Kam Y. Lau

Potential improvement of tumor control probability by induction chemotherapy for advanced nasopharyngeal carcinoma

PURPOSE To assess the reduction of tumor bulk and improvement of tumor control probability (TCP) by using induction chemotherapy for advanced nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS From February to December 2005, 20 patients with Stage III-IVB NPC were treated with induction-concurrent chemotherapy and intensity-modulated radiotherapy with accelerated fractionation. Combination of cisplatin and 5-fluorouracil was used in the induction phase and single agent Cisplatin in the concurrent phase. All patients were irradiated at 2Gy per fraction, 6 daily fractions per week, to a total dose of 70Gy. RESULTS Nineteen (95%) patients completed all 3 cycles of induction chemotherapy and 90% had 2 cycles of concurrent chemotherapy. Induction chemotherapy achieved significant down-staging of T-category in 35% of patients (p=0.016) and reduction of gross tumor volume (GTV_P) from 55.6 to 22.9cc (mean 61.4%, p<0.001). Although the mean radiation dose did not show any substantial change, the volume within GTV_P that failed to reach 70Gy was reduced from 10.2% to 3.8% (p=0.017). The estimated local TCP increased from 0.83 to 0.89 (p=0.002). CONCLUSIONS Induction chemotherapy using cisplatin-5-fluorouracil could significantly reduce tumor bulk leading to potential improvement in tumor control.

Parapharyngeal Extension of Nasopharyngeal Carcinoma: Still a Significant Factor in Era of Modern Radiotherapy?

PURPOSE To retrospectively analyze the prognostic value of parapharyngeal space (PPS) extension after conformal radiotherapy for nasopharyngeal carcinoma. PATIENTS AND METHODS Between 1998 and 2005, 700 patients were treated with conformal radiotherapy at 2 Gy/fraction daily to a total of 70 Gy. All patients underwent staging with magnetic resonance imaging. The incidence of PPS was determined, and the extent of involvement was further subclassified regarding the presence or absence of carotid space (CS) involvement. The prognostic parameters, including age, gender, stage, chemotherapy, additional boosting, and extent of PPS involvement, were analyzed by univariate and multivariate analyses. RESULTS The median duration of follow-up was 51 months, and the 5-year overall survival rate for the whole group was 73%. The overall incidence of PPS extension was high (74%), and 29% had additional extension to the CS. Multivariate analysis showed age, gender, chemotherapy, T stage, and N stage to be significant prognostic factors, but not PPS involvement with or without CS extension. In the subgroup of patients with Stage T2 disease (n = 242), the presence of PPS involvement alone or PPS plus CS extension had no statistically significant effect in terms of local control (p = 0.68), distant metastases (p = 0.34), or overall survival (p = 0.24) compared with those without PPS involvement (Stage T2a). CONCLUSIONS With better tumor delineation by magnetic resonance imaging and improved coverage using modern radiotherapy techniques, PPS extension per se no longer predicts for disease outcome. Hence, subcategorizing Stage T2 disease is no longer important in future International Union Against Cancer/American Joint Committee on Cancer classifications.

Association of diffusion weighted imaging abnormalities and recurrence in transient global amnesia

Since the first description of transient global amnesia (TGA) in 1964, its etiology has remained obscure. Reversible diffusion weighted imaging (DWI) hyperintensities in the hippocampus have been found on MRI of some patients with TGA during acute events. The implication of this is not well understood. We identified 47 patients with TGA between November 2004 and November 2009, and enrolled 27 patients with brain MRI within 72 hours of symptom onset for analysis and recorded subsequent relapse or stroke occurrence during follow-up. Nine of the 27 patients had reversible hippocampal punctuate hyperintensities, with complete resolution noted on a second MRI on average 4 months after the initial TGA. Patients with a first relapse (their second TGA attack) had a significantly higher association of DWI hippocampal abnormalities (p=0.03) compared to patients with their first TGA event. None of the 27 patients had a stroke or further relapse during the mean follow-up period of 32.6 months. Thus, patients with recurrent TGA have a significantly higher association of reversible DWI abnormality.