Analysis of simultaneous modulated accelerated radiotherapy (SMART) for nasopharyngeal carcinomas

Six fractions weekly as accelerated fraction radiotherapy: Is it applicable for nasopharyngeal cancer? A review

Standard therapy for nasopharyngeal cancer (NPC) is concurrent chemoradiation. Nevertheless, therapeutic outcomes are often unsatisfactory particularly for locally advanced stage. To enhance the therapeutic outcome, we may consider using altered fraction radiotherapy. Altered fraction radiotherapy is divided into two large groups for the therapy of NPC: hyperfraction radiotherapy and accelerated fraction radiotherapy. One of the accelerated fraction regimens suitable for NPC therapy is an accelerated regimen of six radiotherapy fractions weekly. This regimen is considered safe whether using conventional 2D planning technique or advance technique. Response to radiotherapy is better owing to the decrease in overall treatment time (OTT). Furthermore, acute or late side effects for this therapy are not very different to those of standard therapy. The conclusion is that we recommend the use of an accelerated regimen of six radiotherapy fractions weekly for locally advanced stage NPC with contraindication to concurrent chemoradiation, due to the high degree of clinical outcome as well as better tolerated side effect for NPC patients, particularly for those with locally advanced stage NPC.

Dosimetric Effects of Head and Neck Immobilization Devices on Multi-field Intensity Modulated Radiation Therapy for Nasopharyngeal Carcinoma

Background: In practice, the dose perturbation effect of head and neck immobilization devices is often overlooked in intensity-modulated radiation therapy (IMRT) for nasopharyngeal carcinoma (NPC). Purpose of this study is to verify and analyze the dosimetric effect of head and neck immobilization devices on NPC multi-field IMRT. Methods: Ten patients with nasopharyngeal carcinoma were randomly selected. Two sets of body contours were established for each patient. One set of body contours did not contain the immobilization device, and the other contour set included the immobilization device. For each patient, dose calculations were conducted for the two sets of contours using the same 9-field IMRT plan, which were recorded as Plan- and Plan+. The dose difference caused by the head and neck immobilization devices was assessed by comparing the dose-volume histogram (DVH) parameter results and by plan subtraction. The gafchromic EBT3 film and anthropomorphic phantom were used to verify the calculated doses. Results: The target coverage and average dose of Plan+ were lower than those of Plan- : the prescription dose coverage rates for PTVnx, PTVnd, PTV1 and PTV2 decreased by 2.4%, 9.9%, 1.5%, and 3.6%, respectively, and the mean doses were reduced by 0.9%, 1.9%, 1.1%, and 1.5%, respectively. Doses in the organs at risk showed no significant differences or slight reductions (the maximum reduction in mean dose was 1.7%). From the EBT3 measurements, the skin dose on the posterior neck was increased by approximately 53%. Conclusion: The attenuation and bolus effects of the head and neck immobilization device reduce dose coverage rate and average dose of the planning target volumes in nasopharyngeal carcinoma and lead to an increase in the skin dose. During treatment planning and dose calculation, the immobilization device should be included within body contour to account for the dose attenuation and skin dose increment.

A randomized phase III study between sequential versus simultaneous integrated boost intensity-modulated radiation therapy in nasopharyngeal carcinoma

PURPOSE

This study was performed to compare the acute and late toxicities between sequential (SEQ) and simultaneous integrated boost (SIB) intensity-modulated radiotherapy (IMRT) in nasopharyngeal carcinoma (NPC).

MATERIALS AND METHODS

Stage I-IVB NPC patients were randomized to receive SEQ-IMRT or SIB-IMRT. SEQ-IMRT consisted of two plans: 2 Gy × 25 fractions to low-risk planning target volume (PTV) followed by a sequential boost (2 Gy × 10 fractions) to high-risk PTV, while SIB-IMRT treated low- and high-risk PTVs with doses of 56 and 70 Gy in 33 fractions. Toxicities and survival outcomes were analyzed.

RESULTS

Between October 2010 and September 2015, of the 209 patients who completed treatment, 102 in the SEQ and 107 in the SIB arm were analyzed. The majority had undifferentiated squamous cell carcinoma (82%). Mucositis and dysphagia were the most common grade 3-5 acute toxicities. There were no statistically significant differences in the cumulative incidence of grade 3-4 acute toxicities between the two arms (59.8% in SEQ vs. 58.9% in SIB; P = 0.892). Common grade 3-4 late toxicities for SEQ and SIB included hearing loss (2.9 vs. 8.4%), temporal lobe injury (2.9 vs. 0.9%), cranial nerve injury (0 vs. 2.8%), and xerostomia (2 vs. 0.9%). With the median follow-up of 41 months, 3‑year progression-free and overall survival rates were 72.7 vs. 73.4% (P = 0.488) and 86.3 vs. 83.6% (P = 0.938), respectively.

CONCLUSION

SEQ and SIB provide excellent survival outcomes with few late toxicities. According to our study, SIB with a satisfactory dose-volume constraint to nearby critical organs is the technique of choice for NPC treatment due to its convenience.

Knockdown of LMP1-induced miR-155 sensitizes nasopharyngeal carcinoma cells to radiotherapy in vitro

The present study aimed to confirm the promotion of microRNA (miR)-155 expression by latent membrane protein 1 (LMP1), and to recognize the oncogenic role of LMP1 and LMP1-promoted miR-155 in nasopharyngeal carcinoma (NPC), particularly the influence of miR-155 knockdown on the radiosensitivity of CNE-2 cells. Following the regulation of the levels of LMP1 or miR-155 and/or subsequent to radiation treatment, the proliferation ability of CNE-2 cells was examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation and Cell Counting Kit-8 assays. The results demonstrated that miR-155 was upregulated by overexpression of LMP1 in CNE-2 cells, and LMP1 overexpression and miR-155 mimic transfection increased CNE-2 cell proliferation, whereas miR-155 knockdown attenuated the promotion of CNE-2 cell growth induced by LMP1 overexpression. Furthermore, knockdown of miR-155 enhanced the radiosensitivity of CNE-2 cells. In conclusion, the present study confirmed the oncogenic role of miR-155 in NPC, and demonstrated that knockdown of miR-155 inhibited the growth of NPC cells and sensitized NPC cells to radiotherapy.