Mehra, Ranee

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 .