Evaluation of liver segmental dose threshold for hepatocyte regeneration following liver stereotactic body radiation therapy.

BACKGROUND OBJECTIVES: There is limited evidence studying the relationship of liver segmental dose and segmental volume changes. The segmental dose thresholds could potentially allow for segmental regeneration after liver stereotactic body radiation therapy (SBRT). Given improved survival in hepatocellular cancer (HCC) and liver metastases and more salvage therapy options, this has become an important clinical question to explore. This study assesses the impact of liver segmental dose on segmental volume changes (gain or loss) after SBRT. METHODS: Liver segmental contours were delineated on baseline and serial follow up triphasic computed tomography scans. The volumes of total liver and doses to total liver, uninvolved liver and individual segments were noted. A correlation was evaluated between liver/segmental volume and dose using Pearson's correlation. Furthermore, receiver operator's curve (ROC) analysis was performed to find the segmental dose, i.e . predictive for liver volume loss. RESULTS: A total of 140 non-tumour liver segments were available for analysis in 21 participants. Overall, 13 participants showed loss of overall liver volume and eight showed gain of overall liver volume. The median dose in segments reporting an increase in volume was 9.1 Gy (7-36 Gy). The median dose in segments losing volume was 15.5 Gy (1-49 Gy). On ROC analysis, segmental dose >11 Gy was associated with volume loss. On univariate analysis, only liver segmental dose contributed to a significant segmental volume loss. INTERPRETATION CONCLUSIONS: We propose from the findings of this study that in SBRT for large hepatocellular cancer or liver metastases, liver segments should be individually delineated. Furthermore, 3-5 liver segments may be preferentially subjected to <9 Gy to facilitate hepatocyte regeneration. Preferential sparing of uninvolved liver segments may improve outcomes in liver stereotaxyas lower segmental doses were associated with liver regeneration. This may have implications on future liver SBRT planning where segmental doses may be as important as the mean dose.

Quantitative Comparison of Dosimetric Data Between the Indigenous Baseplate and Commercially Available Carbon Fiber Baseplate for 6 and 15 MV Photon Energy.

Background: This study aims to design an indigenous baseplate (ID baseplate) that is economically viable and dosimetrically comparable for radiotherapy patient treatment. An ID baseplate was designed and manufactured using wood plastic composition materials that are readily available in the market and were compared dosimetrically with the commercially available carbon fiber baseplate (CF baseplate). Materials and Methods: Surface dose and beam attenuation properties of both the baseplates (ID and CF) were measured using a parallel plate chamber and compared with the dose calculated from the treatment planning system (TPS). Separate computer tomography images of both the baseplates were acquired by placing solid water phantoms. These images were used for surface dose calculation in the TPS and were validated with experimental measurements. Proper densities were assigned to the couch and baseplates to avoid uncertainties in dose calculations. All measurements were performed at field sizes 10 cm × 10 cm for 6 MV and 15 MV photon beams. Results: The percentage surface dose measured for the ID baseplate and CF baseplate was found to be matching for 6 MV beam (98.2% and 97%, respectively); however, for the 15 MV beam, the ID baseplate showed a higher surface dose of 98.6% compared to CF baseplate (87.4%). For the ID baseplate, the percentage difference in the surface dose between that TPS calculated value and the measured values were 1.6% and 1.4% for 6MV and 15MV, respectively. The ID baseplate showed higher beam attenuation than the CF baseplate by 2.2% for the 6MV beam and 3.4% for the 15MV beam when proper electron densities were not assigned. The difference between the TPS calculated dose and delivered dose was achieved within 3% after assigning proper electron density to the couch and baseplate. Conclusions: The ID baseplate has shown acceptable dosimetric results and can be an economically viable alternative to the commercially available CF baseplates. The manufacturing cost of the ID baseplate was ten times cheaper than the CF baseplate.

Radiation oncology in times of COVID-2019: A review article for those in the eye of the storm - An Indian perspective.

The global COVID-2019 pandemic has presented to the field of radiation oncology a management dilemma in providing evidence-based treatments to all cancer patients. There is a need for appropriate measures to be taken to reduce infectious spread between the medical healthcare providers and the patient population. Such times warrant resource prioritization and to continue treatment with best available evidence, thereby reducing the risk of COVID-2019 transmission in times where the workforce is reduced. There has been literature presented in different aspects related to providing safety measures, running of a radiation department and for the management of various cancer subsites. In this article, we present a comprehensive review for sustaining a radiation oncology department in times of the COVID-2019 pandemic.

Stereotactic body radio therapy for inoperable large hepatocellular cancers: results from a clinical audit.

OBJECTIVES: To evaluate the outcomes of stereotactic radiotherapy (SBRT) in the treatment of inoperable hepatocellular carcinomas (HCC) that are unsuitable for, or refractory to other liver-directed therapies. METHODS: Between March 2015 and June 2018, patients with primary HCCs refractory to or unsuitable for treatment with other liver-directed therapies were treated with SBRT. Patients of Child status A5-B7 and with normal liver reserve ≥ 700 cc were preferred. Local control (LC), overall survival (OS), progression free survival (PFS) and effect of prognostic factors were analysed. RESULTS: 21 patients with inoperable HCCs were treated. The median tumour diameter was 9.6 cm (5-21) and median tumour volume was 350 cc (32.9 - 2541). The median SBRT dose prescription was 42 Gy/6 fractions (25 - 54 Gy/6#). The 1- and 2-year LC rate was 88 and 43 % respectively. Overall rate of > grade III toxicity was 14 %. Patients with Child A5 liver function had a better median OS than A6 and B7 patients [21 vs 11 vs 8 months]. Also, tumours with GTV < 350 cc volumes had a better OS compared to GTV of greater than 350 cc [24 months vs 8 months, p value = 0.004]. CONCLUSIONS: This study showed that SBRT can be used safely and effectively to treat inoperable HCCs with or without prior loco-regional therapies, resulting in good local control and survival with acceptable toxicity. ADVANCES IN KNOWLEDGE: Use of SBRT in inoperable HCC is safe and effective.

High-dose-rate interstitial brachytherapy in recurrent head and neck cancer: an effective salvage option.

PURPOSE: High-dose-rate (HDR) interstitial brachytherapy has an established role in head and neck malignancies and offers good survival rates; however, there is scant data on improved local control (LC) and treatment-related complications in recurrent cases. We present our results in patients with recurrent head and neck cancers treated with HDR interstitial brachytherapy. MATERIAL AND METHODS: Twenty-five patients with recurrent head and neck cancers were treated with HDR interstitial brachytherapy using Iridium 192 between 2009 and 2016. Of these, 75% received radical brachytherapy, and 25% received external beam radiation therapy (EBRT) followed by brachytherapy boost. Treatment sites included oral cavity (15/25) and oropharynx (10/25). Median dose of 4.5 Gy was administered twice per day, with median total brachytherapy dose of 40.5 Gy in radical and 27 Gy for EBRT cases. RESULTS: With median follow-up of 25 months, 4 local recurrences were observed within first year of follow-up. Two-year local control and overall survival outcomes for the entire group were 75% and 68%, respectively. Local control rate with radical BRT vs. BRT as a boost following EBRT was found to be significant (2-year LCR 62% vs. 85%; p < 0.02). Dosimetric assessment revealed D90 - 4.08 Gy, V100 - 94.1%, V150 - 24.7%, and V200 - 10.1%. Xerostomia, altered taste, and dysphagia were the major complications commonly grade 1 and 2. Grade 3 toxicity was only 2%. Pre-treatment volume > 85 cc had a negative impact on overall survival (26 months vs. 12 months; p = 0.02), and interval time between primary and recurrence more than 15 months had an impact on the local control rate (p < 0.01). CONCLUSIONS: Results of HDR interstitial brachytherapy have shown acceptable local control and overall survival rates along with tolerable toxicities and morbidity in recurrent head and neck cancers.

High-dose-rate interstitial brachytherapy in head and neck cancer: do we need a look back into a forgotten art - a single institute experience.

PURPOSE: To evaluate the treatment outcomes with high-dose-rate (HDR) interstitial brachytherapy (HDR-BRT) in head and neck cancers (HNC). MATERIAL AND METHODS: Fifty-eight patients with HNC as per American Joint Committee on Cancer (AJCC) TNM staging criteria were analyzed retrospectively between 2008 and 2015. Forty-two patients received external beam radiotherapy (EBRT) with HDR-BRT and 16 patients received BRT alone. The survival was calculated with respect to median biological equivalent doses (BED) and median 2 Gy equivalent dose (EQD2), keeping α/ß = 10 for tumor. Loco-regional control and disease free survival was assessed. RESULTS: The median follow-up period was 25 months (2-84 months). The disease-free survival (DFS) probability at year 1 was 82.7%, and 68% at year 7. The overall survival probability was 91.3% at year 1 and 85.8% at year 7. The local control rate was 70%. The rate of recurrence was 30%. Distant metastasis rate was 17.2%. The median BED and EQD2, respectively, were 86.78 Gy and 71.6 Gy. The DFS was 74.1% and 75.9% in patients receiving a dose more than median BED and EQD2, respectively, and was 64.8% and 61.5% for less than the median dose. CONCLUSIONS: The overall outcome was good with implementation of HDR-BRT used alone or as boost, and shows DFS as better when the dose received is more than the median BED and median EQD2. The role of HDR-BRT in HNC is a proven, effective, and safe treatment method with excellent long term outcome as seen in this study, which reflects the need for reviving the forgotten art and science of interstitial brachytherapy in HNC.