By Chris Berrie
BERLIN -- September 30, 2009 -- Intensity-modulated radiotherapy (IMRT) significantly reduces risk of subjective xerostomia compared with conventional RT (CRT) in patients with pharyngeal cancers, according to a study presented here at the joint 15th Congress of the European Cancer Organisation (ECCO) and 34th Congress of the European Society for Medical Oncology (ESMO).
Although RT for head and neck cancer is frequently curative, it can be accompanied by significant long-term side effects. One such problem can be xerostomia, which leads to reduced speech and swallowing functions, accelerated dental caries, and osteoradionecrosis.
"Intensity-modulated radiotherapy produces complex dose distributions which can reduce the dose to salivary glands," said principal investigator Christopher Nutting, MD, Royal Marsden Hospital Foundation Trust, London, United Kingdom, on September 24. This parotid-sparing IMRT can thus allow maintained saliva production.
The multicentre, randomised, controlled phase 3 Parotid Sparing Intensity-Modulated Radiotherapy (PARSPORT) study included 94 patients with confirmed squamous cell carcinoma of the head and neck, with an oropharynx or hypopharynx location.
Patients were randomised to receive CRT or parotid-sparing IMRT. Baseline characteristics were similar between groups.
The primary endpoint was incidence of late effects in normal tissues subjective, objective, management and analytic scales (LENT-SOMA) >=G2 xerostomia at 1 year post-RT. Secondary endpoints were acute and late radiation toxicity, overall survival (OS), quantitative saliva flow, and quality of life.
The mean RT dose for radical treatments provided 65 Gy for both treatment arms; with CRT, this gave the contralateral parotid a mean dose of 60 Gy, which was reduced to 26 Gy with IMRT. "A similar pattern of radiation dose delivery was seen in postoperative patients, with the mean dose for the contralateral parotid of 27 Gy," Dr. Nutting added.
Incidence of >=G2 acute toxicity during and up to 8 weeks post-RT was according to Common Toxicity Criteria for Adverse Events v3.0 grading. Significant reductions over CRT were seen for IMRT for (respectively) salivary gland (95% vs 80%; P = .03); rash (93% vs 76%; P = .02); and dry mouth (91% vs 71%; P = .02). Fatigue was seen to increase with IMRT: 41% versus 76% (P < .01).
For the primary endpoint, at 1 year, LENT-SOMA >G2 xerostomia scores were observed in 74% of RT-treated patients and 39% of IMRT-treated patients (P = .004), with increasing benefit seen through the treatment period to 18 months.
There were no significant differences between CRT and IMRT for late toxicities, for 1-year OS (90.8% vs 93.6%), and for 1-year locoregional progression-free survival (88.0% vs 87.3%).
IMRT significantly reduces the risk of subjective xerostomia by about 50% for patients with pharyngeal cancers, although acute radiation fatigue was more prevalent with IMRT, potentially due to low-dose irradiation of normal tissue, Dr. Nutting indicated.
While further follow-up is required to define the maximum benefit of IMRT, "These data support the use of IMRT as the standard of care for head and neck cancer patients," he said.
[Presentation title: First Results of a Phase III Multicenter Randomized Controlled Trial of Intensity Modulated Versus Conventional Radiotherapy (RT) in Head and Neck Cancer. Abstract G4]
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