In the present study, the treatment method was recognized as a prognostic factor in patients with MSSCC, while treatment-related adverse effects were similar in the two groups. The CRT group underwent superselective and retrograde chemotherapy. An angiography-assisted CT scan could confirm that the entire tumor volume was covered in both methods of chemotherapy. To discuss differences between the groups, the infusion speed was compared. However, since there was no detailed information in the patients’ medical records, the next step was to validate the infusion speed in trans-arterial administrations. Five and three patients relapsed in the CRT and S groups, respectively. All five patients with tumor recurrence in the S group expired despite additional second-line therapies. In contrast, two out of three patients with relapse in the CRT group survived after surgical resection. Therefore, intra-arterial chemoradiotherapy was proposed as a definite treatment for MSSCC, providing improved outcomes as compared to chemoradiotherapy followed by surgery.
Although we cannot exclude the possibility of selection bias, the patients exhibited improved five-year OS and PFS rates. In this regard, Nishimura et al. (
19) reported a five-year OS rate of 59.2% in 40 patients with locally advanced MSSCC treated with CRT. Similarly, Hayashi et al. (
8) reported a five-year OS rate of 68.5% and a local control (LC) rate of 84% in 62 MSSCC patients, treated with multi-modality therapy. Additionally, Nibu et al. (
20) reported a five-year OS rate of 74% in 33 MSSCC patients treated with preoperative chemoradiotherapy, surgery, and postoperative radiotherapy. The five-year OS rate reported in the present study (93%) suggests that CRT has more clinical advantages than treatment methods used in previous studies.
To increase the intensity of therapy locally for MSSCC patients, several researchers have used high-dose intra-arterial chemoradiotherapy. In this regard, Kaneko et al. (
21) reported that intra-arterial chemoradiotherapy with weekly low-dose cisplatin led to a five-year LC rate of 63.0% and a five-year OS rate of 75% in MSSCC patients. Similarly, Yoshimura et al. (
22) reported a five-year OS rate of 63% in 110 MSSCC patients treated with radiotherapy, intra-arterial chemotherapy, and antrotomy.
Moreover, Homma et al. (
23) showed that the five-year local progression survival and five-year OS rates were 65.8% and 67.9% in MSSCC patients treated with intra-arterial cisplatin infusion and concomitant radiotherapy, respectively. They also conducted a dose-escalation study to determine the optimal dose of cisplatin for intra-arterial chemoradiotherapy (
24). In the present study, intra-arterial infusion using a superselective catheter allowed for the administration of a high dose of cisplatin. Besides, the use of CT-assisted monitoring ensured the coverage of the entire tumor, contributing to improved clinical outcomes using CRT. Overall, surgical interventions were significantly associated with a poor prognosis.
Several studies have demonstrated that nodal involvement is not a significant predictive factor for neck cancer relapse (
25,
26). Consistently, in the current study, nodal involvement was not a significant predictive factor for recurrence. Considering the limited lymph drainage through the emissary veins, neck lymph node involvement can suggest high tumor invasiveness. Further studies are required to elucidate the significance of nodal involvement in the recurrence of MSSCC.
In the present study, no patients treated with CRT alone developed adverse effects (grade 4 toxicity or higher). In this regard, Rasch et al. (
14) reported that the frequency of grade 2 renal toxicity (or higher) was significantly lower in patients treated with intra-arterial CRT. One patient suffered from grade 2 renal dysfunction, which was temporary. Also, one patient in the CRT group developed facial nerve palsy after chemoinfusion. Moreover, Sugiyama et al. (
27) showed that cisplatin infusion into the middle meningeal artery (MMA) resulted in facial nerve palsy, because the feeding artery of the facial nerve arises from the petrosal branch of MMA. In the current study, to minimize the likelihood of facial nerve palsy, the chemotherapeutic agents were infused in the second portion of the maxillary artery, as maxillary sinus carcinoma extended to the lateral pterygoid muscle. However, this adverse event is limited to superselective chemotherapy, and it is preventable with an accurate knowledge of MMA anatomy.
The main limitations of this study were the retrospective design and several possible biases. To deal with the effect of bias, statistical analysis was performed using a Cox proportional-hazards model, which is a multivariate analysis. Moreover, the baseline characteristics of the patients could vary depending on many factors, such as chemotherapeutic agents and intra-arterial chemotherapy techniques. However, this study revealed that the therapeutic transition was not distressing for the patients, because the OS rate improved based on the comparison of the CRT and S groups. Finally, despite the ability of superselective CRT to improve the outcomes, the superselective intra-arterial infusion of chemotherapeutic agents is technically challenging; this problem could be overcome by the appropriate technical training of physicians and the improvement of catheters and guidewires. Overall, a multi-institutional phase III trial is needed to demonstrate the effectiveness of intra-arterial chemotherapy in patients with advanced MSSCC.
In conclusion, patients in the CRT group showed significantly prolonged OS rates compared to the S group. The definitive intra-arterial chemoradiotherapy increased the OS of patients with advanced MSSCC, based on a multivariate analysis. In the future, we will conduct a phase II clinical trial for a comprehensive comparison of CRT and S groups.