ESTRO meets Asia 2024 - Abstract Book

S31

Invited Speaker

ESTRO meets Asia 2024

Abstract

Platinum-based concurrent chemoradiotherapy is the cornerstone of care for patients with locoregionally advanced nasopharyngeal carcinoma (LA-NPC). Nonetheless, 20-30% of LA-NPC patients have disease recurrence after receiving definitive concurrent chemoradiotherapy, indicating additional adjuvant/neoadjuvant therapies are needed to further reduce the risk of recurrence and death. Although currently a matter of some debate, considerable research interest has been focused on exploring the optimal systemic chemotherapy modality combined with radiotherapy for LA-NPC. Studies showed that addition of cisplatin–gemcitabine (GP) or cisplatin, fluorouracil, and docetaxel (TPF) induction chemotherapy to concurrent chemoradiotherapy significantly improved failure-free survival, distant metastasis-free survival and overall survival in LA-NPC with acceptable toxicity. These breakthroughs indicate that induction chemotherapy has the capacity of eliminating distant micrometastases, reducing the incidence of metastasis, and subsequently improving patient prognosis. However, some studies also pointed out that the delay in initiating radiotherapy due to induction chemotherapy might result in possibly worse locoregional control. To enhance locoregional tumor control rates and achieve better survival benefits, investigators also focused on investigating the efficacy of adding adjuvant chemotherapy to concurrent chemoradiotherapy. Despite the unsatisfactory outcome from the adjuvant cisplatin–fluorouracil chemotherapy trial, other important studies, such as the adjuvant cisplatin–gemcitabine and adjuvant capecitabine trials, yielded encouraging results. Besides, investigators also found that survival benefit with adjuvant chemotherapy was mainly due to significantly improved locoregional control, suggesting that adjuvant chemotherapy has a role in eliminating residual tumor clones in the nasopharynx and neck after radiotherapy. Adjuvant chemotherapy can also reduce distant metastasis, albeit of a lesser magnitude. Nevertheless, adjuvant cisplatin–gemcitabine chemotherapy is poorly tolerated, which puts into question whether monotherapy capecitabine, given the reported compliance rates of over 70%, should be the preferred regimen for adjuvant chemotherapy for patients received induction plus concurrent chemoradiotherapy. Finally, updated results from the network meta-analysis of chemotherapy in nasopharyngeal carcinoma suggested that the addition of either induction chemotherapy or adjuvant chemotherapy to chemoradiotherapy improves overall survival over chemoradiotherapy alone in LA-NPC. However, the relative efficacy of these two combinations is not significantly different, except for distant progression, in which the results favor induction chemotherapy. Considering this, investigators proposed a plausible concept of using pretreatment Epstein-Barr virus DNA level for treatment stratification, in which patients with high levels are recommended for induction chemotherapy before concurrent chemoradiotherapy to target occult distant metastatic clones and those with low levels are recommended for adjuvant chemotherapy after chemoradiotherapy. Still, there is an unmet need for more future randomized trials to help further identify the optimal systemic therapy regimen with high patient compliance.

517

Delineation of Clinical Target Volumes (CTV) for Nasopharyngeal Carcinoma – Revisited

Anne W.M. Lee

Clinical Oncology Center, University of Hong Kong - Shenzhen Hospital, Shenzhen, China

Abstract

Radiotherapy is the primary treatment modality for nasopharyngeal carcinoma (NPC). Accurately delineating the gross tumor volume (GTV) based on the best available imaging methods is a crucial initial step in the treatment process. Due to the highly infiltrative nature of NPC, it is equally crucial to properly delineate the clinical target volume (CTV) to encompass areas at a higher risk of microscopic involvement.