Objective to describe and set the target area of intensity modulated radiotherapy for nasopharyngeal carcinoma

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Objective to describe and set the target area of intensity modulated radiotherapy for nasopharyngeal carcinomaAbstract: intensity modulated

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Objective to describe and set the target area of intensity modulated radiotherapy for nasopharyngeal carcinoma

Abstract: intensity modulated radiotherapy improves the local and regional control rate and reduces the complications. CT and MRI fusion can more fully display the primary lesion of nasopharyngeal carcinoma, is considered to be an ideal image mode; the key factor that cervical lymph node is a description of how the range of cervical lymph node partition is converted into an image boundary for the CT level can be described, and the common description specification reduces the difference in delineation of tumor center cervical lymph node region and recommended; the world's major center of tumor of nasopharyngeal carcinoma IMRT plan specification, the general definition of the tumor area is basically the same, and the prescription dose close to or even higher than that of 80Gy, the main difference is the definition of nasopharyngeal CTV range, prescription dose scheme and nasopharyngeal CTV and on the neck. According to the follow-up results, the recommended range of CTV in nasopharyngeal primary tumor in the nasopharynx extending certain edge diameter, should also include the nasopharynx, retropharyngeal lymph node area, the slope and the skull base bone structure, pterygopalatine fossa, parapharyngeal space, sphenoid sinus, nasal cavity and maxillary sinus after 1 / 3, and prescription the dose should be greater than or equal to 60Gy; bilateral neck lymph node metastasis should be classified as high-risk areas, given the exposure of at least 60Gy.

Keywords: nasopharyngeal carcinoma intensity modulated radiotherapy target delineation dose

The current status the and determination the and their dose prescription scheme for the nasopharyngeal cancer with intensity targets modulated radiotherapy of of delineation

Zhu SuYu, Hu BingQiang

Abstract: IMRT has increased the local-regional control and decreased the complications of the nasopharyngeal cancer, hence be deemed as the future pursuit. CT and MRI are complementary and their fusion is currently taken as the optimal modality to delineate the extent of the primary spread of this disease. The key factor inflicting the neck node delineation is how to translate anatomic node regions into the CT boundaries. The consensus guideline which narrowed the gap among different cancer centers is recommended in delineating the boundary of the cervical lymph node regions. The definition of the GTV of the NPC is clear and almost the same among the main cancer centers in their IMRT planning protocols. The actual dose to the GTV is close To or more than 80Gy the main differences are the; definition of the CTV and its dose prescription scheme, and also the dose to the high cervical region is different among those centers. According to their long-term follow-up results It is, suggested that, besides the 5-10mm margins be added to the primary lesions, the immediate high risk (structures including the entire nasopharyngeal cavity, retropharyngeal space, clivus base, of the skull, pterygoid plates and muscles, parapharyngeal space, the sphenoid and partial ethmoid sinuses, and the posterior third of the maxillary sinuses and the nasal cavity should be included and) also be prescribed to more than 60Gy, the bilateral node B level I, II and a should be ranked as high V risk R Egions and differentially prescribed to no less than 60Gy. and the surrounding structure according to the specific risk ranges were defined as CTV1 and CTV2 CTV2, the actual range should also have included high-risk areas surrounding the nasopharynx, but the prescription dose was 54Gy/30fx, so the planned dose in some areas between CTV2 and CTV1 dose compared with other tumor treatment Center low. The MSKCC definition of PTVm does not encompass the entire nasopharyngeal peripheral high-risk structure, and the prescription dose of 54Gy/30fx, but also lower than other tumor center planning dose. Nevertheless, MSKCC in 74 cases of nasopharyngeal carcinoma treatment reported for 3 years, primary tumor control rate was 91%; the regional control rate was 93%; the total survival rate was 83%; 69 cases (92%) underwent concurrent chemotherapy, chemotherapy is probably a contributing factor for local and regional control rate. The results showed that 3 cases of nasopharyngeal carcinoma (NPC) were treated with intensity-modulated radiotherapy (IMRT) at the Zhongshan University. The results were similar to those of the patients with nasopharyngeal carcinoma (NPC). The results showed that the intensity of local and regional control rate was 93.2% and the overall survival rate was about 122, respectively, with a total survival rate of about 85.1%. 67 cases of patients with nasopharyngeal carcinoma UCSF 5 reported, although the stage III + 75%, a median follow-up of 31 months, only 1 cases of nasopharyngeal primary tumor and 1 cases of cervical lymph node recurrence, curative effect reached 4 years of local and regional control rate was 98% and the total survival rate of 88%. According to the follow-up results, the IMRT plans of nasopharyngeal carcinoma in CTV should include the whole nasopharynx, retropharyngeal lymph node area, the slope and the skull base bone structure, pterygopalatine fossa, parapharyngeal space, sphenoid sinus, nasal cavity and maxillary sinus after 1 / 3, and should be more than 60Gy prescription dose.

Another important point is the difference in dose of cervical lymph node region, Hongkong Queen Marry hospital in 21 nasopharyngeal carcinoma to bilateral neck I B, II, III, V A cervical lymph node 70Gy/35fx prescription dose. Hongkong Prince of Wales prescription dose 20 hospital and Tumor Hospital of China Academy of Medical Sciences in 22 for 60 ~ 66Gy/33fx, and the prescription dose of UCSF 17, RTOG0225, MSKCC and the Zhongshan University cancer center is 50.4 ~ 54Gy/30 ~ 33fx. Neck and neck lymph node metastasis of nasopharyngeal carcinoma is the most frequent site, about 80% of patients with nasopharyngeal carcinoma with cervical lymph node metastasis of lymph nodes, even not found on imaging, many researchers still defined a higher dose of radiation prevention area of 23,24 for high risk area. But I and II B anatomical boundary region and the submandibular and deep lobe of the parotid gland and oral mucosa closely adjacent, high dose is bound to make the IMRT plan to achieve most of the functions to keep these vital organs, so as to reduce the complications of the main. Hongkong Queen Marry hospital reported 3 grade 78% and grade 3 mucositis skin reactions 46%, may be related to set too large range of targets given the high dose of. The clinical study of Avraham Eisbruch et al. Showed that there was a threshold effect on the parotid gland function under the irradiation dose of parotid gland, and the parotid gland function was expected to be preserved when the average dose of parotid gland was 26Gy (). Study on a series of malignant tumors of head and neck IMRT revealed to neck lymph node region high-risk 60Gy dose irradiation can not only achieve the purpose of keeping with radiotherapy can achieve the ideal, the regional control rate of 5,26, in addition, excessive irradiation will include cervical lymph node irradiation range and high dose of lead to neck the function of muscle atrophy and subcutaneous tissue fibrosis and other long-term complications increased, but these results need longer follow-up and larger samples to verify the results. So, at the present stage, the eclectic range and dose is a reasonable choice.

 

4 Summary

Intensity modulated radiotherapy for nasopharyngeal carcinoma has achieved a better therapeutic effect than conventional radiotherapy, and improved the quality of life of patients. The world cancer center of nasopharyngeal carcinoma IMRT plans, the definition of GTV is basically the same as the primary tumor of nasopharynx and neck lymph node metastasis, the prescription dose is more than 70Gy, the equivalent biological dose close to or even higher than that of 80Gy, CT and MRI can make complementary primary tumor of nasopharynx delineated more accurately. There are differences on the definition of CTV and prescription dose, suggest that in addition to the primary tumor in the nasopharynx extending certain edge diameter, the nasopharynx, retropharyngeal lymph node area, the slope and the skull base bone structure, pterygopalatine fossa, parapharyngeal space, sphenoid sinus, nasal cavity and maxillary sinus after 1 / 3 should be fully and include given the dose higher than 60Gy; bilateral neck neck or should be classified as high-risk regions of lymph node metastasis, is different from the area and giving prophylactic irradiation dose of at least 60Gy. The imaging scope of cervical lymph nodes should be unified and standardized

 

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