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Results of a phase III multi-centre randomised controlled trial of intensity modulated (IMRT) vs conventional radiotherapy (RT) in head and neck cancer (PARSPORT: ISRCTN48243537; CRUK/03/005)

Chris Nutting

Royal Marsden Hospital, London, UK

Background
Xerostomia is the commonest late toxicity of RT to the head and neck. IMRT dose distributions reduce the dose delivered to parotid gland. PARSPORT investigated the role of IMRT in reducing xerostomia in patients with head and neck cancer.

Method
The PARSPORT trial compared two radiotherapy delivery methods in the treatment of patients with pharyngeal tumours (T1-4, N0-3, M0).  Patients received 65Gy in 30 fractions over 6 weeks delivered using either CT planned parallel opposed lateral fields or parotid-sparing IMRT.  Stratification was by site of tumour and centre. The primary endpoint was incidence of LENT-SOMA ≥G2 xerostomia one year after treatment. Secondary endpoints included acute toxicities (CTCAE v3) and other late RTOG and LENT-SOMA radiation toxicities.  Saliva collection was attempted from both parotid glands. Proportions of patients with ≥G2 toxicity were compared using exact tests.  For secondary endpoints a significance level of 1% was used.

Results
94 patients (47 RT; 47 IMRT) were randomised between 2003 and 2007 from six UK centres.  80 patients had oropharyngeal tumours and 14 hypopharyngeal.  Radiotherapy was given as primary treatment in 71 patients and post-operatively in 23.  22 patients had AJCC stage I/II disease.  Median follow-up was 31.9 months (IQR: 23.6 – 38.8).  Twelve month LENT-SOMA ≥G2 xerostomia scores were observed in 74% (25/34) of RT and 39% (15/38) of IMRT patients (p=0.004). Corresponding values at 18 months were 71% (15/21) and 29% (9/31) (p=0.003). On the RTOG scale, 12 month ≥G2 xerostomia was reported in 64% (21/33) RT vs 41% (15/37) IMRT patients (p=0.05).  The 18 month incidence was 81% 17/21 RT vs 20% (6/30) IMRT (p<0.001).  Acute radiotherapy related ≥G2 fatigue was more prevalent in the IMRT group (76% vs 41% p=0.001).  No differences in acute mucositis or pain scores were seen.  At 12 months, no statistically significant differences were seen in other late toxicities.  Sialometry measurements confirm the LENT-SOMA outcome with 18% (3 months), 33% (6 months) and 24% (12 months) of patients having contralateral measurable saliva in the IMRT arm compared with 0% at each time point in the conventional RT arm (p=0.008 at 12 months).  No differences were observed between overall survival and locoregional control rates.

Conclusion
Sparing the salivary glands through use of IMRT preserves salivary flow and significantly reduces the incidence of xerostomia in patients with pharyngeal tumours.