Postoperative Radiotherapy in breast cancer- ICMR guidelines

Postoperative RT using Linac or telecobalt to the breast/ chest wall with or without lymphatic areas is indicated in most cases, except after mastectomy for a DCIS or early node negative cancer. Several large RCTs have shown that post mastectomy radiotherapy in women with T3-4, N+ cancers, improve loco-regional control as well as survival41,42 Large randomized trials have also shown that radiotherapy after conservative surgery is integral in achieving loco-regional control comparable to mastectomy and with improved body . The aim is to use an appropriate technique for safely giving adequate doses of radiation, equivalent to 50Gy/25#/5weeks, to control subclinical disease in tissues at risk (chest wall/ breast+/-SCF).

It is required for all the doctors to be aware of the implications of the disease as well as the effective execution of postoperative radiotherapy.

In 2016, Indian Council Of Medical Research, ICMR issued guidelines/ Consensus document on postoperative Radiotherapy of Breast Cancer. Following are its major recommendations for the Management of the disease.

A. Indications for postoperative Radiotherapy

Post Mastectomy RT (PMRT) to chest wall +/- nodal area

• >3 axillary nodes positive

• Any number of nodes positive after NACT

• Clinically or Pathologically T3 or T4 Tumour

• Positive resection margins

• Known residual disease in axilla

• Initial involvement of SCF/IMC

• For 1-3 nodes +ve, PMRT is being increasingly considered following recent EBCTCG metaanalysis (McGale et al. Lancet. 2014), which showed improvement in breast cancer specific mortality. With routine use of more effective chemotherapy, the absolute benefit of PMRT in patients with 1-3 node +ve but smaller tumours with favourable features is likely to be less and may be individualized based on age and comorbidity.

After Breast Conservative Surgery: All cases of BCT require postoperative RT. However, RT may be avoided in selected elderly women with small, node –ve, low grade, ER/PR+ve tumours with low risk of recurrence as seen in the recent PRIME trial (Kunkler et al Lancet Oncology, 2015)

IMC RT: RT to IMC fell into disuse after its associated excess cardiac mortality became evident. Two recent RCTs - EORTC (Poortman et al, NEJM 2015) and MA-20 (Whelan et al, NEJM 2015) evaluating the role of RT to SCF plus IMC in patients with medial or central quadrant tumours or those with axillary node +ve, showed a modest improvement in DFS but no difference in overall survival. Moreover, the contribution of IMC RT in the very modest benefit with SCF plus IMC RT is likely to be even smaller. In addition there are technical challenges in planning and delivering cardiac safe IMC RT. Hence most centres around the world continue to offer IMC RT only for cases with radiological or pathological evidence of IMC node involvement.

Axilla: It is a common practice in many Indian centres to treat axilla for all node +ve cases, possibly due to sub-optimal axillary surgery or histopathological evaluation in practice settings. As post-op axillary RT can increase arm & shoulder morbidity, it is advocated for residual axillary disease or node +ve after inadequate axillary surgery and revision surgery is not being considered for various reasons. Recently the EORTC-AMAROS trial (Donker et al, Lancet Oncol. 2014) shows that in T1-2 clinically node negative with sentinel node biopsy +ve, axillary RT results in excellent disease control comparable to completion axillary dissection but with different morbidity pattern.

B. Treatment Area and Technique for Radiotherapy

1. Chest wall: Bitangential portals, isocentric or with breast cone. Bolus if skin was involved or at high risk of recurrence. For left sided tumours, minimize cardiac dose with appropriate beam angulation and cardiac shielding if required.

2. Whole Breast: Bitangential portals; Isocentric, with appropriate wedges. 3DCRT or IMRT if large breasts to reduce acute/late toxicity in areas of dose inhomogeneity. LINAC preferable but Telecobalt can be used if Interfiled separation is <18cm & breast is not large. Avoid cardiac dose with beam placement or cardiac shielding.

3. SCF (in axillary N+ cases or initial SCF involvement): Direct anterior portals, avoiding overlap with tangents to prevent matchline fibrosis and rare occurrence of brachial plexopathy.

4. Axilla: When indicated, axilla can be irradiated with an anterior extended SCF field with posterior axillary boost.

5. IMC (in known IMC involvement): CT planned partially wide tangents or mixed electron/photon ports on LINAC.

6. Tumor Bed boost (In all cases of BCT except for DCIS and in postmenopausal women with small tumors with favorable histology and-ve margins): Enface electrons, 3D CRT or in selected cases, HDR brachytherapy in expert centres.

C. Radiotherapy dose and fractionation

50Gy in 25 daily fractions over 5 weeks or its equivalent hypofractionated regime of 40Gy/15 fractions over 3 weeks or 42.5Gy/16# over 3 weeks45,46. Hypofractionated regimen is equivalent to the conventional regimen in terms of disease control and survival. These hypofractionated regimens results in significantly lower incidence of acute and late breast toxicity and without excess cardiac morbidity at 15 year. The 3 week hypofractionated regime has become the standard of care in the UK, Canada and many large volume Indian centres for BCT and post mastectomy RT. For hypofractionated regimes, appropriate planning should be done to minimize dose inhomogeneity and cardiac dose. Tumor Bed Boost after whole breast RT for BCT is given with appropriate energy electrons or 3DCRT photons to a dose of 10–16Gy with 2-2.5 Gy per fraction. For HDR boost a twice daily regimen of 4.5 - 5 Gy x 2 or 3.4Gy x 3 fractions.

D. Accelerated partial breast radiation (APBI) This short and convenient course of RT has been tested in several large RCTs which are yet to report long-term results. Hence it should be considered an investigational approach. Currently, centres with experience are offering APBI to carefully select postmenopausal women with node negative, small tumors with clear margins and no adverse pathological features47. A recent European RCT compared multicatheter interstitial APBI with whole breast RT + boost in 1184 women >40 years of age with up to 3 cm tumour, pNo or pNmi. It shows equivalent disease control and survival at a median follow up of 6.6 years (Strnad et al, Lancet, 2015) and this was evident in all age groups above 40 years and in all tumor types.

E. Palliative Radiotherapy

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