Recurrences after conformal parotid-sparing radiotherapy for head and neck cancer.

BACKGROUND AND
PURPOSE: Evaluation of loco-regional failure patterns and survival after parotid-sparing three-dimensional conformal and intensity modulated radiotherapy (IMRT) for head and neck cancer. PATIENTS AND METHODS: From June 1999 to July 2002, seventy-two patients with lateralised head and neck tumours, excluding nasopharyngeal tumours and patients with bilateral or contralateral neck disease, were irradiated with a parotid-sparing technique. Three-dimensional conformal planning was used in 68 patients, 4 patients were treated with dynamic IMRT. Bilateral neck node irradiation was performed in all patients, the junctional (or high level II) nodes, contralateral to the tumour, however, were excluded from the clinical target volume to spare the adjacent parotid from irradiation. In 20 patients with persistent or recurrent loco-regional disease, the localisation and volume of the treatment failure, as determined by computed tomography (CT), was copied on the pre-treatment CT-study used for treatment planning. Minimum, mean and maximum doses administered to the region of the failure were calculated and dose--volume histograms were computed of each failure. The failures were divided in three groups depending on the percentage of their volume receiving 95% of the prescribed dose. Recurrences were defined to be in-field (IF) if >95% of their volume received 95% of the prescribed dose and out-field (OF) if <20% of their volume received 95% of the prescribed dose. When 20-95% of the volume of the recurrence received 95% of the prescribed dose, this recurrence was defined as extending outside the field (EOF).
RESULTS: With a median follow-up time of 19 months, the 2-year loco-regional control rate was 69% with primary radiotherapy and 63.5% with surgery followed by irradiation (P = 0.77). The 2-year overall survival rate for the entire patient population was 67.4%. At the time of analysis, 20 of the 72 patients had developed a loco-regional failure; 2 patients (2/20) presented with a loco-regional relapse combined with distant metastasis. Fifteen of the 20 loco-regional failures (15/20) occurred within the high dose region (IF). Five patients (5/20) developed a failure of which the bulky tumour mass was located within the high dose region but extending outside the treatment volume (EOF). No relapses were seen out-field (OF) and no patients relapsed in the spared junctional area contralateral to the tumour.
CONCLUSIONS: The selection of patients treated with parotid-sparing radiotherapy, by omitting irradiation to the junctional nodes contralateral to the tumour, proved to be safe in our hands, since no recurrences developed in the spared area. As this parotid-sparing technique reduces significantly the dose to the contralateral parotid and is easy to perform, it should be considered for all selected patients.