Thomas, Giovana R.

6036 Background: E3311 is a phase II randomized study of intermediate risk HPV+ OPC patients who underwent TOS by credentialed surgeons and were then treated by pathology-guided, deintensified post-operative treatment. Recent retrospective population data suggest that time to post-operative radiotherapy (PORT) > 6 weeks is associated with worse progression-free survival (PFS). Methods: We retrospectively analyzed demographics, pathologic characteristics, and oncologic outcomes in E3311 by time to initiation of PORT (short vs long, exploring both 6 and 7 weeks postop as the cutpoint). Binary and categorical variables were compared using a chi-square test (or a Fisher’s exact test for small sample sizes). Ordinal variables were compared using a Wilcoxon rank sum test. PFS and overall survival (OS) were estimated using the Kaplan-Meier method and compared using a log-rank test, which was stratified by intermediate- (Arms B/C) vs high-risk (Arm D). Results: Among 321 evaluable patients, the median time to initiation of PORT was 5.1 weeks (range 0.7-15.7); 5.0 (0.7-15.7) for Arm B, 5.1 (2.4-7.0) for Arm C, 5.6 (3.6-7.9) for Arm D. No significant difference in PFS or OS was observed whether PORT commenced by 6 or 7 weeks postoperatively, compared with longer time to initiation of PORT (p = 0.62 and 0.65, p = 0.30 and p = 0.41, respectively). 3-yr PFS rates were 93.5% (95% CI: 89.4%, 96.0%) among those treated ≤6 weeks, and 91.2% (95% CI: 81.4%, 95.9%) among those treated > 6 weeks; 3-yr OS rates were 96.1% (95% CI: 92.7%, 98.0%) among those treated ≤6 weeks, and 94.1% (95% CI: 84.9%, 97.8%) among those treated > 6 weeks. No significant differences in outcomes were observed between intermediate risk treatment arms (deintensified (50Gy) or standard dose (60Gy) RT). Additional demographic and pathologic characteristics, including primary site, margin status, histologic grade, stage, and extranodal extension were not significantly different between those with short vs long time to PORT, whether 6 or 7 weeks was used as the cutpoint. There were more T2 tumors in those treated > 7 weeks postop (84% vs. 49%, p = 0.007). PS = 1 patients were more numerous among those with shorter time to PORT (10% vs 0%, with the 7 week cutpoint). Conclusions: In contrast to retrospective NCDB data, intermediate- and high-risk HPV+ OPC patients enrolled on E3311 had favorable 3-yr PFS and OS rates that were not significantly worse when adjuvant therapy was started > 6 wks or > 7wks. These results argue against a survival advantage for initiation of PORT within 6 or 7 weeks for early-stage HPV+ OPC managed with high-quality transoral resection. The optimal time window to initiate PORT in HPV+ OPC patients remains to be determined. Clinical trial information: NCT01898494 .

6077 Background: E3311 is a phase II randomized study which showed favorable outcomes among intermediate (INT) risk HPV+ OPC patients (pts) who underwent TOS followed by pathology-guided or adapted, deintensified adjuvant treatment. Among HPV+ pts treated with definitive chemoradiation, survival outcomes are worse among those who smoked > 10 pack years (pk-yrs). Methods: We retrospectively analyzed demographics, pathologic results, and efficacy outcomes from E3311 by smoking group (current (C) vs. former (F) and > 10 vs. ≤10 pk-yrs – the latter a pre-specified stratification factor for INT patients). Binary and categorical variables were compared using a chi-square test (or Fisher’s exact test for small sample sizes). Ordinal variables were compared using a Wilcoxon rank sum test. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method and compared using a log-rank test. Results: Among 359 evaluable pts, performance status (PS) was significantly worse for pts with > 10 pk-yrs vs. ≤10 pk-yrs (15.4% vs. 7.9% with PS of 1, p = 0.034). Primary site, margin status, histologic grade, stage, and extranodal extension were not significantly different between the groups of > 10 vs. ≤10 pk-yrs. Smoking status (F vs. C) was available for 182 pts with a history of smoking. Slightly more C vs. F smokers had tonsil as primary site (79.5% vs. 65.0%, p = 0.09). Positive margins were significantly more frequent among C smokers (10.3% vs. 2.1%; p = 0.029). Overall, there were no significant differences in PFS (p = 0.55) or OS (p = 0.94), comparing those with > 10 vs. ≤10 pk-yrs, or comparing C vs. F smokers (p = 0.76, p = 0.82, respectively). Similarly, no significant differences were observed within the treatment arms. (Table 1) Conclusions: In this analysis of smoking status in E3311, INT risk HPV+ OPC pts who are C smokers or have a history of > 10 pk-yrs had favorable 3-yr PFS and OS rates that were not significantly worse than those with < 10 pk-yrs history. This data represents the first treatment approach for HPV+ OPC in which outcomes were not influenced by smoking status. Clinical trial information: NCT01898494. [Table: see text]

6010 Background: Definitive or postoperative chemoradiation (CRT) is highly curative for human papillomavirus-associated (HPV+) oropharynx cancer (OPC) but induces significant toxicity. As a potential deintensification strategy, we studied primary transoral surgery (TOS) and, in intermediate pathologic risk patients, reduced dose postoperative RT (PORT). Methods: E3311 is a phase II trial with randomization to reduced- or standard-dose PORT for resected stage III-IVa (AJCC7) intermediate pathologic risk HPV+ OPC, stratified by smoking history. Primary endpoints have been reported; we now present updated 3-year PFS and patient-reported outcomes (PRO), including head and neck-cancer specific quality of life (FACT-H&N) and swallowing perception and performance (MDADI). Results: Of 519 enrolled patients, 495 underwent TOS. The primary oncologic endpoint was 2-year PFS for 50 Gy (Arm B) or 60Gy (Arm C). Among 360 eligible and treated patients (ETP), Arm A (observation, N = 38) enrolled 11%, Arms B (N = 100) or C (N = 109) randomized 58%, and Arm D (66Gy + weekly cisplatin, N = 113) enrolled 31%. With 35.1 months median follow-up, 3-year PFS Kaplan-Meier estimate is 96.9% (90% CI [91.9%, 100%]) for Arm A; 94.9% (90% CI [91.3%, 98.6%]) for Arm B; 93.5% (90% CI [89.4%, 97.9%]) for Arm C; and 90.7% (90% CI [86.2%, 95.4%]) for Arm D. Recurrences and death without recurrence were 4 and 1 in Arm B, and 5 and one in Arm C. Smokers ( > 10 pack-years) did not have worse 3-year PFS in Arms B or C. Treatment arm distribution and outcome for ineligible patients who started adjuvant therapy mirrored the 360 ETP. A comparison combining arms B/C versus arm D in the proportion of patients stable/improved in FACT-H&N total score, from baseline to 6 months post-treatment as a pre-specified endpoint, was 56% vs. 38% (p value = 0.011, one-sided Fisher’s exact test); however, underlying differences in treatment and risk may be confounding. An exploratory comparison between Arms B and C revealed improvement in FACT H&N (63% in Arm B vs. 49% in Arm C had a stable/improved score, p-value = 0.056). Conclusions: Primary TOS and reduced PORT retained outstanding oncologic outcome at 35 months follow up, with favorable QOL and functional outcomes, in intermediate risk HPV+ OPC. Clinical trial information: NCT 01898494.

6500 Background: ECOG-ACRIN 3311 examines reduced postoperative therapy in patients with “intermediate risk” p16+ oropharynx cancer (OPC) undergoing primary transoral surgical management. We report the primary endpoint of 2-year progression free survival (PFS) for patients randomized to 50Gy vs 60Gy without chemotherapy. Methods: Between December 2013 and July 2017, 82 credentialed surgeons performed transoral resection (TOS) for 519 OPC patients (cT1-2 stage III/IV AJCC7 without matted neck nodes); post-operative management was determined by pathologically assessed risk. Among 353 eligible and treated patients, Arm A enrolled 10% (N=37) for clear margins, 0-1 nodes, no extranodal extension (ENE)), Arms B (50Gy, N=102) or C (60Gy, N=104) randomized 58%, for clear/close margins, 2-4 + nodes, or ENE ≤1mm, while Arm D (N=110, 60-66Gy plus weekly cisplatin, 40 mg/m2, positive margin with any T stage, >4 + nodes, or >1mm ENE) enrolled 31%. Arm D assignment was based on >1mm ENE (76%), > 4 nodes (27%), and/or positive margins (11%). Intermediate-risk patients were stratified by smoking history (>10 pk-yr). Of the 80 pts (15%) deemed ineligible, 28 had scans/labs not done per protocol, however treatment arm distribution for all patients mirrored that for the 353 pts eligible and treated. Results: Median follow-up was 31.8 months. 2 yr PFS for Arms A, B and C were 93.9% (90% CI=87.3%, 100%), 95.0% (90% CI=91.4%, 98.6%) and 95.9% (90% CI=92.6%, 99.3%) respectively, while Arm D was 90.5% (90% CI=85.9%, 95.3%). The regimen of TOS + low-dose radiation is considered worthy of further study, since the primary endpoint of the upper bound of the 90% CI (in the intermediate risk group) exceeding 85% was met. Of 17 progression events, 7 were locoregional. There were 10 distant recurrences: Arm A=1, Arm B=2, Arm C=4, Arm D=3. Grade III/IV treatment-related AE rates were 15%/2% during surgery, 13%/2% for Arm B and 25%/0% for Arm C. There were 2 treatment-related deaths (one surgical and one Arm D). Conclusions: Transoral resection of p16+ OPC is safe and results in good oncologic outcome, presenting a promising deintensification approach. For patients with low-risk disease, 2-yr PFS is favorable without post-operative therapy. For those with uninvolved surgical margins, <5 involved nodes, and minimal (<1mm) ENE, reduced dose postoperative RT without chemotherapy appears sufficient. Transoral surgery plus 50Gy should be compared to optimal non-surgical therapy in a phase III trial. Clinical trial information: NCT01898494 .