Comparison of practice patterns and treatment techniques for regional nodal irradiation with breast conservation vs. postmastectomy in stage I-II breast cancer

Abstract

Purpose/ObjectiveRegional nodal irradiation (RNI) after mastectomy has been the subject of much debate and has generated multiple guidelines about which population of node-positive breast cancer patients benefit most and how radiation should be executed. It is unclear whether similar criteria for RNI are being applied following breast conservation (BC) and mastectomy. The purpose of this study was to utilize the Patterns of Care Study (PCS) to examine how RNI was implemented in Stage I-II cases for BC compared to postmastectomy (PM).Materials/MethodsPCS used a two-staged stratified random sample to perform two separate surveys of breast cancer patients treated in 1998–99:353 survey cases (71,877 weighted sample size [wss]) who underwent radiation after BC surgery and 405 survey cases (wss = 13,720) who received radiation PM. The surveys were conducted simultaneously at 59 randomly selected institutions. For this study, the analyzed population is node-positive and any node-negative breast cancer case that received RNI from both surveys. This resulted in 53 survey (wss = 11,105) BC cases and 208 survey (wss = 7,020) PM cases. Multivariate analysis was done to compare what factors were associated with the type of RNI utilized.ResultsThe populations that received RNI after BC and PM had statistically similar characteristics in terms of the distribution of ethnicity, principal payer, and menopausal status. Patients in the BC group who received RNI are slightly older: mean age was 59.3 yrs vs. 52.7 yrs in the PM group (p = 0.03). PM patients were more likely to be treated at higher volume facilities (treating >500 cases/year, p = 0.01), and academic facilities (p = 0.0003) than their BC counterparts. Similar size tumors were treated with a mean tumor size of 2.1 cm for BC vs. 2.6 cm in the PM group (p = 0.10). Axillary dissection was performed for 72% of the BC cases and 100% of the PM cases (p = 0.004) with similar numbers of nodes within the specimen, (17.9 vs. 17.3 respectively; p = 0.76). After dissection in the BC group 25.4% were node-negative, 56.1% had 1–3 positive nodes, and 18.5% had ≥4 positive nodes compared to 10.9% node negative, 40.3% 1–3 positive nodes, and 48.8% ≥4 positive nodes for PM (p = 0.06). The distribution of nodal metastases differed significantly between BC and PM for≥4 positive nodes, (p = 0.02). Extra capsular extension was more frequent in the PM cases, 30.1% vs. 11.1% (p = 0.056).In the BC survey 47.4% of the patients with 1–3 and 90.6% of the ≥4 positive nodes underwent RNI. When RNI was performed in the BC survey, it included a supraclavicular field (SCL) 80.2%, an axillary (AX) field 36.7%, and internal mammary field (IM) 4.9% as compared to the PM survey, when RNI included a SCL for 98.8% (p = 0.0495), AX 42.5% (p = 0.64), and IM 28.2% (p = 0.005). CT based treatment planning for RNI was used for 35.8% for the BC patients compared to 21.1% for the PM (p = 0.26). In the PM group, lower energy (<8 MV/MEV) was used more frequently for the SCL (p = 0.0495) and AX (p = 0.10) fields. There were no other significant differences between the BC and PM groups in the radiation type (electron or photons), dose, and where the dose was recorded.On multivariate analysis of the BC cases, a T-2 tumor was associated with receiving RT to the SCL field (OR 4.3, p = 0.04). In the PM survey, a T-2 tumor size was associated with RNI to the AX field (OR 2.9, p = 0.03). When the two surveys are combined for multivariate analysis, patients with positive nodes (p < 0.0001) and patients in the PM survey (p = 0.004) had a higher chance of receiving RNI to the SCL field than negative node and BC patients respectively.ConclusionsPatients with Stages I-II breast cancer who received RNI in 1998–99 after BC had similar size tumors but were less likely to have ≥4 positive nodes compared to those treated PM. RNI after BC was significantly less likely to include the internal mammary nodes. Having had a mastectomy rather than BCT was associated with the use of RNI Purpose/ObjectiveRegional nodal irradiation (RNI) after mastectomy has been the subject of much debate and has generated multiple guidelines about which population of node-positive breast cancer patients benefit most and how radiation should be executed. It is unclear whether similar criteria for RNI are being applied following breast conservation (BC) and mastectomy. The purpose of this study was to utilize the Patterns of Care Study (PCS) to examine how RNI was implemented in Stage I-II cases for BC compared to postmastectomy (PM). Regional nodal irradiation (RNI) after mastectomy has been the subject of much debate and has generated multiple guidelines about which population of node-positive breast cancer patients benefit most and how radiation should be executed. It is unclear whether similar criteria for RNI are being applied following breast conservation (BC) and mastectomy. The purpose of this study was to utilize the Patterns of Care Study (PCS) to examine how RNI was implemented in Stage I-II cases for BC compared to postmastectomy (PM). Materials/MethodsPCS used a two-staged stratified random sample to perform two separate surveys of breast cancer patients treated in 1998–99:353 survey cases (71,877 weighted sample size [wss]) who underwent radiation after BC surgery and 405 survey cases (wss = 13,720) who received radiation PM. The surveys were conducted simultaneously at 59 randomly selected institutions. For this study, the analyzed population is node-positive and any node-negative breast cancer case that received RNI from both surveys. This resulted in 53 survey (wss = 11,105) BC cases and 208 survey (wss = 7,020) PM cases. Multivariate analysis was done to compare what factors were associated with the type of RNI utilized. PCS used a two-staged stratified random sample to perform two separate surveys of breast cancer patients treated in 1998–99:353 survey cases (71,877 weighted sample size [wss]) who underwent radiation after BC surgery and 405 survey cases (wss = 13,720) who received radiation PM. The surveys were conducted simultaneously at 59 randomly selected institutions. For this study, the analyzed population is node-positive and any node-negative breast cancer case that received RNI from both surveys. This resulted in 53 survey (wss = 11,105) BC cases and 208 survey (wss = 7,020) PM cases. Multivariate analysis was done to compare what factors were associated with the type of RNI utilized. ResultsThe populations that received RNI after BC and PM had statistically similar characteristics in terms of the distribution of ethnicity, principal payer, and menopausal status. Patients in the BC group who received RNI are slightly older: mean age was 59.3 yrs vs. 52.7 yrs in the PM group (p = 0.03). PM patients were more likely to be treated at higher volume facilities (treating >500 cases/year, p = 0.01), and academic facilities (p = 0.0003) than their BC counterparts. Similar size tumors were treated with a mean tumor size of 2.1 cm for BC vs. 2.6 cm in the PM group (p = 0.10). Axillary dissection was performed for 72% of the BC cases and 100% of the PM cases (p = 0.004) with similar numbers of nodes within the specimen, (17.9 vs. 17.3 respectively; p = 0.76). After dissection in the BC group 25.4% were node-negative, 56.1% had 1–3 positive nodes, and 18.5% had ≥4 positive nodes compared to 10.9% node negative, 40.3% 1–3 positive nodes, and 48.8% ≥4 positive nodes for PM (p = 0.06). The distribution of nodal metastases differed significantly between BC and PM for≥4 positive nodes, (p = 0.02). Extra capsular extension was more frequent in the PM cases, 30.1% vs. 11.1% (p = 0.056).In the BC survey 47.4% of the patients with 1–3 and 90.6% of the ≥4 positive nodes underwent RNI. When RNI was performed in the BC survey, it included a supraclavicular field (SCL) 80.2%, an axillary (AX) field 36.7%, and internal mammary field (IM) 4.9% as compared to the PM survey, when RNI included a SCL for 98.8% (p = 0.0495), AX 42.5% (p = 0.64), and IM 28.2% (p = 0.005). CT based treatment planning for RNI was used for 35.8% for the BC patients compared to 21.1% for the PM (p = 0.26). In the PM group, lower energy (<8 MV/MEV) was used more frequently for the SCL (p = 0.0495) and AX (p = 0.10) fields. There were no other significant differences between the BC and PM groups in the radiation type (electron or photons), dose, and where the dose was recorded.On multivariate analysis of the BC cases, a T-2 tumor was associated with receiving RT to the SCL field (OR 4.3, p = 0.04). In the PM survey, a T-2 tumor size was associated with RNI to the AX field (OR 2.9, p = 0.03). When the two surveys are combined for multivariate analysis, patients with positive nodes (p < 0.0001) and patients in the PM survey (p = 0.004) had a higher chance of receiving RNI to the SCL field than negative node and BC patients respectively. The populations that received RNI after BC and PM had statistically similar characteristics in terms of the distribution of ethnicity, principal payer, and menopausal status. Patients in the BC group who received RNI are slightly older: mean age was 59.3 yrs vs. 52.7 yrs in the PM group (p = 0.03). PM patients were more likely to be treated at higher volume facilities (treating >500 cases/year, p = 0.01), and academic facilities (p = 0.0003) than their BC counterparts. Similar size tumors were treated with a mean tumor size of 2.1 cm for BC vs. 2.6 cm in the PM group (p = 0.10). Axillary dissection was performed for 72% of the BC cases and 100% of the PM cases (p = 0.004) with similar numbers of nodes within the specimen, (17.9 vs. 17.3 respectively; p = 0.76). After dissection in the BC group 25.4% were node-negative, 56.1% had 1–3 positive nodes, and 18.5% had ≥4 positive nodes compared to 10.9% node negative, 40.3% 1–3 positive nodes, and 48.8% ≥4 positive nodes for PM (p = 0.06). The distribution of nodal metastases differed significantly between BC and PM for≥4 positive nodes, (p = 0.02). Extra capsular extension was more frequent in the PM cases, 30.1% vs. 11.1% (p = 0.056). In the BC survey 47.4% of the patients with 1–3 and 90.6% of the ≥4 positive nodes underwent RNI. When RNI was performed in the BC survey, it included a supraclavicular field (SCL) 80.2%, an axillary (AX) field 36.7%, and internal mammary field (IM) 4.9% as compared to the PM survey, when RNI included a SCL for 98.8% (p = 0.0495), AX 42.5% (p = 0.64), and IM 28.2% (p = 0.005). CT based treatment planning for RNI was used for 35.8% for the BC patients compared to 21.1% for the PM (p = 0.26). In the PM group, lower energy (<8 MV/MEV) was used more frequently for the SCL (p = 0.0495) and AX (p = 0.10) fields. There were no other significant differences between the BC and PM groups in the radiation type (electron or photons), dose, and where the dose was recorded. On multivariate analysis of the BC cases, a T-2 tumor was associated with receiving RT to the SCL field (OR 4.3, p = 0.04). In the PM survey, a T-2 tumor size was associated with RNI to the AX field (OR 2.9, p = 0.03). When the two surveys are combined for multivariate analysis, patients with positive nodes (p < 0.0001) and patients in the PM survey (p = 0.004) had a higher chance of receiving RNI to the SCL field than negative node and BC patients respectively. ConclusionsPatients with Stages I-II breast cancer who received RNI in 1998–99 after BC had similar size tumors but were less likely to have ≥4 positive nodes compared to those treated PM. RNI after BC was significantly less likely to include the internal mammary nodes. Having had a mastectomy rather than BCT was associated with the use of RNI Patients with Stages I-II breast cancer who received RNI in 1998–99 after BC had similar size tumors but were less likely to have ≥4 positive nodes compared to those treated PM. RNI after BC was significantly less likely to include the internal mammary nodes. Having had a mastectomy rather than BCT was associated with the use of RNI