Correlation of Dose Volume Parameters with Dysphagia and Pharyngeal Constrictor Muscle Thickness in Dysphagia Optimized IMRT

PURPOSE/OBJECTIVE(S)

Reduced radiation dose to the pharyngeal constrictor muscles (PCM) using dysphagia optimized intensity-modulated RT (DO-IMRT) is associated with improved swallowing outcomes in oropharyngeal cancers (OPCs). Purpose was to evaluate the relationship between dose of radiation delivered and acute dysphagia in patients with OPC treated with IMRT, after delineation of PCM.

MATERIALS/METHODS

Twenty-five patients with newly diagnosed OPC who underwent definitive IMRT with concurrent cisplatin were included in the study. PCM mean dose < 50 Gy was used as the dose constraint. Target volume was divided into high, intermediate and low risk areas receiving doses in the range of 60-66 Gy, 54-58 Gy, 51-56 Gy in 30-33 fractions over 6-6.5 weeks, respectively. PCM dose-volume parameters were collected and logistic regression was used to analyze these data relative to percent weight loss during RT and duration of feeding tube use. Thickness of constrictor muscle in pre-treatment and 3 months post-therapy CT scan were assessed. Weekly assessment of dysphagia was based on RTOG toxicity gradings. Aim of the study was to evaluate the correlation between dysphagia grades with dose-volume parameters and PCM thickness.

RESULTS

Median age was 55.0 years (mean 54.3) with 24 males and stage II:III-16:9 patients. Dmean to PCM was 49.86 Gy (range 48.22 -57.63) with median Dmax of 70.24 Gy. For patients with dysphagia (grade ≥1), V50 ranged from 48.2-57.23%, while in those with no dysphagia, it ranged from 47.92-52.18 % (Mean 51.36%). Nine patients needed feeding tube after RT end. Median feeding tube duration was 64 days. The correlation between Dmean ≥ 50 Gy and dysphagia at 1st, 2nd, 3rd and 6th month was found statistically significant (p < 0.01). Table 1 shows the Pearson correlation and P-value of the dosimetric parameters with dysphagia. The correlation of V50 was found statistically significant with grade of dysphagia at 3rd and 6th month post-treatment (p<0.001). The mean thickness range and median thickness of constrictors before and 3 months after treatment were 1.8-3.2 mm, 2.4 mm, and 2.8-6.2 mm,4.1 mm, respectively. The increase in thickness of constrictor muscle correlated significantly (p<0.05) with dysphagia grades and also with V50, V60 and Dmean (p<0.001) but no statistical significance was seen with Dmax (p = 0.232). With a median follow-up of 18 months (range 7-24), 1-year actuarial local control was 92%.

CONCLUSION

DO-IMRT may prove beneficial in the OPC by preventing dysphagia and aspiration post therapy and hence improving the quality of life of patients. Dmean ≥ 50Gy, V50 > 51.4% and V60 > 35.5% are the parameters correlating significantly with dysphagia (p<0.001) and change in mean thickness of PCM (p<0.001).

Assessment of Cranial Radiotherapy Treatment in T-cell Lymphoblastic Lymphoma: Retrospective Study from Tertiary Care Center

Introduction Leukemia-like regimens given for acute lymphoblastic leukemia (ALL) are the cornerstone of treatment for T-cell lymphoblastic lymphoma (LBL) and can produce complete remission rates exceeding 90%. For central nervous system (CNS) prophylaxis, intrathecal chemotherapy and cranial irradiation are used to prevent future CNS recurrence.

Objective The purpose of this study was to assess CNS relapse rate after cranial prophylaxis treatment given at our institute.

Materials and Methods In this retrospective analysis, between July 2013 and June 2019, 149 files of lymphoblastic lymphoma were reviewed. Out of these, 53 patients received cranial irradiation. All patients were given CNS-directed therapy in the form of intrathecal methotrexate and patients with CNS-negative disease and primary tumor complete response or more than partial response after chemotherapy were given prophylactic cranial irradiation (18 Gy/10#), and in patients with upfront CNS involvement, therapeutic cranial irradiation (24 Gy/12#) was delivered. Radiotherapy was delivered as per the standard conventional protocol on a linear accelerator.

Results Out of 53 patients (age range: 2–50 years, mean–16.79 years, 26 [49.1%] pediatric [<14 years], 27 [50.9%] adults [>14 years]), 13/53 (24.5%), and 40/53 (75.5%) patients were on MCP 841 and BFM 90 protocols, respectively. Also, 48 (90.56%) patients received prophylactic cranial irradiation (25 [52.1%] pediatric, 23 [47.9%] adults). Moreover, 3/48 (6.25%) (2 [4.16%] pediatric, 1 [2.08%] adult) patients had CNS failure after receiving prophylactic cranial irradiation. For 48 target patients, with the median follow-up of 27.27 months (26.1 months–pediatric, 28.2 months– adults), EFS (event-free survival) in the brain was 93.8% (92%: pediatric, 95.7%: adults). Also, the difference between pediatric and adult groups was not statistically significant (p-value = 0.662). Five (9.43%) patients had CNS-positive disease upfront and received therapeutic cranial irradiation.

Conclusion In BFM 90/MCP 841 protocol in lymphoblastic lymphoma, prophylactic cranial irradiation and intrathecal methotrexate have been the standard of care as the CNS-directed therapy to prevent cranial infiltration. Though our results are not at par with the published world literature, further research and efforts are required to prevent CNS relapse in a selected sub-set of patients with lymphoblastic lymphoma.

Calculation of dose volume parameters and indices in plan evaluation of HDR interstitial brachytherapy by MUPIT in carcinoma cervix

BACKGROUND

Evaluation of a HDR- interstitial brachytherapy plan is a challenging job. Owing to the complexities and diversity of the normalization and optimization techniques involved, a simple objective assessment of these plans is required. This can improve the radiation dose coverage of the tumour with decreased organ toxicity.

AIM

To study and document the various dose volume indices and parameters required to evaluate a HDR interstitial brachytherapy plan by Volume normalization and graphical optimization using MUPIT (Martinez Universal Perineal Interstitial Template) in patients of carcinoma cervix.

SETTINGS AND DESIGN

Single arm, retrospective study.

METHODS AND MATERIALS

35 patients of carcinoma cervix who received EBRT and HDR brachytherapy using MUPIT, were selected. The dose prescribed was 4 Gray/Fraction in four fractions (16Gy/4) treated twice daily, at least 6 hours apart. CTV and OARs were delineated on the axial CT image set. Volume normalization and graphical optimization was done for planning. Coverage Index (CI), Dose homogeneity index (DHI), Overdose index (OI), Dose non-uniformity ratio (DNR), Conformity Index (COIN) and dose volume parameters i.e. D2cc, D1cc, D0.1cc of rectum and bladder were evaluated.

STATISTICAL ANALYSIS

SPSS version 16 was used.

RESULTS AND CONCLUSION

CI was 0.95 ± 1.84 which means 95% of the target received 100% of the prescribed dose. The mean COIN was 0.841 ± 0.06 and DHI was 0.502 ± 0.11. D2cc rectum and bladder was 3.40 ± 0.56 and 2.95 ± 0.62 respectively which was within the tolerance limit of this organs. There should be an optimum balance between these indices for improving the quality of the implant and to yield maximum clinical benefit out of it, keeping the dose to the OARs in limit. Dose optimization should be carefully monitered and an institutional protocol should be devised for the acceptability criteria of these plans.

Dosimetric comparison of volume-based and inverse planning simulated annealing-based dose optimizations for high-dose rate brachytherapy

The aim of this study was to compare the clinical benefits of inverse planning simulated annealing (IPSA)-based optimization over volume-based optimization for high-dose rate (HDR) cervix interstitial implants. Overall, 10 patients of cervical carcinoma were considered for treatment with HDR interstitial brachytherapy. Oncentra Master Plan brachytherapy planning system was used for generating 3-dimensional HDR treatment planning for all patients. All patient treatments were planned using volume-based optimization and inverse planning optimization (IPSA). The parameters V100, V150, and V200 for the target; D(2 cm³) of bladder, rectum, and sigmoid colon; and V80 and V100 for bladder, rectum, and sigmoid colon were compared using dose-volume histograms (DVHs). The conformity index (CI), relative dose homogeneity index, overdose volume index (ODI), and dose nonuniformity index (DNR) were computed from cumulative DVHs. Good target coverage for prescription dose was achieved with volume-based optimization as compared with IPSA-based dose optimization. Homogeneity was good with the IPSA-based technique as compared with the volume-based dose optimization technique. Volume-based optimization resulted in a higher CI (with a mean value of 0.87) compared with the IPSA-based optimization (with a mean value of 0.76). ODI and DNR are better for the IPSA-based plan as compared with the volume-based plan. Mean doses to the bladder, rectum, and sigmoid colon were least with IPSA. IPSA also spared the critical organs but with considerable target conformity as compared with the volume-based plan. IPSA significantly reduces overall treatment planning time with improved reduced doses to the organs at risk compared with the volume-based optimization treatment planning method.

Plasmacytoma of scalp

An interesting case of plasmacytoma of the scalp is described. Extramedullary plasmocytoma of scalp is rarely reported. This patient was treated with external radiotherapy dose of which was 40 Gy/20 fraction. Disease responded very well to radiotherapy.