Treatment of nasopharyngeal carcinoma using simultaneous modulated accelerated radiation therapy via helical tomotherapy: a phase II study

P67.5 is a single-center, prospective, phase II clinical study, with a registration code of ChiCTR-ONC-14004895. The research ethics board of the Chinese PLA General Hospital approved the study with an official number of S2014-048-01, and all eligible patients provided informed consent in written form.

Inclusion criteria were as follows: histologically proven type I and II NPC according to World Health Organization (WHO) criteria; stage I–IVa according to the Union for International Cancer Control (UICC) 2002 Staging System; aged between 15 and 75 years; Karnofsky performance status score ≥ 70; white blood cell count ≥ 3,500/μL, platelet count ≥ 100,000/μL, serum creatinine concentration < 133 umol/L, and liver transaminase level < 2.0 times of the upper normal value. Exclusion criteria were as follows: distant metastasis; concomitant diseases (heart disease, tuberculosis, etc.) that interfere with the completion of treatment, increase incidence of adverse reactions or influence the prognosis; withdrawal during the treatment or violation of the protocol due to any factors; diagnosed with or treated for other malignances.

Between August 2011 and September 2013, 132 newly diagnosed non-metastatic NPC patients were included in the study. There were 95 males and 37 females. The median age was 47 years old. All patients underwent nasopharyngeal and skull base magnetic resonance imaging (MRI), chest computed tomography (CT), endoscopic evaluation, complete blood counts, hepatic and renal function tests, neck and abdomen ultrasound, and bone scans. Positron emission tomography (PET) was optional. Clinica l stage was practiced according to the UICC 2002 staging system (Table 1).

We compared the preliminary results of the P67.5 study with the retrospective P70 study, in which a dose of 70–74 Gy (2.12–2.24 Gy per fraction) was delivered to the primary tumor (pGTVnx) and metastatic nodes (pGTVnd), 60–62.7 Gy (1.82–1.89 Gy per fraction) to the high risk planning target volume (PTV1) and 52–56 Gy (1.63–1.70 Gy per fraction) to the low risk planning target volume (PTV2), in 33 fractions.³Table 2 summarizes patients’ characteristics in the two studies.

Patients were placed in the supine position and the head and neck immobilized with a thermoplastic mask. Plain and enhanced CT images with 3-mm slice thickness were taken for treatment planning then transmitted to the Pinnacle³ 8.0 workstation and fused. Enhanced CT, MRI or PET images were used as a guide for target contours. Target naming and delineation were consistent with the P70 study³, and CT images together with the contour objects created by the physicians were transferred to Hi Art TomoTherapy 2.2.4.1 workstation. Physicists in the same group designed and verified the treatment plans. The three main parameters of field width, pitch, and modulation factor were set to the same values as in the P70 study.

During HT treatment, all patients underwent megavoltage computed tomography (MVCT) imaging everyday to rectify setup errors. The range of the CT scans typically included the central area of the whole target volume, ensuring that crystals were avoided. Automated and manual registration of the MVCT images with the planning CT images was based on bone and tissue anatomy.

The planned D95 was 67.5 Gy for pGTVnx and pGTVnd, 60 Gy for PTV1 and 54 Gy for PTV2, in 30 fractions. No more than 5% of the PTV received more than 110% of the prescribed dose. The dose-volume constraints for OARs (organs at risk) were the same as the P70 study.³

Biological effective dose (BED) is calculated with linear quadratic (LQ) radiobiological model: BED = nd × [1 + d/(α/β)].⁴ In the formula, “n” represents the number of fractions and “d” fraction dose. The α/β value of tumor tissue or early response normal tissues is 10 Gy and that of late response normal tissues is 3 Gy or 5 Gy. If the impact of overall treatment time (OTT) and tumor proliferation is considered, the adjusted formula is BED = nd × [1 + d/ (α/β)] - γ/α × (T - Tk).⁵ The “γ/α” equals 0.6. “T” and “Tk” represent OTT (including weekends) and 7 days, respectively.

In this study, patients at stage III or IV (including stage II with lymph node metastasis) generally underwent neoadjuvant chemotherapy plus concurrent chemotherapy. Two cycles of neoadjuvant chemotherapy were routinely used, some patients with stage III and IV or whose tumor volume reduced less than 30% had additional 1–2 cycles. One hundred and one patients underwent 1–4 cycles of neoadjuvant chemotherapy with DP (docetaxel 75 mg/m², d1, and cisplatin 75 mg/m², d1, every 3 weeks) according to the primary tumor size or chemotherapy response. In accordance with the physical condition, clinical staging, treatment tolerance, 115 cases underwent two patterns of concurrent chemotherapy: 1) cisplatin 80 mg/m², d1, every 3 weeks; 2) cisplatin 60 mg/² and docetaxel 60 mg/m², d1, every 3 weeks. Concurrent anti-EG-FR Mab treatment (cetuximab with a loading dose of 400 mg/m² and then 250 mg/m² or nimotuzumab 200 mg every week) was used in 45 patients. Adjuvant DP chemotherapy as used in the neoadjuvant setting was administered in 68 patients (range 1–4 cycles, median 1.93 cycles).

Acute side-effects were evaluated weekly and peak toxicities were recorded. Acute and late side-effects were identified according to the established RTOG/EORTC criteria.⁶ The preliminary response was evaluated 1–3 months after the end of radiation therapy based on the Response Evaluation Criteria in Solid Tumors (RECIST) Version 1.1.⁷ Patients received follow-up examinations including nasopharyngeal and skull base MRI, nasopharyngoscopy, neck ultrasound, etc., to evaluate the therapeutic effects every 3 months during the first year, and then every 6 months afterwards. By the end of October 2014, the median follow-up period was 23.7 (12–38) months with a follow-up rate of 100%. Survival analysis was performed with Kaplan-Meier method and Log-rank test was used to evaluate the differences between the 2 studies. Comparison of rates and means between the two groups was performed by Pearson χ² test and t test, respectively. A two-sided value of p < 0.05 was considered significant. The analyses were executed with SPSS 19.0 (Statistical Product and Service Solutions Inc., Chicago, IL).

The prescription dose in the study for tumor targets was 67.5 Gy (2.25 Gy × 30F) with a BED of 82.7 Gy. If the impact of OTT was considered, the adjusted BED would be 62.9 Gy, 0.9 Gy higher than that of the P70 study, and would theoretically result in better tumor control. For normal tissues, radiation doses to both early and late response tissues were lower in this study than in the P70 study (Table 3).

The mean dose (Dmean) to pGTVnx, pGTVnd, PTV1 and PTV2 was 70.2 Gy, 70.1 Gy, 64.9 Gy and 56.7 Gy, respectively (Table 3). Except the Dmean of inner ears and Dmean of both parotid glands, the dose delivered to OARs which generally met the established constrains were significantly lower in the P67.5 study than in the P70 study (Table 4).

All patients completed radiation therapy but one who underwent 27 fractions because of severe gastrointestinal side-effects. One hundred and twenty-four cases finished their radiation therapy in 6 weeks, and radiation therapy was interrupted for 10.9 days on average in 7 patients because of grade 3 acute pharyngitis-esophagitis or hematologic toxicity. Acute radiation related side-effects were mainly problems graded as 1 or 2 with skin, oral mucosa, salivary glands, and pharynx-esophagus. Grade 3 skin toxicities were noted in 7 cases, mucositis in 12 and pharyngitis-esophagitis in 2. Some patients who received neoadjuvant and/or concurrent chemotherapy suffered from different degrees of hematologic toxicities. Distribution of acute side-effects is shown in Table 5. The differences were statistically significant between the incidences of xerostomia and hematologic toxicities of the two studies. At the end of radiation therapy, there was an average weight loss by 10.6%, ranging from 0% to 21.4%.

Late toxicities generally appeared 3 months after radiation therapy and the most common one was xerostomia. Although patients generally had less dry feeling as time passed by and 24 patients had no signs of late xerostomia at all, there were 102 and 6 cases suffering from grade 1 and 2 xerostomia during the follow-up, respectively. The sense of taste diminished in 6 patients and was lost completely in 1 patient. Forty-one patients had audition test abnormal on one side, 30 of whom had no obvious clinical symptoms; however, 12 and 5 cases appeared to have grade 1 and 2 hearing loss, respectively. Fifteen cases developed otitis media that needed surgical treatment. Seventeen patients had a difficulty in opening mouth, and 3 of them had a mouth opening less than a one-finger width. Increased tooth sensitivity occurred in 30 patients; gingival recession in 16 patients; tooth fracture or loss in 10 patients. One 39-year-old female had a menstrual disorder and one female patient had hypothyroidism requiring medical treatment.

At a median time of 1.5 months (at least one month and no more than 3 months) after the end of radiation therapy, evaluation of primary tumors showed that 49 patients had complete responses (CR), 71 partial responses (PR), and 12 stable disease (SD); evaluation of involved nodes in 113 patients showed 42 CR, 62 PR, and 9 SD, with an effective rate of 100%.

Sixteen patients suffered from treatment failure during the follow-up, including 3 local recurrences (2 intra-target recurrences and 1 marginal recurrence), 4 regional recurrences and 9 distant metastases. In the patients with local recurrence, the T3N2M0 case received re-irradiation alone, the T3N0M0 case underwent re-irradiation with concurrent chemotherapy, and the T3N1M0 case refused salvage treatment. All these three patients died of bleeding with a mean survival time of 7.7 (3–10) months from recurrence to death. Among the regional recurrence patients, 3 had a neck node recurrence and 1 had an ipsilateral parotid metastasis; these patients underwent re-irradiation, chemotherapy, concurrent chemo-radiotherapy and brachytherapy respectively and were all alive throughout the follow-up. Distant metastasis was the most common failure pattern and the most common distant organs involved were liver (4 cases), lung (2 cases), bone (2 cases), and liver-lung (1 case). Seven of the 9 cases received chemotherapy, of whom 2 had also concurrent Anti-EGFR Mab treatment (4 cases died, 3 cases alive); and the other 2 cases had no salvage treatment and died in 4 and 7 months, respectively (Table 6). The local relapse-free survival (LRFS), nodal relapse-free survival (NRFS), local-nodal relapse-free survival (LNRFS), distant metastasis-free survival (DMFS) and overall survival (OS) were 96.7%, 95.5%, 92.2%, 92.7% and 93.2%, at 2 years, respectively, with no significant difference compared with the P70 study.