RADIOTHERAPY FOR NASOPHARYNGEAL CARCINOMA - SHIELDING THE PITUITARY MAY IMPROVE THERAPEUTIC RATIO

Purpose: Nasopharyngeal carcinoma (NPC) is well known for its invasive ness and erosion of the base of the skull is not uncommon. Before the advent of computed tomography, the evaluation of the base of the skull was by plain radiography. Because of the low sensitivity of these inv estigations, traditional teaching has included the sphenoid sinus in t he volume of irradiation. Increase in longevity of patients allows the manifestation and documentation of the long-term sequelae of irradiat ing the hypothalamic-pituitary axis and the temporal lobes. This study is an attempt to evaluate whether the hypothalamic-pituitary axis can be shielded from the target volume in a proportion of NPC patients. M ethods and Materials: One hundred fifty-two NPC patients with no evide nce of erosion of the base of the skull and sphenoid, nor extension to the nasal fossa and ethmoid sinuses were randomized to receive standa rd radiotherapy covering the whole sphenoid sinus or radiotherapy usin g a modified technique that shields the pituitary and the anterior par t of the hypothalamus. This modified technique also shields a large pa rt of the lower temporal lobes that are otherwise covered by standard treatment portals. The characteristics and treatment of the two subgro ups of patients were otherwise comparable. Results: At a median follow -up of 31.5 months, the tumor control between the two subgroups of pat ients were comparable (p = 0.3928). However, 8 of the 71 patients in t he unshielded group had developed symptomatic neuroendocrine complicat ions, while none of the other group did (p = 0.0061). Two patients dev eloped secondary hypothyroidism, one patient developed oligomenorrhoea associated with raised prolactin, and five patients developed tempora l lobe necrosis. Conclusions: The protective effect on neuroendocrine complication of this shield was demonstrated at median follow-up of 31 .5 months, and the local control was not jeopardized. Modification of treatment technique as presently described, which is applicable to one -third of NPC patients to improve the therapeutic ratio, is recommende d for general use.