by Dr. C.H. Weaver M.D. updated 11/2018
With the use of combined modality therapy, and newer precision cancer medicines the clinical outcomes for treatment of head and neck cancer (HNC) have improved dramatically over the past two decades.
The use of aggressive combined modality therapy however is associated with increased acute side effects. Some of the most common associated with chemo-radiation include mucositis, xerostomia, dysphagia and nutritional deficits.
With the increased use of targeted therapies including PD-1 checkpoint inhibitors, the side effect profile appears to be changing again.
In addition late side effects of therapy have begun to garner increased attention as more patients are surviving longer. Function preservation remains one of the most important late outcome measures in the head and neck patient population.
Epidermal Growth Factor Inhibitor Side Effects
The EGFR pathways are responsible for maintaining skin, hair and nail integrity. When these pathways are blocked, the normal repairative pathways are inhibited. Thus, patients treated with Erbitux and other EBFR inhibitors experience skin, hair and nail toxicities. While these are usually modest and frequently cosmetic in nature, they are unsightly and bothersome to patients.
What is Xerostomia?
Xerostomia, also known as dry mouth is dryness in the mouth which may be associated with a change in the composition of saliva or reduced salivary flow
Xerostomia remains one of the most significant acute and late effects of radiation therapy. Although chemotherapy may in and of itself result in modest levels of xerostomia, the xerostomia secondary to radiation is more severe and long lasting. It occurs shortly after the institution of radiation therapy and results in profound and often permanent damage to salivary function. Some research suggests that salivary loss is related to the dose of radiation delivered to the salivary gland. Thus, doctors have tried to develop radiation techniques that limit dose to the salivary gland may result in decreased loss of salivary function.
Intensity-modulated radiation therapy (IMRT) is an advanced type of radiation therapy used to treat cancer. IMRT uses advanced technology to manipulate photon and proton beams of radiation to conform to the shape of a tumor and limit side effects to adjacent tissues.
Research confirms the ability of IMRT to effectively limit radiation to the salivary gland thereby limiting permanent loss of salivary gland function. For example, 84 patients with nasopharyngeal cancer were treated with IMRT or conventional radiation and compared. Twenty-five patients in each arm were asked to participate in a prospective salivary function assessment. Participating patients were tested for whole and stimulated salivary flow at baseline, and 2, 6, and 12 months post treatment. Results demonstrated decrease in salivary flow after completion of treatment with both IMRT and conventional radiation. By 12 months post-treatment, patients treated with IMRT had return of whole and stimulated salivary flow to 26% and 114% of baseline levels respectively. For patients treated with conventional radiation therapy, the 12 month post treatment whole and stimulated salivary flow was 5% and 0% of baseline. The difference was statistically significant at all post treatment time points favoring IMRT.
Mucositis is one of the most devastating acute effects of radiation-based therapy for head and neck cancer. With the increasing use of concurrent chemoradiation, the rates of mucositis have increased dramatically.
Anemia - Growth Factors
Patients with head and neck cancer frequently present with anemia. Numerous studies in head and neck cancer patients have demonstrated that pre-treatment anemia is associated with decreased survival.10 In addition, patients treated with radiation therapy may develop anemia over the course of therapy. This is most prominent in patients receiving concurrent chemotherapy. Thus, erythroid stimulating agents have been investigated to determine whether they can decrease anemia, decrease transfusions, and most importantly, increase survival.
The greatest recent advances in functional preservation are in the treatment of laryngeal and vocal cord cancers. Use of the KTP laser, which eradicates blood vessels in a process called photoangiolysis is especially effective in treating vocal-cord cancer. Since radiation can damage the non-cancerous tissue of one or both vocal cords and conventional laser surgery destroys more delicate vocal tissue than is necessary, KTP laser treatment typically produces better vocal results while being more cost-effective according to the results of a recent report.
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