Radiosurgical Decompression of Trigeminal Nerve and Its Correlation with Functional Outcome in Tumor-Related Trigeminal Neuralgia.

BACKGROUND: Target selection during Gamma Knife radiosurgery (GKRS) in cases of tumor-related trigeminal neuralgia is always debatable. We analyzed the correlation of regression of tumor size and degree of release of the nerve with long-term pain control. METHODS: Between March 2012 and March 2023, 50 cases of tumor-related trigeminal neuralgia were treated with GKRS (tumor was targeted). Radiological findings after GKRS were categorized into 3 types: 1) tumor volume remained same or decreased, additional segment of nerve not seen; 2) tumor volume decreased, additional segment of trigeminal nerve seen, but tumor still adherent to the nerve; 3) tumor volume decreased, adjacent nerve seen completely separated from tumor. Pain score before and after GKRS (Barrow Neurological Institute I-III: good; Barrow Neurological Institute IV and V: poor) was correlated with these subgroups. RESULTS: At median follow-up of 46.5 months, 18 cases showed type 1 radiological response, 23 showed type 2 response, and 9 showed type 3 response. Good pain control was achieved in 10 (55.5%) patients with type 1, 15 (65.21%) with type 2, and 7 (77.8%) with type 3 responses. The outcome differences among these 3 groups were not statistically significant (P = 0.519). Five patients with type 3 radiological response were off medication, which was statistically better than type 1 and type 2 radiological responses, with 3 patients (P = 0.012) and 2 patients (P = 0.002), respectively, still receiving medication. CONCLUSIONS: Tumor volume reduction after GKRS may be associated with good pain control in tumor-related trigeminal neuralgia. Further, this allows visualization of additional segment of nerve that can be targeted in a second session for treating recurrent or failed cases.

Morphology of intra tumoral cystic vestibular schwannoma and their response to gammaknife radiosurgery.

BACKGROUND: Cystic vestibular schwannoma (CVS) traditionally considered as poor responder to gammaknife radiosurgery (GKRS). Their longterm radiobiological behavior is less known. Here we discuss 38 cases with intra tumoral cyst CVS primarily treated with GKRS. Tumor morphology was assessed to understand their response to GKRS. METHODS: Total 38 patients(21 male and 17 female with median age of 41.7 years) of CVS treated with GKRS were retrospectively analysed. Tumors were divided as predominantly (greater than50% of total tumor volume) cystic or solid. They were subclassified as type 1 (predominantly cystic CVS, single cyst), type 2 (predominantly solid CVS, single cysts), type 3 (multicystic CVS). The entire cyst was incorporated for radiosurgery. The results were compared with volume matched control of 58 solid tumors(SVS). RESULT: The median tumor volume of CVS was 5.8 cc. The median tumor volume reduction was 44.5 % at a median follow-up of 68.5 months (30-110 months). Median tumor volume reduction was 68.5 %, 34.0%, 11.0.%, 30.5% at a median follow up of 52.5months, 66 months, 78.6 months, 96.5 months for type 1 CVS, type 2 CVS, type 3 CVS and SVS respectively. One patient with multicystic CVS showed increased tumor volume and expired after 9 months of surgery.The tumor volume reduction in type 1CVS was statistically significant as compared to type 3 CVS and SVS. However the tumor volume reduction among other groups did not differ significantly. CONCLUSION: Intra tumoral cystic components respond better to gammaknife radiosurgery in CVS. Tumor with single cyst respond better than multicystic vestibular schwannoma.

MR Venography in Gamma Knife Radiosurgery for Parasagittal Meningiomas: A Technical Note with the Rationale of Venous Protection and a Review of Literature.

Postradiosurgery symptomatic brain edema may be seen with parasagittal meningioma owing to its proximity to major venous sinuses and cortical veins. Venous preservation radiosurgery planning is less described. Here, we discuss a new method of tumor volume contouring on postcontrast magnetic resonance venogram (CEMRV) images safely excluding the adjacent cortical veins and sinuses. Six cases of parasagittal meningiomas where Gamma Knife radiosurgery was planned on CEMRV sequence were studied in detail. A double-contrast injection method was used to obtain CEMRV images. The differential contrast enhancement showed the displaced and compressed sinuses and cortical veins in the vicinity of meningioma. Tumor was contoured on both contrast magnetic resonance imaging (CEMRI) and MRV image for comparative analysis. 15 Gy at 50% marginal isodose was prescribed and quantitative assessment showed reduced exposure to the adjacent veins and sinuses on the MRV plan as compared to the CEMRI plan. All patients remain asymptomatic at a mean follow-up of 34.2 months. Postcontrast MRV is a simple sequence and can delineate the adjacent venous structures in parasagittal meningiomas. Tumor contouring directly on this sequence guides the surgeon to prescribe adequate radiation dose while sparing cortical veins and sinuses in radiosurgery planning.

A technique to increase the treatment plan indices in GammaKnife: A retrospective study.

The study was to find the optimal values of priority in the inverse planning module of Leksell GammaPlan which would give better treatment plan indices in GammaKnife SRS. The study showed that the best optimised setting of the weighting or priority in the inverse planning module of Leksell GammaPlan were 0.6 for coverage, 0.3 for gradient index and 0.5 for beam on time. Inverse plans (Hybrid Inverse Plan, HIP) which were made using this optimal priority setting were compared with forward plans (FP) with all 95% coverage. The results showed that the average selectivity index (SI) was 83.05±9.68 for FP and 85.35±8.03 for HIP. So, SI improved in the HIP technique by about 2.3% compare to FP. Similarly, average gradient index (GI) for FP and HIP were respectively 2.82±0.23 and 2.76±0.33. And the average beam on time (BT) of FP and HIP were, respectively, 48.15±23.14 min and 48.35±18.09 min. So, all plan indices show improvement in the hybrid inverse planning technique over forward plans. Consequently, this will improve the quality of patient treatment in GammaKnife.

Acute effects of chemoradiation on cardiac function in oesophageal cancer: a MUGA scan and echo-based study.

OBJECTIVE: To study the acute effects of concurrent chemoradiation on global and regional cardiac contractility and correlate with radiation dose. METHODS: 16 patients of locally advanced oesophageal squamous cell carcinoma were serially followed up with multiple-gated acquisition (MUGA) scans and echocardiograms during the course of concurrent chemoradiation to evaluate the ejection fractions (EFs) and pericardial status, respectively. Changes in cardiac contractility were correlated with the doses received by the heart. RESULTS: Concurrent chemoradiation resulted in a significant reduction in the contractility of both left ventricle (LV) and right ventricle (RV), with a mean reduction of LVEF by 5.6% and RVEF by 6.5% over the course of treatment, which had a significant correlation with the radiation doses received by the ventricles (p=0.001). On further analysis, correlation between radiation dose and decrease in contractility was more significant in the boost phase (16 Gy in 8 fractions over one and a half weeks; p=0.001 for LV and p=0.008 for RV) compared with the initial phase (40 Gy in 20 fractions over 4 weeks; p=0.184 for LV and p=0.269 for RV). One out of 16 patients developed mild acute pericarditis. CONCLUSIONS: Concurrent chemoradiation resulted in acute decrease in EF of both ventricles in a dose-dependent manner. Correlation between cardiac doses and decrease in EF was more marked in the boost phase, suggesting a possible threshold of 40 Gy for this impairment. Nevertheless, conclusions regarding this possible threshold need to be interpreted with caution given the small sample size.

CT and MR image fusion of tandem and ring applicator using rigid registration in intracavitary brachytherapy planning.

The purpose of this study is to find the uncertainties in the reconstruction of MR compatible ring-tandem intracavitary applicators of high-dose rate image-based brachytherapy treatment planning using rigid registration of 3D MR and CT image fusion. Tandem and ring reconstruction in MR image based brachytherapy planning was done using rigid registration of CT and MR applicator geometries. Verifications of registration for applicator fusion were performed in six verification steps at three different sites of tandem ring applicator set. The first site consists of three errors at the level of ring plane in (1) cranio caudal shift (Cranial Shift) of ring plane along tandem axis, (2) antero-posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (3) lateral shift (Lat Shift) perpendicular to the plane containing the tandem at the level of ring plane. The other two sites are the verifications at the tip of tandem and neck of the ring. The verification at the tip of tandem consists of two errors in (1) antero-posterior shift (AP Shift) perpendicular to tandem axis on the plane containing the tandem, and (2) lateral shift (Lat Shift) perpendicular to the plane containing the tandem. The third site of verification at the neck of the ring is the error due to the rotation of ring about tandem axis. The impact of translational errors from -5 mm to 5 mm in the step of 1 mm along x-, y-, and z-axis and three rotational errors about these axes from -19.1° to 19.1° in the step of 3.28° on dose-volume histogram parameters (D(2cc), D(1cc), D(0.1cc), and D(5cc) of bladder, rectum, and sigmoid, and D90 and D98 of HRCTV were also analyzed. Maximum registration errors along cranio-caudal direction was 2.2 mm (1 case), whereas the errors of 31 out of 34 cases of registration were found within 1.5 mm, and those of two cases were less than 2mm but greater than 1.5 mm. Maximum rotational error of ring about tandem axis was 3.15° (1.1 mm). In other direction and different sites of the ring applicator set, the errors were within 1.5 mm. The impacts of registration errors on DVH parameters of bladder, rectum, and sigmoid were very sensitive to antero-posterior shift. Cranio-caudal errors of registration also largely affected the rectum DVH parameters. Largest change of 17.95% per mm and 20.65% per mm in all the DVH parameters of all OARs and HRCTV were observed for ϕ and Ψ rotational errors as compare to other translational and rotational errors. Catheter reconstruction in MR image using rigid registration of applicator geometries of CT and MR images is a feasible technique for MR image-based intracavitary brachytherapy planning. The applicator regis-tration using the contours of tandem and neck of the ring of CT and MR images decreased the rotational error about tandem axis. Verification of CT MR image fusion using applicator registration which consists of six steps of verification at three different sites in ring applicator set can report all the errors due to translation and rotational shift along θ, ϕ, and Ψ. ϕ and Ψ rotational errors, which produced potential changes in DVH parameters, can be tackled using AP Shift and Lat Shift at the tip of tandem. The maximum shift was still found along the tandem axis in this technique.

Dosimetric comparison of vaginal vault ovoid brachytherapy versus intensity-modulated radiation therapy plans in postoperative patients of cervical carcinoma following whole pelvic radiotherapy.

INTRODUCTION: Dosimetric study to compare high dose rate (HDR) vaginal vault ovoid brachytherapy plan versus intensity-modulated radiation therapy (IMRT) boost plan for doses delivered to target volume and organs at risk (OAR) in postoperative patients of cervical carcinoma following whole pelvic radiotherapy (WPRT). MATERIALS AND METHODS: Fifteen postoperative patients of cervical carcinoma suitable for vaginal ovoid brachytherapy following WPRT of 46 Gy/23 fractions/4.5 weeks were included. All were treated with brachytherapy (two sessions of 8.5 Gy each). The equivalent dose for IMRT was calculated by computing biologically effective dose of brachytherapy by linear quadratic model. Dose of brachytherapy (two sessions of 8.5 Gy) was equivalent to IMRT dose of 26 Gy/13 fractions. Doses to target volume and OAR were compared between HDR and IMRT plans. RESULTS: Target volume was well covered with both HDR and IMRT plans, but dose with brachytherapy was much higher (P < 0.05). Mean doses, doses to 0.1, 1, 2, and 5cc, 1/3 (rd) , 1/2, and 2/3 (rd) volume of bladder and rectum were significantly lower with HDR plans. CONCLUSION: In postoperative patients of cervical carcinoma, HDR brachytherapy following WPRT appears to be better than IMRT for tumor coverage and reducing dose to critical organs.

Clinical and cosmetic results of breast boost radiotherapy in early breast cancer: a randomized study between electron and photon.

INTRODUCTION: Breast-conserving surgery followed by radiation therapy (RT) to the intact breast is now clearly established as the most acceptable strategy for women with early-stage invasive breast cancer. Recommended techniques for radiotherapy is whole breast irradiation (WBI) followed by boost to the tumor bed. AIMS: The aim of this study is to compare the modalities of three-dimensional conformal RT (3DCRT) and electron beam therapy as boost in post-lumpectomy patients of early stage breast cancer, following WBI. MATERIALS AND METHODS: The study comprised of selecting 50 patients of early-stage post-lumpectomy breast cancer. Each patient was initially treated by WBI (40 Gy in 16 fractions) and then followed by tumor bed boost (16 Gy in 8 fractions) with either electron beam therapy or with photon (3DCRT), 25 patients in each arm. Patients were evaluated regularly for acute and chronic radiation toxicities, cosmesis, and pattern of failure. Dosimetric comparison of the plans was also done. RESULTS: Median age of the patients was 42 years with 66% being premenopausal. Median duration of follow-up was 23 months. In arm A (electrons), two patients had grade III-IV reactions at treatment completion with one patient required RT interruption. Whereas, in arm B (3DCRT), five patients had grade III-IV reactions at treatment completion with three patients required RT interruption. At 6 months and 2 years follow-up, both the arms had almost similar skin, subcutaneous toxicity, and cosmetic score. At the end of 2 years, there were totally four failures among 50 patients, with one locoregional failure in both arms (4%). Dosimetric analysis revealed that conformality (radiation conformity index (RCI)), dose homogeneity index (DHI) and planning target volume (PTV) coverage was significantly better in 3DCRT boost plans. Organs at risk (OAR) dosimetry also revealed significant decrease in ipsilateral lung and heart doses with 3DCRT plans in which tangential or oblique fields were used; and whereas in electron beam, only single direct fields were used. CONCLUSIONS: Both electrons and 3DCRT can be used for boost planning to the tumor bed in post-lumpectomy patients. Though there was slightly increased acute skin toxicity with 3DCRT photon which led to interruption of therapy, overall cosmesis at 2 years is similar in both modalities. 3DCRT boost is a better option than electrons dosimetrically, considering the fact that conformality; PTV coverage and OAR dosimetry were superior with photons. Thus in centers where electron beam therapy is not available, 3DCRT photon can be used effectively for tumor bed boost.

Dosimetric comparison of doses to organs at risk using 3-D conformal radiotherapy versus intensity modulated radiotherapy in postoperative radiotherapy of periampullary cancers: implications for radiation dose escalation.

CONTEXT: Postoperative periampullary cancers with high risk features are managed with adjuvant chemo radiotherapy. Doses of 40-50 Gy have generally been used in conventional radiotherapy. Dose escalation with conventional radiotherapy has been restricted due to surrounding critical organs. OBJECTIVE: The objective of this dosimetric analysis was to evaluate the dose of radiation received by organs at risk using 3D conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT). METHODS: Ten postoperative patients of periampullary cancers were selected for this dosimetric analysis. Planning CT scans films were taken with slice thickness of 2.5 mm and transferred to Eclipse treatment planning system. The clinical target volume (CTV) included the postoperative tumor bed and draining lymph nodal areas. A 1 cm margin was taken around the CTV to generate the planning target volume (PTV). Critical structures contoured for evaluation included bowel bag, bilateral kidneys, liver, stomach and spinal cord. IMRT plans were generated using seven field coplanar beams and 3DCRT planning was done using one anterior and two lateral fields. A dose of 45 Gy in 25 fractions was prescribed to the PTV. RESULTS: V45 for bowel bag was 212.3 ± 159.0 cc (mean volume ± standard deviation) versus 80.9 ± 57.4 cc in 3DCRT versus IMRT (P=0.033). The V28 dose analysis for bilateral kidneys showed a value of 32.7±23.5 cc (mean volume ± standard deviation) versus 7.9 ± 7.4 cc for 3DCRT versus IMRT, respectively (P=0.013). The D60 for liver using 3DCRT and IMRT was 28.4 ± 8.6 Gy (mean dose ± standard deviation) and 19.9 ± 3.2 Gy, respectively (P=0.020). CONCLUSIONS: Doses to bowel bag, liver and kidneys was significantly reduced using IMRT leaving ample scope for dose escalation.