Outcomes of Moderately Dose Escalated Hypofractionated Chemoradiation for Pancreatic Cancer

PURPOSE/OBJECTIVE(S)

A modestly hypofractionated course of chemoradiation (CRT) consisting of 36 Gy/15 fractions (F) concurrent with gemcitabine used in PREOPANC and phase II trials has become increasingly common for the treatment of borderline resectable (BR) and locally advanced (LA) pancreatic cancer (PC). Achieving an R0 resection remains a key prognostic factor in PC. We tested whether escalating dose beyond standard dosing (SD) of 36-39 Gy/15 F (or 50-54 Gy/25-30 F) would improve R0 resection rates and outcomes while respecting nearby organs at risk.

MATERIALS/METHODS

This was a retrospective analysis of consecutive patients at our institution from 2012-2022 with BR/LA PC treated with moderate dose escalated (MDE) (45 Gy/15 F, N = 45) or SD (36-39 Gy/15 F, N = 68 or 50-54 Gy/25-30 F, N = 25) CRT. For MDE, a 5 mm expansion from the duodenum, small bowel, and stomach was created (GI_PRV); PTV was cropped from this structure and prescribed 45 Gy/15 F. The primary endpoint was R0 resection rate with secondary endpoints of cumulative incidence of local progression (LP, recurrence after surgery/imaging progression if no surgery) with death as a competing risk (LP after occurrence of distant metastasis [DM] were still captured), cumulative incidence of DM, and overall survival (OS). Univariable and multivariable competing risks regression analyses were performed to determine the association between baseline covariates and LP.

RESULTS

We identified 45 patients treated with MDE and 93 treated with SD. Most patients presented with BR disease (55.6% MDE; 54.8% SD) and received neoadjuvant chemotherapy with FOLFIRINOX (98% MDE; 99% SD). All patients in the MDE group and 99% in the SD group received concurrent chemotherapy with gemcitabine used most often (96% MDE; 77% SD). Median follow-up was 17 m (IQR 13-27 m). Surgical resection rates were similar between groups (33.3% MDE vs. 39.8% SD, p = 0.46). Amongst patients that had surgery, R0 resection rates were non-significantly higher in the MDE group (73.3% vs. 47.4%, p = 0.09). Cumulative incidence of LP at 18 m was significantly lower in the MDE group (9.0% vs. 24.8%, p = 0.04). No difference in rates of DM (51.2% MDE vs. 59.6% SD, p = 0.92) or OS at 18 m (53.9% vs. 53.6%, p = 0.89) were observed. On multivariable analysis, MDE (HR = 0.39, p = 0.03) and pancreatic head location (HR = 0.51, p = 0.04) were the only factors independently associated with LP. Rates of grade 2+ gastrointestinal toxicity during CRT (20% MDE vs. 20.9% SD, p = 0.91) and ≤90 days of completing CRT (11.6% MDE vs. 14.8%, p = 0.62) were similar between groups, as were rates of grade 3+ hematologic toxicity (52.3% MDE vs. 41.3% SD, p = 0.23).

CONCLUSION

In this single institutional study, we found MDE is a simple, safe, and effective strategy associated with improved local control, higher R0 resection rates, and similar toxicity to SD CRT for patients with BR/LA PC. Further prospective data is needed to clarify the role of dose-escalated RT in the management of this lethal malignancy.

Are All Prognostic Stage IB Breast Cancers Equivalent?

PURPOSE/OBJECTIVE(S)

The 8th edition of the American Joint Committee on Cancer (AJCC) has recognized the prognostic influence of histologic grade and biomarker status for breast cancer (BC). Contemporary BC staging includes both anatomic tumor extent and prognostic stage. However, prognostic stage IB remains heterogeneous and includes patients with locally advanced anatomic pathologic stage IIIA-B (pT3N1 or pT1-3N2, G1-2) hormone-receptor positive/HER2-negative BC (LA-HR+/HER2-) as well as patients with early-stage anatomic clinical/pathologic stage IA (T1cN0, G2-3) triple-negative BC (ES-TNBC). We hypothesized that although both are classified as prognostic stage IB BC, overall survival (OS) is worse for LA-HR+/HER2- compared to ES-TNBC.

MATERIALS/METHODS

We used the National Cancer Database to identify patients with surgically-resected LA-HR+/HER2- BC (pT3N1 or pT1-3N2, grade 1-2) and those with ES-TNBC (T1N0, grade 2-3) from 2004-2017. Patients were excluded if receptor status, tumor grade, and/or TNM staging data were unknown. HR+/HER2- patients treated with neoadjuvant therapy were also excluded. The primary endpoint was OS. Multivariable Cox regression analysis was used to evaluate differences in OS between LA-HR+/HER2- BC and ES-TNBC (adjusting for baseline patient demographic characteristics) in the entire cohort and in the subset of patients that received appropriate treatment based on anatomic stage: radiation (RT), chemotherapy (CT) and hormone therapy for LA-HR+/HER2- BC and CT or CT+RT for ES-TNBC treated with mastectomy or lumpectomy, respectively. We report hazard ratios (HR) with 95% confidence intervals (CI) with p<0.05 considered statistically significant.

RESULTS

A total of 45,818 patients met inclusion criteria (N = 17,359 with LA-HR+/HER2- BC and N = 28,459 with ES-TNBC). Over 75% of the LA-HR+/HER2- BC patients have anatomic pathologic stage IIIB disease (pT1-3N2, G1-2). With a median follow-up of 56 months, the 6-year OS rates were 86.1% (LA-HR+/HER2-) vs. 90.4%patients (ES-TNBC) which corresponded to a 63% relative increased risk of death in LA-HR+/HER2- patients compared to ES-TNBC patients (HR = 1.63, 95% CI 1.53-1.73, p<0.0001) after adjusting for all covariates. Approximately 66% (N = 11,533) LA-HR+/HER2- and 69% (N = 19,512) ES-TNBC received appropriate therapy. The 6-year OS was 91.8% (LA-HR+/HER2-) vs. 93.3% (ES-TNBC) which corresponded to a 35% increased risk of death in the LA-HR+/HER2- patients compared to ES-TNBC (adjusted HR = 1.35, 95% 1.24-1.48, p<0.0001). Other covariates associated with OS were age, income, insurance status, facility type, and ethnicity/race.

CONCLUSION

We found that LA-HR+/HER2- BC has significantly worse OS compared to ES-TNBC despite both being classified as prognostic stage IB, even when accounting for treatments delivered. The categorization of pT3N1 or pT1-3N2, G1-2 HR+/HER2- BC as prognostic stage IB needs to be reconsidered in order to provide patients with more accurate information regarding expected OS.

Omission of Adjuvant Radiotherapy in Low-Risk Elderly Males with Breast Cancer

PURPOSE/OBJECTIVE(S)

Randomized clinical trials demonstrate that lumpectomy + hormone therapy (HT) without radiation therapy (RT) yields equivalent survival and acceptable local-regional outcomes in elderly women with early-stage, node-negative (T1-2N0) hormone-receptor positive (HR+) breast cancer. Whether these data apply to men with the same inclusion criteria remains unknown. We hypothesized that outcomes in males would be comparable to those seen in females, with RT not conferring an overall survival (OS) benefit over HT alone.

MATERIALS/METHODS

We conducted a retrospective matched-cohort study using the National Cancer Database for males ≥65 years with pathologic T1-2N0 (≤3 cm) HR+ breast cancer treated with breast conserving surgery with negative margins from 2004-2019. Patients who received chemotherapy, had nodal or distant metastases, or unknown follow-up were excluded. Adjuvant treatment was classified as HT alone, RT alone, or HT+RT. Due to limitations of survival analysis on retrospective data, male patients were matched with female patients to determine comparable outcomes based on age (± 3 years), Charlson Deyo comorbidity score, T-stage, and adjuvant treatment. Survival analysis was performed using Cox regression and Kaplan-Meier analysis. To adjust for confounding, inverse probability of treatment weighting (IPTW) was used.

RESULTS

A total of 523 patients met inclusion criteria, with 24.4% receiving HT, 16.3% receiving RT, and 59.2% receiving HT+RT. Median follow-up was 6.9 years (IQR: 5.0-9.4 years). Unadjusted 5-yr OS rates in the HT, RT, and HT+RT cohorts were 79.2% (95% CI 70.7-85.5%), 80.9% (95% CI 70.3-88.0%), and 93.3% (95% CI 89.7-95.7%), respectively. Adjusted 10-yr OS rates in the HT, RT, and HT+RT cohorts were 82.3% (95% CI 78.6-85.5%), 83.6% (95% CI 80.0-86.7%), and 92.8% (95% CI 90.1-94.8%), respectively. On unadjusted multivariable Cox regression analysis (MVA), relative to HT, receipt of HT+RT was associated with improvements in OS (HR: 0.603; 95% CI: 0.410-0.888; p = 0.01). RT alone was not associated with improved OS (HR: 1.116; 95% CI: 0.710-1.755; p = 0.633). On adjusted MVA, relative to HT, receipt of HT+RT was associated with improvements in OS (HR: 0.551; 95% CI: 0.370-0.820; p = 0.003). Again, RT alone was not associated with improved OS (HR: 0.991; 95% CI: 0.613-1.604; p = 0.972). Other factors associated with OS included age, Charlson Deyo score, T stage, and grade. Overall, in the matched women, the same trends were found as in the men, the best survival was in HT+RT, but no difference in OS between HT vs. RT.

CONCLUSION

Among men ≥65 years old with T1-2N0 HR+ breast cancer, RT alone did not confer an OS benefit over HT alone. Combined RT+HT did yield improvements in OS, though there are likely significant unmeasured confounders contributing to these outcomes in patients treated with the most aggressive approach. Our findings support that RT omission may be a reasonable option in elderly men with T1-2N0 HR+ breast cancer treated with lumpectomy + HT.

Abstract OT2-04-04: Multi-institution phase II trial of intraoperative electron beam radiotherapy boost at the time of breast conserving surgery with oncoplastic reconstruction in women with early-stage breast cancer

Background: In women amenable to breast conserving therapy, lumpectomy followed by adjuvant whole breast irradiation (WBI) remains the standard of care. Randomized trials demonstrate that addition of a lumpectomy cavity boost significantly reduces the risk of ipsilateral breast tumor recurrences but also increases the risk of breast fibrosis. Contemporary randomized trials define the lumpectomy cavity boost volume as a 1.7 cm isometric expansion on the lumpectomy cavity as delineated on CT. However, identifying the lumpectomy cavity can be challenging, especially in women that receive adjuvant chemotherapy and in cases in which surgical clips are not present. Recently, the use of oncoplastic techniques in breast conserving surgery has increased. These techniques are used to prevent the poor cosmetic results that can occur when a large volume of breast tissue is resected. Women that undergo oncoplastic reconstruction represent especially difficult cases for lumpectomy cavity delineation. Retrospective series have evaluated the use of intraoperative electron radiotherapy (IOERT) as a boost prior to WBI in women receiving lumpectomy without oncoplastic reconstruction. In the largest series of IOERT boost prior to WBI the local control rate of this approach was &gt;99%. Prospective data regarding IOERT boost in women undergoing oncoplastic reconstruction are limited. The advantages of this approach include direct visualization/irradiation of the tumor bed, sparing the skin of irradiation, and reducing the treatment time by ˜1 week. We hypothesize that IOERT boost followed by WBI will result in acceptably low rates of grade 3 fibrosis in women undergoing lumpectomy with oncoplastic reconstruction.

Trial Design: This is a single-arm, prospective study to evaluate the safety, toxicity and efficacy of IOERT boost at the time of breast conserving surgery in women with early-stage breast cancer undergoing oncoplastic reconstruction. Eligible women will receive 1 dose of 8 Gy to the surgical bed after lumpectomy but prior to oncoplastic reconstruction. Women will then receive adjuvant WBI of 40 Gy in 15 fractions or 50 Gy in 25 fractions.

Eligibility: Key criteria include age≥18 yo, clinically node-negative stage I/II, any breast cancer subtype.

Specific Aims: To determine the rate of grade 3 breast fibrosis at 1 year. Additional aims include surgical complication rates, cosmesis, and local regional cancer control.

Statistical Methods: Safety will be evaluated by the rate of surgical complications necessitating hospital readmission or return to the operating room within 30 days of surgery+IOERT. If ≥4 events in the first 10 patients, ≥7 events in the first 20 patients, or ≥9 events in the first 30 patients are seen, the study will be halted. We hypothesize that the grade 3 fibrosis rate in our study will be ≤5%. Assuming an actual rate of 4%, an unacceptable rate of 9%, and a drop-out rate of 10%, the expected sample size is 176.

Sites: Ohio State University, Avera Medical Group, University of North Carolina-Chapel Hill

Patient Accrual: Current accrual is 5/176.

Contact Information: Jose Bazan (jose.bazan2@osumc.edu)

Funding Source: Intraop Medical

Citation Format: Bazan JG, Stephens J, Agnese D, Skoracki R, Arneson K, Reiland J, Gupta G, Gallagher K, McElroy S, Gupta N, White JR. Multi-institution phase II trial of intraoperative electron beam radiotherapy boost at the time of breast conserving surgery with oncoplastic reconstruction in women with early-stage breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT2-04-04.

Abstract P3-12-03: Analysis of radiation dose in the gap region between the supraclavicular target volume to the internal mammary target volume in women receiving regional nodal irradiation

Purpose: Consensus guidelines for regional nodal irradiation (RNI)/postmastectomy radiation (PMRT) clinical target volumes (CTV) have slight variations amongst leading national organizations. In the US, the Radiation Therapy Oncology Group (RTOG) defines the caudal edge of the supraclavicular (SCV) CTV as the junction of the brachiocephalic and axillary vessels while the internal mammary nodal (IMN) CTV starts at the superior aspect of the medial first rib. This leaves an anatomical gap between the two target volumes. The European Society of Radiation Oncology (ESTRO) does not recommend leaving a gap between the SCV CTV and IMN CTV. We set to analyze radiation dose and patterns of failure in this region.

Materials and Methods: We identified consecutive patients treated with RNI/PMRT at our institution from 2013-2016. Patients with metastatic or recurrent disease were excluded. All patients received 50 Gy/25 fractions to the breast/chestwall+regional nodes (including IMN PTV) +/- boost to the lumpectomy cavity/mastectomy scar using 3D conformal radiotherapy (3DCRT) or intensity modulated radiation therapy (IMRT). We retrospectively contoured the vessels from one slice below the caudal border of the SCV PTV contour to one slice cranial to the first IMN PTV contour. We calculated the mean dose and the relative V40Gy, V45Gy, and V47.5Gy of the gap region.A gap failure was defined as a first recurrence in this region with or without simultaneous loco-regional recurrence (LRR) or distant metastases (DM). We used the cumulative incidence method to calculate the gap recurrence rate with DM, LRR, and death, as competing risks.

Results: 230 patients were included with median age 52 years, predominantly stage III disease (60%), and most treated with preoperative (51%) or postoperative (41%) systemic therapy. Breast cancer subtype was ER+/HER2- in 138 patients, triple negative in 44 patients, and HER2+ in 48 patients. The median (IQR) mean dose, V40Gy, V45Gy, and V47.5 Gy in the gap region were: 20.3 Gy (14.8-26.2 Gy), 6% (1.3%-20.0%), 0.6% (0%-7.0%), and 0% (0%-1.3%). The mean dose to the gap region was slightly higher in patients treated with IMRT (N=68) compared to 3DCRT (N=162): 25.3 Gy (SD 7.5 Gy) vs. 19.5 Gy (SD 8.0 Gy), p&lt;0.0001. With median follow-up of 32 months, there were 2 recurrences in the gap region, both of which occurred with simultaneous distant metastases. No patients had isolated recurrences in the gap region. The 3-year cumulative incidence of recurrence in the gap region was 0.8%. The predominant pattern of failure was DM (N=31) with a 3-year rate of 14.4% followed by LRR (N=6, 4 with simultaneous distant metastases) with a 3-year rate of 3.1%.

Conclusion: In a clinical practice in which we routinely contour and treat the IMN PTV and SCV PTV with a gap region between those two volumes, we found that the mean radiation dose to this region is low, at about 50% or less compared to the prescription dose. Despite this, recurrences in this region are exceedingly uncommon and have not yet occurred in the absence of simultaneous DM. While the follow-up is limited, these data support the current guidelines of not routinely targeting this region.

Citation Format: Bazan JG, Dicostanzo D, Healy E, Beyer S, White JR. Analysis of radiation dose in the gap region between the supraclavicular target volume to the internal mammary target volume in women receiving regional nodal irradiation [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-12-03.

Abstract P3-12-04: Analysis of radiation dose to the shoulder by treatment technique and correlation with patient reported outcomes in patients receiving regional nodal irradiation

Background: Shoulder/arm morbidity is a late complication of breast cancer treatment. Postmastectomy radiation therapy (PMRT)/regional nodal irradiation (RNI) increases dose to the muscles and soft tissues of the shoulder and upper neck and back. Most patients are treated with 3D conformal radiation therapy (3DCRT) or Intensity modulated radiation therapy (IMRT). Here, we set to analyze the impact of 3DCRT vs. IMRT on radiation dose to the shoulder, and to retrospectively explore the relationship of treatment technique on long term patient-reported outcomes in the subset of patient who had completed the quick Disabilities of the Arm, Shoulder, and Hand (q-DASH) questionnaire.

Materials/Methods: We identified consecutive patients in our department treated with PMRT/RNI for curative intent from 2013-2016. We excluded patients treated for recurrent disease, those with metastatic disease, and those with unresected disease in the supraclavicular (SCV) fossa and/or axillary apex requiring a radiation boost to that area. We contoured the shoulder as all of the muscles/soft tissue/bone from 2 cm above the ipsilateral SCV planning target volume (PTV) to the cranial aspect of the breast or chestwall PTV. No planning constraints were set for the shoulder since this was retrospectively contoured. We used the dose volume histogram to determine the volume of shoulder receiving at least 5 Gy, 10 Gy,...,50 Gy (V5-V50, respectively). We identified patients that completed a q-DASH questionnaire ≥6 months from the end of PMRT/RNI. Descriptive statistics were used to summarize the shoulder dose and q-DASH values. Differences between groups were assessed by the t-test or chi-square test with p&lt;0.05 considered significant.

Results: We found 237 patients treated with PMRT/RNI with median age of 52 y (IQR 44-60 y), 75% treated with mastectomy, 85% had axillary lymph node dissection (ALND), median of 18 nodes removed (IQR 12-26). All patients received 50 Gy/25 fractions. A total of 68 patients (28.7%) were treated with IMRT. IMRT significantly reduced the V20-V50 to the shoulder vs. 3DCRT (e.g., V45Gy=21.7 mL vs. 208.4 mL, p&lt;0.0001). Of the 237 patients, 66 had completed a q-DASH at least 6 months from the end of radiation therapy (median, 14.5 months). Patients that completed the q-DASH vs. not were similar in age (p=0.29), number of nodes removed (p=0.17), use of ALND (p=0.13), use of chemotherapy (p=0.49) and use of mastectomy (p=0.22). The median (IQR) and mean (SD) q-DASH were 20.5 (6.8-38.6) and 24.3 (20.2) for all patients; 20.5 (9.1-38.6) and 24.1 (19.4) for the 53 mastectomy patients; 18.2 (4.5-45.5) and 25.2 (24.2) for the 13 lumpectomy patients. Most patients (N=49) were treated with 3DCRT. Compared to patients treated with 3DCRT, IMRT patients had a trend towards lower q-DASH mean scores: 16.9 vs. 26.9, p=0.077.

Conclusion: In summary, we found that IMRT reduces radiation dose to the shoulder and is associated with a trend towards reduced q-DASH scores at least 6 months after PMRT/RNI in a subset of our cohort. These results support prospective evaluation of IMRT as a technique to reduce shoulder morbidity in breast cancer patients receiving PMRT/RNI.

Citation Format: Bazan JG, Dicostanzo D, Hock K, Healy E, Beyer S, White JR. Analysis of radiation dose to the shoulder by treatment technique and correlation with patient reported outcomes in patients receiving regional nodal irradiation [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-12-04.

Abstract P2-11-07: Evaluation of lung and heart dose in patients treated with radiation for breast cancer

BACKGROUND: A recent systematic review of women receiving radiation therapy (RT) for breast cancer combined with modeled estimated risks of mortality from heart disease and lung cancer found that the mean heart dose (MHD) was 4.4 Gy (5.2 Gy for left-sided, 3.7Gy for right-sided) and the mean total lung dose (TLD) was 5.7 Gy. Estimated excess cardiac mortality ranged from 0.3-1.2% and lung cancer mortality ranged from 0.2-4.4% with modern RT. Using these data as a benchmark, we set to review the MHD and mean TLD for our patients receiving adjuvant breast RT in a modern era when RT planning includes meeting normal tissue constraints.

METHODS: We evaluated the MHD and mean TLD for patients with unilateral breast cancer treated with curative intent between January 2012 and May 2017 at our institution. Dosimetric data was complete for 793 patients. During this time period the MHD constraint was 4 Gy and lung V20 was 20% for breast only and 35% for regional nodal irradiation (RNI). RNI included the axillary, supraclavicular and internal mammary nodes.. Patients were evaluated by laterality (right vs. left), prone vs. supine position, breast only whole breast irradiation (WBI) and RNI with intact breast or chestwall post-mastectomy. The RNI group was examined by treatment technique, intensity modulated radiation therapy (IMRT) vs. 3D conformal (3DCRT). We compared differences in the MHD and mean TLD within those groups using the Student's t-test.

RESULTS: We identified 651 patients: 481 WBI only and 170 RNI. In the RNI group, 77 (45.3%) received IMRT. Of the WBI only group, 229 (47.6%) were right-sided and 313 (65.1%) were treated prone. The mean TLD for the WBI only group was significantly lower in the prone vs. supine position (0.62 Gy vs. 3.90 Gy, p&lt;0.0001). The prone position resulted in lower MHD for both left-sided WBI (1.17 Gy vs. 1.67 Gy, p&lt;0.0001) and right-sided WBI (0.51 Gy vs. 0.64 Gy, p=0.1067). In patients that received RNI, the mean TLD was 8.20 Gy (SD 1.03) and the MHD was 2.67 Gy (3.25 Gy for left-sided vs. 1.83 Gy for right-sided, p=0.0001). Compared to 3DCRT, IMRT increased the MHD (2.46 Gy vs. 4.23 Gy for left-sided, p&lt;0.0001; 0.94 Gy vs. 2.85 Gy, p&lt;0.0001 for right-sided) and mean TLD (8.50 Gy vs. 7.95 Gy, p=0.0005).

CONCLUSIONS: In the era of RT treatment planning that incorporates normal tissue constraints, very low MHD and lower TLD are achievable in prone or supine position patients receiving WBI only for breast conserving treatment. This means lower late cardiac and lung cancer mortality risks from RT. Women that receive RNI also have acceptably low MHD but high mean TLD. Node positive breast cancer patients derive a disease free survival benefit from RNI, which must be balanced against potential late risk for lung cancer, especially in smokers. More attention should be focused on identifying lung cancer risk, smoking cessation and screening efforts in node positive breast cancer patients with indications for RNI to minimize late radiation risks.

Citation Format: Healy EH, Pratt DN, DiCostanzo D, Bazan JG, White J. Evaluation of lung and heart dose in patients treated with radiation for breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-11-07.

Abstract OT2-03-01: Multi-institution phase II trial of intraoperative electron beam radiotherapy boost at the time of breast conserving surgery with oncoplastic reconstruction in women with early-Stage breast cancer

Background: In women amenable to breast conserving therapy, lumpectomy followed by adjuvant whole breast irradiation (WBI) remains the standard of care. Randomized trials have demonstrated that the addition of a lumpectomy cavity boost significantly reduces the risk of ipsilateral breast tumor recurrences but also increases the risk of breast fibrosis. Contemporary randomized trials define the lumpectomy cavity boost volume as a 1.7 cm isometric expansion on the lumpectomy cavity as delineated on CT. However, identifying the lumpectomy cavity can be challenging, especially in women that receive adjuvant chemotherapy and in cases in which surgical clips are not present. Recently, the use of oncoplastic techniques in breast conserving surgery has increased. These techniques are used to prevent the poor cosmetic results that can occur when a large volume of breast tissue is resected. Women that undergo oncoplastic reconstruction represent especially difficult cases for lumpectomy cavity delineation. Retrospective series have evaluated the use of intraoperative electron radiotherapy (IOERT) as a boost prior to WBI in women receiving lumpectomy without oncoplastic reconstruction. In the largest series of IOERT boost prior to WBI the local control rate of this approach was &gt;99%. Prospective data regarding IOERT boost in women undergoing oncoplastic reconstruction are limited. Advantages of this approach include direct visualization/irradiation of the tumor bed, sparing the skin of irradiation, and reducing the treatment time by ˜1 week. We hypothesize that IOERT boost followed by WBI will result in acceptably low rates of grade 3 fibrosis in women undergoing lumpectomy with oncoplastic reconstruction.

Trial Design: This is a single-arm, prospective study to evaluate the safety, toxicity and efficacy of IOERT boost at the time of breast conserving surgery in women with early-stage breast cancer undergoing oncoplastic reconstruction. Eligible women will receive 1 dose of 8 Gy to the surgical bed after lumpectomy but prior to oncoplastic reconstruction. Women will then receive adjuvant WBI of 40 Gy in 15 fractions or 50 Gy in 25 fractions.

Eligibility: Key inclusion criteria include age≥18 yo, clinically node-negative stage I/II, any breast cancer subtype.

Specific Aims: Our primary aim is to determine the rate of grade 3 breast fibrosis at 1 year. Additional aims include surgical complication rates, cosmesis, and local regional cancer control.

Statistical Methods: Safety will be evaluated by the rate of surgical complications necessitating hospital readmission or return to the operating room within 30 days of surgery+IOERT. If ≥4 events in the first 10 patients, ≥7 events in the first 20 patients, or ≥9 events in the first 30 patients are seen, the study will be halted. We hypothesize that the grade 3 fibrosis rate in our study will be ≤5%. Assuming an actual rate of 4%, an unacceptable rate of 9%, and a drop-out rate of 10%, the expected sample size is 176.

Patient Accrual: Current accrual is 0 of 176.

Contact Information: Soyhum McElroy (soyhun.mcelroy@osumc.edu) or Jose Bazan (jose.bazan2@osumc.edu)

Funding Source: Intraop Medical

Citation Format: Bazan JG, Stephens J, Terando A, Skoracki R, McElroy S, Sexton J, Gupta N, White J. Multi-institution phase II trial of intraoperative electron beam radiotherapy boost at the time of breast conserving surgery with oncoplastic reconstruction in women with early-Stage breast cancer [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr OT2-03-01.

Abstract P1-11-05: Influence of race and age on mastectomy rates in women with stage I, hormone-sensitive breast cancers: A SEER-based study

Background: Breast conserving therapy (lumpectomy [L] and breast radiotherapy [RT]) results in equivalent cancer control outcomes in comparison to mastectomy (M) for early stage breast cancer (BC) based on randomized controlled trials (RCT). Since 2004, RCT support that L alone without RT yields equivalent survival and acceptable local regional outcomes in women ≥70 years old with stage I (T1N0) hormone-sensitive (HS) BC on endocrine therapy. Based on this, we hypothesized that M rates should decrease substantially in this low risk elderly population and sought to examine the influence of race on M rates in this group and how these trends compare to younger aged Stage I HS patients.

Methods: We used the Surveillance Epidemiology and End Results (SEER) registry data to conduct this study. We included women with T1N0 HS BC classified as either ER-positive or PR-positive from 2000-2012 divided into 2 age groups [elderly (≥70 years old) and non-elderly (20-69 years old)] and 3 race groups [white, black, and Asian-Pacific-Islander/American Indian/Alaskan Native (API)]. We compared M rates in women diagnosed before 2004 compared to those diagnosed from 2005-2012. Statistical analyses were performed using differences in proportions (p&lt;0.05 considered statistically significant).

Results: 261,079 women met the study criteria (N=87,009 elderly; N=174,070 non-elderly). In elderly Stage I HS BC, a 5.2% reduction in the M rate is seen: 32.6% before 2004 to 27.4% after 2004 (p&lt;0.0001). M rates remained higher (with less reduction) in elderly Black (30.8 %) and API (33.6 %) vs. White (26.8%) [p&lt;0.0001 for White vs. Black and for White vs. API]. In non-elderly Stage I HS BC, after 2004 M rates increased from 29.2% to 31.8% (p&lt;0.0001). Non-elderly white women had the largest absolute increase in M rates (31.2% vs. 28.5%, p&lt;0.0001) followed by API women (35.1% vs. 37.1%, p=0.0222). M rates did not change after 2004 in non-elderly black women (31.7% vs. 31.7%, p=0.9953).

Conclusions: In patients with favorable stage I HS BC, M rates have decreased only modestly in elderly women since 2004 when L alone w/o RT was established as appropriate treatment. In comparison, M has increased since 2004 in non-elderly women. These trends are driven mostly by white women in both the elderly and non-elderly. Further research is needed to identify why M, which is associated with higher cost and morbidity than L alone, has not changed substantially in elderly very favorable BC, particularly for non-whites.

Citation Format: Bazan JG, Bittoni MA, Fisher JL, White JR. Influence of race and age on mastectomy rates in women with stage I, hormone-sensitive breast cancers: A SEER-based study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-11-05.

Abstract P3-12-01: Locoregional failure rates do not vary by breast cancer subtype after mastectomy in a modern cohort of patients with T1-2 tumors with 1-3 pathologically involved lymph nodes

Purpose/Objective(s): A recent meta-analysis of 22 randomized trials accrued between 1964-86 demonstrated significantly higher rates of locoregional failure (LRF), total failure (TF) and breast-cancer mortality in women with 1-3 positive (+) axillary lymph nodes (ALN) who did not receive radiotherapy after mastectomy (mast.). Given the improvements in diagnostic and therapeutic approaches, the challenge today is whether breast cancer patients with T1-T2 tumors with 1-3+ ALN have similar substantial risk that routinely warrants the delivery of post mastectomy radiotherapy (PMRT). We further set out to explore whether the risk of failure varies by breast cancer subtype.

Materials/Methods: We reviewed patients with pathologic T1-2N1 breast cancer treated with initial mast. and adjuvant systemic therapy (ST) from 2000-2013. The primary endpoint was LRF, defined as a recurrence in either the ipsilateral chestwall or regional lympatics (axillary, internal mammary, or supraclavicular nodes). Secondary endpoints include rates of TF (LRF or distant metastases), disease-free survival (DFS, failure or death), and overall survival (OS). Patients were classified into 3 basic subtypes: hormone receptor positive/HER2 negative (HR+), HER2 positive (HER2+), and triple negative (TN). Survival analysis was performed using the Kaplan-Meier method. The log-rank test was used to compare survival between groups.

Results: We identified 550 eligible patients from our prospectively maintained cancer registry. Median follow-up was 5 years. Baseline characteristics included median age 53 yrs, 61% pathologic T2, 39% grade 3, 48% with lymphovascular invasion. Subtypes included 72% HR+ (n=393), 16% HER2+ (n=89), 12% TN (n=66) and 0.4% unknown (n=2). Treatment included chemotherapy in 78% (n=428), PMRT in 15% (n=82), and anti-endocrine therapy in 70% (n=385). A median of 18 ALN (range, 1-68) were removed, 10% (N=55) had sentinel-lymph node biopsy only, and 17%(N=95) had micrometastases (N1mic) only. A total of 296 pts had 1+ node, 165 pts 2+ nodes and 89 pts 3+ nodes. The 5 yr LRF rate for the entire cohort was 3.9% and patients with 1+, 2+, and 3+ nodes had 5 yr LRF of 2.6%, 4.7% and 6.4%, respectively (p=0.79). The 5 yr LRF for HR+, HER2+ and TN was 3.9%, 1.5%, and 6.6%, respectively (p=0.39). When stratified by 1+, 2+ or 3+ nodes, the 5 yr LRF for HR+ vs. HER2+ vs. TN were 2.4%, 6.8%, and 0% vs. 5.8%, 15.4%, and 0% vs. 5.7%, 0%, and 4.8%, p=0.43. The 5 yr TF, DFS, and OS rates for HR+, HER2+ and TN were 90.5% vs. 88.5%. vs. 83.6% (p=0.76); 84.9% vs. 82.6% vs. 79.2% (p=0.85); and 91.4% vs. 86.2% vs. 81.3% (p=0.83).

Conclusions: In a cohort of patients with T1-2N1 breast cancer treated with modern therapy, we found low rates of LRF which did not vary amongst HR+, HER2+ and TN patients. In particular, HR+ patients with 1+ LN had extremely low rates of LRF Given these low recurrence rates, caution should be given in routinely recommending PMRT for every woman with 1-3+ ALN after mast. and adjuvant ST.

Citation Format: Bazan JG, Majithia L, Quick AM, Terando AM, Agnese D, Mrozek E, Farrar W, White JR. Locoregional failure rates do not vary by breast cancer subtype after mastectomy in a modern cohort of patients with T1-2 tumors with 1-3 pathologically involved lymph nodes. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-12-01.