Radiotherapy of the regional lymph nodes: shooting at the sheriff?

Hypothesis: can the abscopal effect explain the impact of adjuvant radiotherapy on breast cancer mortality?

Radiotherapy is an integral component of loco-regional therapy for breast cancer. Randomized controlled trials indicate that increasing the extent of extirpative surgery primarily reduces the risk of local recurrences, while the addition of radiotherapy to surgery can also reduce the risk of distant recurrences, thereby lowering breast cancer-specific mortality. This may suggest an “abscopal” effect beyond the immediate zone of loco-regional irradiation that favorably perturbs the natural history of distant micrometastases. Immunological phenomena such as “immunogenic cell death” provide a plausible mechanistic link between the local and systemic effects of radiation. Radiotherapy treatment can stimulate both pro-immunogenic and immunosuppressive pathways with a potential net beneficial effect on anti-tumor immune activity. Upregulation of programmed cell death ligand (PD-L1) by radiotherapy is an immunosuppressive pathway that could be approached with anti-PD-L1 therapy with potential further improvement in survival. The world overview of randomized trials indicates that the breast cancer mortality reduction from adjuvant radiotherapy is delayed relative to that of adjuvant systemic treatments, and similar delays in the separation of survival curves are evident in the majority of randomized immunotherapy trials demonstrating treatment efficacy. In this article, we hypothesize that an abscopal effect may explain the benefit of radiotherapy in reducing breast cancer mortality, and that It might be possible to harness and augment this effect with systemic agents to reduce the risk of late recurrences.

Improvement of survival with postmastectomy radiotherapy in patients with 1-3 positive axillary lymph nodes: A systematic review and meta-analysis of the current literature

In breast cancer with >4 positive axillary lymph nodes, it is common practice to deliver radiotherapy to the affected site following mastectomy. However, less is known regarding the benefits this may confer on women with 1-3 positive lymph nodes. In this meta-analysis, we aimed to assess whether post-mastectomy radiotherapy (PMRT) was beneficial for such patients. A literature review was conducted using the PubMed and Ovid databases. Selected studies were analysed and data regarding overall survival (OS) and locoregional recurrence (LRR) rates were extracted. Statistical analysis was then conducted in order to develop a combined risk ratio (RR) for both OS and LRR in the setting of PMRT in women with breast cancer with 1-3 positive lymph nodes. PMRT in women with 1-3 positive lymph nodes significantly reduced the risk of LRR, with a RR of 0.3 [95% confidence interval (CI): 0.23-0.38] and also showed a minor benefit in terms of OS (RR=1.03, 95% CI: 1.00-1.07). Therefore, in breast cancer patients with 1-3 positive lymph nodes, PMRT significantly reduced the risk of LRR and was associated with a minor OS benefit. Until the results of ongoing randomised controlled trials are published, PMRT should be recommended in this group of patients following a careful multidisciplinary discussion.

Breast cancer sentinel lymph node and axillary lymphadenectomy: new tools for new challenges

Axillary lymph node status at the time of diagnosis is the most important prognostic indicator for women with breast cancer, and may influence management decisions. However, at present its role is controversial, as some groups recommend avoiding axillary lymph node dissection (ALND) in cases with metastasis of any size in the sentinel lymph nodes. Molecular analysis allows full examination of the sentinel lymph nodes in a short time period, discriminatation between macrometastasis, micrometastasis and isolated tumor cells, and helps to predict the performance of ALND. ALND may be the treatment of choice in some patients, even in cases of low-volume metastasis, as chemotherapy does not control regional disease well. In addition, the collection of metastatic cells, as well as the local immune surveillance, is susceptible to further molecular studies that will offer prognostic and predictive information, which may have an impact on therapeutic decisions, so that individualized treatments can be adequately designed.

Radiation during deep inspiration allows loco-regional treatment of left breast and axillary-, supraclavicular- and internal mammary lymph nodes without compromising target coverage or dose restrictions to organs at risk

BACKGROUND AND PURPOSE

Loco-regional radiotherapy of left-sided breast cancer represents a treatment planning challenge when the internal mammary chain (IMC) lymph nodes are included in the target volume. This treatment planning study evaluates the reduction in cardiopulmonary doses when radiation is given during deep inspiration breath-hold (DIBH). This was achieved without compromising dose coverage to the planning target volume (PTV).

PATIENTS AND METHODS

Seventeen patients with early breast cancer, referred for adjuvant radiotherapy, were included. For each patient two computed tomography (CT)-scans were acquired; the first during free breathing (FB) and the second during DIBH. The scans were monitored by the Varian RPM respiratory gating system. Audio-visual guidance was used. The treatment planning of the two CT studies was performed focusing on good coverage (V95% > 98%) of the PTV. Doses to the heart, left anterior descending (LAD) coronary artery, lungs and contralateral breast were assessed.

RESULTS

With equal PTV coverage, average mean heart dose was reduced from 6.2 Gy to 3.1 Gy in DIBH plans as compared to FB. Average volume receiving 25 Gy or more (V25Gy) was reduced from 6.7% to 1.2%, and the number of patients with V25Gy > 5% was reduced from 8 to 1 utilizing DIBH. The average mean dose to the LAD coronary artery was reduced from 25.0 Gy to 10.9 Gy. The average ipsilateral lung volume receiving 20 Gy or more (V20Gy) was reduced from 44.5% to 32.7% with DIBH. In 11 of the DIBH plans V20Gy was lower than 35%, in accordance with national guidelines, while none of the FB plans fulfilled this recommendation.

CONCLUSION

Respiratory gated radiotherapy during DIBH is a suitable technique for loco-regional breast irradiation even when IMC lymph nodes are included in the PTV. Cardiopulmonary doses are considerably decreased for all dose levels without compromising the dose coverage to PTV.