Locoregional recurrences after post-operative volumetric modulated arc radiotherapy (VMAT) in oral cavity cancers in a resource constrained setting: experience and lessons learned.

Objective: The conformal nature of dose distribution produced by volumetric modulated arc radiotherapy (VMAT) increases the risk of geographic miss. Data regarding patterns of failure after VMAT in oral cavity cancers in resource-constrained settings are scarce. The aim of the present study was to ascertain the patterns of failure in patients receiving adjuvant VMAT intensity-modulated radiotherapy (IMRT) for oral cavity cancer in Malabar Cancer Center, Kerala, India.

Methods: Data of patients with oral cavity cancer receiving adjuvant VMAT IMRT between April 2012 and March 2014 were collected. Recurrent volumes were delineated on the treatment planning images and classified as defined by Dawson et al (Dawson LA, Anzai Y, Marsh L, Martel MK, Paulino A, Ship JA, et al. Patterns of local-regional recurrence following parotid-sparing conformal and segmental intensity-modulated radiotherapy for head and neck cancer. Int J Radiat Oncol Biol Phys 2000; 46: 1117-26).

Results: 75 patients with a median follow-up of 24 months were analysed. 41 (55%) patients had oral tongue cancers and 52 (69%) of the patients had Stage IVA cancers. The 2-year locoregional recurrence-free survival, disease-free survival and overall survival were 88.9%, 82.1% and 80.5%, respectively. With a median time to failure of 6.5 months, five infield and three outfield failures were identified.

Conclusion: A relatively low rate of outfield failure and lack of marginal failure attests to the efficacy of VMAT in such patients. Modifications to our existing target delineation policy have been proposed.

Advances In Knowledge: The use of standardized target delineation methods allows safe use of VMAT IMRT even in resource-constrained settings.