Unintended coverage: how standard breast radiotherapy irradiates the internal mammary nodes.
- 1Department of Radiation Oncology, All India Institute of Medical Sciences Jodhpur, Jodhpur, India.
- 2Department of Medical Oncology, All India Institute of Medical Sciences Jodhpur, Jodhpur, India.
- 3Department of Surgical Oncology, All India Institute of Medical Sciences Jodhpur, Jodhpur, India.
Abstract
Breast cancer is the most common malignancy in women worldwide. Irradiation of regional nodes, including the internal mammary nodes (IMNs), may improve outcomes, but routine IMN irradiation remains controversial because of toxicity. Modern breast radiotherapy may incidentally irradiate the ipsilateral IMNs. We quantified incidental IMN doses and factors affecting coverage in patients without targeted IMN irradiation. In this retrospective dosimetric study, 104 women with clinical stage I-III disease were analysed. The ipsilateral IMNs (levels I-III) were contoured on planning CT scans according to the RTOG guidelines. Dose-volume histogram (DVH) metrics (minimum, mean, and maximum doses; V95%, V90%, and V50%) were recorded. Group comparisons [mastectomy vs. breast-conserving surgery (BCS) and 3DCRT vs. VMAT)] were performed using statistical tests, with p < 0.05 considered statistically significant. The median age was 52 years; 56.7% of patients were aged > 50 years; left- and right-sided tumours were equally represented. Seventy-five per cent underwent mastectomy and 25% underwent BCS. Eighty-one per cent received 3DCRT; 46% received supraclavicular/axillary irradiation; the median follow-up was 40 months. The mean IMN volume was 7.30 ± 1.76 cm3. The mean IMN dose was 35.53 ± 6.20 Gy, and the minimum dose was 7.73 ± 6.37 Gy. On average, 47.3% of the IMN volume received ≥ 95% of the prescribed dose. Mastectomy plans delivered a higher mean IMN dose than BCS plans (36.55 vs. 32.48 Gy, p = 0.0046). 3DCRT plans provided better IMN coverage than VMAT plans (mean V95%, 51.4% vs. 29.1%; p = 0.0012). Radiotherapy modality and type of surgery were significant in the multivariate analysis. Standard tangential fields provide only partial IMN coverage with wide variability. Most patients did not reach therapeutic IMN doses, highlighting the need for explicit contouring and dedicated planning when IMN irradiation is indicated.
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BibTeX
@article{nair2026unintended,
title = {{Unintended coverage: how standard breast radiotherapy irradiates the internal mammary nodes.}},
author = {Rishi P Nair and Depanshu Aggarwal and Puneet Pareek and Atul Gupta and Akanksha Solanki and Bharti Devnani and Parmod Kumar and Jeewan Ram Vishnoi and Dharma Ram Poonia and Nivedita Sharma and Suraj Sharma},
journal = {Reports of practical oncology and radiotherapy : journal of Greatpoland Cancer Center in Poznan and Polish Society of Radiation Oncology},
year = {2026},
month = nov,
doi = {10.5603/rpor.113321},
url = {https://europepmc.org/article/MED/42997858},
note = {CC BY-NC-ND},
}
RIS
TY - JOUR
TI - Unintended coverage: how standard breast radiotherapy irradiates the internal mammary nodes.
AU - Rishi P Nair
AU - Depanshu Aggarwal
AU - Puneet Pareek
AU - Atul Gupta
AU - Akanksha Solanki
AU - Bharti Devnani
AU - Parmod Kumar
AU - Jeewan Ram Vishnoi
AU - Dharma Ram Poonia
AU - Nivedita Sharma
AU - Suraj Sharma
PY - 2026
DA - 2026/11/01
JO - Reports of practical oncology and radiotherapy : journal of Greatpoland Cancer Center in Poznan and Polish Society of Radiation Oncology
DO - 10.5603/rpor.113321
UR - https://europepmc.org/article/MED/42997858
AB - Breast cancer is the most common malignancy in women worldwide. Irradiation of regional nodes, including the internal mammary nodes (IMNs), may improve outcomes, but routine IMN irradiation remains controversial because of toxicity. Modern breast radiotherapy may incidentally irradiate the ipsilateral IMNs. We quantified incidental IMN doses and factors affecting coverage in patients without targeted IMN irradiation. In this retrospective dosimetric study, 104 women with clinical stage I-III disease were analysed. The ipsilateral IMNs (levels I-III) were contoured on planning CT scans according to the RTOG guidelines. Dose-volume histogram (DVH) metrics (minimum, mean, and maximum doses; V95%, V90%, and V50%) were recorded. Group comparisons [mastectomy vs. breast-conserving surgery (BCS) and 3DCRT vs. VMAT)] were performed using statistical tests, with p < 0.05 considered statistically significant. The median age was 52 years; 56.7% of patients were aged > 50 years; left- and right-sided tumours were equally represented. Seventy-five per cent underwent mastectomy and 25% underwent BCS. Eighty-one per cent received 3DCRT; 46% received supraclavicular/axillary irradiation; the median follow-up was 40 months. The mean IMN volume was 7.30 ± 1.76 cm3. The mean IMN dose was 35.53 ± 6.20 Gy, and the minimum dose was 7.73 ± 6.37 Gy. On average, 47.3% of the IMN volume received ≥ 95% of the prescribed dose. Mastectomy plans delivered a higher mean IMN dose than BCS plans (36.55 vs. 32.48 Gy, p = 0.0046). 3DCRT plans provided better IMN coverage than VMAT plans (mean V95%, 51.4% vs. 29.1%; p = 0.0012). Radiotherapy modality and type of surgery were significant in the multivariate analysis. Standard tangential fields provide only partial IMN coverage with wide variability. Most patients did not reach therapeutic IMN doses, highlighting the need for explicit contouring and dedicated planning when IMN irradiation is indicated.
SN - 1507-1367
SN - 2083-4640
ER -