Radiation Treatment Breaks: Are They Detrimental to Outcomes for Oropharyngeal Carcinoma Treated with Definitive Chemoradiation?

Abstract

Varying practices exist to account for radiation treatment breaks (rTBs) resulting from institutional holidays during treatment of oropharyngeal squamous cell carcinoma (OPSCC) cancer patients undergoing concurrent chemoradiation (CRT). Studies in radiation biology suggest that local therapy delays may result in accelerated repopulation of residual tumor cells, however the clinical effects of this model in the setting of concurrent systemic therapy are unclear. We, therefore, evaluated the effect of rTBs in patients who received CRT on disease-free survival (DFS) in a consecutive cohort of patients with OPSCC. Patients with recurrent OPSCC, M1 disease, less than 6 months follow-up, or those treated with surgery or RT alone were excluded. Data collected included age, sex, KPS, smoking status, T stage, N stage, p16 IHC or HPV ISH status, RT dose and fractions, systemic therapy, total treatment duration, number of total and cumulative rTBs, overall survival/local/regional/distant failure (calculated from start of RT). rTBs were defined as any breaks taken during RT. Cumulative rTBs were defined as largest number of consecutive rTBs, not including weekends. The Kaplan-Meier method was used to estimate time-to-event outcomes on univariate analysis (UVA) and the Cox proportional hazards model was used to determine the effects of covariates on multivariate analysis (MVA). 462 OPSCC patients meeting inclusion criteria treated between 1/1/2010 and 12/31/2015. Median follow up was 5 years (6 months -10 yrs). Median total treatment duration was 48 days (41-64 days). 457 (99%) patients received 70 Gy of RT, 1 patient received a 400 cGy boost, and 4 patients received 66-68 Gy. 54 (12%) patients received induction chemotherapy. 369 (80%) patients received a cisplatin-based regimen and 93 (20%) received a non-cisplatin regimen. 345 (75%) were HPV or p16 positive, 45 (10%) were negative, and 72 (15%) were unknown. Table 1 describes the rTBs experienced by our cohort and results of our analysis. On UVA, only cumulative rTBs of 3 days were found to be significant (p = 0.04). On MVA, however, treatment duration, total rTBs, and cumulative rTBs were not significantly associated with DFS. We did not find a significant decrease in DFS for patients who had rTBs of 3 days in the setting of CRT for OPSCC. However, extended consecutive breaks (>3 days) may be associated with poorer outcomes, warranting further investigation.Abstract 3986; TableResults of UVA and MVA for DFSn (%)UVAMVATotal Breaks (days) 0140 (30) 1166 (36)p = 0.21p = 0.63HR 1.68 [0.21-13.65] 279 (17)p = 0.72p = 0.71HR 1.48 [0.19-11.44] 329 (6)p = 0.95p = 0.96HR 0.93 [0.10-9.32] 417 (4)p = 0.41p = 0.51HR 0.42 [0.03-5.70] 5+*31 (7)p = 0.10p = 0.81HR 1.34 [0.12-15.24]Cumulative Breaks (days) 0147 (32) 1256 (55)p = 0.34p = 0.96HR 0.92 [0.12-7.03] 225 (5)p = 0.53p = 0.71HR 1.55 [0.16-14.59] 314 (3)p = 0.04p = 1.00HR 1.00 [0.10-10.03] 410 (2)p = 0.52p = 0.83HR 0.73 [0.04-13.08] 510 (2)p = 0.38p = 65HR 1.83 [0.14-24.79]*Range 5-14 days. Open table in a new tab