Accuracy of methionine-PET in predicting the efficacy of heavy-particle therapy on primary adenoid cystic carcinomas of the head and neck.

BACKGROUND: We evaluated whether or not PET or PET/CT using L-methyl-[11C]-methionine (MET) can allow for the early prediction of local recurrence and metastasis, as well as the prognosis (disease-specific survival), in patients with adenoid cystic carcinoma of the head and neck treated by carbon ion beam radiotherapy. METHODS: This was a retrospective cohort study of sixty-seven patients who underwent a MET-PET or PET/CT study prior to and one month after the completion of carbon ion radiotherapy (CIRT). The minimum follow-up period for survivors was 12 months. The MET accumulation of the tumor was evaluated using the semiquantitative tumor to normal tissue ratio (TNR). A univariate analysis was conducted using the log-rank method, and the Cox model was used in a multivariate survival regression analysis. RESULTS: The average TNR prior to and following treatment was 4.8 (±1.5) and 3.0 (±1.3), respectively, showing a significant decrease following treatment. In the univariate analysis, a high TNR prior to treatment (TNRpre) was a significant factor for predicting the occurrence of metastasis and the disease-specific survival. A high TNR following treatment (TNRpost) was a significant factor for predicting the development of local recurrence. The residual ratio of TNR changes (TNRratio) seemed to be less useful than the TNRpre. In the multivariate analysis, the TNRpost and tumor size were the factors found to significantly influence the risk of local recurrence. The TNRpre, TNRratio and tumor size were all significant factors influencing the occurrence of metastasis. Regarding the disease-specific survival, the TNRpre and age were the only factors with a significant influence on the outcome. CONCLUSIONS: The TNRpre was a factor that was significantly related to the occurrence of metastasis and the disease-specific survival after CIRT for adenoid cystic carcinoma of the head and neck. The TNRpost was a factor that was significantly related to the development of local recurrence. Thus, MET-PET or PET/CT can be useful for predicting or determining the therapeutic efficacy of CIRT.

A study on the prognostic evaluation of carbon ion radiotherapy for head and neck adenocarcinoma with C-11 methionine PET.

PURPOSE: Carbon ion radiotherapy (CIRT) has been developed, and a phase I/II CIRT trial has been conducted in patients with adenocarcinoma in the head and neck region. We evaluated whether the L-methyl [11C]-methionine (MET) uptake could be an early predictor for local recurrence, metastasis, and the prognosis in patients with adenocarcinoma in the head and neck region. METHODS: Twenty-six patients were prospectively studied by MET-positron emission tomography (PET) before and about 1 month after CIRT. The tumor MET uptake was measured with the semiquantitative tumor to normal tissue ratio (TNR). The tumor TNR and relevant clinical parameters were then evaluated by both univariate and multivariate analyses. RESULTS: The average TNRs before and after the treatment were 6.2 (± 2.2) and 3.9 (± 1.7), respectively, and significant differences were observed between them. In a univariate analysis, both local recurrence and metastasis were observed more frequently in the group with a higher TNR before and after the treatment than a lower TNR, and the prognosis was also poor. The cut-off values were 9.3, 4.9, and 5.1 before the treatment and 4.9, 4.2, and 4.3 after the treatment, respectively. In the rate of TNR changes before and after the treatment, metastasis was observed more frequently in the group with lower rates of change, and the prognosis was poor. The cut-off values for metastasis and prognosis determination were 18.0% and 16.9%, respectively. In a multivariate analysis, significant differences were observed for all relationships except for the relationship between the TNR before the treatment and local recurrence. Significant differences were observed for metastasis and prognosis in the rate of TNR changes before and after the treatment. CONCLUSIONS: The determination of treatment effectiveness using TNR in CIRT for head and neck adenocarcinoma is an independent factor for predicting local recurrence, the incidence of metastasis, and the prognosis. MET-PET is therefore considered to be useful for determining the treatment effectiveness in patients with head and neck adenocarcinoma undergoing CIRT.

11C-methionine-PET for evaluation of carbon ion radiotherapy in patients with pelvic recurrence of rectal cancer.

PURPOSE: Progress of the novel carbon ion radiotherapy (CIRT) in the treatment of cancers has created the need for a method to accurately evaluate the response. We investigated whether L-[11C]methyl-methionine (11C-methionine) uptake at pre- and post-CIRT could be an early response predictor in patients with pelvic recurrence of rectal cancer. PROCEDURES: 11C-Methionine-positron emission tomography (PET) was performed prospectively in 53 patients with pelvic recurrence of rectal cancer before CIRT, and 48 patients were performed 11C-methionine PET at 1 month after CIRT. 11C-Methionine tumor uptake was measured by the tumor to muscle ratio (T/M ratio). The T/M ratios were evaluated in relation to clinical outcomes such as local re-recurrence, distant metastasis, and survival. The response to CIRT was also judged by computed tomography (CT) and magnetic resonance imaging (MRI). 11C-Methionine PET judgment was compared with CT/MRI judgment regarding the relevance to clinical outcome. RESULTS: Baseline T/M ratio was 5.27+/-1.90 (mean+/-SD) in patients without developing local re-recurrence and 7.66+/-3.17 in patients with local re-recurrence (p=0.023, Mann-Whitney U test). Post-CIRT T/M ratios were 3.10+/-1.28 in patients without local re-recurrence and 6.15+/-2.98 in patients with local re-recurrence (p=0.006, Mann-Whitney U test). By Kaplan-Meier analysis with log-rank test, patients with a baseline T/M ratio of