title: Prospective longitudinal assessment of parotid gland function using dynamic quantitative pertechnate scintigraphy and estimation of dose-response relationship of parotid-sparing radiotherapy in head-neck cancers.
abstract: OBJECTIVE
  To estimate dose-response relationship using dynamic quantitative (99m)Tc-pertechnate scintigraphy in head-neck cancer patients treated with parotid-sparing conformal radiotherapy.
  
  
  METHODS
  Dynamic quantitative pertechnate salivary scintigraphy was performed pre-treatment and subsequently periodically after definitive radiotherapy. Reduction in salivary function following radiotherapy was quantified by salivary excretion fraction (SEF) ratios. Dose-response curves were modeled using standardized methodology to calculate tolerance dose 50 (TD50) for parotid glands.
  
  
  RESULTS
  Salivary gland function was significantly affected by radiotherapy with maximal decrease in SEF ratios at 3-months, with moderate functional recovery over time. There was significant inverse correlation between SEF ratios and mean parotid doses at 3-months (r = -0.589, p<0.001); 12-months (r = -0.554, p<0.001); 24-months (r = -0.371, p = 0.002); and 36-months (r=-0.350, p=0.005) respectively. Using a post-treatment SEF ratio <45% as the scintigraphic criteria to define severe salivary toxicity, the estimated TD50 value with its 95% confidence interval (95% CI) for the parotid gland was 35.1Gy (23.6-42.6Gy), 41.3Gy (34.6-48.8Gy), 55.9Gy (47.4-70.0Gy) and 64.3Gy (55.8-70.0Gy) at 3, 12, 24, and 36-months respectively.
  
  
  CONCLUSIONS
  There is consistent decline in parotid function even after conformal radiotherapy with moderate recovery over time. Dynamic quantitative pertechnate scintigraphy is a simple, reproducible, and minimally invasive test of major salivary gland function.
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. tejpalgupta@rediffmail.com.|Department of Epidemiology & Clinical Trials Unit - Clinical Research Secretariat, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. tejpalgupta@rediffmail.com.
authors.forename: Tejpal
authors.initials: T
authors.lastname: Gupta
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. drchandni.h@gmail.com.
authors.forename: Chandni
authors.initials: C
authors.lastname: Hotwani
authors.affiliation: Department of Epidemiology & Clinical Trials Unit - Clinical Research Secretariat, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. skannan@actrec.gov.in.
authors.forename: Sadhana
authors.initials: S
authors.lastname: Kannan
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. masterzubin@gmail.com.
authors.forename: Zubin
authors.initials: Z
authors.lastname: Master
authors.affiliation: Department of Nuclear Medicine & Molecular Imaging, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. drvrangarajan@gmail.com.
authors.forename: Venkatesh
authors.initials: V
authors.lastname: Rangarajan
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. vedangmurthy@gmail.com.
authors.forename: Vedang
authors.initials: V
authors.lastname: Murthy
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. ashwini.budrukkar@gmail.com.
authors.forename: Ashwini
authors.initials: A
authors.lastname: Budrukkar
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. sarbanilaskar@gmail.com.
authors.forename: Sarbani
authors.initials: S
authors.lastname: Ghosh-Laskar
authors.affiliation: Department of Radiation Oncology, Tata Memorial Hospital and ACTREC, Tata Memorial Centre, Parel, Mumbai, 400 012, India. agarwaljp@tmc.gov.in.
authors.forename: Jai Prakash
authors.initials: JP
authors.lastname: Agarwal
mesh_terms: D000328:Adult; D000368:Aged; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D059351:Organ Sparing Treatments; D010306:Parotid Gland / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000528:radiation effects; D011379:Prognosis; D011446:Prospective Studies; D011877:Radionuclide Imaging / Q000379:methods; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated; D012588:Scintillation Counting / Q000379:methods*; D013670:Sodium Pertechnetate Tc 99m / Q000493:pharmacokinetics*; D014018:Tissue Distribution
chemical_list: D019275:Radiopharmaceuticals; D013670:Sodium Pertechnetate Tc 99m