ESTRO 2021 Abstract Book

S856

ESTRO 2021

trial from July 2011-July 2013, who underwent to a personalized RAIT after performing 124I-PET/CT. Clinical/laboratory data were collected every 6/12months. In the case of strong suspect of relapse, contrast- enhanced-TC and/or 18FDG-PET/CT were also performed. Response to therapy was assessed according to ATA2015 guidelines. Results Mean FU was 73.5 months (range:108-17). All pts received prior RAIT, with an average administered 131I activity of 9195.5MBq(range:1110-25900). 15/30(50%) pts had negative 124I-PET/CT and RxWBS scans;11/15 pts received 3700MBq while 4/15 pts refused treatment. At last FU, 4/15 pts had indeterminate response (IR), one pt had biochemical persistence (BP), 7/15 pts had structural persistence (SP), one pt died for disease not- related causes and 2/15 pts were lost at FU. 15/30(50%) pts had positive 124I-PET/CT and RxWBS scans but in 2/15 pts dosimetry was not performed because of the influence of intestinal activity. All those pts received an 131I activity of at least 7400MBq. Overall, dosimetry was performed to 34 lesions. In 5/13(38%) pts lesions received less than the target dose of 80Gy(average dose:14.25Gy;range:1.47-60.50); at last FU 2/5 pts had SP and 3/5 pts died for progression disease. In 2/15(15%) pts the majority of lesions received less than 80Gy and at last FU one pt had SP and one had IR. In 6/13(46%) pts lesions received more than 80Gy (average dose:393Gy;range:163.73-1283.12); at last FU 2/5 pts had SP, 2/5 pts had an excellent response, one pt died for disease not-related causes and one pt was lost at FU. Conclusion 124I-PET/CT imaging may drive the choice of optimal 131I administered activity; long-term FU data confirmed that pts who received more than 80 Gy to the lesions have a better response disease than those who received lower activities. PO-1028 Inter-correlations between various high-risk pathological factors in squamous cell carcinoma tongue P. Ahlawat 1 , A. Krishnan 1 , M. Gairola 1 , S. Tandon 1 , S. Purohit 1 , N. Sachdeva 1 , M.I. Sharief 1 , K. Dobriyal 1 , T. Singh 1 1 Rajiv Gandhi Cancer Institute and Research Centre, New Delhi, Radiation Oncology, New Delhi, India Purpose or Objective While exploring histopathological high-risk factors for squamous cell carcinoma of oral cavity most studies have included mixed population of oral cavity subsites such as oral tongue, buccal mucosa, retromolar trigone, gingivo-buccal sulcus, floor of mouth, hard palate and alveolus. Oral tongue have different natural history and hence may behave differently from other sites with regard to high-risk pathological factors. The objective of this study was to explore inter-correlations between various pathological high-risk factors found in resected specimen of OTSCC. Materials and Methods It was a retrospective analysis in which we reviewed the final histopathology of surgical specimen of 202 patients with OTSCC who had undergone upfront surgical resection followed by adjuvant therapy. Inter- correlations were performed between various pathological factors using Spearman’s correlation test. Factors assessed were pathological T stage, pathological nodal stage (N Stage), lymphovascular invasion (LVI), perineural invasion (PNI), depth of invasion (DOI), tumour thickness (TT), worst pattern of invasion (WPOI), and extranodal extension (ENE). Results Various inter-correlation between factors found are shown in Table.

Factors

pT Stage pN Stage DOI Grade PNI LVI TT WPOI ENE

pT Stage -

Yes

Yes No

Yes No Yes No Yes

pN Stage Yes

-

No No

Yes Yes Yes Yes Yes

Grade No

No

No -

No No No Yes No

PNI

Yes

Yes

Yes No

- Yes Yes Yes Yes

LVI

Yes

Yes

Yes No

Yes - Yes Yes Yes

DOI

Yes

No

- No

Yes No Yes No No

TT

Yes

No

Yes No

Yes Yes - Yes Yes

WPOI

Yes

Yes

Yes No

Yes Yes No -

Yes

ENE

Yes

Yes

No No

Yes Yes No No -

Conclusion pT stage has significant positive correlation with pN stage, DOI, PNI, TT and ENE. pN stage has significant positive correlation with PNI, LVI, TT, WPOI and ENE. Grade has significant correlation with WPOI. PNI has significant correlation with DOI, LVI, TT, WPOI and ENE. LVI has significant correlation with pT stage, DOI, PNI, TT, WPOI and ENE. DOI has significant correlation with pT stage, PNI and TT. TT has significant correlation with pT stage, DOI, PNI, LVI, WPOI and ENE. WPOI has significant correlation with pT stage, pN stage, DOI, PNI and LVI. ENE has significant correlation with pT stage, pN stage, PNI and LVI. Many of these correlations are not shown in most other studies on oral cancer.

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PO-1029 STUPP protocol and hypofractionated RT for glioblastoma in clinical practice G. Sara 1 , I. Clara 1 , L. Nuria 1