Incidental radiation to axilla in early breast cancer treated with intensity modulated tangents and comparison with conventional and 3D conformal tangents

Incidental Axillary Dose of Tomotherapy in Hypofractionated Whole Breast Radiotherapy for Early Breast Cancer: A Dosimetrical Analysis

Background and Objectives: Intensity-modulated radiation therapy (IMRT) is becoming a more common method of performing whole breast irradiation (WBI) for early breast cancer. This study aimed to examine the incidental dose to the axillary region using tomotherapy, a unique form of IMRT. Patients and Methods: This study included 30 patients with early-stage breast cancer who underwent adjuvant WBI using TomoDirect IMRT. A hypofractionation scheme of 42.4 Gy delivered in 16 fractions was prescribed. The plan comprised of two parallel-opposed beams, along with two additional beams positioned anteriorly at gantry angles of 20° and 40° from the medial beam. The incidental dose received at axillary levels I, II, and III was evaluated using several dose-volume parameters. Results: The study participants had a median age of 51 years, and 60% had left-sided breast cancer. The mean dose of the axilla for levels I, II, and III were 15.5 ± 4.8 Gy, 14.9 ± 4.2 Gy, and 1.5 ± 1.6 Gy, respectively. Adequate coverage of the axilla, defined as V95%[%], was achieved for 4.7 ± 3.9%, 4.8 ± 3.7%, and 0 ± 0% for levels I, II, and III, respectively. The results were compared with those of previously published studies, and the axillary mean dose and V95%[%] of TomoDirect IMRT were low, comparable to other IMRT techniques, and lower than those of traditional tangential therapy. Conclusions: While incidental axillary radiation during WBI has been proposed to assist in regional disease control, the TomoDirect plan was demonstrated to decrease this dose, and a hypofractionation scheme would further lower its biological effectiveness. Future clinical studies should incorporate dosimetrical analysis of incidental axillary dose, in order to facilitate hypofractionated IMRT planning with risk-adjusted axilla coverage in early breast cancer.

A Meta-Analysis of Trials of Partial Breast Irradiation

PURPOSE

Partial breast irradiation (PBI) is the delivery of radiation therapy (RT) limited to the tumor bed after breast conserving surgery. The results of recent trials of PBI compared with whole breast irradiation (WBI) have suggested conflicting results with respect to local control and toxicity. The purpose of this meta-analysis was to assess effectiveness of PBI and to compare the different techniques.

METHODS AND MATERIALS

A meta-analysis of aggregate data from published randomized trials was performed to examine the effectiveness of PBI compared with WBI in patients with invasive breast cancer and ductal carcinoma in situ. Relevant data were extracted. The primary outcome was any ipsilateral breast event (invasive or noninvasive). Secondary outcomes included acute and late toxicity. The results of randomized trials were pooled using a fixed effects model and the inverse variance method.

RESULTS

Fifteen trials involving 16,474 patients were identified. The majority of enrolled patients were >60 years of age and had T1N0 grade 1 to 2 disease treated with hormone therapy. The percent of ipsilateral breast events was higher in patients treated with PBI compared with WBI (5.0% vs 2.8%; risk ratio [RR], 1.72; 95% confidence interval [CI], 1.47-2.02). Heterogeneity (P = .0002) was observed between the 4 PBI techniques: external beam RT without computed tomography (CT) planning (RR, 2.06; 95% CI, 1.36-3.12); brachytherapy (RR, 1.21; 95% CI, 0.65-2.25); intraoperative RT (RR, 2.79; 95% CI, 2.08-3.73); and external beam RT with CT planning (RR, 1.25; 95% CI, 0.99-1.58). When external beam RT without CT planning and intraoperative RT trials were excluded, the percent of ipsilateral breast events was 3.3% versus 2.6%, respectively (RR, 1.25; 95% CI, 1.00-1.55; P = .05), and no heterogeneity was observed (P = .92). Overall, acute toxicity was less with PBI, and the effect on late toxicity varied by technique.

CONCLUSIONS

Overall, WBI was more effective than PBI, but the effectiveness of PBI was technique related. PBI was less effective when given by external beam RT without CT planning or intraoperative therapy. Although PBI given by multicatheter brachytherapy or external beam RT with CT planning tended to be statistically less effective than WBI, the absolute difference between groups for ipsilateral breast events was very small (<1%), supporting these approaches for women considering PBI.

Dosimetric Evaluation of Incidental Irradiation to the Internal Mammary Chain After Surgery in Breast Cancer Patients

Background and Purpose

The low rate of internal mammary node (IMN) recurrence was attributed to systemic therapy and internal mammary chain (IMC) coverage by the tangential fields of irradiation. This study aimed to evaluate the incidental irradiation dose to the IMC in breast cancer patients after surgery and to estimate the clinical predictive parameters affecting the magnitude of the IMC.

Materials and Methods

A total of 138 patients treated with postmastectomy radiotherapy and 210 patients undergoing radiotherapy after breast-conserving surgery (BCS) in our hospital were retrospectively analyzed. The mean dose (Dmean) to the IMC and the first to third intercostal spaces of IMC levels (ICS1–3) were evaluated. We evaluated the IMC coverage according to the type of surgery and whether the ipsilateral supraclavicular fossa (SCF) was included in the irradiation field.

Results

The incidental radiation dose to the IMC was 29.69 Gy, and the dose delivered to the IMC, ICS1, and ICS2 showed a greater coverage in the modified radical mastectomy (MRM) group when compared with the BCS group (32.85 vs. 27.1 Gy, 26.6 vs. 12.5 Gy, 34.63 vs. 30.42 Gy). The dose delivered to ICS3 showed no difference between the MRM and BCS groups (37.41 vs. 36.24 Gy). Furthermore, 131 patients (37.64%) received radiotherapy to the chest wall and ipsilateral SCF. In the univariate analysis, both surgery type and SCF irradiation were parameters affecting the Dmean of incidental radiation to the IMC (r = −0.179, P = 0.001; r = −0.175, P = 0.001). In the multivariate analysis, surgery type was the only correlative factor that affected incidental radiation dose to the IMC (r = –3.534, P = 0.000).

Conclusion

The real influencing factor of incidental dose to the IMC was the surgery form rather than the accession of SCF irradiation.

Incidental axillary dose delivery to axillary lymph node levels I-III by different techniques of whole-breast irradiation: a systematic literature review

BACKGROUND AND OBJECTIVE

In breast cancer treatment, radiotherapy is an essential component for locoregional management. Axillary recurrence in patients with invasive breast carcinoma remains an issue. The question of whether breast irradiation may unintentionally include levels I, II, and III, and may decrease the risk of axillary recurrence, remains a topic of discussion.

PATIENTS AND METHODS

A literature search was performed in PubMed and the Cochrane Library to identify articles that have published data regarding dose-volume analysis of axillary levels in breast irradiation. The following MESH terms were used: "breast cancer/lymph nodes" AND "radiotherapy dosage."

RESULTS

Thirteen articles were identified. The irradiation technique, initial dose prescribed to the breast, delineated volumes, and dose received at axillary levels were heterogeneous. The average dose delivered to axilla levels I, II, and III with three-dimensional conformal radiotherapy using standard fields (ST) ranged between 22 and 43.5 Gy, 3 and 35.6 Gy, and 1.0 and 20.5 Gy, respectively. The average doses delivered to axilla levels I, II, and III with three-dimensional conformal radiotherapy using "high tangential" fields (HT) ranged between 38 and 49.7 Gy, 11 and 47.1 Gy, and 5 and 44.7 Gy, respectively. Finally, the average doses delivered to axilla levels I, II, and III using intensity-modulated radiation therapy (IMRT) were between 14.5 and 42.6 Gy, 3.4 and 35 Gy, and 1.2 and 25.5 Gy, respectively.

CONCLUSION

Our literature review suggests that the incidental dose delivered to the axilla during whole-breast irradiation is heterogenous and dependent on the irradiation technique used. However, whether this observation can be translated into a therapeutic effect is still a matter of debate.

[Diffusion prophylactic axillary irradiation in breast cancer - Literature review]

PURPOSE

In breast cancer, radiotherapy is an essential component of the treatment. However, indications of irradiation of the internal mammary chain and axillary area are debatables. Axillary recurrence in patients with invasive breast carcinoma remains an issue. Currently, the substitution of axillary lymph node dissection by sentinel node biopsy leads to revisit the role of axillary irradiation. Breast irradiation including level I, II and III might decrease the risk of axillary recurrence.

MATERIAL AND METHODS

A literature search was performed in PubMed and the Cochrane library to identify articles publishing data regarding dose-volume analysis of axillary levels in breast irradiation aiming to determine the potential therapeutic implications.

RESULTS

Eleven articles were retained. A total of 375 treatment plans were analyzed. The results concerning the irradiation technique, initial dose prescribed to breast, delineated volumes and dose received at axillary levels were heterogeneous. The average dose delivered to axilla levels I-III with 3D-conformal radiotherapy using standard fields were between 24Gy and 43.5Gy, 3Gy and 32.5Gy and between 1.0Gy and 20.5Gy respectively. The average doses delivered to axilla levels I-III with 3D-conformal radiotherapy using high tangential fields were between 38Gy and 49.7Gy, 11Gy and 47.1Gy and 5Gy 38.7Gy, 32.1Gy and 5Gy (result available for only one study) respectively. Finally, the average doses delivered to axilla levels I-III with intensity modulated radiation therapy were between 14.5Gy and 42.6Gy, 3.4Gy and 35Gy and between 1.2Gy and 25.5Gy respectively.

CONCLUSIONS

Incidental axillary dose seems insufficient to be therapeutic regardless of the irradiation technique. There are meaningful differences between intensity modulated radiation therapy and 3D-conformal radiotherapy.

Effect of hypofractionation on the incidental axilla dose during tangential field radiotherapy in breast cancer

Objective

Tangential field irradiation in breast cancer potentially treats residual tumor cells in the axilla after sentinel lymph node biopsy (SLNB). In recent years, hypofractionated radiotherapy has gained importance and currently represents the recommended standard in adjuvant breast cancer treatment for many patients. So far, the impact of hypofractionation on the effect of incidental lymph node irradiation has not be addressed.

Materials and methods

Biological effective dose (BED) and tumor control probability (TCP) were estimated for four different hypofractionated radiation schemes (42.50 Gy in 16 fractions [Fx]; 40.05 Gy in 15 Fx; 27 Gy in 5 Fx; and 26 in 5 Fx) and compared to conventional fractionation (50 Gy in 25 Fx). For calculation of BED and TCP, a previously published radiobiological model with an α/β ratio of 4 Gy was used. The theoretical BED and TCP for incidental irradiation between 0 and 100% of the prescribed dose were evaluated. Subsequently, we assessed BED and TCP in 431 axillary lymph node metastases.

Results

The extent of incidental lymph node irradiation and the fractionation scheme have a direct impact on BED and TCP. The estimated mean TCP in the axillary nodes ranged from 1.5 ± 6.4% to 57.5 ± 22.9%, depending on the patient’s anatomy and the fractionation scheme. Hypofractionation led to a significant reduction of mean TCP of lymph node metastases for all schedules.

Conclusion

Our data indicate that hypofractionation might affect the effectiveness of incidental radiotherapy in the axilla. This is particularly relevant for patients with positive sentinel lymph nodes who receive SLNB only.

Central Review of Radiation Therapy Planning Among Patients with Breast-Conserving Surgery: Results from a Quality Assurance Process Integrated into the INSEMA Trial

PURPOSE

After publication of the radiation field design in the American College of Surgeons Oncology Group Z0011 trial, a radiation therapy quality assurance review was integrated into the Intergroup-Sentinel-Mamma (INSEMA) trial. We aimed to investigate the role of patient characteristics, extent of axillary surgery, and radiation techniques for dose distribution in ipsilateral axillary levels.

METHODS AND MATERIALS

INSEMA (NCT02466737) has randomized 5542 patients who underwent breast-conserving surgery. Of these, 276 patients from 108 radiation therapy facilities were included in the central review, using the planning records of the first 3 patients treated at each site.

RESULTS

Of the 276 patients, 41 had major deviations (ie, no axillary contouring or submission of insufficient records) leading to exclusion. A total of 235 (85.1%) radiation therapy planning records were delineated according to the INSEMA protocol, including 9 (3.8%) cases with minor deviations. At least 25% of INSEMA patients were unintentionally treated with ≥95% of the prescribed breast radiation dose in axillary level I. Approximately 50% of patients were irradiated with a median radiation dose of more than 85% of prescription dose in level I. Irradiated volumes and applied doses were significantly lower in levels II and III compared with level I. However, 25% of patients still received a median radiation dose of ≥75% of prescription dose to level II. Subgroup analysis revealed a significant association between incidental radiation dose in the axilla and obesity. Younger age, boost application, and fractionation schedule showed no impact on axillary dose distribution.

CONCLUSIONS

Assuming ≥80% of prescribed breast dose as the optimal dose for curative radiation of low-volume disease in axillary lymph nodes, at least 50% of reviewed INSEMA patients received an adequate dose in level I, even with contemporary 3-dimensional techniques. Dose coverage was much less in axillary levels II and III, and far below therapeutically relevant doses.

Factors Influencing the Incidental Dose Distribution in Internal Mammary Nodes: A Comparative Study

Objective: To investigate the effect of anatomic and technical parameters on the incidental internal mammary lymph node (IMN) irradiation (IIMNI) dose among postmastectomy patients.

Methods: We retrospectively delineated the IMN on planning CT images from 138 patients who had undergone postmastectomy radiotherapy (PMRT). We analyzed the IIMNI dose coverage and its relationship with anatomic and technical parameters.

Results: The IIMNI mean dose was 32.85 ± 9.49 Gy, and 10 of 138 patients (7.25%) treated with PMRT received ≥45 Gy. In univariate analysis, the body weight, body mass index, body surface area, thoracic transverse diameter (D_T), ratio of D_T to the thoracic anteroposterior diameter (D_AP)(R_T/AP), planning target volume of IMN (PTV_IMN) included in PTV (IMNin) and the ratio of IMNin to PTV_IMN (R_IMNin) and PTV posterior border were the parameters affecting IIMNI dose. In multivariate analysis, body weight, R_T/AP, and R_IMNin were correlative factors that affected IIMNI dose.

Conclusions: For patients who underwent PMRT without IMN irradiation (IMNI), there was a wide variety in IIMNI doses. A minority of patients had adequate IIMNI dose coverage, and the higher IIMNI doses were associated with the less body weights and more R_IMNin.

SPECT-CT localization of axillary sentinel lymph nodes for radiotherapy of early breast cancer

Purpose

To evaluate the opportunities of single photon emission tomography/computerized tomography (SPECT-CT) for localization of axillary sentinel lymph nodes (ASLNs) and subsequent radiotherapy planning in women with early breast cancer.

Material and methods

Individual topography of ASLN was determined in 151 women with clinical T1-2N0M0 breast cancer. SPECT-CT visualization of ASLNs was initiated 120 min after intra-peritumoral injection of 99mTc-radiocolloids. Doses absorbed by virtual ASLNs after the whole breast irradiation with standard and extended tangential fields were calculated on a treatment planning station.

Results

SPECT-CT demonstrated a large variability of ASLN localization. They were detected in the central subgroup in 94 (61%) patients, in pectoral - in 77 (51%), and in interpectoral - in 4 (3%) patients. Sentinel lymph nodes "lying on the chest" were revealed in 35 (23%) cases.We found that with standard tangential fields coverage of ASLNs was obtained only in 20% of evaluated women. Extended tangential fields can effectively irradiate ASLNs localized in all axillary sub-regions with the exception of ASLNs "lying on the chest".

Conclusion

SPECT-CT mapping of ASLNs in women with cT1-2N0M0 breast cancer reveals their variable localization. This information can be important for planning of radiation treatment in women that underwent breast conserving surgery without an axillary surgery.

Dosimetric comparison of incidental radiation to the internal mammary nodes after breast-conserving surgery using 3 techniques-inverse intensity-modulated radiotherapy, field-in-field intensity-modulated radiotherapy, and 3-dimensional conformal radiotherapy: A retrospective clinical study

BACKGROUND

The study aimed to evaluate and compare the dosimetric parameters of incidental irradiation to internal mammary node (IMN) from inverse intensity-modulated radiotherapy (I-IMRT) and field-in-field IMRT (F-IMRT), and 3-dimensional conformal radiotherapy (3D-CRT) in patients after breast-conservation surgery (BCS).

METHODS

Eighty-four patients with BCS were selected. The breast, tumor bed, and IMN, including intercostal spaces (ICS) 1 to 3, were contoured. Three plans were generated. The prescription doses for the breast and tumor bed were 50.4 Gy/28 F and 60.2 Gy/28 F, respectively. If there was no tumor bed boost, patient was treated with 50 Gy/25 F for the whole breast only. The IMN was not included in planning target volume.

RESULTS

The median mean dose (Dmean) of the IMNtotal (ICS 1-3) was 2740.2 cGy, 2973.9 cGy, and 2951.4 cGy for I-IMRT, F-IMRT, and 3D-CRT, respectively. Differences were not detected between any of the plans. After separating ICS 1 to 3 for further analysis, neither of the Dmean of ICS 1 to 2 was significantly different between the plans. However, for ICS 3, the median Dmean was highest for I-IMRT, and those for 3D-CRT and F-IMRT were not significantly different. After separating the 3 techniques for further analysis, the median Dmean was highest in ICS 3 and lowest in ICS 1 for all the 3 techniques.

CONCLUSION

All 3 techniques failed to attain an adequate dose to cure subclinical disease, and there were no significant differences among the 3 techniques. It is risky to avoid IMN irradiation (IMNI) using any of the 3 techniques during whole-breast radiotherapy in women with indications for elective IMNI. However, in era of systematic therapy, whether the incidental dose could meet clinical acquirements needs further follow-up.

Standard Tangential Radiation Fields Do Not Provide Incidental Coverage to the Internal Mammary Nodes

PURPOSE

The purpose of the study was to evaluate the incidental dose delivered to the internal mammary nodes (IMNs) in patients treated with tangential 3-dimensional conformal radiation therapy and to identify potential parameters that may affect the IMN mean dose.

METHODS AND MATERIALS

The study cohort consisted of 362 consecutively treated patients with breast cancer in our center between January 2015 and July 2017 who had received adjuvant whole-breast radiation therapy or postmastectomy radiation with or without a supraclavicular ± axillary field and without intentional inclusion of the IMN chain. The clinical target volume (CTV) for the IMNs was contoured per the Radiation Therapy Oncology Group 3509/3510 protocol and was then divided into 3 subregions: upper, mid, and lower thirds. The planning target volume for the IMNs was generated by adding 5 mm to the CTV. The primary endpoint was to assess the V40 (volume receiving 40 Gy) to the IMN planning target volume and its potential influencing parameters using a linear regression model.

RESULTS

The mean (±standard deviation) dose to the CTV IMN chain was 36% ± 28.7%. The Kruskal-Wallis test demonstrated significant differences in the median dose delivered to each level: upper third (7.2%), mid third (21.5%), and lower third (41.7%) (P < .001). The mean V40 IMN planning target volume was 14.2% (standard deviation, 18.7%). Presternal fat thickness (regression coefficient [RC] = -16.4; P < .001), postmastectomy radiation (RC = 24; P < .001), reconstruction after mastectomy (RC = -22.4; P < .001), and the addition of a supraclavicular field (RC = 8.8; P = .03) were all significantly associated with IMN mean dose.

CONCLUSIONS

For patients receiving standard breast/chest wall tangential radiation fields, the IMN chain is not incidentally covered with therapeutic doses in the vast majority of cases. Therefore, if regional nodal radiation is intended to include the IMNs, contouring and careful plan review are necessary to ensure adequate therapeutic coverage.

Incidental dose distribution to locoregional lymph nodes of breast cancer patients undergoing adjuvant radiotherapy with tomotherapy - is it time to adjust current contouring guidelines to the radiation technique?

Purpose/objective(s)

Along with breast-conserving surgery (BCS), adjuvant radiotherapy (RT) of patients with early breast cancer plays a crucial role in the oncologic treatment concept. Conventionally, irradiation is carried out with the aid of tangentially arranged fields. However, more modern and more complex radiation techniques such as IMRT (intensity-modulated radio therapy) are used more frequently, as they improve dose conformity and homogeneity and, in some cases, achieve better protection of adjacent risk factors. The use of this technique has implications for the incidental- and thus unintended- irradiation of adjacent loco regional lymph drainage in axillary lymph node levels I-III and internal mammary lymph nodes (IMLNs). A comparison of a homogeneous “real-life” patient collective, treated with helical tomotherapy (TT), patients treated with 3D conformal RT conventional tangentially arranged fields (3DCRT) and deep inspiration breath hold (3DCRT-DIBH), was conducted.

Materials/methods

This study included 90 treatment plans after BCS, irradiated in our clinic from January 2012 to August 2016 with TT (n = 30) and 3D-CRT (n = 30), 3DCRT DIBH (n = 30). PTVs were contoured at different time points by different radiation oncologists (> 7). TT was performed with a total dose of 50.4 Gy and a single dose of 1.8 Gy with a simultaneous integrated boost (SIB) to the tumor cavity (TT group). Patients irradiated with 3DCRT/3DCRT DIBH received 50 Gy à 2 Gy and a sequential boost. Contouring of lymph drainage routes was performed retrospectively according to RTOG guidelines.

Results

Average doses (DMean) in axillary lymph node Level I/Level II/Level III were 31.6 Gy/8.43 Gy/2.38 Gy for TT, 24.0 Gy/11.2 Gy/3.97 Gy for 3DCRT and 24.7 Gy/13.3 Gy/5.59 Gy for 3DCRT-DIBH patients. Internal mammary lymph nodes (IMLNs) Dmean were 27.8 Gy (TT), 13.5 Gy (3DCRT), and 18.7 Gy (3DCRT-DIBH). Comparing TT to 3DCRT-DIBH dose varied significantly in all axillary lymph node levels and the IMLNs. Comparing TT to 3DCRT significant dose difference in Level I and IMLNs was observed.

Conclusion

Dose applied to locoregional lymph drainage pathways varies comparing tomotherapy plans to conventional tangentially arranged fields. Studies are warranted whether dose variations influence loco-regional spread and must have implications for target volume definition guidelines.

Postmastectomy radiotherapy using three different techniques: a retrospective evaluation of the incidental dose distribution in the internal mammary nodes

Objective

To evaluate the incidental coverage dose to the internal mammary nodes (IMN) in patients treated with postmastectomy radiotherapy (PMRT) and its relationship with the treatment plan.

Patients and methods

We retrospectively analyzed 138 patients undergoing PMRT and divided them into three groups: three-dimensional conformal radiotherapy (3D-CRT), field-in-field forward intensity-modulated radiotherapy (F-IMRT), and inverse intensity-modulated radiotherapy (I-IMRT). The IMN were contoured according to the Radiation Therapy Oncology Group consensus and not included in the planning target volume. We analyzed incidental IMN dose coverage and its relationship with the lung and heart.

Results

The mean dose (Dmean) to the IMN was 32.85 Gy for all patients, and the dose delivered to the IMN showed no differences in 3D-CRT, F-IMRT, and I-IMRT (33.80, 29.65, and 32.95 Gy, respectively). In addition, 10.42%, 2.04%, and 9.76% of patients achieved ≥45 Gy with 3D-CRT, F-IMRT, and I-IMRT, respectively. No differences were evident among the three treatment plans regarding IMN dose in the first three intercostal spaces (ICS1-3). The Dmean, V20, V30, V40, and V50 of ICS2 and ICS3 were superior to those of ICS1 for all three plans. For 3D-CRT, a moderate positive correlation was evident between the Dmean to the IMN and the Dmean to the heart. For F-IMRT and I-IMRT, positive correlations were evident between the Dmean of the IMN and the Dmean and V20 of the lung.

Conclusion

The mean incidental dose to the IMN for IMRT (F-IMRT and I-IMRT) and 3D-CRT after modified radical mastectomy was insufficient to treat subclinical disease. A substantial dose was delivered to the IMN in some patients. Higher incidental doses to the IMN were associated with a higher heart mean dose for 3D-CRT and a higher dose to the lung for IMRT. Future prospective studies should further explore subgroups that do not require IMN irradiation.

Dosimetric evaluation of incidental irradiation to the axilla during whole breast radiotherapy for patients with left-sided early breast cancer in the IMRT era

The purpose of this study was to compare the dosimetric parameters for incidental irradiation to the axilla during whole breast radiotherapy (WBRT) with 3-dimensional conformal radiotherapy (3D-CRT) and intensity-modulated radiotherapy (IMRT). Twenty left breast cancer patients treated with WBRT after breast-conserving surgery (BCS) were enrolled in this study. Remnant breast tissue, 3 levels of the axilla, heart, and lung were delineated. We used 2 different radiotherapy methods: 3D-CRT with field-in-field technique and 7-field fixed-beam IMRT. The target coverage of IMRT was significantly better than that of 3D-CRT (Dmean: 49.72 ± 0.64 Gy vs 50.24 ± 0.66 Gy, P < 0.001; V45: 93.19 ± 1.40% vs 98.59 ± 0.30%, P < 0.001; V47.5: 86.43 ± 2.72% vs 95.00 ± 0.02%, P < 0.001, for 3D-CRT and IMRT, respectively). In the IMRT plan, a lower dose was delivered to a wider region of the heart and lung. Significantly lower axillary irradiation was shown throughout each level of axilla by IMRT compared to 3D-CRT (Dmean for level I: 42.58 ± 5.31 Gy vs 14.49 ± 6.91 Gy, P < 0.001; Dmean for level II: 26.25 ± 10.43 Gy vs 3.41 ± 3.11 Gy, P < 0.001; Dmean for level III: 6.26 ± 4.69 Gy vs 1.16 ± 0.51 Gy, P < 0.001; Dmean for total axilla: 33.9 ± 6.89 Gy vs 9.96 ± 5.21 Gy, P < 0.001, for 3D-CRT and IMRT, respectively). In conclusion, the incidental dose delivered to the axilla was significantly lower for IMRT compared to 3D-CRT. Therefore, IMRT, which only includes the breast parenchyma, should be cautiously used in patients with limited positive sentinel lymph nodes and who do not undergo complete axillary lymph node dissection.

Dose coverage of axillary level I-III areas during whole breast irradiation with simplified intensity modulated radiation therapy in early stage breast cancer patients

PURPOSE

This study was designed to evaluate the dose coverage of axillary areas during whole breast irradiation with simplified intensity modulated radiation therapy (s-IMRT) and field-in-field IMRT (for-IMRT) in early stage breast cancer patients.

METHODS

Sixty-one consecutive patients with breast-conserving surgery and sentinel lymph node biopsy were collected. Two plans were created for each patient: the s-IMRT and for-IMRT plan. Dosimetric parameters of axillary areas were compared.

RESULTS

The average of mean doses delivered to the axillary level I areas in s-IMRT and for-IMRT plan were 27.7Gy and 29.1Gy (p = 0.011), respectively. The average of V47.5Gy, V45Gy and V40Gy (percent volume receiving≥ 47.5Gy, 45Gy and 40Gy) of the axillary level I in s-IMRT plan was significantly lower than that in for-IMRT plan (p < 0.001). For for-IMRT plans, patients with upper tangential border to humeral head ≤2cm, breast separation >19.3cm and body width >31.9cm had significantly higher mean dose in axillary level I area (p = 0.002, 0.007, 0.001, respectively).

CONCLUSION

Compared with for-IMRT plan, the s-IMRT plan delivered lower dose to axillary level I area. For centers using s-IMRT technique, caution should be exercised when selecting to omit axillary lymph node dissection for patients with breast conserving surgery and limited positive SLNs.

The value of completion axillary treatment in sentinel node positive breast cancer patients undergoing a mastectomy: a Dutch randomized controlled multicentre trial (BOOG 2013-07)

BACKGROUND

Trials failed to demonstrate additional value of completion axillary lymph node dissection in case of limited sentinel lymph node metastases in breast cancer patients undergoing breast conserving therapy. It has been suggested that the low regional recurrence rates in these trials might partially be ascribed to accidental irradiation of part of the axilla by whole breast radiation therapy, which precludes extrapolation of results to mastectomy patients. The aim of the randomized controlled BOOG 2013-07 trial is therefore to investigate whether completion axillary treatment can be safely omitted in sentinel lymph node positive breast cancer patients treated with mastectomy.

DESIGN

This study is designed as a non-inferiority randomized controlled multicentre trial. Women aged 18 years or older diagnosed with unilateral invasive clinically T1-2 N0 breast cancer who are treated with mastectomy, and who have a maximum of three axillary sentinel lymph nodes containing micro- and/or macrometastases, will be randomized for completion axillary treatment versus no completion axillary treatment. Completion axillary treatment can consist of completion axillary lymph node dissection or axillary radiation therapy. Primary endpoint is regional recurrence rate at 5 years. Based on a 5-year regional recurrence free survival rate of 98 % among controls and 96 % for study subjects, the sample size amounts 439 per arm (including 10 % lost to follow-up), to be able to reject the null hypothesis that the rate for study and control subjects is inferior by at least 5 % with a probability of 0.8. Results will be reported after 5 and 10 years of follow-up.

DISCUSSION

We hypothesize that completion axillary treatment can be safely omitted in sentinel node positive breast cancer patients undergoing mastectomy. If confirmed, this study will significantly decrease the number of breast cancer patients receiving extensive treatment of the axilla, thereby diminishing the risk of morbidity and improving quality of life, while maintaining excellent regional control and without affecting survival.

TRIAL REGISTRATION

The BOOG 2013-07 study is registered in the register of ClinicalTrials.gov since April 10, 2014, Identifier: NCT02112682 .

Three-Dimensional Breast Radiotherapy and the Elective Radiation Dose at the Sentinel Lymph Node Site in Breast Cancer

Background

Several trials are presently randomizing clinically node-negative breast cancer patients treated with breast-conserving therapy (BCT) to sentinel lymph node biopsy (SLNB) or watchful waiting. We aimed to investigate the elective radiation dose at the sentinel lymph node (SLN) site while evaluating two techniques for SLN localization, in breast cancer patients treated with lumpectomy and three-dimensional (3D) whole-breast radiotherapy.

Methods

The SLN site of consecutive Tis-2N0 breast cancer patients undergoing lumpectomy and forward intensity-modulated whole-breast radiotherapy was determined by the location of the hotspot on preoperative single-photon emission computed tomography (SPECT)/computed tomography (CT) and by a surgical clip placed at the removed SLN(s) during SLNB. The radiation dose at the SLN site was subsequently determined on the postoperative radiotherapy planning CT. An elective radiation dose to the SLN site was defined as at least 95 % of the breast dose.

Results

Of the 42 included patients, the mean percentage of the breast dose on the SLN site was 90 % (standard deviation 26, range 7–132, median 99), with a non-significant difference between the two techniques (surgical clip or SPECT/CT) (p = 0.608). In 32/42 patients (76 %) the SLN site received an elective radiation dose.

Conclusions

A surgical clip placed at the removed SLN(s) during SLNB proved to be an adequate method of determining the radiation dose at the SLN site when compared with using SPECT/CT. With the use of 3D radiotherapy, the site of the SLN is treated with an elective radiation dose in the majority of patients who are treated with BCT.