Abhinav Dewan

Is volumetric modulated arc therapy (RapidArc) better than intensity modulated radiotherapy for gynecological malignancies? A dosimetric comparison

AIMS Evaluation of the dosimetric advantage, if any, of RapidArc (double arc and triple arc [DA and TA]) over standard fixed field intensity-modulated radiation therapy (IMRT) in gynecologic malignancies. MATERIALS AND METHODS A total of 20 cases of gynecologic malignancies were included. Static IMRT sliding window, single arc (SA), DA and TA plans were generated with eclipse planning system. The prescribed dose was 50.4 Gy/28# to the planning target volumes. RESULTS IMRT provided target coverage equivalent to DA and inferior to TA (D95% [in Gy]--49.94, 49.58, 49.96, 50.17 for IMRT, SA, DA and TA respectively--all observations in the same sequence). Conformity index 90 (CI 90 (0.964, 0.927, 0.918, 0.822) and homogeneity index (0.0683, 0.119, 0.098, 0.097) of IMRT were superior. TA was superior to other arcs in all parameters except CI 90 (P=0.805) and bladder dose (lower in DA). Rectal, bladder and bowel sparing was best achieved with IMRT followed by TA; bilateral femur dose was lower in arcs. The total monitor units and treatment time of arcs were significantly lower than IMRT, reduced by a factor of 2.41-2.59 and 3.2-3.5 respectively (All P values significant). CONCLUSION IMRT provided better overall plan for gynecologic malignancies with lower organs at risk dose and target coverage equivalent to DA and TA. Treatment delivery efficiency was higher with RapidArc. The TA plan is dosimetrically superior to DA, but the gain is small. The decision whether or not to add a third arc for a small gain should be individualized.

Impact of Adaptive Radiotherapy on Locally Advanced Head and Neck Cancer - A Dosimetric and Volumetric Study

UNLABELLED Objective of the study is to evaluate volumetric and dosimetric alterations taking place during radiotherapy for locally advanced head and neck cancer (LAHNC) and to assess benefit of replanning in them. MATERIALS AND METHODS Thirty patients with LAHNC fulfilling the inclusion and exclusion criteria were enrolled in a prospective study. Planning scans were acquired both pre-treatment and after 20 fractions (mid-course) of radiotherapy. Single plan (OPLAN) based on initial CT scan was generated and executed for entire treatment course. Beam configuration of OPLAN was applied to anatomy of interim scan and a hybrid plan (HPLAN30) was generated. Adaptive replanning (RPLAN30) for remaining fractions was done and dose distribution with and without replanning compared for remaining fractions. RESULTS Substantial shrinkage of target volume (TV) and parotids after 4 weeks of radiotherapy was reported (p<0.05). No significant difference between planned and delivered doses was seen for remaining fractions. Hybrid plans showed increase in delivered dose to spinal cord and parotids for remaining fractions. Interim replanning improved homogeneity of treatment plan and significantly reduced doses to cord (Dmax, D2% and D1%) and ipsilateral parotid (D33%, D50% and D66%) (p<0.05). CONCLUSIONS Use of one or two mid-treatment CT scans and replanning provides greater normal tissue sparing alongwith improved TV coverage.

Squamous Cell Carcinoma of the Superior Gingivobuccal Sulcus: An 11-Year Institutional Experience of 203 Cases

OBJECTIVE The report presents an 11-year Institutional experience of 203 cases with superior gingivobuccal sulcus tumours receiving surgical intervention at a comprehensive tertiary cancer care centre. METHODS A retrospective chart review of patients with a confirmed diagnosis of squamous cell carcinoma of superior gingivobuccal sulcus was done and data related to patient demographic profile; details of surgical procedure, follow-up and survival were collected. RESULTS Infratemporal fossa clearance was performed in 56 patients. The 10-year overall survival and disease-free survival was observed to be 39 and 52%, respectively, with a median follow-up of 15 months. The overall survival was 40 and 36%, respectively, in cases with and without infratemporal fossa clearance. Similarly, the disease-free survival was found to be 58 and 49%, respectively, in cases with and without infratemporal fossa clearance. CONCLUSION Patients with higher stage tumours who underwent infratemporal fossa clearance showed better overall and disease-free survival than those who did not undergo infratemporal fossa clearance.

Oral tuberculosis following successful treatment of oral malignancy

Coexistence of tuberculosis and neoplastic lesion in the oral cavity is a rare phenomenon. Till date, only three such cases have been reported in the English literature. A case of oral tuberculosis manifesting 3 months following the successful treatment of cancer of the oral tongue with chemoradiotherapy is presented. The diagnostic dilemma it posed, and its eventual successful control by anti-tubercular treatment, is discussed.

Comparative Evaluation of a 6MV Flattened Beam and a Flattening Filter Free Beam for Carcinoma of Cervix – IMRT Planning Study

Purpose: Intensity modulated radiotherapy (IMRT) plan quality, beam on time and integral dose were compared using 6MV FB (Flattened Beam) and FFFB (Flattening filter free beam) for carcinoma of cervix. Materials and Methods: Ten patients with stage II–IIIB cervix cancer (Ca.Cx) were retrospectively identified from the department database. Target volume (TV) and organ at risk (OAR) were delineated as per Radiation Therapy Oncology Group (RTOG) cancer guidelines. Dose prescribed to planning target volume (PTV) was 50.4Gy in 28 fractions. Two plans (6MV FB IMRT and 6MV FFFB IMRT) were generated to achieve 95% of prescription dose to PTV and sparing OAR as per normal tissue guidelines. Numbers of beams and their orientations were the same for all plans. The homogeneity index (HI), conformity index (CI), treatment monitor unit (MU), beam on time (BOT) and non-tumor integral dose (NTID) were chosen for comparison. Results: FFFB generated plans were clinically acceptable. There was a statistically significant difference among the FB IMRT and FFFB IMRT plans with respect to CI, HI, D50%, D2% in PTV coverage, bladder V50Gy, MU, mean NTID and non-tumor low dose volume. Conclusions: 6MV flattened and flattening filter free photon beams produce comparable plans by IMRT. FFF beams allow time efficient treatment delivery and may help reduce the risk of secondary malignances in carcinoma cervix cases.

Dosimetric Comparison of Pencil-Beam Scanning and Photon-Based Radiation Therapy as a Boost in Carcinoma of Cervix

Purpose Brachytherapy is essential for local treatment in cervical carcinoma, but some patients are not suitable for it. Presently, for these patients, the authors prefer a boost by using intensity-modulated radiation therapy (IMRT). The authors evaluated the dosimetric comparison of proton-modulated radiation therapy versus IMRT and volumetric-modulated arc therapy (VMAT) as a boost to know whether protons can replace photons. Patients and Methods Five patients who received external beam radiation therapy to the pelvis by IMRT were reviewed. Three different plans were made, including pencil beam scanning (PBS), IMRT, and VMAT. The prescribed planning target volume (PTV) was 20 Gy in 4 fractions. The dose to 95% PTV (D95%), the conformity index, and the homogeneity index were evaluated for PTV. The Dmax, D2cc, and Dmean were evaluated for organs at risk along with the integral dose of normal tissue and organs at risk. Results The PTV coverage was optimal and homogeneous with modulated protons and photons. For PBS, coverage D95% was 20.01 ± 0.02 Gy (IMRT, 20.08 ± 0.06 Gy; VMAT, 20.1 ± 0.04 Gy). For the organs at risk, Dmax of the bladder for PBS was 21.05 ± 0.05 Gy (IMRT, 20.8 ± 0.21 Gy; VMAT, 21.65 ± 0.41 Gy) while the Dmax for the rectum for PBS was 21.04 ± 0.03 Gy (IMRT, 20.81 ± 0.12 Gy; VMAT, 21.66 ± 0.38 Gy). Integral dose to normal tissues in PBS was 14.17 ± 2.65 Gy (IMRT, 25.29 ± 6.35 Gy; VMAT, 25.24 ± 6.24 Gy). Conclusions Compared with photons, modulated protons provide comparable conformal plans. However, PBS reduces the integral dose to critical structures significantly compared with IMRT and VMAT. Although PBS may be a better alternative for such cases, further research is required to substantiate such findings.

Treatment Planning With Unflattened as Compared to Flattened Beams for Bilateral Carcinoma of the Breast

Aim: To evaluate the plan quality of 6MV unflattened (UFB) and flattened beam (FB) photon energy using AAA dose calculation algorithms for volumetric arc therapy. Materials and Methods: Plans were generated for bilateral carcinoma of breast and the dose prescribed was 50.4Gy in 28 fractions. Two different plans were made for each patient using 6MV FB and 6MV UFB. Dose calculations were performed on an AAA dose calculation algorithm. Plans were generated on Eclipse TPS and were capable of being delivered with a true beam STx linear accelerator. The homogeneity index (HI), conformity index (CI), normal tissue integral dose (NTID), and effect of low dose volume on normal tissue and monitor units (MU) were noted. Results: All the plans were clinically acceptable. The HI and CI of 6MV UF rapid arc (RA) plans were higher than with the 6MV FB plan (1.16±0.05 and 0.12±0.00 respectively). There was no appreciable difference observed in Organ at risk (OAR) doses. The mean NTID and low dose volume were significantly low with 6MV RA UFB as compared to FB. 6MV RA UFB required a 35% higher MU than with the 6MV RA plan (p<0.05). Conclusion: RA plans generated with UFB on Eclipse TPS achieved target volume coverage and preserved OAR’s essentially similar to 6MV RA FB plans. However RA plans generated in Varian Eclipse of UFB were superior with respect to mean NTID and low dose volumes in normal tissue.

Improving the accuracy of target volume delineation by combined use of computed tomography, magnetic resonance imaging and positron emission tomography in head and neck carcinomas

OBJECTIVE Conformal radiation therapy mandates accurate delineation of target volumes, which requires incorporation of modern imaging modalities like magnetic resonance imaging (MRI) and positron emission tomography (PET) in addition to conventionally used computed tomography (CT). This can resolve discrepancies in target delineation in head and neck carcinomas resulting in better local control. We hereby report the comparison of Gross Tumor Volumes (GTVs) (primary) drawn using PET, CT and MRI and their concordance indices. METHODS AND MATERIAL Twenty five patients with head and neck cancer were taken into this study. MRI, PET and CT planning scans were done as per standard guidelines. Three sets of primary GTVs namely GTV- PET, GTV-CT and GTV-MRI were contoured on fused images. All the three volumes and concordances among the volumes were analyzed. RESULT The mean GTV-CT, GTV-PET and GTV-MRI volumes were 29.65 cc ± 31.27, 32.05 cc ± 33.75 and 24.85 cc ± 25.28 respectively. There was a significant difference in the GTV-MRI & GTV-CT volumes (P = 0.023) and GTV-PET & GTV-MRI volumes (P = 0.049). However, there was no significant difference in the GTV-PET & GTV-CT volume (P = 0.468). The mean CI (PET-MRI), CI (CT-MRI) and CI (PET-CT) was 0.42, 0.46 and 0.47 respectively, which depicts a moderate concordance. CONCLUSION PET and MRI are useful imaging tools in head and neck malignancies and should be used in conjunction with CT scan for improved target volume delineation.

Primary gastric Burkitt's lymphoma

The primary gastrointestinal non-Hodgkin’s lymphoma, although rare, is among the most common extra-nodal lymphomas, considering that gastric lymphomas are more common than intestinal lymphomas. Burkitt’s lymphoma (BL) is an aggressive form of B-cell lymphoma that is typically endemic in Africa, while non-endemic cases are found in the rest of the world. Primary gastric BL is extremely rare and only around 50 cases have been reported worldwide. Here we present the case of a young HIV-negative male, who was referred to our department with a stage IV gastric BL. He was planned for palliative chemotherapy, but after the first cycle of chemotherapy he succumbed to the progression of the disease.