Influence of Breast Reconstruction Type and Placement on Radiation Therapy Outcomes: Clinical Insights and Implications

Highlight

• Prepectoral and subpectoral breast reconstructions increase mean heart radiation dose compared with nonreconstruction.

• Subpectoral placement is associated with reduced ipsilateral lung dose during radiation therapy.

• Prepectoral reconstruction more frequently results in internal mammary node omission during radiation planning.

• Device type (immediate implant versus tissue expander) does not significantly affect radiation dose metrics or treatment timing.

Study Background

Breast reconstruction after mastectomy has become an integral component of comprehensive breast cancer treatment, aiming to restore breast form and improve quality of life. Over the past decade, prepectoral breast reconstruction—with the implant placed above the pectoralis major muscle—has gained popularity compared to traditional subpectoral placement, where the implant lies beneath the muscle. Concurrently, radiation therapy (RT) remains a cornerstone of breast cancer treatment to reduce recurrence risk following surgery.

Despite widespread adoption of these reconstructive techniques, the interactions between reconstruction attributes (timing, device type, and placement) and RT planning and delivery remain inadequately characterized. It is clinically relevant to understand how reconstruction influences radiation dosimetry to critical structures such as the heart and lungs, particularly given the risk of radiation-induced cardiopulmonary toxicity. Additionally, comprehensive nodal coverage, including internal mammary nodes (IMNs), is imperative for oncologic control but may be complicated by the presence and location of reconstructive devices.

This knowledge gap prompted a detailed evaluation of how device type (immediate implant versus delayed tissue expander), placement (prepectoral versus subpectoral), and reconstruction status impact RT metrics, timing, and complications in contemporary clinical practice.

Study Design

This single-institution, prospective cohort study included 161 patients who underwent mastectomy or lumpectomy followed by radiation therapy between 2021 and 2024. Among them, 80 patients received breast reconstruction (29 with immediate implants and 51 with tissue expanders), while 81 did not undergo reconstruction. The device placements were nearly evenly split between prepectoral (41 patients) and subpectoral (39 patients) positions.

The primary radiation therapy outcomes assessed were:

• Mean heart dose (MHD)

• Volume of lung irradiated on the ipsilateral side

• Volume of “cold spots”—areas receiving reduced radiation dose

• Volume of “hot spots”—areas receiving increased radiation dose

• Coverage of internal mammary nodes (IMNs)

Additional outcomes included time from surgery to initiation of RT, the incidence of IMN omission, tissue expander deflation events, and skin toxicity complications.

Key Findings

Both prepectoral and subpectoral reconstructions were associated with an increased mean heart dose compared to patients who did not undergo reconstruction, indicating a subtle increase in cardiac radiation exposure when implants or expanders are present irrespective of device position. However, the volume of cold spots was reduced in reconstructed breasts, suggesting an overall improvement or more uniform radiation dose coverage.

Interestingly, subpectoral reconstruction demonstrated lower ipsilateral lung dose compared with nonreconstruction and prepectoral placement. This finding may relate to the altered anatomy and device positioning beneath the muscle, potentially shielding lung tissue from radiation beams, particularly when IMNs are targeted.

Prepectoral devices were more frequently linked with the omission of IMN coverage during radiation therapy planning. This phenomenon could be caused by challenges in achieving proper dose distribution around anteriorly positioned implants or concerns about radiation toxicity to overlying reconstructed tissue.

Importantly, no significant differences were observed in the time to radiation therapy initiation across reconstruction status, device type, or placement, alleviating concerns that reconstruction delays RT. Similarly, rates of tissue expander deflation and skin toxicity were comparable across groups, suggesting reconstruction does not confer additional acute treatment complications.

Device type—comparing immediate implants and delayed tissue expanders—did not significantly alter radiation dose metrics or treatment timelines, highlighting that the positioning of the device rather than the type has a more pronounced role in RT planning effects.

Expert Commentary

This study adds valuable clinical insights into the complex interplay between breast reconstruction and radiation therapy. With the trend toward prepectoral reconstruction, awareness of potential IMN coverage omission is vital, as comprehensive nodal irradiation is crucial for high-risk breast cancer patients. Radiation oncologists must carefully tailor RT plans to accommodate prepectoral devices to optimize oncologic outcomes without compromising reconstruction integrity.

The increased mean heart dose observed with reconstruction aligns with prior radiotherapy dosimetry studies indicating anatomical changes influence beam paths. Although the magnitude of increase appears modest, long-term cardiac toxicity risk must be continually balanced against reconstructive benefits.

The protective effect of subpectoral placement on ipsilateral lung dose may offer a dosimetric advantage when IMN irradiation is indicated. These findings suggest that reconstructive technique choice could be individualized based on anticipated radiation fields and patient-specific anatomical considerations.

Limitations include single-center design and relatively short follow-up, restricting assessment of late toxicity or long-term oncologic outcomes. Further multi-institutional studies with longer observation are warranted to validate these findings and optimize multidisciplinary management.

Conclusion

Breast reconstruction device placement influences radiation therapy dose distribution but does not significantly impact radiation treatment timeliness or acute complications. While both prepectoral and subpectoral reconstruction increase mean heart dose compared to no reconstruction, subpectoral placement may confer lung dose sparing advantages. Prepectoral implants pose a higher risk of internal mammary node treatment omission, warranting meticulous radiation planning.

Clinicians should integrate these findings when planning comprehensive breast cancer treatment to balance reconstructive outcomes with oncologic safety. Multidisciplinary collaboration remains essential to optimize individualized patient care and improve long-term survival and quality of life for breast cancer survivors.

Funding and ClinicalTrials.gov

No specific funding was disclosed for this study. Clinical trial registration details were not provided.

References

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