An appraisal of radiation therapy techniques for adjuvant and neoadjuvant therapy in gastric cancer

The analysis of absorbed dose by pancreas during gastric cancer radiotherapy

INTRODUCTION

The toxicity of radiotherapy is a very important issue in the everyday work of radiation oncologist. The tolerance to certain doses of radiotherapy in organs at risk determines the safety of radiotherapy. Despite the increasing number of publications concerning the injury of the pancreas after radiotherapy, this organ does not have common directives. We decided to reanalyse our previously published data in terms of the dose of radiation absorbed by the pancreas to determine a dose-effect relationship with the use of radiation-induced hypoamylasaemia and hypolipasaemia.

MATERIALS AND METHODS

We reanalysed a group of 127 gastric cancer patients after preoperative or postoperative chemoradiotherapy who were treated with a total dose of 45 Gy administered in 25 fractions. To identify the absorbed doses, the pancreas was contoured based on the CT scans used for radiotherapy planning and divided into anatomical parts: the head, the body and the tail.

RESULTS

We found that 80% of the whole pancreatic volume absorbed at least 44.5 Gy. The body, tail and head absorbed 100%, 90% and 70% of the abovementioned dose, respectively. The mean dose absorbed by the whole pancreas ranged from 32 to 48 Gy, with a mean of 44 Gy. A total dose of 45 Gy administered to gastric cancer patients can lead to subclinical insufficiency of the pancreas (hypolipasaemia and hypoamylasaemia). This dose is not able to cause symptomatic damage to the pancreas.

Protection of organs at risk during neoadjuvant chemoradiotherapy for gastric cancer based on a comparison between conformal and intensity-modulated radiation therapy

The aim of the present study was to compare the techniques of dynamic intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiotherapy (3DCRT) in patients with gastric cancer. Implementation of the IMRT technique does not significantly affect the minimum and maximum dose levels in the planning target volume (PTV), but more effectively protects the critical organs. The study group consisted of 25 patients. The results of the analysis of the conformity index (CI) and the homogeneity index (HI) showed that the doses in the PTV regions were at a comparable level. The CI for the PTV was 0.95 for the 2-field technique, 0.95 for the 3-field technique, 0.96 for the 4-field technique and 0.94 for the IMRT technique. The CIs for these techniques for the clinical target volume (CTV) were 0.96, 0.96, 0.97 and 0.96, respectively, and the CIs for the gross tumor volume (GTV) were 0.99, 0.99, 0.99 and 0.98, respectively. The HI values for the PTV were 1.12 for the 2-field technique, 1.12 for the 3-field technique, 1.09 for the 4-field technique and 1.09 for the IMRT technique, and the HI values for the CTV were 1.12, 1.12, 1.09 and 1.08 for the same techniques, respectively. The HI values for the GTV were 1.09, 1.09, 1.07 and 1.06, respectively, which indicated significantly superior performance in the regions of healthy tissue. Statistical study was based on Friedman's rank analysis of variance to determine the level of reliability of the tested groups of variables (P<0.001). The present study demonstrated that the IMRT technique in the pre-operative radiotherapy of gastric cancer patients results in superior treatment tolerance and reduces the risk of damage to healthy tissue that is in close proximity to the irradiated area.

Radiation-induced injury of the exocrine pancreas after chemoradiotherapy for gastric cancer

BACKGROUND AND PURPOSE

The pancreas is located almost entirely within the treatment area for radiotherapy of gastric cancer. The aim of this study was to analyze radiation-induced injury of the exocrine pancreas.

MATERIAL AND METHODS

The study included 127 gastric cancer patients, who underwent preoperative or postoperative chemoradiotherapy. A total dose of 45 Gy was given in 25 fractions. Concurrent chemotherapy was 5-fluorouracil-based. Lipase and α-amylase were assayed before, during and after treatment.

RESULTS

Lipase and α-amylase deficiencies were found in 48.2% and 19.7% of patients, respectively. In the univariant analysis, age and pretreatment α-amylase and lipase activities influenced on risk of injury of the exocrine pancreas (p<0.05). Younger patients (<65 years) had a lower risk of hypoamylasemia than older patients. The probability of insufficiency was lower than 0.2 for patients with pretreatment α-amylase and lipase activities above 50 U/L and 55 U/L, respectively. The multivariate analyses of the time to hypolipasemia showed that only pretreatment lipase activity was significant.

CONCLUSIONS

Gastric cancer patients have an increased risk of exocrine pancreatic insufficiency after chemoradiotherapy. Thus, the pancreas should be regarded as an OAR. Measuring lipase activity should be the standard for assessing radiation-induced pancreatic injury.

Influence of interfraction motion on margins for radiotherapy of gastric cancer

OBJECTIVE

The aim of this study was to evaluate interfraction uncertainties using kilovoltage (kV) radiographs for patients with gastric cancer during chemoradiotherapy and to calculate the planning target volume (PTV) margins.

METHODS

1284 measurements of set-up errors were analysed for treated patients. The measurements of craniocaudal (axis y), laterolateral (axis x) and anteroposterior (axis z) shifts in kV radiographs were performed. Interfraction clinical target volume (CTV)-PTV margins for all directions were calculated using the van Herk formula.

RESULTS

The main shift for the y-axis was 0.7 mm [standard deviation (SD), ±7.6], for the x-axis was 0.4 mm (SD, ±3.7) and for the z-axis was 0.6 mm (SD, ±3.5). The CTV-PTV margin in the x, y and z directions was 8.3, 15.5 and 8.0 mm, respectively. We observed that the interfractional motion for patients increased approximately 0.0034 cm along the x direction with each subsequent fraction, whereas a 0.0058-cm reduction in length along the y-axis was observed. No time effects for the z direction were noticed.

CONCLUSION

According to our experience, a PTV margin of 9 mm along the x-axis, 16 mm along the y-axis and 8 mm along the z direction should be considered in the absence of image-guided radiotherapy.

ADVANCES IN KNOWLEDGE

This knowledge concerning PTV set-up margins could be particularly useful for centres without a kV on-board imaging system.

Radiotherapy and chemoradiotherapy as a novel option for the treatment of locally advanced inoperable gastric adenocarcinoma: A phase II study

This phase II trial aimed to evaluate the tolerance and efficacy of radical radiotherapy or chemoradiotherapy in patients with primarily inoperable gastric cancer. The analysis was based on 13 patients with primarily inoperable gastric cancer. A total of 6 (46.2%) patients refused surgery and 7 (53.8%) had contraindications to anesthesia due to cardiological or respiratory reasons (4 and 3 patients, respectively). The treatment regimen consisted of radiotherapy and chemotherapy based on 5-fluorouracil. Half of the patients were not qualified to receive chemotherapy due to the presence of comorbidities. A total dose of 45 Gy was administered in 25 fractions. Of the 13 patients who started treatment, 12 (92.3%) completed radiotherapy. Local treatment response was observed in 6/12 patients (50%), with 5/12 (41.7%) displaying clinical complete response and 1/12 (8.3%) partial response. The 1- and 3-year overall survival rates and the median survival were 59 and 48% and 17.1 months, respectively. In conclusion, radical radiotherapy, either alone or in combination with chemotherapy, is safe for patients with inoperable locally advanced gastric cancer and may prolong survival.