Nasopharyngeal carcinoma (NPC) is a very uncommon malignancy in most parts of India, the age-adjusted incidence rate in population-based registry Bangalore which is located in southern part of India is less than 1 per 1,00,000 population, however the incidence is more in the north-eastern parts of India, rate ranging from 3 in Sikkim to 19.4 per 1,00,000 in Kohima. These low rates are comparable to those commonly quoted for other Caucasoid populations of 0.5 to 2.0 per 100 000.

However higher incidence is seen in Chinese populations with an age adjusted rate of 30 per 100 000 for males and 13 per 100 000 for females [1]. Tumor volume has been recognized as an important prognostic factor in the outcome of NPC, in addition to histopathologic type, tumor stage and intracranial extension [2,3,4]. However, the most common staging systems used for nasopharyngeal carcinoma that is the Ho's and AJCC staging do not take tumour volume or size of disease into consideration but take anatomical site involved and extension to surrounding structures to classify the T stage [5].

But numerous studies have shown a significant association of tumor volume and outcome in NPC, but most of these studies are done in oriental populations where the incidence of NPC is high. Radiotherapy (RT) has been the mainstay of treatment of NPC over many years as its anatomical location is not easily amenable to surgery and also NPC is a radiosensitive malignancy which responds well to RT. The results of chemo radiation have been good in early stage disease and mixed in locally advanced disease. Various studies have proven the efficacy of concurrent chemo radiotherapy (CCRT) over RT alone in the treatment of locally advanced [6]. We have taken up this study to assess the volume of disease and correlate the outcome with the tumor volume in our patients treated with chemo radiation who are mainly from Bangalore which is low incidence region and to compare the results with those of high incidence region.

This study is a retrospective analytical study conducted in the department of Radiation oncology, Kidwai Memorial Institute of Oncology, Bangalore

Patient Selection: Inclusion Criteria & Exclusion Criteria

Patient and Treatment Characteristics (Table 1): All the 50 patients had received concurrent Chemoradiation, among them majority received cisplatin 44 (88%) and only 6 (12%) received carboplatin, however 23 (46%) received adjuvant chemotherapy, and the rest 27 (54%) did not.

Tumor volume and Stratification (Table 2): The median Gross tumor volume of primary disease was 61.6 cubic centimetres (cc) (range 14.9–191.6 cc), and that of node was 35.4 cubic centimetres (range 0-196.9). The patients were divided into two groups High volume disease (HVD) and Low volume disease (LVD) based on the median gross tumor volume of the primary (GTVp) disease.

Patients with GTVp of less than or equal to 61.6cc were categorized into LVD and those with GTVp of more than 61.6cc were categorized as HVD. The patient and treatment characteristics were similar in both the groups except node positivity which is comparatively higher in HVD group (P value- 0.065).

Treatment outcomes: The median follow up period was 24 months ranging from 12 to 66 months. The 2 year Disease free survival (DFS) and overall survival (OS) for the entire group was 64% and 68% respectively. The OS and DFS of LVD group was 80% and 78% respectively at 24 months, which was significantly better than OS of 55% and DFS of 52% in HVD group at 24 months (Figure I). Table 3 shows the pattern of recurrence in both the groups. The addition of Adjuvant chemotherapy had no effect on the DFS in LVD group (Figure II), but in HVD group it improved the both metastasis free survival and DFS (Figure III).

Table-1: Patient and Treatment Characteristics.

Figure II: The Metastasis free (MFS) and Disease free survival in Low volume disease group.

Figure III: The Metastasis free (MFS) and Disease free survival in High volume disease group.

Numerous studies have shown primary tumor volume to be a significant factor of treatment outcome. Study by Chua et al [7] observed PTV to be an independent prognostic factor much better than the traditional Ho’s T classification as a predictor of local control. Chen et al [10] found that tumour volume was better at predicting cumulative survival for patients with NPC than the widely used AJCC staging system. This was confirmed by Multivariate analysis after adjusting for T stage, N stage and disease stage. But most of these studies are done in populations where NPC is endemic, where as our study is done in a population where NPC is uncommon.

The median volume of primary disease in our study was 61.6ccm with range from 14.9 to 191.6 ccm, which is large as compared studies by wu et al [7] and chu et al [8], where the median primary tumor volume was 20.35 ml (range, 0.44 − 192.63 ml) and 12.94 mL (range, 1.25–69 mL) respectively.

In our study the OS and DFS are significantly better in LVD group compared to HVD group, which is similar to studies published by chu et al [7] and willner et al who showed that PTV more than 60ccm and 64ccm had poor outcome [8].

The patients treated in our center had large volume primary disease compared to similar patients in endemic areas, the OS and DFS was significantly better in LVD patients, adjuvant chemotherapy after concurrent chemoradiotherapy had no additional benefit for LVD patients but improved DFS and MFS in HVD Patients.

To the best of our knowledge this is the first study from our country which has looked at tumor volume and treatment outcomes in Nasopharyngeal tumors.

There is extensive literature on this topic mainly from countries such as china, Taiwan and Korea where the incidence is high, but limited studies are present from places of low incidence such as other Asian countries. Our study from low incidence area shows how the disease behaves differently in terms of having large disease volumes, and its correlation with treatment outcome.

S D Shamsundar: Formulated the idea for study, collection of data, manuscript writing and editing. Jaganath K P: Collection of data, editing manuscript. Niveditha S: Formulated the idea for study, collection of data. K Aradhana: collection of data, statistical analysis. R Nanda: Collection of data, manuscript writing and editing. B Thejaswini: Formulated the idea for study.