Adjuvant Radiotherapy and Local Control in ACC

Adjuvant Therapy

Adjuvant radiotherapy in adrenocortical carcinoma (ACC) refers to postoperative irradiation of the adrenal bed or regional operative field after curative-intent resection, with the aim of reducing locoregional recurrence. Within ACC management, it is a local adjunct to surgery rather than a substitute for resection, and it is generally considered in patients with localized disease whose operative or pathologic findings suggest a substantial risk of residual microscopic disease.¹²

The rationale for this approach derives from the recurrence pattern of ACC. Even after apparently complete adrenalectomy, relapse is common, and a portion of failures occur in the operative bed or retroperitoneum, especially when margins are positive or resection has been difficult.¹ However, the evidence supporting postoperative radiotherapy remains limited. Most published data are retrospective, treatment allocation is nonrandom, and commonly used datasets provide incomplete information on radiation fields, dose, toxicity, and locoregional control endpoints.³²¹

Accordingly, adjuvant radiotherapy has not been established as routine treatment for all resected ACC. Available evidence more often supports a selective, risk-adapted role in higher-risk postoperative settings than a general survival benefit across unselected patients.²¹ Interpretation is further complicated by confounding from surgical quality, margin status, nodal assessment, and use of multimodality therapy, all of which may strongly influence outcomes in retrospective comparisons.³¹

Diagnostic and postoperative context

Surgery remains the central curative-intent treatment for localized ACC, and postoperative decision-making is organized primarily around resection status and pathologic risk features.¹ In this framework, adjuvant radiotherapy is intended to address the possibility of persistent microscopic local disease, not to compensate for inadequate surgery or to prevent distant metastatic relapse on its own.

What is relatively reliable is that adverse surgical-pathologic features identify patients at higher risk of recurrence, particularly when residual local disease is plausible.¹ What is less reliable is the size of any radiotherapy-specific benefit, because retrospective series do not cleanly separate the local effect of radiation from the effects of patient selection, operative complexity, and concurrent systemic treatment.³² Clinically, this means the question is usually not whether all patients should receive postoperative radiation, but whether an individual patient’s recurrence risk is sufficiently concentrated in the operative field to justify local intensification.

Risk phenotypes relevant to local control

Positive surgical margins are the most consistently emphasized high-risk feature in the available literature. Margin-positive (R1) resection is associated with worse overall survival and provides the clearest biologic rationale for considering postoperative locoregional treatment, especially when re-resection is not feasible.¹

Other factors that may increase interest in adjuvant local therapy include technically difficult retroperitoneal dissection, concern for capsular disruption, and other operative findings suggestive of residual microscopic disease, although these features are less consistently captured in large registries.²¹ The practical implication is that selection for radiotherapy remains individualized and multidisciplinary rather than protocolized for all localized ACC.

This distinction also clarifies the limits of the modality. Radiotherapy may be most relevant when the dominant threat is local recurrence, whereas its expected contribution is less clear when the major risk is early systemic dissemination.⁴¹ Thus, risk stratification in ACC is not only prognostic but also helps determine whether a local adjuvant strategy is biologically plausible.

Evidence for outcomes

Across the included studies, the most reproducible finding is prognostic rather than definitively therapeutic: postoperative outcomes are heterogeneous, and margin-positive disease marks a poorer-risk subgroup.¹ This supports the clinical logic for considering adjuvant treatment in selected patients, but it does not itself establish that radiotherapy independently improves outcomes.

Signals of benefit appear narrower and are most suggestive in selected high-risk subsets rather than across all resected ACC. Retrospective national data suggest that adjuvant systemic therapy alone does not clearly improve overall survival in unselected localized ACC or in several examined higher-risk subgroups.⁴ By contrast, among node-negative or node-unknown patients with R1 resection, combined adjuvant radiation plus chemotherapy has been associated with improved overall survival compared with no adjuvant therapy.¹

Taken together, these findings suggest that any postoperative benefit may be concentrated in margin-positive disease and may depend on combined-modality treatment rather than radiotherapy as an isolated intervention.¹ What is reasonably supported is a hypothesis that selected R1 patients may benefit from intensified adjuvant management; what is not reliably established is that radiotherapy alone independently improves survival.⁴¹

An additional interpretive issue is the choice of endpoint. Because the principal purpose of adjuvant radiotherapy is local control, overall survival is an imperfect surrogate, particularly in a disease where distant progression and subsequent therapies may dominate prognosis.³¹ In practical terms, absence of a clear survival signal does not exclude a local-control effect, but current datasets are often insufficient to define that effect with confidence.

Limitations and pitfalls in interpretation

The literature on adjuvant radiotherapy in ACC is constrained by substantial selection bias. Patients who receive postoperative radiation may differ systematically from untreated patients in margin status, disease extent, access to specialty care, and likelihood of also receiving systemic therapy.³¹ These differences may create associations that cannot be assumed to represent a causal treatment effect.

Heterogeneity within irradiated cohorts is another major limitation. Retrospective analyses show that outcomes among patients treated with adjuvant radiotherapy still vary according to other oncologic characteristics, underscoring that prognosis is not determined by radiation exposure alone.³ This makes simple treated-versus-untreated comparisons especially vulnerable to confounding and limits generalizability across institutions.

A further limitation is incomplete technical reporting. Many datasets do not provide detailed information on target volumes, dose, fractionation, toxicity, or patterns of locoregional failure, making it difficult to identify which radiotherapy approaches, if any, are most effective.²¹ Clinically, current evidence is therefore more useful for identifying patients who warrant multidisciplinary discussion than for defining a universal standard.

Role in management and research

Current evidence places adjuvant radiotherapy as a selective postoperative option in localized ACC, most plausibly for patients with R1 resection or other strong indicators of residual local risk.²¹ It is not supported as routine therapy after every adrenalectomy, and its potential value must be weighed against the dominant influence of surgical quality, tumor biology, and systemic relapse risk.⁴¹

This selective role has also been reflected in broader reviews, which have described postoperative radiotherapy as reasonable in some higher-risk cases but insufficiently supported for definitive universal recommendations.² What is relatively reliable is the identification of higher-risk postoperative phenotypes, especially margin-positive disease; what remains uncertain is the magnitude of added benefit, the optimal integration with systemic therapy, and the patients most likely to derive meaningful local-control advantage.²³¹

Because ACC is rare, progress in this area is likely to depend on collaborative datasets and more standardized reporting rather than isolated institutional experience alone.² Future research is most likely to be informative if it focuses on clearly defined high-risk groups, incorporates locoregional recurrence endpoints, and documents radiation technique and concurrent therapies in enough detail to distinguish local treatment effects from underlying case selection.³¹

Included Articles

• PMID 33168156: In a National Cancer Data Base cohort of 577 patients undergoing curative-intent resection for localized ACC, adjuvant chemotherapy was not associated with improved overall survival overall or in examined higher-risk subgroups including lymphovascular invasion, positive margins, and T3 disease. Receipt of adjuvant chemotherapy was more common with private insurance, lymphovascular invasion, stage II disease, and radiotherapy.⁴

• PMID 36568465: In a retrospective National Cancer Database cohort of 1644 adults with localized ACC after adrenalectomy, positive surgical margins were associated with worse overall survival. Among node-negative or node-unknown patients with R1 resection, adjuvant combined radiation plus chemotherapy was associated with improved overall survival versus no adjuvant therapy, while benefit was not clearly shown in other pathologic subgroups.¹

• PMID 34301459: A 2021 National Cancer Database study examined patients with ACC treated with adjuvant radiotherapy and found that survival within this cohort varied according to associated oncologic characteristics, underscoring heterogeneity and likely selection effects in retrospective radiation analyses.³

• PMID 28874901: A 2017 population-based single-centre review and literature synthesis described adjuvant radiotherapy as a selective option, particularly for R1 disease, but concluded that available data were insufficient for definitive recommendations. It also stressed the need for collaborative databases and consensus guidelines because of the rarity of ACC and the limited quality of existing evidence.²

References

Footnotes

1. Impact of multimodal therapy on margin status on overall survival for patients undergoing adrenalectomy for localized adrenocortical carcinoma.. Indian J Urol. 2022. PMID: 36568465. Local full text: 36568465.md ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²²

2. Adrenocortical carcinoma: patterns of care and role of adjuvant radiation therapy-a population-based study and review of the literature.. Curr Oncol. 2017. PMID: 28874901. Local full text: 28874901.md ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

3. Identification of oncological characteristics associated with improved overall survival in patients with adrenocortical carcinoma treated with adjuvant radiation therapy: Insights from the National Cancer Database.. Urol Oncol. 2021. PMID: 34301459. Local full text: 34301459.md ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

4. Analysis of adjuvant chemotherapy in patients undergoing curative-intent resection of localized adrenocortical carcinoma.. Am J Surg. 2021. PMID: 33168156. Local full text: 33168156.md ↩ ↩² ↩³ ↩⁴ ↩⁵