Submandibular gland sparing in intensity-modulated radiotherapy for N0-stage nasopharyngeal carcinoma

Abstract

Objective: This study evaluated and quantified the feasibility of submandibular gland (SMG) sparing in intensity-modulated radiotherapy (IMRT) for N0-stage nasopharyngeal carcinoma (NPC). Methods: Ten patients with N0-stage NPC were enrolled in the study. Four IMRT plans were produced for each, with different limiting conditions. In plan A, SMG sparing was ignored; in plans B, C and D, the mean dose to SMGs was restricted to 39 Gy. In addition, at least 95% of planning target volume (PTV)-IIa (PTV of clinical target volume involving level IIa lymph node) in plan C and 90% of PTV-IIa in plan D were required to have a 60 Gy covering. Results: The average mean dose to SMGs was 54.6 6 3.6 Gy in plan A and was lower, 39.3 6 0.3, 49.3 6 1.9 and 46.7 6 2.8 Gy, in plans B, C and D, respectively. The volume of PTV-IIa covered by 60 Gy was 98.9%, 81.6%, 95.2% and 90.8% in plans A, B, C and D, respectively, and showed a parallel association between dose reduction to SMGs and the covering deficit of PTV-IIa. Conclusion: Reducing the mean dose received by SMG to 39 Gy or less in IMRT for N0-stage NPC is feasible.

Survival and quality of life in oropharyngeal cancer patients treated with primary chemoradiation after salivary gland transfer

“…Normally, a contralateral submandibular gland in its correct anatomical position is expected to receive a dose of 45–50 Gy in the standard intensity modulated radiotherapy protocol 28 . In the submental space, a cumulative dose of less than 20 Gy is usually reached 29 .…”

Implementation of submandibular gland transfer: A multi‐institutional study of feasibility and time to treatment

“…In patients undergoing primary surgery, median time was 32 days (IQR, and in patients undergoing primary nonsurgical therapy, median time was 46.5 days (IQR, [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]. Time from tissue diagnosis to SMGT was 28 days (IQR, 21-44), and from surgery to adjuvant therapy was 33 days (IQR, [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47]. Thirteen patients suffered a treatment delay: seven patients due to >60 days from diagnosis to treatment initiation (7/49; 14%) and six due to >6 weeks from surgery to adjuvant radiation (6/19; 32%).…”

“…33,34 Other reports demonstrate that IMRT only reduces the SMG dose to [35][36][37][38][39][40][41][42][43][44][45] Gy. [35][36][37] It has been recommended that doses beyond 25 Gy should be avoided if significant salivary function is to be preserved. 33,38 Furthermore, self-reported degree of xerostomia at rest is only 30% less severe after IMRT compared to conventional RT, and xerostomia during meals is only 37% less severe .…”

Effects of omitting elective neck irradiation to nodal Level IB in nasopharyngeal carcinoma patients with negative Level IB lymph nodes treated by intensity-modulated radiotherapy: a Phase 2 study

“…However, it may not be feasible to limit the D mean of SMGs to 39 Gy in patients with extensive nodal disease as defined in our study. Nevertheless, the relatively low Level IB failure rate in the present study suggests that further studies should be conducted to investigate whether constraining the SMG D mean to 39 Gy is feasible, in an attempt to preserve SMG function in selective early-staged and node-negative patients 21.…”