 55 Gy in 25 fractions), with concurrent weekly cisplatin (40 mg/m2). Patients received IGBT of 7 Gy each in 4 fractions to high-risk clinical target volume (HR-CTV). First fraction was done under MRI, and subsequent fractions were performed under CT guidance. Primary endpoint was acute toxicity, and secondary endpoints were 2-year loco-regional control and late toxicity. Results: The median age was 52 years, and FIGO 2018 stage distribution was IIA2, IIB, IIIB, and IIIC1 in 12%, 40%, 20%, and 28% patients, respectively. All patients received concurrent chemotherapy with median number of 5 cycles (range, 4-5 cycles). Grade 1 and 2 diarrhea, and grade 1 cystitis was reported in 4 (16%), 3 (12%), and 2 (8%) patients, respectively. Grade 1 and 2 anemia, and grade 1 and 2 dermatitis were observed in 3 (12%) and 2 (8%), and 3 (12%) and 3 (12%) patients, respectively. No patient reported grade 3-4 acute toxicity. At median follow-up of 29.5 months (range, 25-37 months), late grade 1 bladder toxicity was observed in 1 (4%) patient. Loco-regional control at 1 and 2 years were 96% and 92%, respectively. Conclusions: The combination of IG-IMRT and IGBT yielded excellent outcomes in terms of acute toxicity and loco-regional control.

Toxicities and clinical outcome of adjuvant dysphagia optimized versus standard intensity-modulated radiotherapy for post-operative oral cavity cancers: A prospective comparative study.

BACKGROUND: We prospectively assessed acute and late toxicity in post-operative oral cavity squamous cell carcinoma (PO-OCSCC) treated with adjuvant dysphagia optimized intensity-modulated radiotherapy (Do-IMRT) versus standard IMRT (S-IMRT). MATERIAL AND METHODS: Fifty-six patients of PO-SCC without indications of concurrent chemotherapy were alternatively allocated to adjuvant Do-IMRT (n = 28) versus S-IMRT (n = 28) arms. High- and low-risk planning target volume received 60 and 54 Gy, respectively, in 30 fractions over 6 weeks. Dysphagia aspiration-related structures (DARS) were contoured in both arms. While dosimetric constraints were given in Do-IMRT arm, doses to DARS were only observed without dose constraints in S-IMRT arm. Acute and late toxicity were assessed by common terminology criteria for adverse events (CTCAE) v5.0 and RTOG criteria, respectively. RESULTS: The primary site of disease was buccal mucosa (64% vs. 53%) and oral tongue (21% vs. 32%), in Do-IMRT and S-IMRT, respectively. The mean doses to DARS was significantly less with Do-IMRT (all p < 0.001) as compared to S-IMRT. Median follow-up was 24.2 months. Grade ≥2 oral pain was less in the Do-IMRT arm (50% vs. 78.6%, p = 0.05). Grade ≥2 late dysphagia at 2 years were significantly less in Do-IMRT arm (0% vs. 17.9%, p = 0.016). Two-year locoregional control was 89.2% in Do-IMRT and 78.5% in S-IMRT (p = 0.261). CONCLUSION: DARS can be spared in PO-OCSCC patients treated with Do-IMRT without compromising coverage of the target volumes. Limiting doses to DARS leads to lesser acute and late toxicity without compromising locoregional control.

Prospective evaluation of dose-escalated preoperative concurrent chemo-radiation with image guided-IMRT in locally advanced rectal cancers.

Purpose: To analyse the safety and efficacy of neoadjuvant chemoradiation (NACRT) with dose-escalated image-guided intensity modulated radiation therapy (IG-IMRT) in locally advanced (T3/4; T1-4N1-2) rectal cancers (LARCs). Materials and methods: Twenty patients with the diagnosis of LARC were recruited in this prospective interventional single-arm study treated by IG-IMRT with 45 Gray (Gy) in 25 fractions to elective nodal volumes and 55 Gy in 25 fractions to the gross primary and nodal disease with concurrent capecitabine 825 mg/m2 twice daily on radiotherapy days. Patients underwent total mesorectal excision 6-8 weeks post completion of NACRT followed by adjuvant chemotherapy (Capecitabine and oxaliplatin every 3 weekly for 6-8 cycles). Primary end point was acute toxicity assessment and secondary end points were pathological complete response (pCR) and loco-regional control (LRC). Results: Clinical T stage was T3:T4 in 19:1 and clinical N0:N1: N2 in 2:7:11 patients, respectively. With a median follow up of 21.2 months (13.8-25.6 months), 18 of 20 (90%) patients received the full course of treatment. Tumour and nodal downstaging was achieved in 78% and 84% of patients, respectively. pCR and overall complete response (defined as pCR and near CR) was achieved in 22.2% and 44.4% of patients, respectively. 2 (10%) patients completed NACRT, and achieved complete clinical response but refused surgery. Adjuvant chemotherapy course was completed by 17/18 (94.5%) patients. Grade 3 toxicities were observed in 2 (10%) patients during NACRT. All patients were disease-free at the time of the last follow up. Conclusion: Dose-escalation of NACRT therapy with IG-IMRT in LARC patients offers decent rates of pCR and overall response with excellent LRC and acceptable toxicities.

Correlation of PD-L1 expression with toxicities and response in oropharyngeal cancers treated with definitive chemoradiotherapy.

Introduction: The programmed death receptor ligand 1 (PD-L1) is a cell-surface glycoprotein expressed in tumour cells (TCs) and is also upregulated in tumour infiltrating lymphocytes. The effect of PD-L1 expression on TCs and tumour-infiltrating lymphocytes (TILs) on acute radiation toxicity and response in oropharyngeal squamous cell carcinoma treated with concurrent chemoradiotherapy is less known. Material and methods: Squamous cell carcinoma of oropharynx with stage II-IVA (AJCC 8th) were recruited in this prospective observational study. Definitive radiation therapy (RT) of 70 Gray in 35 fractions at 2 Gray per fraction, 5 fractions a week in 2 phases was delivered with concurrent chemotherapy (cisplatin 40 mg/m2 weekly). Patients were assessed weekly for acute toxicities with Radiation Therapy Oncology Group criteria. Response assessment was done at 3 months post RT according to World Health Organization response assessment criteria. The programmed death receptor ligand 1 expression in TCs and TILs was correlated with acute toxicity and survival. Results: Of 51 patients, 20 (39.2%) had PD-L1 expression in TCs and 18 (35.3%) in TILs. Patients with PD-L1 expression in TCs had fewer grade ≥ 3 oral mucositis (25% vs. 58%; p = 0.02) and grade ≥ 3 dysphagia (25% vs. 55%; p = 0.046). The programmed death receptor ligand 1-tumour infiltrating lymphocytes positives had lower ≥ 3 grade oral mucositis (22% vs. 58%; p = 0.02) and ≥ 3 grade dysphagia (17% vs. 58%; p = 0.007). Two-year overall and progression-free survival rate for the PD-L1-tumour-positive vs. PD-L1-tumour-negative group was not different (p > 0.5). Conclusions: Positive PD-L1 expression is associated with fewer acute radiation toxicities, and this could be used as a potential biomarker.

Long term outcome and late toxicity Of SIB-IMRT in definitive management of head and neck cancers in patients not suitable for chemo-radiotherapy.

Objective: To evaluate efficacy and late toxicity of intensity-modulated radiotherapy with simultaneous integrated boost (IMRT-SIB) in definitive management of head-and-neck cancers. Methods: In this prospective interventional study, histological proven squamous cell carcinoma of oropharynx, hypopharynx, or larynx with stage T1-3 N0-3 M0 who were not candidates for concurrent chemotherapy were treated with IMRT-SIB with radical intent. Doses prescribed for IMRT-SIB to meet the clinical needs of nodal volumes were either SIB-66 schedule 66 Gray (Gy) prescribed to high risk (HR) planned target volume (PTV), 60 (Gy) to intermediate risk (IR) PTV and 54 Gy to low risk (LR) PTV in 30 fractions or SIB-70 schedule 70 Gy to PTV-HR, 59.4 Gy to PTV-IR and 56 Gy to PTV-LR in 33 fractions. Result: Forty-five patients were included. Forty-two patients were treated with SIB-66 schedule and three patients with SIB-70 schedule. The median follow-up period was 21 (6-68) months. There was residual disease in three patients. Recurrence was observed in 24 patients. Most recurrences were in HR volume (n = 19) and three patients had distant failure. Estimated 2-year locoregional control, disease-free survival, and overall survival were 55.55%, 49.7%, and 51.1%, respectively. Grade 3 late skin toxicity, subcutaneous fibrosis, and xerostomia were observed in three patients. Conclusions: Efficacy and late toxicity of IMRT-SIB observed in our study suggest it as a suitable treatment option for patients who are not fit for chemoradiation.

Patterns of failure and clinical outcomes of post-operative buccal mucosa cancers treated with adjuvant ipsilateral radiotherapy.

PURPOSE: Adjuvant radiotherapy (RT) in buccal mucosa cancers is guided by histopathological factors. The decision to treat ipsilateral or bilateral draining lymph node is on physician discretion and guidelines do not have a defined indication regarding this. We aimed to analyze the failure patterns and survival in buccal mucosa cancers treated with adjuvant ipsilateral RT. MATERIALS AND METHODS: One hundred sixteen cases of post-operative buccal mucosa cancers-pT3 or more, node positive, close margins (1-5 mm), lymphovascular invasion positive, perineural invasion positive, depth of invasion >4 mm-treated with RT to primary and ipsilateral nodes from May 2013 to May 2019 were retrospectively analyzed. Patients were treated to a dose of 60-66 Gy (44 Gy in the first phase and a coned down boost of 16-22 Gy in the second phase) with three-dimensional conformal radiotherapy on a linear accelerator. Primary end point was to assess control rates and secondary end point was to evaluate the overall survival (OS) and disease-free survival (DFS) outcomes. RESULTS: Median age was 46 years with male; female ratio of 110:6. The edition of the American Joint Committee on Cancer stage distributions were I (3.4%), II (34.4%), III (24.1%), and IV (37.9%). At a median follow-up of 22 months, crude rates of local failure, regional failure, and contralateral neck failure were 9.4%, 10.3%, and 3.4%, respectively. The 2-year contralateral neck control rate was 94.9%. Pathological positive node portended poorer OS (86.6% vs. 68.6%; p = 0.015) and DFS (86.5% vs. 74.9%; p = 0.01). CONCLUSION: Incidence of contralateral recurrence with ipsilateral irradiation in buccal mucosa cancers is low with descent survival outcomes, particularly in node negative cases.

Effect of different definitions of prescription point "A" in high dose rate brachytherapy for cervical cancer.

AIM: This study intended to compare the dosimetric parameters using different definitions of prescription point A in high dose rate (HDR) brachytherapy of cervical cancer patients. BACKGROUND: Manchester point A has been widely used for prescribing dose in brachytherapy. However, due to certain limitations of this point, a new definition of point A has been recommended by the American Brachytherapy Society (ABS). MATERIALS AND METHODS: We retrospectively investigated 55 computed tomography-based plans of 20 cervical cancer patients treated with Ir-192-based intracavitary HDR brachytherapy. The dose of 7 Gy in 3 fractions each was prescribed to point A using revised Manchester definition of point A (AMAN) and ABS guideline definition (AABS). The effect of both definitions on various parameters including dose to point A and 90% of tumor volume (D90), dose received by 2cc volume of bladder, rectum and small bowel and treatment volume receiving 100% of prescription dose (V100) was analyzed. RESULTS: Mean percentage difference of point AMAN dose and AABS dose with respect to prescription dose was 1.25% ± 1.43% and 1.21% ± 1.01%, respectively. Mean V100 was 80.4 ± 20.45cc and 88.47 ± 16.78cc for AMAN and AABS plans, respectively, while mean percentage difference between prescribed dose and D90 was found to be -37.90% ± 25.06% and -30.47% ± 25.50% respectively for both the definitions. CONCLUSION: Doses to both Manchester point A and ABS point A may be recorded during the transition period. However, ABS point A can be preferred over the Manchester point A as it conforms better with the desired dosimetric outcome and is found to be more static.

Evaluation of XRCC1 Gene Polymorphism as a Biomarker in Head and Neck Cancer Patients Undergoing Chemoradiation Therapy.

PURPOSE: We evaluated the correlation of the x-ray repair cross complementing gene 1 (XRCC1) Arg194Trp polymorphism with clinical outcomes in head and neck squamous cell carcinoma (HNSCC) patients treated with concurrent chemoradiation therapy (CCRT). METHODS AND MATERIALS: In this prospective cohort study, we included 101 patients with HNSCC (oral cavity, pharynx, and larynx) who were aged ≥ 18 years, had stage III to IVB disease, had a Karnofsky Performance Status ≥ 80, and were deemed fit for CCRT. DNA extraction was done through polymerase chain reaction, and the genotypes of XRCC1 polymorphism were detected using designed restriction fragment length polymorphism. The genetic polymorphisms were classified into wild and polymorphic variants (Arg194Trp CT and TT). Radiation therapy was delivered with conventional parallel opposed lateral and low anterior neck fields with concurrent weekly cisplatin, 35 mg/m2. Acute toxicity was graded per Radiation Therapy Oncology Group criteria, and treatment response was assessed per World Health Organization criteria. Overall survival and progression-free survival (PFS) were estimated using the Kaplan-Meier method. RESULTS: Of the patients, 62 had the wild type and 39 had polymorphic variants. Patients with polymorphic variants had higher rates of grade > 2 oral mucositis, with 35.8% versus 16.0% (odds ratio [OR], 2.91; 95% confidence interval [CI], 1.13-7.46; P = .023); dermatitis, with 30.7% versus 8.0% (OR, 5.076; 95% CI, 1.62-15.8; P = .003); and laryngeal toxicity, with 25.6% versus 6.4% (OR, 5; 95% CI, 1.44-17.54; P = .006). Complete response rates in polymorphic versus wild variants were 76.9% versus 56.0% (P = .209). At a median follow-up of 21 months, the 2-year PFS and overall survival rates for patients with polymorphic versus wild variants were 57.0% versus 42.2% (P = .077) and 73.0% versus 55.5% (P = .143), respectively. CONCLUSIONS: Polymorphic variant XRCC1 HNSCC patients treated with CCRT have significantly increased acute radiation morbidities and may have a trend toward better PFS in comparison with the wild variant.

Quantitative Extra Long PCR to Detect DNA Lesions in Patients Exposed to Low Doses of Diagnostic Radiation

Background: Radiation causes oxidative lesions and strand breaks in DNA of exposed cells. Extended length PCR is a reliable method for assessing DNA damage. Longer DNA strands with DNA damage are difficult to amplify compared to smaller DNA strands by PCR. The present study was aimed to evaluate DNA damage caused by ionising radiation exposure in therapeutic and diagnostic medicine. Materials and Methods: The study group comprised 50 cases with low dose single exposure (LDS), low dose multiple exposure (LDM) and low dose angiography (LDA) which were compared with 25 high dose controls (HDC) and 25 controls with no exposure (NEC). Blood samples were collected within 1 hour of radiation exposure. DNA was isolated using a kit based protocol, 50 ng aliquots of DNA were used to amplify a long 13kbp DNA fragment of the ß-actin gene by conventional PCR and band intensity was then quantified. Relative amplification was calculated and damage was expressed in terms of lesions per kilobase (kbp) by assuming a Poisson distribution. Result: Relative amplification was found to be 1.0, 0.87, 0.86, 0.72 and 0.69 with NEC, LDS, LDM, LDA and HDC groups, respectively. Cases undergoing angiography as well as high dose controls had high values, compared to NEC. The lesions/kbp calculated for LDS was 0.13, for LDM 0.15, for LDA 0.32 and for HDC 0.37 suggesting a linear increase in quantity with increasing radiation dose. Conclusion: DNA damage, even at low doses of radiation can be assessed by quantitative extra long PCR.

Flow cytometric detection of gamma-H2AX to evaluate DNA damage by low dose diagnostic irradiation.

INTRODUCTION: γH2AX assay has been used for DNA damage assessment at higher doses of radiation exposure. Its expression has not been studied in cases with diagnostic low dose radiation exposure. Concerns have been raised about the after-effects of radiation in diagnostic procedures like Computed Tomography (CT) scan, Angiography etc especially when such scans are repeated within short span of time. The purpose of the present study was to assess immediate DNA damage after exposure to low level of ionizing radiation by the flow cytometric method of gamma-H2AX. MATERIAL AND METHODS: Study sample includes total 60, cases and controls with two groups Group I-Normal controls (n = 15); Group II-Low dose, further divided in three groups: Group IIA-single CT scan (n = 15); Group IIB-Multiple CT scans (n = 15); and Group IIC-angiography single exposure (n = 15). For Low dose group blood was collected within 1 h after exposure in EDTA vaccutainers and immediately kept on ice. Lymphocytes were isolated and were fixed in 80% chilled ethanol and stored at -20 °C till further analysis. The H2AX assay was done and 10,000 cells were analysed for gamma H2AX positivity in flowcytometer. RESULTS: Significant gamma-H2AX positivity was found in cases versus control, the most significant DNA damage amongst cases was observed in cases with multiple CT scans. CONCLUSION: The exposure to multiple CT scans causes more double strand breaks as compared to single scan. DNA damage can be studied by flow cytometric analysis of gamma-H2AX in human peripheral lymphocytes.

Pelvic bone anatomy vs implanted gold seed marker registration for image-guided intensity modulated radiotherapy for prostate carcinoma: Comparative analysis of inter-fraction motion and toxicities.

OBJECTIVES: We compared the prostate motion variability and toxicities between patients treated with gold marker registration based IG-IMRT (IG-IMRT-M) and bony landmark registration based IG-IMRT (IG-IMRT-B). METHODS: T1c-T3b (node negative), intermediate and high risk (non-metastatic) adenocarcinoma of prostate, age ≥18years, Karnofsky Performance Status of ≥70 were included in this retrospective study. The prostate motion variability, acute and late radiation toxicities between the two treatment arms (IG-IMRT-M versus IG-IMRT-B) were compared. RESULTS: Total of 35 patients (17 for IG-IMRT-M and 18 for IG-IMRT-B) were treated with a median radiotherapy dose of 76 Gray. The prostate variability observed with and without markers in millimeter was 4.1±2.3 vs 3.7±2.1 [Antero-Posterior (A-P); p=0.001], 2.3±1.5 vs 2.1±1.2 [Superior-Inferior (S-I); p=0.095] and 1.1±1.7 vs 0.4±1.4 [Left-Right (L-R); p=0.003]. There was higher acute toxicity in IG-IMRT-B arm compared to IG-IMRT-M arm in terms of grade ≥2 diarrhea [50% vs 11% OR=7.5 (1.3-42.7); p=0.02] and grade ≥2 proctitis [38% vs 5.8%, OR=10.1 (1.09-94.1); p=0.04]. At a median follow up of 36months, the late genitourinary toxicities grade ≥2 [27% vs 0%; p=0.04] were higher in the IG-IMRT-B arm compared to IG-IMRT-M arm. CONCLUSIONS: IG-IMRT-M detects higher prostate motion variability as compared to IG-IMRT-B, inferring a significant prostate motion inside fixed pelvic bony cavity. The addition of marker based image guidance results in higher precision of prostate localization and lesser acute and late toxicities.

A Dosimetric Study on Slab-pinewood-slab Phantom for Developing the Heterogeneous Chest Phantom Mimicking Actual Human Chest.

The aim is to study the density, isodose depths, and doses at different points in slab-pinewood-slab (SPS) phantom, solid phantom SP34 (made up of polystyrene), and chest level of actual patient for developing heterogeneous chest phantom mimicking thoracic region of human body. A 6 MV photon beam of field size of 10 cm × 10 cm was directed perpendicular to the surface of computed tomography (CT) images of chest level of patient, SPS phantom, and SP34 phantom. Dose was calculated using anisotropic analytical algorithm. Hounsfield units were used to calculate the density of each medium. Isodose depths in all the three sets of CT images were measured. Variations between planned doses on treatment planning system (TPS) and measured on linear accelerator (LA) were calculated for three points, namely, near slab-pinewood interfaces (6 and 18 cm depths) and 10 cm depth in SPS phantom and at the same depths in SP34 phantom. Density of pinewood, SP34 slabs, chest wall, lung, and soft tissue behind lung was measured as 0.329 ± 0.08, 0.999 ± 0.02, 0.898 ± 0.02, 0.291 ± 0.12, and 1.002 ± 0.03 g/cc, respectively. Depths of 100% and 90% isodose curves in all the three sets of CT images were found to be similar. Depths of 80%, 70%, 60%, 50%, and 40% isodose lines in SPS phantom images were found to be equivalent to that in chest images, while it was least in SP34 phantom images. Variations in doses calculated at 6, 10, and 18 cm depths on TPS and measured on LA were found to be 0.36%, 1.65%, and 2.23%, respectively, in case of SPS phantom, while 0.24%, 0.90%, and 0.93%, respectively, in case of SP34 slab phantom. SPS phantom seemed equivalent to the chest level of human body. Dosimetric results of this study indicate that patient-specific quality assurance can be done using chest phantom mimicking thoracic region of human body, which has been fabricated using polystyrene and pinewood.

A study on the necessity of kV-CBCT imaging compared to kV-orthogonal portal imaging based on setup errors: considering other socioeconomical factors.

PURPOSE: Evaluation of setup accuracy in kV-orthogonal portal imaging (OPI)-based and kV-CBCT-based radiotherapy treatment and to find out the necessity of cone-beam computed tomography (CBCT) compared to OPI. MATERIALS AND METHODS: A retrospective study was carried out on 30 patients, who received radiotherapy to the Brain, Head and Neck, and Pelvis. In the OPI technique, anterior-posterior and right-lateral portal images were taken by the On Board Imaging (OBI) system and were superimposed on the reference images. Similarly, in the kV-CBCT technique, CBCT was performed by the OBI system and CBCT images were superimposed on the reference CT images. A total of 150 comparison sets of kV-OPI and kV-CBCT images were analyzed and evaluated. Shifts in the Lateral, Longitudinal, and Vertical directions were noted in both techniques. The iso displacement vector (IDV) was calculated for all imaging. RESULTS: The mean IDV (in cm) are found to be 0.3395 (SD: 0.1477) and 0.3088 (SD: 0.1593) in cases of the brain, 0.4266 (SD: 0.1511) and 0.3666 (SD: 0.1533) in cases of the head and neck, and 1.0339 (SD: 0.5893) and 0.9498 (SD: 0.6047) in cases of the pelvis for the CBCT and OPI techniques, respectively. The P values were 0.3201, 0.0515, and 0.4829 for the brain, head and neck, and pelvic cases, respectively. CONCLUSIONS: There is statistically no significant difference between both the imaging techniques. As the dose delivered by the CBCT technique is higher than that by the OPI technique, from the socioeconomical and radiation safety point of view, the OPI technique is possibly better than the CBCT technique. Hence, it can be concluded that CBCT is not a mandatory technique compared to the OPI technique in routine brain, head and neck, and pelvic cases, except in those cases where better information about interfraction movements of soft tissue is necessarily required for positioning of the target, as is the case in prostate carcinoma.