18-Fluorodeoxy-Glucose Positron Emission Tomography- Computed Tomography (18-FDG-PET/CT) for Gross Tumor Volume (GTV) Delineation in Gastric Cancer Radiotherapy

From twilight to starlight? Debating the role of chemoradiotherapy in gastric cancer in the D2 dissection era

Patients affected by resectable locally advanced gastric cancer (GC) should receive perioperative chemotherapy as a standard of care. However, an additional benefit of adjuvant chemoradiation (CRT) has been negated by modern trials in the era of extended surgical dissection, and CRT is currently only considered on an individual basis in case of suboptimal resection. However, the dismal prognosis of GC and the modest treatment completion rates of perioperative chemotherapy have pushed to reconsider CRT, particularly as a preoperative treatment, in light of modern treatment techniques, advances in the understanding of the immune landscape and development of targeted agents. The aim of this review is to critically assess the historical role of CRT, the limitations of current evidence and to debate its potential role in an integrated neoadjuvant strategy for patients with resectable GC.

Current landscape of gastrointestinal radiation oncology in Spain: a multicenter real-life survey and comparison with key clinical guidelines

Background

The GI Tumors Workgroup, a division of the Spanish Society of Radiation Therapy, conducted a survey in December 2020 to assess the adherence of radiation oncologists in Spain to international guidelines for gastrointestinal tumors.

Materials and methods

Using Google Forms, we designed a survey covering treatments for esophageal, gastric, pancreatic, and rectal cancers.

Results

In esophageal cancer treatment, neoadjuvant chemoradiation was the standard in 76.7% of institutions. Radiation doses range from 41.1 to 50.4 Gy in conventional fractionation. Planning positron emission tomography-computed tomography (PET-CT) was performed in 83.3% of centers, and intensity-modulated radiation therapy/volumetric-arc radiation therapy (IMRT/VMAT) was the preferred technique in 86.7% of institutions. For gastric cancer, 71.4% followed perioperative chemotherapy guidelines. In the case of adjuvant radiotherapy, the majority prescribed 45-50.4 Gy, and 82.1% used IMRT/VMAT for treatment. For pancreas cancer, neoadjuvant chemotherapy followed by surgery in borderline resectable tumors and induction chemotherapy followed by radical radiotherapy for non-resectable tumors were the most frequent approaches. IMRT/VMAT was the primary technique. Locally advanced rectal cancer treatment is mainly based on neoadjuvant radiotherapy in all institutions. The preferred radiation doses typically range from 45 to 50 Gy in conventional fractionation. IMRT/VMAT was standard in most Institutions.

Conclusions

Spain's radiotherapy practices among respondents generally align with international guidelines for GI tumors highlighting Spain's commitment to evidence-based medical practice.

A quantitative model based on gross tumor volume of gastric adenocarcinoma corresponding to N-stage measured at multidetector computed tomography for preoperative determination of resectability: A case control study

PURPOSE

To develop and validate a quantitative model based on gross tumor volume (GTV) of gastric adenocarcinoma (GA) corresponding to N-stage measured at multidetector computed tomography (CT) for preoperative determination of resectability.

MATERIALS AND METHODS

493 consecutive patients with confirmed GA undergoing contrast-enhanced CT two weeks before treatments were randomly enrolled into the training cohort (TC, n = 271), internal validation cohort (IVC, n = 107) and external validation cohort (EVC, n = 115). GTV was measured on CT by multiplying sums of all tumor areas by section thickness. In TC, univariate and multivariate analyses were performed to select factors associated with resectability. Receiver operating characteristic (ROC) analysis was to determine if N-stage based GTV could identify resectability. In IVC and EVC, unweighted Cohen's Kappa tests were to evaluate performances of the ROC models.

RESULTS

According to univariate analysis, age, cT stage, cN stage and GTV were related to resectability in TC (all P-values < 0.05), and multivariate analysis suggested that cN stage and GTV were independent risk factors with odds ratios of 1.594 (95% confidence interval [CI]: 1.105-2.301) and 1.055 (95%CI: 1.035-1.076), respectively. ROC analysis in TC revealed the cutoffs of 21.81, 21.70 and 36.93 cm3 to differentiate between resectable and unresectable cancers in stages cN0-3, cN2 and cN3 with areas under the curves of more than 0.8, respectively, which was validated in IVC and EVC with average Cohen k-values of more than 0.72.

CONCLUSIONS

GTV and cN stage can be independent risk factors of unresectable GA, and N-stage based GTV can help determine resectability.

Comparison of the Gross Target Volumes Based on Diagnostic PET/CT for Primary Esophageal Cancer

Background

Clinically, many esophageal cancer patients who planned for radiation therapy have already undergone diagnostic Positron-emission tomography/computed tomography (PET/CT) imaging, but it remains unclear whether these imaging results can be used to delineate the gross target volume (GTV) of the primary tumor for thoracic esophageal cancer (EC).

Methods

Seventy-two patients diagnosed with thoracic EC had undergone prior PET/CT for diagnosis and three-dimensional CT (3DCT) for simulation. The GTV_3D was contoured on the 3DCT image without referencing the PET/CT image. The GTV_PET-ref was contoured on the 3DCT image referencing the PET/CT image. The GTV_PET-reg was contoured on the deformed registration image derived from 3DCT and PET/CT. Differences in the position, volume, length, conformity index (CI), and degree of inclusion (DI) among the target volumes were determined.

Results

The centroid distance in the three directions between two different GTVs showed no significant difference (P > 0.05). No significant difference was found among the groups in the tumor volume (P > 0.05). The median DI values of the GTV_PET-reg and GTV_PET-ref in the GTV_3D were 0.82 and 0.86, respectively (P = 0.006). The median CI values of the GTV_3D in the GTV_PET-reg and GTV_PET-ref were 0.68 and 0.72, respectively (P = 0.006).

Conclusions

PET/CT can be used to optimize the definition of the target volume in EC. However, no significant difference was found between the GTVs delineated based on visual referencing or deformable registration whether using the volume or position. So, in the absence of planning PET–CT images, it is also feasible to delineate the GTV of primary thoracic EC with reference to the diagnostic PET–CT image.