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Objective:To investigate the feasibility of individualized primary clinical target volume (CTV) delineation in intensity-modulated radiotherapy for nasopharyngeal carcinoma (NPC).Methods:Clinical data of 87 consecutive patients newly diagnosed with lateralized NPC in Jiangsu Cancer Hospital between October 2016 and February 2018 were retrospectively analyzed. Lateralized NPC is defined as tumor invasion not exceeding the contralateral wall. According to the tumor spread, the primary CTV was optimized as follows: CTV2 only covered the medial part of the contralateral pterygopalatine fossa, whereas the contralateral foramen oval was not included; on the level of parapharyngeal space, the contralateral side of CTV only covered the posterior lateral lymph nodes, whereas the contralateral internal jugular vein was not regularly covered. Failure patterns and 5-year survival [local control rate (LCR), progression-free survival (PFS) and overall survival (OS)] were evaluated by Kaplan-Meier method. Paired t-test and rank-sum test were used to analyze the dose variation in the optimized region and adverse reactions. Results:The median follow-up time was 59.5 months. The 5-year LCR, PFS, and OS were 98.9%, 86.5% and 92.1%, respectively. There was no local recurrence in the optimized area of CTV. Dosimetric comparison results showed that the doses of parotid gland, temporal lobe, cochlea and middle ear on the contralateral side were reduced by 13.45%, 9.14%, 38.83%, and 29.36%, respectively. Four cases (4.6%) developed grade 3 hearing loss, all on the ipsilateral side. The optimized scheme significantly alleviated the hearing loss on the contralateral side compared to that on the ipsilateral side ( P<0.001). Other grade 3 late adverse reactions included cranial nerve injury, subcutaneous fibrosis in the neck and visual impairment, with 1 case each. Conclusion:Individualized primary CTV for lateralized NPC is feasible and safe, with obvious dosimetric advantages and reduced adverse reaction rate, which is worthy of clinical promotion.
RESUMO
Objective:To determine the safety of prophylactic irradiation dose CTV 60Gy optimized to CTV 50Gy for II b region in patients with stage N 0-N 1 nasopharyngeal carcinoma (NPC) and the dose advantage and clinical value for parotid gland protection, and to understand the diagnostic value of PET-CT and diffusion-weighted imaging (DWI) for suspicious positive lymph nodes in the neck (5 mm≤maximum short diameter<10 mm). Methods:Clinical data of 157 patients with primary non-metastatic NPC (N 0-N 1) admitted to our hospital from June 2015 to March 2017 were retrospectively analyzed. 104 patients underwent II b clinical target volume optimization guided by multimodal imaging system. Survival analysis was performed by Kaplan - Meier method. Univariate/multivariate regression analysis was performed to analyze the pattern of cervical lymph node recurrence. Paired t-test was used to compare the differences in target volume and parotid gland dose parameters before and after dose optimization. Results:Sixty patients underwent single-neck optimization in stage N 1, 25 patients received double-neck optimization (only those with retropharyngeal lymph node metastasis), and 19 patients underwent double-neck optimization in stage N 0. Three patients had cervical regional recurrence, all in-field. The 5-year overall survival rate was 93.3%. The lymph node recurrence-free survival rate, local recurrence-free survival rate, distant metastasis-free survival rate and disease-free survival rate were 97.1%, 91.3%, 88.5% and 80.8%, respectively. Cervical lymph node recurrence was associated with local recurrence in the nasopharynx, regardless of retropharyngeal lymph node status. Fourteen patients had suspicious positive cervical lymph nodes in II b region, with a mean maximum short diameter of 7.1 (5~9) mm on the largest cross-sectional plane, and 11 of them were positive on PET-CT, with a mean SUV max of 2.96 (2.5~3.3). There was no significant difference in GTV after optimization ( P>0.05). D mean, D max, D 50% and V 26Gy of parotid gland were significantly lower than those of conventional plan (all P<0.01). Conclusions:It is safe to optimize CTV 60Gy to CTV 50Gy in II b region in patients with N 0-N 1 NPC, and the exposure dose to normal tissues around the parotid gland and neck is significantly reduced. For small lymph nodes that do not meet the diagnostic criteria, it needs to be individualized in combination with multimodality imaging systems, such as PET-CT and DWI.