Reirradiation of salivary gland tumors with carbon ion radiotherapy at CNAO.

Aims: To report oncologic and functional outcomes in terms of tumor control and toxicity of carbon ion radiotherapy (CIRT) in reirradiation setting for recurrent salivary gland tumors at CNAO.
Methods: From November 2013 to September 2016, 51 consecutive patients with inoperable recurrent salivary gland tumors were retreated with CIRT in the frame of the phase II protocol CNAO S14/2012C for recurrent head and neck tumors.
Results: Majority of pts (74.5%) had adenoid cystic carcinoma, mainly rcT4a (51%) and rcT4b (37%). Median dose of prior photon based radiotherapy was 60 Gy. Median dose of CIRT was 60 Gy [RBE] at a mean of 3 Gy [RBE] per fraction. During reirradiation, 19 patients (37.3%) experienced grade G1 toxicity, 19 pts (37.3%) had G2 and 2 pts (3.9%) had G3. Median follow up time was 19 months. Twenty one (41.2%) patients had stable disease and 30 (58.8%) tumor progression at the time of last follow up. Furthermore, 9 (18%) patients had G1 late toxicity, 19 (37%) had G2 and 9 (17. 5%) had G3. Using the Kaplan Meier method, progression free survival (actuarial) at one and two years were 71.7% and 52.2% respectively. Estimated overall survival (actuarial) at one and two years were 90.2% and 64%, respectively.
Conclusions: CIRT is a good option for retreatment of inoperable recurrent salivary gland tumors with acceptable rates of acute and late toxicity. Longer follow up time is needed to assess the effectiveness of CIRT in reirradiation setting of salivary gland tumors.
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