Radiotherapy in Asia: Making progress step by step

Determining the library size for the optimal output plan in the RapidPlan knowledge-based planning system using multicriteria optimization

OBJECTIVES

The aim of this study was to determine the number of trade-off explored (TO) library plans required for building a RapidPlan (RP) library that would generate the optimal clinical treatment plan.

METHODS

We developed 2 RP models, 1 each for the 2 clinical sites, head and neck (HN) and cervix. The models were created using 100 plans and were validated using 70 plans (VP) for each site respectively. Each of the 2 libraries comprising 100 TO plans was divided into 5 different subsets of library plans comprising 20, 40, 60, 80, and 100 plans, leading to 5 different RP models for each site. For every validation patient, a TO plan (TO_VP) was created. For every patient, 5 RP plans were automatically generated using RP models. The dosimetric parameters of the 6 plans (TO_VP + 5 RP plans) were compared using Pearson correlation and Greenhouse-Geisser analysis.

RESULTS

Planning target volume (PTV) dose volume parameters PTVD95% in 6 competing plans varied between 97.6 ± 0.7% and 98.1 ± 0.6% in HN cases and 98.8 ± 0.3% and 99.0 ± 0.4% in cervix cases. Overall, for both sites, the mean variations in organ at risk (OAR) doses or volumes were within 50 cGy, 0.5%, and 0.2 cc between library plans, and if TO_VP was included the variations deteriorated to 180 cGy, 0.4%, and 15 cc. All OARs in both sites, except D0.1 ccspine, showed a statistically insignificant variation between all plans.

CONCLUSIONS

Dosimetric variation among various output plans generated from 5 RP libraries is minimal and clinically insignificant. The optimal output plan can be derived from the least-weighted library consisting of 20 plans.

ADVANCES IN KNOWLEDGE

This article shows that, when the constituent plans are subjected to trade-off exploration, the number of constituent plans for a knowledge-based planning module is not relevant in terms of its dosimetric output.

Nasopharyngeal carcinoma among the pediatric patients in a non-endemic region: our experience at a tertiary care teaching hospital in Eastern India

Background

Nasopharyngeal carcinoma (NPC) is an extremely rare malignant lesion among the pediatric age group. The relative rarity of pediatric NPC makes the diagnosis difficult. This rarity is often associated with delayed diagnosis which may lead to advanced loco-regional disease. Here, we study the clinical presentations, investigations, and treatment of nasopharyngeal carcinoma in the pediatric age group in a non-endemic region.

Result

This is a retrospective study where 21 pediatric patients were enrolled with age under 18 years. They were managed at a tertiary care teaching hospital between December 2010 and January 2019. Majority of the patients in this study were boys (66.7%). All children diagnosed with NPC were treated with radiotherapy covering entire nasopharynx and some children with chemotherapy. Until the patient is in a late stage, most children diagnosed with NPC were presenting with symptoms of neck mass (90.5%), bleeding from the nose (66.7%), nasal blockage (57.1%), and hearing loss (47.6%). Pathological report revealed WHO type III in the majority of the patients. All patients were treated with radiotherapy to primary and enlarged neck nodes.

Conclusion

Children with NPC have excellent survival except for those with distant metastatic disease. NPC in the pediatric age is usually not suspected clinically until patient in late stage. The TNM staging has the most relevant prognostic factor. Unfortunately, NPC tends to be locally advanced at the time of diagnosis in the pediatric age group and is sometimes associated with distant metastasis. In our study, most children were diagnosed with NPC along with neck node enlargement and were treated with radiotherapy. The diagnosis of pediatric NPC should prompt timely treatment.