ESTRO 2020 Abstract book

S401 ESTRO 2020

distinction between populations was found when testing for distant recurrences. Conclusion D90 did not distinguish between patient populations with different outcomes. EUBED integrates biological effect over a volume in a manner very similar with gBEUD for negative a . Such exponents are typically used in relation with Local Control emphasizing ‘cold spots’. Interestingly, a large ‘hot’ volume is present in all T&O and T&R applications and some practitioners even emphasize contiguity of 150% or 200% isosurfaces in their plans. gBEUD for positive values [3..5] proved to be the only metric that successfully predicted patients with no recurrence. Based on these findings, gBEUD should be included routinely to the set of dosimetric parameters used to evaluate implants. PD-0660 Radical chemoradiation with IMRT-SIB for LAHNSCC: Preliminary outcome. T. Basu 1 , B. Patineedi 1 , H. Vyaas 1 , P. Kendre 2 , A. Karpe 2 , N. Raut 2 , I. Ambulkar 2 , D. Nayek 3 , S. Rao 3 , S. Gawde 4 , U. Saxena 1 , S. Vangipuram 1 , A. Kasat 4 , K. Arrmugam 5 1 HCG Cancer Centre, Radiation Oncology, Mumbai, India ; 2 HCG Cancer Centre, Medical Oncology, Mumbai, India ; 3 HCG Cancer Centre, Surgical Oncology, Mumbai, India ; 4 HCG Cancer Centre, Nuclear Medicine, Mumbai, India ; 5 HCG Cancer Centre, Medical Physics, Mumbai, India Purpose or Objective To evaluate early clinical results from a uniform protocol of adaptive modulated simultaneous integrated boost (SIB) chemoradiation (CRT) as definite treatment for non- metastatic locally advanced squamous cell carcinoma of head and neck (SCHNC). It also analysed efficacy of adaptive radiotherapy (ART), PETCT surveillance, failure patterns and toxicity profiles. Material and Methods 150 patients were treated over twenty months. All had baseline radiological, fibre-optic laryngoscopy (FOL) and biopsy with HPV as needed. CRT was uniform protocol with modulated RT SIB of 66-70Gy in 33 fractions over 6.5 weeks and 80% received concurrent chemotherapy mostly with cisplatin. ART was planned at 4 weeks and 70% had replan. First surveillance PETCT was between 10-14 weeks post CRT. The failure patterns were assessed by Hopkins scoring in PETCT and types A-E after deformable image registration. PETCT and modulated RT failures were reviewed by two blinded nuclear medicine physician and radiation oncologists separately. The toxicities were graded as per CTCAE version 3.0. Patients were followed up every 3 months and second surveillance PETCT scheduled between 5-6 months depending on 1 st response. Statistical analyses were carried out using SPSS version 20. Results Median follow-up was 18 months and median age 60 years. 30% were beyond 70 years with median G8 screening score of 15. 85% patients were male and 50% had oropharyngeal primaries with 13% HPV positive. 93.5% received SIB-IMRT 70Gy in 33 fractions and 80% had concurrent cisplatin. 50% had 3 weekly cisplatin. Baseline PETCT was available in 50% cases. At 1 st follow up complete response (CR) at primary site was 85% on both FOL and PETCT (Hopkins score 1-2). Till last follow up 60% had complete response, 16% had loco-regional failure and 2% distant metastases. Nine patients died till last follow up and 5 were lost to Poster discussion: CL: Head and neck 2

D90 shows excellent dosimetric quality across all sites and treatments. Two populations were created for each site, patients with no recurrences and patients with local recurrences. The two populations were compared using all variables. No dosimetric variable was able to distinguish between the two populations, with the exception of gBEUD for a positive exponent between 3 and 5, at high levels of statistical significance p- (0.027, 0.038). No such