3716 - Long Term Dysphagia Outcomes in Patients of Post Operative Oral Cavity Cancers Treated with Adjuvant Dysphagia Optimized vs. Standard Intensity Modulated Radiotherapy

M. Rastogi^1,2, A. K. Gandhi², A. Patni³, V. K. Mishra², A. K. Srivastava², R. Hadi⁴, R. Khurana², and S. P. Mishra²; ¹Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow, India, ²Department of Radiation Oncology, Dr Ram Manohar Lohia Institute of Medical Sciences, Lucknow, India, ³Bhagwan Mahaveer Cancer Hospital & Research Centre, Jaipur, India, ⁴Department of Radiation Oncology, Dr. Ram Manohar Lohia Institute of Medical Sciences, Lucknow, India

Purpose/Objective(s): This prospective comparative study was carried out with the hypothesis that, in post operative oral cavity squamous cell carcinoma (PO-OCSCC) receiving adjuvant RT alone without concurrent chemotherapy, sparing DARS with dysphagia optimized IMRT (Do-IMRT) may lead to less acute and late dysphagia related toxicity than standard IMRT (S-IMRT). We had earlier reported acute toxicities. Herein, we report long term dysphagia related and clinical outcome of this study cohort. Materials/Methods: Between February 2020 and June 2022, 56 PO-SCC patients without indications of concurrent chemotherapy (margin negative/no extra-nodal extension) were alternatively allocated into adjuvant Do-IMRT (n = 28) or S-IMRT (n = 28) arms. High risk and low risk planning target volumes received 60 Gray and 54 Gray respectively in 30 fractions over 6 weeks. Acute toxicities were assessed as per the CTCAE v5.0 and RTOG Late Morbidity Scoring Schema were used for late toxicities. Loco-regional control (LRC) was evaluated using Kaplan Meier method.

Results: Male: Female ratio for the entire cohort was 48:8. Rest of the patient characteristics is summarized in Table 1. 36.9 months was the median follow-up period (range: 15-48 months). When comparing Do-IMRT vs S-IMRT, Grade 1 and Grade 2 late dysphagia at 3 years were 12.3% vs. 26.8% (p=0.07) and 0% vs. 22% (p=0.023), respectively; Grade 1 and grade 2 xerostomia were 25.7% vs. 15.4% (p=0.34) and 8.2% vs. 16.3% (p=0.48) respectively. Grade 1 subcutaneous fibrosis was observed in 3 patients in the Do-IMRT arm and 4 patients in the S-IMRT arm. Dmean of =50 Gray to superior and middle pharyngeal constrictor muscle, supraglottic larynx; Dmean =40 Gray for inferior pharyngeal constrictor and =45 Gray for glottic larynx (GL) correlated with higher late grade = 2 dysphagia (all p<0.05). 3-year LRC was 79.8% in Do-IMRT and 73.6% in S-IMRT (p=0.32).

Conclusion: Sparing DARS with Do-IMRT leads to lesser late dysphagia in PO-OCSCC patients without compromising loco-regional control as compared to S-IMRT. Abstract 3716 – Table 1

Factors	n (%) (N=56)	Do-IMRT n (%) (N=28)	S-IMRT n (%) (N=28)	p-value
Site				0.717 0.365 (Tongue vs Non-tongue)
Buccal mucosa	33 (58.9)	18 (64.3)	15 (53.6)
Tongue	15 (26.8)	6 (21.4)	9 (32.1)
GBS + RMT + Alveolus + Hard palate	8 (14.3)	4 (14.3)	4 (14.3)
Overall TNM stage group (8th ed)
I	2 (3.6)	1 (3.6)	1 (3.6)	0.282
II	23 (41.1)	14 (50)	9 (32.1)
III	14 (25)	5 (17.9)	9 (32.1)
IV	17 (30.4)	8 (28.6)	9 (32.1)
LVI+	16 (28.6)	7 (25)	9 (32.1)	0.768
PNI+	8 (14.3)	5 (17.9)	3 (10.7)	0.705
Close margin	13 (23.2)	5 (17.9)	8 (28.6)	0.205