Dose to the Larynx Predicts for Swallowing Complications Following IMRT and Chemotherapy

Reviewer: Eric Shinohara MD, MSCI
Abramson Cancer Center of the University of Pennsylvania
Ultima Vez Modificado: 30 de octubre del 2007

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Presenter: Hale B. Caglar, MD
Presenter's Affiliation: Head and Neck Oncology Program Dana-Farber Cancer Institute/Brigham and Women's Hospital, Boston, MA
Type of Session: Scientific

Background

  • The combination of chemotherapy and radiation therapy has improved survival and local control outcomes in patients with head and neck cancer. However, there has been an accompanying increase in toxicity with combined treatment. 
  • Aspiration and strictures can lead to further comorbidities such as aspiration pneumonias and permanent feeding tubes. Permanent feeding tubes and swallowing dysfunction can seriously affect patients’ quality of life.
  • The present study was designed to evaluate swallowing function after chemotherapy and radiation and to determine which factors are associated with aspiration and stricture.

Materials and Methods

  • The present study is a retrospective analysis of 96 patients treated with chemoradiation from September 2004 to August 2006.
  • Demographics:
    • The median age of patients was 55 and 82% of patients were male. 
    • Squamous cell carcinomas from all head and neck sites were included:
      • 43/96 patients had orpharyngeal cancers
      • 17/96 patients had hypopharynx/larynx cancers
      • 13/96 patients had oral cavity cancers
      • 11/96 patients had nasopharyngeal cancers
      • 2/96 patients had maxillary sinus cancers
      • 10/96 patients had unknown primaries
  • Radiation:
    • The parotids, spinal cord and oral cavity were specifically avoided, but no other structures were specifically defined as organs at risk.
    • All patients were treated using IMRT. Median dose for definitive radiation was 70 Gy (daily fractionation) and 64 Gy for post operative treatment.
    • 75% of patients had definitive radiation treatment and 25% had post operative radiation.
  • Chemotherapy:
    • 28 patients had induction and concurrent chemotherapy. 59 had concurrent chemotherapy and nine had radiation alone.  Concurrent chemotherapy was most commonly carboplatin and taxol weekly.
    • Induction chemotherapy was most commonly docetaxol, cisplatin and 5-fluorouracil (TPF).
  • All patients had a feeding tube placed prophylacticly.
  • Variables which were studied includes: age, race, gender, primary site, definitive versus adjuvant radiation, use of induction chemotherapy and smoking and alcohol histories were studied. Dose was also examined. Volumes to the larynx, pharyngeal constrictors (divided into superior, middle and inferior) and cervical esophagus were added retrospectively and doses were calculated to these structures.
  • Swallowing function was formally evaluated after treatment and evidence of swallowing dysfunction prompted a video swallow study. Swallowing dysfunction was classified as either aspiration or stricture.
    • Aspiration was defined by a change in swallowing function which required modification of the patient’s diet based on the Swallowing Performance Scale (Rosenbek et al. 1996).
    • Strictures were identified using video fluoroscopy.  

Results

  • 31 patients had aspiration and 36 patients had structure. 31/36 patients with stricture were treated with dilatation. 
  • There was no association between chemotherapy, primary disease site or radiation intension and stricture or aspiration. Prior tobacco use was the only variable which was significantly associated with the risk of developing both strictures and aspiration on univariate and multivariate analysis (p=0.05). 
  • No aspiration was seen in patients who had a mean laryngeal dose of less than 48 Gy. 
  • No strictures or aspiration was seen in patients with a mean inferior constrictor muscle dose of 54 Gy. 
  • If the V50 was less than 21% for the larynx and 51% for the inferior constrictor muscle there was no aspiration or stricture formation. 

Author's Conclusions

  • A mean dose limit of 48 Gy or a V50 of less than 21% to the larynx can decrease the risk of developing aspiration or strictures. 
  • These data are consistent with results seen with the use of a laryngeal block. 
  • The above dose parameters are now in use at the study institution.
  • Defining the larynx as a target of avoidance may be easier than defining dose constraints for the pharyngeal constrictors.

Clinical/Scientific Implications

  • As this is a retrospective study there was no preradiation evaluation of the patient’s swallowing function. Hence, it is not possible to determine the effects of the chemoradiation on swallowing function independent of tumor effects.
  • With the superior conformality which is now possible with IMRT, areas of avoidance can be more precisely defined. Furthermore, precise dose gradients can be created to limit dose as much as possible to structures to preserve function in the head and neck. However, a threshold for toxicity has not been defined for many of the structures involved with swallowing. This study presents data to help define organs of avoidance and dosimetric parameters which may limit toxicity.
  • As IMRT continues to be used in head and neck cancers and more experience is accumulated it may be possible to decrease treatment volumes further limiting toxicity, though clearly more data is needed.
  • The use of protons and the potential for IMPT may allow further decrease in the dose to these structures.

Partially funded by an unrestricted educational grant from Bristol-Myers Squibb.


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