Verification of representative data for output factors of SRS cones utilizing IAEA TRS 483 recommendations.

Measurements of small fields continue to be a clinical challenge despite the recent work done to identify their characteristics. Due to this challenge, many physicists use representative data supplied by their vendors to verify their own measurements for small field output factors. However, with recent guidelines being released in IAEA TRS 483, the question remains if this representative data provides an accurate representation for small field dosimetry. A Sun Nuclear EDGE detector, PTW 60012 stereotactic diode, and GafChromic EBT3 films were used to measure the output factor for a set of Varian SRS cones (4 mm-17.5 mm diameters) on a TrueBeam linear accelerator. The measured output factors were then compared to the Varian provided SRS representative data. IAEA TRS 483 recommendations for measuring small field output factors were applied and the impact of those recommendations were examined. The EDGE detector showed good agreement with the representative data when correction factors were not applied (0.01%-1.64% difference) but the PTW 60012 diode showed larger deviation (0.61%-3.35% difference). The EBT3 film showed the largest difference with the representative data (0.66%-9.19%). After application of IAEA TRS 483 detector specific correction factors the output factors measured by the diodes showed good agreement with the EBT3 film for 6MV (<1.8% difference) but showed a large deviation with the representative data (up to 9% difference). The 6FFF energy output factors agreed between the EDGE, the PTW 60012, and EBT3 Film. This work shows that the use of uncorrected representative data on the Truebeam can lead to a significant over estimation of the SRS cone output factors.

A New Technique Using 4DCT Scans to Create Custom Cardiac Blocks for Left-Sided Breast Cancer Treatments.

PURPOSE: For patients who receive treatment for left breast cancer, cardiac toxicity increases with increased radiation dose to the heart. A new method was developed using 4-dimensional computed tomography (CT) scans to improve custom cardiac blocks to minimize heart dose. METHODS AND MATERIALS: Four-dimensional CT scans were acquired, and a maximum intensity projection (MIP) heart was contoured for 20 patients. Custom heart blocks were created to fully block the MIP heart volume. A heart block based on the standard free-breathing (FB) CT image was retrospectively created. Differences in heart block sizes were compared. Differences in heart block areas and dose statistics were analyzed. RESULTS: In all 20 cases, the heart block created using the 4-dimensional scan had a larger area than the corresponding FB block. The mean increase in multileaf collimator coverage was 3.9 mm (range, 0.5-20.1 mm). The mean increase in the area of the heart block was 2.58 cm2 (range, 0.22-6.65 cm2). The dose-volume histogram showed that the MIP heart received 17.8 cGy (range, 0.02-70.3 cGy) more than the FB heart on average. Replanning with an FB heart block showed that the mean dose to the MIP heart increased by 16.2 cGy (range, 1.8-44.8 cGy) compared with the FB heart dose. CONCLUSIONS: Four-dimensional heart blocks accounting for intrinsic respiratory motion and cardiac motion were greater in size than FB heart blocks. These larger blocks resulted from the larger contour created from the MIP image and blocked more dose to the heart. This technique for improving custom heart blocks can be easily implemented with 4DCT machine capabilities that are currently available in clinical practice.

Management of Ductal Carcinoma In Situ (DCIS) of the Breast: Present Approaches and Future Directions.

PURPOSE OF REVIEW: Ductal carcinoma in situ (DCIS; intraductal carcinoma) of the breast is commonly found in an asymptomatic woman on routine screening mammography. The purpose of this review is to describe current approaches to the management of DCIS as well as areas for future investigation. RECENT FINDINGS: Randomized trials have demonstrated that adding radiation treatment after breast conservation surgery (lumpectomy; surgical excision) reduces the rate of ipsilateral local recurrence by about half, and that adding hormonal therapy reduces the rate of all breast cancer events (ipsilateral plus contralateral). Early clinical studies attempted to stratify the risk of recurrence using conventional clinical and pathologic features. More recent clinical studies have attempted to define prospectively patients with lower risk DCIS for whom omission of radiation treatment after lumpectomy is a reasonable option. Molecular profiling is a newer approach to define risk stratification for DCIS. Combining molecular profiling with clinical and pathologic features appears to be more accurate in defining and stratifying the risk of recurrence after lumpectomy. After lumpectomy for DCIS, risk stratification using clinical and pathologic characteristics, and more recently molecular profiling, can help guide clinical decision-making for the use of radiation treatment and hormonal therapy. Ongoing studies are evaluating the possibility of de-escalating therapy, and in some studies, even using core biopsy alone, without surgical excision.

Association of Magnetic Resonance Imaging and a 12-Gene Expression Assay With Breast Ductal Carcinoma In Situ Treatment.

IMPORTANCE: Advanced diagnostics, such as magnetic resonance imaging (MRI) and gene expression profiles, are potentially useful to guide targeted treatment in patients with ductal carcinoma in situ (DCIS). OBJECTIVES: To examine the proportion of patients who converted to mastectomy after MRI and the reasons for those conversions and to measure patient adherence to radiotherapy guided by the 12-gene DCIS score. DESIGN, SETTING, AND PARTICIPANTS: Analysis of a prospective, cohort, nonrandomized clinical trial that enrolled women with DCIS on core biopsy who were candidates for wide local excision (WLE) from 75 institutions from March 25, 2015, to April 27, 2016, through the Eastern Cooperative Oncology Group-American College of Radiology Imaging Network trial E4112. INTERVENTIONS: Participants underwent breast MRI before surgery, and subsequent management incorporated MRI findings for choice of surgery. The DCIS score was used to guide radiotherapy recommendations among women with DCIS who had WLE as the final procedure and had tumor-free excision margins of 2 mm or greater. MAIN OUTCOMES AND MEASURES: The primary end point was to estimate the conversion rate to mastectomy and the reason for conversion. RESULTS: Of 339 evaluable women (mean [SD] age, 59.1 [10.1] years; 262 [77.3%] of European descent) eligible for WLE before MRI, 65 (19.2%; 95% CI, 15.3%-23.7%) converted to mastectomy. Of these 65 patients, conversion was based on MRI findings in 25 (38.5%), patient preference in 25 (38.5%), positive margins after attempted WLE in 10 (15.4%), positive genetic test results in 3 (4.6%), and contraindication to radiotherapy in 2 (3.1%). Among the 285 who had WLE performed after MRI as the first surgical procedure, 274 (96.1%) achieved successful breast conservation. Of 171 women eligible for radiotherapy guided by DCIS score (clear margins, absence of invasive disease, and score obtained), the score was low (<39) in 82 (48.0%; 95% CI, 40.6%-55.4%) and intermediate-high (≥39) in 89 (52.0%; 95% CI, 44.6%-59.4%). Of these 171 patients, 159 (93.0%) were adherent with recommendations. CONCLUSIONS AND RELEVANCE: Among women with DCIS who were WLE candidates based on conventional imaging, multiple factors were associated with conversion to mastectomy. This study may provide useful preliminary information required for designing a planned randomized clinical trial to determine the effect of MRI and DCIS score on surgical management, radiotherapy, overall resource use, and clinical outcomes, with the ultimate goal of achieving greater therapeutic precision. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT02352883.

Contemporary Guidelines in Whole-Breast Irradiation: An Alternative Perspective.

The American Society for Radiation Oncology produced an evidence-based guideline on whole-breast radiation therapy for patients with early-stage invasive breast cancer and ductal carcinoma in situ. This commentary points out areas where we believe the data are too limited to make definitive recommendations and where alternative approaches are supported by evidence.

Long-term risk of second malignancies in women after breast conservation therapy for ductal carcinoma in situ or early-stage breast cancer.

PURPOSE: Women with ductal carcinoma in situ (DCIS) or early-stage breast cancer have an excellent prognosis, but their risk of developing second malignant neoplasms (SMNs) is not well established. We analyzed SMNs in a large cohort with long follow-up after breast conservation therapy. METHODS: The study population comprised 755 women with DCIS (n = 135) or stage I-II breast carcinoma (n = 620). Subjects were aged 25-89 (median 55) years when they underwent breast-conserving surgery followed by radiotherapy to the entire breast (60-68Gray) between 1992 and 2001. Additional treatment included hormonal therapy and/or chemotherapy based on clinical characteristics. SMNs were grouped by site. The rate of SMNs over time was determined using the Kaplan-Meier method. To compare the probability of developing SMNs overall and for specific organs or sites, probability estimates were obtained for a 55-year-old female from the Surveillance, Epidemiology, and End Results Program (SEER). RESULTS: Median follow-up from radiotherapy was 13.8 years. The 15-year age-adjusted probability of developing any SMN was 12.0%, close to the SEER rate of 12.1% for a non-breast malignancy. Systemic therapy and higher-dose radiotherapy (> 63 Gray) were not associated with significantly increased risks of SMNs. Compared to SEER, significantly increased risk was noted for gynecologic cancers and melanoma. CONCLUSIONS: Most SMNs were unrelated to treatment, and the 15-year incidence was similar to that of cancer in the SEER control group-findings that should be reassuring to patients. Further risk reduction is expected from prophylactic gynecologic surgery. Continued investigations into genetic links with melanoma are warranted.

Breast Cancer-Major changes in the American Joint Committee on Cancer eighth edition cancer staging manual.

Answer questions and earn CME/CNE The revision of the eighth edition of the primary tumor, lymph node, and metastasis (TNM) classification of the American Joint Commission of Cancer (AJCC) for breast cancer was determined by a multidisciplinary team of breast cancer experts. The panel recognized the need to incorporate biologic factors, such as tumor grade, proliferation rate, estrogen and progesterone receptor expression, human epidermal growth factor 2 (HER2) expression, and gene expression prognostic panels into the staging system. AJCC levels of evidence and guidelines for all tumor types were followed as much as possible. The panel felt that, to maintain worldwide value, the tumor staging system should remain based on TNM anatomic factors. However, the recognition of the prognostic influence of grade, hormone receptor expression, and HER2 amplification mandated their inclusion into the staging system. The value of commercially available, gene-based assays was acknowledged and prognostic input added. Tumor biomarkers and low Oncotype DX recurrence scores can alter prognosis and stage. These updates are expected to provide additional precision and flexibility to the staging system and were based on the extent of published information and analysis of large, as yet unpublished databases. The eighth edition of the AJCC TNM staging system, thus, provides a flexible platform for prognostic classification based on traditional anatomic factors, which can be modified and enhanced using patient biomarkers and multifactorial prognostic panel data. The eighth edition remains the worldwide basis for breast cancer staging and will incorporate future online updates to remain timely and relevant. CA Cancer J Clin 2017;67:290-303. © 2017 American Cancer Society.

No impact of breast magnetic resonance imaging on 15-year outcomes in patients with ductal carcinoma in situ or early-stage invasive breast cancer managed with breast conservation therapy.

BACKGROUND: For women undergoing breast conservation therapy (BCT), the added value of breast magnetic resonance imaging (MRI) at the time of initial diagnosis remains controversial. The current study was performed to determine long-term outcomes after BCT for women with and without pretreatment breast MRI. METHODS: Between 1992 and 2001, a total of 755 women with ductal carcinoma in situ or early-stage invasive breast cancer underwent breast-conserving surgery (with axillary lymph node staging for invasive carcinoma) followed by definitive breast radiotherapy. Evaluation at the time of the initial diagnosis included conventional mammography in all subjects and breast MRI in 215 women (28%). Clinical, pathologic, and treatment characteristics were comparable for patients with and without breast MRI. Outcomes were determined using the Kaplan-Meier method and compared using the log-rank method. RESULTS: At a median follow-up of 13.8 years, there were 49 local failures (15 women with and 34 women without breast MRI, respectively). The 15-year local failure rates were 8% for women with and 8% for women without MRI (P = .59). There also were no differences noted between women with and without breast MRI with regard to 15-year rates of overall survival (77% vs 71%; P = .24), freedom from distant metastases (86% vs 90%; P = .08), and contralateral breast cancer (10% vs 8%; P = .10). Multivariate analysis demonstrated no significant impact of breast MRI on local failure (P = .96). CONCLUSIONS: Breast MRI during the initial evaluation for BCT appears to have no significant impact on 15-year rates for local control, overall survival, freedom from distant metastases, or contralateral breast cancer. The routine use of pretreatment breast MRI is not indicated for patients undergoing BCT. Cancer 2017;123:1324-1332. © 2016 American Cancer Society.

Postmastectomy Radiotherapy: An American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Focused Guideline Update.

PURPOSE: A joint American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology panel convened to develop a focused update of the American Society of Clinical Oncology guideline concerning use of postmastectomy radiotherapy (PMRT). METHODS: A recent systematic literature review by Cancer Care Ontario provided the primary evidentiary basis. The joint panel also reviewed targeted literature searches to identify new, potentially practice-changing data. RECOMMENDATIONS: The panel unanimously agreed that available evidence shows that PMRT reduces the risks of locoregional failure (LRF), any recurrence, and breast cancer mortality for patients with T1-2 breast cancer with one to three positive axillary nodes. However, some subsets of these patients are likely to have such a low risk of LRF that the absolute benefit of PMRT is outweighed by its potential toxicities. In addition, the acceptable ratio of benefit to toxicity varies among patients and physicians. Thus, the decision to recommend PMRT requires a great deal of clinical judgment. The panel agreed clinicians making such recommendations for individual patients should consider factors that may decrease the risk of LRF, attenuate the benefit of reduced breast cancer-specific mortality, and/or increase risk of complications resulting from PMRT. When clinicians and patients elect to omit axillary dissection after a positive sentinel node biopsy, the panel recommends that these patients receive PMRT only if there is already sufficient information to justify its use without needing to know additional axillary nodes are involved. Patients with axillary nodal involvement after neoadjuvant systemic therapy should receive PMRT. The panel recommends treatment generally be administered to both the internal mammary nodes and the supraclavicular-axillary apical nodes in addition to the chest wall or reconstructed breast.

Clinical Utility of the 12-Gene DCIS Score Assay: Impact on Radiotherapy Recommendations for Patients with Ductal Carcinoma In Situ.

OBJECTIVE: The aim of this study was to determine the impact of the results of the 12-gene DCIS Score assay on (i) radiotherapy recommendations for patients with pure ductal carcinoma in situ (DCIS) following breast-conserving surgery (BCS), and (ii) patient decisional conflict and state anxiety. METHODS: Thirteen sites across the US enrolled patients (March 2014-August 2015) with pure DCIS undergoing BCS. Prospectively collected data included clinicopathologic factors, physician estimates of local recurrence risk, DCIS Score results, and pre-/post-assay radiotherapy recommendations for each patient made by a surgeon and a radiation oncologist. Patients completed pre-/post-assay decisional conflict scale and state-trait anxiety inventory instruments. RESULTS: The analysis cohort included 127 patients: median age 60 years, 80 % postmenopausal, median size 8 mm (39 % ≤5 mm), 70 % grade 1/2, 88 % estrogen receptor-positive, 75 % progesterone receptor-positive, 54 % with comedo necrosis, and 18 % multifocal. Sixty-six percent of patients had low DCIS Score results, 20 % had intermediate DCIS Score results, and 14 % had high DCIS Score results; the median result was 21 (range 0-84). Pre-assay, surgeons and radiation oncologists recommended radiotherapy for 70.9 and 72.4 % of patients, respectively. Post-assay, 26.4 % of overall recommendations changed, including 30.7 and 22.0 % of recommendations by surgeons and radiation oncologists, respectively. Among patients with confirmed completed questionnaires (n = 32), decision conflict (p = 0.004) and state anxiety (p = 0.042) decreased significantly from pre- to post-assay. CONCLUSIONS: Individualized risk estimates from the DCIS Score assay provide valuable information to physicians and patients. Post-assay, in response to DCIS Score results, surgeons changed treatment recommendations more often than radiation oncologists. Further investigation is needed to better understand how such treatment changes may affect clinical outcomes.

Postmastectomy Radiotherapy: An American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Focused Guideline Update.

A joint American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology panel convened to develop a focused update of the American Society of Clinical Oncology guideline concerning use of postmastectomy radiotherapy (PMRT). METHODS: A recent systematic literature review by Cancer Care Ontario provided the primary evidentiary basis. The joint panel also reviewed targeted literature searches to identify new, potentially practice-changing data. RECOMMENDATIONS: The panel unanimously agreed that available evidence shows that PMRT reduces the risks of locoregional failure (LRF), any recurrence, and breast cancer mortality for patients with T1-2 breast cancer with one to three positive axillary nodes. However, some subsets of these patients are likely to have such a low risk of LRF that the absolute benefit of PMRT is outweighed by its potential toxicities. In addition, the acceptable ratio of benefit to toxicity varies among patients and physicians. Thus, the decision to recommend PMRT requires a great deal of clinical judgment. The panel agreed clinicians making such recommendations for individual patients should consider factors that may decrease the risk of LRF, attenuate the benefit of reduced breast cancer-specific mortality, and/or increase risk of complications resulting from PMRT. When clinicians and patients elect to omit axillary dissection after a positive sentinel node biopsy, the panel recommends that these patients receive PMRT only if there is already sufficient information to justify its use without needing to know additional axillary nodes are involved. Patients with axillary nodal involvement after neoadjuvant systemic therapy should receive PMRT. The panel recommends treatment generally be administered to both the internal mammary nodes and the supraclavicular-axillary apical nodes in addition to the chest wall or reconstructed breast.

Postmastectomy Radiotherapy: An American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology Focused Guideline Update.

Purpose A joint American Society of Clinical Oncology, American Society for Radiation Oncology, and Society of Surgical Oncology panel convened to develop a focused update of the American Society of Clinical Oncology guideline concerning use of postmastectomy radiotherapy (PMRT). Methods A recent systematic literature review by Cancer Care Ontario provided the primary evidentiary basis. The joint panel also reviewed targeted literature searches to identify new, potentially practice-changing data. Recommendations The panel unanimously agreed that available evidence shows that PMRT reduces the risks of locoregional failure (LRF), any recurrence, and breast cancer mortality for patients with T1-2 breast cancer with one to three positive axillary nodes. However, some subsets of these patients are likely to have such a low risk of LRF that the absolute benefit of PMRT is outweighed by its potential toxicities. In addition, the acceptable ratio of benefit to toxicity varies among patients and physicians. Thus, the decision to recommend PMRT requires a great deal of clinical judgment. The panel agreed clinicians making such recommendations for individual patients should consider factors that may decrease the risk of LRF, attenuate the benefit of reduced breast cancer-specific mortality, and/or increase risk of complications resulting from PMRT. When clinicians and patients elect to omit axillary dissection after a positive sentinel node biopsy, the panel recommends that these patients receive PMRT only if there is already sufficient information to justify its use without needing to know additional axillary nodes are involved. Patients with axillary nodal involvement after neoadjuvant systemic therapy should receive PMRT. The panel recommends treatment generally be administered to both the internal mammary nodes and the supraclavicular-axillary apical nodes in addition to the chest wall or reconstructed breast.

Society of Surgical Oncology-American Society for Radiation Oncology-American Society of Clinical Oncology Consensus Guideline on Margins for Breast-Conserving Surgery with Whole-Breast Irradiation in Ductal Carcinoma In Situ.

PURPOSE: Controversy exists regarding the optimal negative margin width for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery and whole-breast irradiation. METHODS: A multidisciplinary consensus panel used a meta-analysis of margin width and ipsilateral breast tumor recurrence (IBTR) from a systematic review of 20 studies including 7,883 patients and other published literature as the evidence base for consensus. RESULTS: Negative margins halve the risk of IBTR compared with positive margins defined as ink on DCIS. A 2-mm margin minimizes the risk of IBTR compared with smaller negative margins. More widely clear margins do not significantly decrease IBTR compared with 2-mm margins. Negative margins narrower than 2 mm alone are not an indication for mastectomy, and factors known to affect rates of IBTR should be considered in determining the need for re-excision. CONCLUSION: Use of a 2-mm margin as the standard for an adequate margin in DCIS treated with whole-breast irradiation is associated with lower rates of IBTR and has the potential to decrease re-excision rates, improve cosmetic outcomes, and decrease health care costs. Clinical judgment should be used in determining the need for further surgery in patients with negative margins narrower than 2 mm.

The Association of Surgical Margins and Local Recurrence in Women with Ductal Carcinoma In Situ Treated with Breast-Conserving Therapy: A Meta-Analysis.

PURPOSE: There is no consensus on adequate negative margins in breast-conserving surgery (BCS) for ductal carcinoma in situ (DCIS). We systematically reviewed the evidence on margins in BCS for DCIS. METHODS: A study-level meta-analysis of local recurrence (LR), microscopic margin status and threshold distance for negative margins. LR proportion was modeled using random-effects logistic meta-regression (frequentist) and network meta-analysis (Bayesian) that allows for multiple margin distances per study, adjusting for follow-up time. RESULTS: Based on 20 studies (LR: 865 of 7883), odds of LR were associated with margin status [logistic: odds ratio (OR) 0.53 for negative vs. positive/close (p < 0.001); network: OR 0.45 for negative vs. positive]. In logistic meta-regression, relative to >0 or 1 mm, ORs for 2 mm (0.51), 3 or 5 mm (0.42) and 10 mm (0.60) showed comparable significant reductions in the odds of LR. In the network analysis, ORs relative to positive margins for 2 (0.32), 3 (0.30) and 10 mm (0.32) showed similar reductions in the odds of LR that were greater than for >0 or 1 mm (0.45). There was weak evidence of lower odds at 2 mm compared with >0 or 1 mm [relative OR (ROR) 0.72, 95 % credible interval (CrI) 0.47-1.08], and no evidence of a difference between 2 and 10 mm (ROR 0.99, 95 % CrI 0.61-1.64). Adjustment for covariates, and analyses based only on studies using whole-breast radiotherapy, did not change the findings. CONCLUSION: Negative margins in BCS for DCIS reduce the odds of LR; however, minimum margin distances above 2 mm are not significantly associated with further reduced odds of LR in women receiving radiation.

Society of Surgical Oncology-American Society for Radiation Oncology-American Society of Clinical Oncology Consensus Guideline on Margins for Breast-Conserving Surgery With Whole-Breast Irradiation in Ductal Carcinoma in Situ.

PURPOSE: Controversy exists regarding the optimal negative margin width for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery and whole-breast irradiation. METHODS AND MATERIALS: A multidisciplinary consensus panel used a meta-analysis of margin width and ipsilateral breast tumor recurrence (IBTR) from a systematic review of 20 studies including 7883 patients and other published literature as the evidence base for consensus. RESULTS: Negative margins halve the risk of IBTR compared with positive margins defined as ink on DCIS. A 2-mm margin minimizes the risk of IBTR compared with smaller negative margins. More widely clear margins do not significantly decrease IBTR compared with 2-mm margins. Negative margins narrower than 2 mm alone are not an indication for mastectomy, and factors known to affect rates of IBTR should be considered in determining the need for re-excision. CONCLUSION: Use of a 2-mm margin as the standard for an adequate margin in DCIS treated with whole-breast irradiation is associated with lower rates of IBTR and has the potential to decrease re-excision rates, improve cosmetic outcomes, and decrease health care costs. Clinical judgment should be used in determining the need for further surgery in patients with negative margins narrower than 2 mm.

Society of Surgical Oncology-American Society for Radiation Oncology-American Society of Clinical Oncology Consensus Guideline on Margins for Breast-Conserving Surgery With Whole-Breast Irradiation in Ductal Carcinoma In Situ.

Background Controversy exists regarding the optimal negative margin width for ductal carcinoma in situ (DCIS) treated with breast-conserving surgery and whole-breast irradiation (WBRT). Methods A multidisciplinary consensus panel used a meta-analysis of margin width and ipsilateral breast tumor recurrence (IBTR) from a systematic review of 20 studies including 7883 patients and other published literature as the evidence base for consensus. Results Negative margins halve the risk of IBTR compared with positive margins defined as ink on DCIS. A 2 mm margin minimizes the risk of IBTR compared with smaller negative margins. More widely clear margins do not significantly decrease IBTR compared with 2 mm margins. Negative margins less than 2 mm alone are not an indication for mastectomy, and factors known to impact rates of IBTR should be considered in determining the need for re-excision. Conclusion The use of a 2 mm margin as the standard for an adequate margin in DCIS treated with WBRT is associated with low rates of IBTR and has the potential to decrease re-excision rates, improve cosmetic outcome, and decrease health care costs. Clinical judgment should be used in determining the need for further surgery in patients with negative margins < 2 mm.