ESTRO 2024 - Abstract Book

S1283

Clinical - Head & neck

ESTRO 2024

Results:

The scoping review revealed significant practice differences on (1) timing for post-IC RT, (2) imaging modalities pre- and post-IC for RT CTV delineation, (3) RT CTV delineation according to risk groups, and (4) RT dose prescription and fractionation. The systematic review revealed that there are no specific recommendations or investigations on optimal timing for post-IC RT and optimal imaging modalities; study or institutional protocols were based on expert opinion. Three guidelines had different recommendations on post-IC RT CTV delineation - two (CSCO-ASCO, ESMO-EURACAN) recommend including the pre-IC gross tumour and nodes in the high-risk CTV, to be treated to an equivalent dose of 70 Gy [1,2], and one (CSCO) recommends response-based RT, including the post-IC gross disease in the high-risk CTV, and including the pre-IC gross disease in an intermediate-risk CTV to be treated to an equivalent dose of 60-64 Gy [3]. These recommendations were based on results of a phase III trial [4], two phase II trials and four retrospective studies. These support that response-based RT allows similar oncologic outcomes with less late toxicity and better quality of life. The ESMO-EURACAN and CSCO guidelines recommend three dose levels [2,3], while the CSCO-ASCO, only two [1].

Since the publication of the above guidelines, the long-term results of the phase III trial were published this year, reaffirming the safety of response-based RT [5].

Conclusion:

There is lack of guidelines and published evidence on post-IC RT timing and optimal imaging modalities; observational studies may inform practice and further research. Guidelines on post-IC CTV and dose levels differ significantly; published evidence from clinical trials are limited. An international consensus development among experts from endemic regions is ongoing [6] and will help harmonize practices and improve the comparison of reported outcomes.

Keywords: nasopharynx, induction CT, radiotherapy volume

References:

1. CHEN, Yu-Pei, ISMAILA, Nofisat, CHUA, Melvin LK, et al. Chemotherapy in combination with radiotherapy for definitive-intent treatment of stage II-IVA nasopharyngeal carcinoma: CSCO and ASCO guideline. Journal of Clinical Oncology, 2021, vol. 39, no 7, p. 840-859. 2. BOSSI, P., CHAN, A. T., LICITRA, L., et al. Nasopharyngeal carcinoma: ESMO-EURACAN Clinical Practice Guidelines for diagnosis, treatment and follow-up. Annals of Oncology, 2021, vol. 32, no 4, p. 452-465. 3. TANG, Ling ‐ Long, CHEN, Yu ‐ Pei, CHEN, Chuan ‐ Ben, et al. The Chinese Society of Clinical Oncology (CSCO) clinical guidelines for the diagnosis and treatment of nasopharyngeal carcinoma. Cancer Communications, 2021, vol. 41, no 11, p. 1195-1227. 4. YANG, Hongru, CHEN, Xin, LIN, Sheng, et al. Treatment outcomes after reduction of the target volume of intensity modulated radiotherapy following induction chemotherapy in patients with locoregionally advanced nasopharyngeal carcinoma: a prospective, multi-center, randomized clinical trial. Radiotherapy and Oncology, 2018, vol. 126, no 1, p. 37-42.