Late nodal metastasis in early-stage node-negative oral cavity cancers after successful sole interstitial brachytherapy: an institutional experience of 42 cases in India.

PURPOSES

Brachytherapy, either alone or in combination with external irradiation, is a useful organ-preserving approach in the treatment of primary head and neck cancers. Treatment of regional nodal drainage area is not warranted in early-stage oral cavity cancers because T1N0 oral cavity cancers have less than 20% likelihood of nodal spread. We reviewed the records of interstitial brachytherapy cases of oral cavity cancers in our brachytherapy unit to assess the clinical outcome of the patients treated.

METHODS AND MATERIALS

We tried to correlate the clinical outcome of the disease with different predictive factors for treatment outcome and to analyze statistically the role of these factors.

RESULTS

Cases treated with combined external irradiation with interstitial brachytherapy included higher T stage, with greater risk for nodal spread, though initially node negative. As these were treated with microscopic dose for nodal clinical target volume, nodal recurrence was fewer (18.5%). On the contrary, although the early-stage (T1N0) oral cavity cancers that were treated with brachytherapy alone had initially a less than 20% chance of nodal metastasis, there was an increased risk up to 80% for late nodal metastasis after treatment. Tumor thickness >6mm (p=0.044) and need for a multiplanar implant (p=0.008) were found to be statistically significant risk factors for nodal recurrence. Other factors like high-grade tumors, ulcero-infiltrative lesions, implant of mobile tongue, and low hemoglobin, though relevant, were not found to be statistically significant.

CONCLUSIONS

We recommend prophylactic nodal irradiation in addition to brachytherapy even for early-stage oral cancers treated with interstitial brachytherapy. Furthermore, the invasive procedure of interstitial brachytherapy causing a disruption of body's physiologic barrier to localize the disease is itself a probable risk factor for late nodal recurrence. Whether this, apart from the poor prognostic factors, causes increased chance of spread of a localized disease needs to be evaluated by a large prospective randomized study. This is needed to find out exactly the scenario where exclusive brachytherapy will be appropriate for treatment of early-stage oral cavity cancers.